Article Paratuberculosis on small ruminant dairy farms in Ontario, Canada: A survey of management practices Cathy A. Bauman, Andria Jones-Bitton, Paula Menzies, Jocelyn Jansen, David Kelton
Abstract — A cross-sectional study was undertaken (October 2010 to August 2011) to determine the risk factors for dairy goat herds and dairy sheep flocks testing positive for paratuberculosis (PTB) in Ontario, Canada. A questionnaire was administered to 50 producers during a farm visit in which concurrently, 20 randomly selected, lactating animals over the age of 2 years underwent sampling for paratuberculosis testing. Only 1 of 50 farms (2.0%) was closed to animal movement, whereas 96.6% of dairy goat farms and 94.1% of sheep farms purchased livestock from other producers. Only 10.3% of dairy goat, and no dairy sheep farms used artificial insemination. Manure was spread on grazing pastures by 65.5% and 70.6% of dairy goat and dairy sheep farms, respectively. Because of the high true-prevalence of paratuberculosis infection detected, no risk factor analysis could be performed. This study demonstrates that biosecurity practices conducive to transmission of PTB are highly prevalent in Ontario small ruminant dairy farms. Résumé — La paratuberculose dans les fermes laitières de petits ruminants de l’Ontario, au Canada : enquête sur les pratiques de gestion. Une étude transversale (d’octobre 2010 à août 2011) a été entreprise afin de déterminer les facteurs de risque pour les troupeaux de chèvres laitières et de brebis laitières obtenant des résultats positifs pour la paratuberculose (PTB) en Ontario, au Canada. Un questionnaire a été soumis à 50 producteurs durant une visite à la ferme pendant laquelle, parallèlement, 20 animaux en lactation âgés de plus de 2 ans, qui étaient choisis au hasard, ont subi un prélèvement pour un test de paratuberculose. Seulement 1 des 50 fermes (2,0 %) était fermée au mouvement des animaux, tandis que 96,6 % des fermes de chèvres laitières et 94,1 % des fermes de brebis achetaient des animaux d’autres producteurs. Seulement 10,3 % des fermes de chèvres laitières, et aucune ferme de brebis laitières, avaient eu recours à l’insémination artificielle. Le fumier était épandu dans les pâturages par 65,5 % et 70,6 % des fermes de chèvres laitières et de brebis laitières, respectivement. En raison de la prévalence réelle élevée détectée pour l’infection par la paratuberculose, aucune analyse de facteur de risque n’a pu être réalisée. Cette étude démontre que les pratiques de biosécurité propices à la transmission de la PTB sont hautement prévalentes dans les fermes de petits ruminants de l’Ontario. (Traduit par Isabelle Vallières) Can Vet J 2016;57:523–530
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Introduction
aratuberculosis (PTB, also known as Johne’s disease) is a well-recognized infectious wasting disease in dairy cattle throughout the world, caused by infection with the bacterium Mycobacterium avium subsp. paratuberculosis (MAP) (1). In Canada, each of the 10 provinces has developed voluntary
control programs aimed at reducing the level of disease in dairy cattle (2). In contrast, there is no paratuberculosis control program for dairy small ruminants in Canada, although there have been published reports of cases of paratuberculosis in goats and sheep. Given our recent report of true PTB herd/flock-level prevalence of 83.0% [95% probability interval (PI): 62.6% to
Department of Population Medicine, University of Guelph, 50 Stone Road, Guelph, Ontario N1G 2W1 (Bauman, Jones-Bitton, Menzies, Kelton); Ontario Ministry of Agriculture, Food and Rural Affairs, 6484 Wellington Road 7, Elora, Ontario N0B 1S0 (Jansen). Address all correspondence to Dr. Cathy Bauman; e-mail: [email protected] Reprints will not be available from the authors. Use of this article is limited to a single copy for personal study. Anyone interested in obtaining reprints should contact the CVMA office ([email protected]) for additional copies or permission to use this material elsewhere. CVJ / VOL 57 / MAY 2016
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98.1%] in dairy goats and 66.8% (95% PI: 41.6% to 91.4%) in dairy sheep (3) the lack of control programs for the small ruminant industry is concerning. Current cattle programs are based on: on-farm risk assessments (RAs), implementation of biosecurity strategies that reduce within-farm and between-farm transmission of the bacteria, and testing for paratuberculosis (individual animal, bulk tank milk, and farm environment) (2). Risk assessments and control strategies were developed from risk factor studies, literature published on methods of transmission of the bacteria, and expert opinion (4). To date, few small ruminant risk factor studies have been published (5) and even fewer include dairy goat or dairy sheep farms, specifically (6). Since dairy animals are managed more intensively (higher indoor-housing times with higher stocking densities) than meat animals, those farms may possess different risk factors. The objectives of the current study were to: i) obtain industry profiles of farm management practices that may serve to increase the risk of paratuberculosis on-farm, and ii) investigate risk factors associated with small ruminant dairy farms testing positive for paratuberculosis, in order to provide a framework for development of future control programs.
Materials and methods The sampling of farms and animals is described in Bauman et al (3). In brief, a cross-sectional study was conducted between October 2010 and August 2011 to determine the prevalence of paratuberculosis in the small ruminant dairy industry in Ontario. A total of 50 farms (29 dairy goat and 21 dairy sheep) were recruited and visited once during this 10-month period. The Ontario Milk Act only licenses dairy goat producers and not dairy sheep producers. Therefore, for the current study, the 29 dairy goat farms were selected from a government list following a randomized, stratified sampling (based on size of the breeding herd). The 21 dairy sheep flocks were selected non-randomly using both contact information obtained from licensed milk processors purchasing their milk and information available from an out-of-date government list from January 26, 2010. During each farm visit, 20 lactating does or ewes (. 2 y old) were randomly selected at milking time. The first animal was selected based on a random number between 1 and 5. Then the size of the milking herd was divided by 20 to give “x” and every “xth” animal afterward was selected. Each selected animal was subsequently sampled for feces from the rectum and for whole blood via jugular venipuncture. At least 20 g of feces were collected into sterile plastic vials using a sterile lubricant (Lubricating Jelly; Healthcare Plus, Canadian Custom Packaging, Toronto) and individual sterile polyethylene gloves for each animal to minimize contamination. Blood was collected into 1 non-additive BD Vacutainer® tube (Becton, Dickinson and Company, Franklin Lakes, New Jersey, USA) and centrifuged for 10 min at 1000 3 g within 12 h of collection. No animals had been vaccinated against paratuberculosis, and the PTB status of each farm and animal was unknown to researchers at the time of the study. Three paratuberculosis tests were all performed according to manufacturer’s instructions: fecal culture (FCUL), direct 524
real-time polymerase chain reaction (FPCR) on feces, and an enzyme-linked immunosorbent assay (ELISA) on serum. Fecal culture was performed using the BD BACTEC TM MGITTM 960 Mycobacterial detection system (Becton Dickinson and Company) and BACTEC TM MGIT TM Para TB medium. Culture-positive samples underwent both acid-fast staining and PCR confirmation with the hspX gene (Culture Confirmation Protocol, MAP Extraction System, Tetracore ®, Rockville, Maryland, USA). The FPCR was performed directly on the feces prior to decontamination using the MAP extraction system by Tetracore® using the cycle threshold (Ct) of # 42.0 as the cut-off for positive selection. The serum samples were processed using the Paracheck® ELISA (Prionics, Schlieren-Zürich, Switzerland) and the positive cut-off of . 0.3 was used. The small ruminant positive cut-off stipulated by the manufacturer is the mean optical density of the negative control 1 0.2. Farm owners/managers received a questionnaire which they completed during the sampling visit or submitted at their earliest convenience (self-addressed, stamped envelope provided). Paratuberculosis test results were not released to the producer until the questionnaire had been received. The questionnaire consisted of 90 questions, took approximately 90 min to complete, collected general herd/flock demographic information, and asked questions regarding management practices. These questions were categorized as follows: animal movements on and off farms, use and handling of replacement livestock, exposure of livestock to other animals, animal housing, feeding of milk and colostrum, manure management, and specific questions related to the farm’s Johne’s disease status. Sixty-two questions were closed-ended: 20 were dichotomous, 38 multiple-choice, 2 were scaling, and 2 were matrix. Fifteen questions were semiclosed-ended as they offered an option to specify an alternative answer to those listed and the remaining 13 questions were open-ended fill-in-the blank and asked for dates or numerical estimates. After development, the questionnaire was pre-tested on 10 goat and sheep producers/industry representatives during the spring of 2010. The individuals were purposively selected to represent different aspects of the small ruminant industries. Any questions considered lengthy or confusing were reworded prior to initiation of the study. Copies of the questionnaire are available upon request from the corresponding author. Questionnaire responses were entered and stored in Excel® (Microsoft, 2007; Redmond, Washington, USA) and all summary descriptive statistics calculated using Stata® 11.2 (StataCorp LP, College Station Texas, USA) and reported at the farm-level. True prevalence was determined using a 3-test Bayesian model constructed separately for each species and is described in detail in Bauman et al (3). In order to statistically determine risk factors from data, infected and non-infected groups of sufficient size are needed. Among the study farms, all of the 29 (100%) goat herds and 18 of the 21 (85.7%) sheep flocks had at least 1 animal test positive on at least 1 test and the true herd-level prevalence (that accounted for imperfect test performance) exceeded 80% and flock-level prevalence exceeded 65% (3). The lack of uninfected farms meant we were not able to determine if any specific practices affected PTB herd/flock CVJ / VOL 57 / MAY 2016
Table 1. Number of Ontario dairy goat and dairy sheep farms that purchased replacement animals in the previous 3 years, categorized by gender and age of animals purchased Males Males Females Females Purchased , 1 year $ 1 year Purchased , 1 year $ 1 year males of age of age females of age of age 28 (96.6%)
26 (92.9%)
15 (53.6%)
11 (37.9%)
9 (81.8%)
9 (81.8%)
Dairy sheep (n = 17 flocks)
17 (100%)
15 (88.2%)
13 (76.4%)
15 (88.2%)
7 (46.7%)
15 (100%)
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Dairy goat (n = 29 herds)
Table 2. Location and number of animals purchased by the 29 Ontario dairy goat and 17 dairy sheep farms that purchased replacements in the last 3 years
Table 3. Quarantine practices of 29 Ontario dairy goat and 17 dairy sheep farms which reported purchasing replacement animals in the last 3 years
Number of replacement animals purchased in last 3 years
Frequency with which purchased Number animals are of farms quarantined # (%)
Mean number of days animals quarantined (range)
Dairy goat Always Sometimes Never
10 (34.5%) 4 (13.8%) 15 (51.7%)
69.7 (2 to 365) 23.3 (7 to 42) 0
Dairy sheep Always Sometimes Never
1 (5.9%) 42 (2 to 180) 1 (5.9%) 21 (2 to 42) 15 (88.2%) 0
Source of purchased animals Other producers Dealer
Dairy goats # 6 15 7 to 20 6 21 to 50 1 $ 51 7 Total 29
1 1 0 2 4
Dairy sheep # 6 3 0 7 to 20 4 0 21 to 50 4 0 $ 51 5 1 Total a
16
Sales barn
Show/ Sale
1 1 0 2 1 0 2 2 4 5 0 0 0 0
0 0 0 0
1 0 0
a Since
animals could be acquired from more than 1 source totals may exceed total number of farms sampled.
status. No statistical modeling was undertaken and no statistical comparisons were made between species.
Results Questionnaires from all 29 goat producers and 18 of the 21 sheep milk producers (85.7%) were returned. All goat producers completed all questions while some questionnaires from sheep producers were incomplete. Overall, there was little variation in the responses to many of the management questions. The questionnaire data were summarized, and a profile was developed of current management practices that possibly contribute to the high prevalence of disease in these industries. Relevant herd and animal summary statistics are presented elsewhere (3). Overall, no goat and only 1 sheep farm were closed to live animal introductions or returns. Animal movements were primarily due to purchase of live animals as all 29 goat herds and 17 of the 18 sheep flocks had purchased animals in the last 3 y. Only 20.7% (6/29) of goat herds and 5.9% of (1/17) sheep flocks had borrowed animals, and 10.3% (3/29) of goat herds and 5.9% (1/17) of sheep flocks had loaned animals out. Since only 3/29 (10.3%) goat herds and no sheep flocks used artificial insemination, 96.6% (28/29) of goat farms and 94.4% (17/18) of sheep farms had purchased male animals for breeding. For the breakdown of age group and genders purchased see Table 1. Producers indicated they had purchased replacement animals from other producers, dealers, sales barns, and from shows or sales in the last 3 y. However, 96.6% (28/29) of goat herds and CVJ / VOL 57 / MAY 2016
94.1% (16/17) of sheep flocks had primarily purchased their animals from other producers. For number of replacements purchased and locations of purchases, see Table 2. Practices for quarantining new introductions are reported in Table 3. Producers who purchased livestock from other producers were asked if they inquired about the disease status of the herd/ flock of origin, specifically history of abortions, Q-fever, PTB, caseous lymphadenitis (CL), and caprine arthritis encephalitis (CAE)/maedi visna (MV). Dairy goat producers were most likely to have asked about CAE (60.7%; 17/28), CL (57.1%; 16/28) and PTB (46.4%; 13/28). Only 2 dairy sheep producers (12.5%) inquired about disease status, and the same 2 producers inquired about the same 5 infectious diseases as mentioned above. No dairy goat producer tested all purchased animals for Johne’s disease; only 1 goat producer (3.6%; 1/28) sometimes tested and the remaining goat producers (96.4%) and all dairy sheep producers never tested. Many (72.4%; 21/29) dairy goat farms reported having 1 or more animal(s) with CL in the last 3 y. Farm-level prevalence of CL was lower on dairy sheep farms (18.8%; 3/16). Despite the high true herd-level prevalence of PTB determined in this study, few producers reported having the disease diagnosed on their farm in the last 10 y [dairy goats: 13.8% (4/29); dairy sheep: 11.1% (2/18)]. However, no farms of either species had any herd-level testing performed, and only 6 of the 29 (20.7%) dairy goat herds and 4 of the 17 (23.5%) dairy sheep flocks had performed some form of individual animal testing. Of the 6 farms reporting previously diagnosed cases, 3 of the 4 dairy goat and both of the dairy sheep farms had purchased the affected animals; on the remaining dairy goat farm, the animal had been born and raised on the farm. No cases of PTB were diagnosed in other species such as cattle, on any farm. 525
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Table 4. Frequency of colostrum and milk feeding practices on 29 dairy goat farms in Ontario Frequently Infrequently Always (. 50% of (, 50% of % (#) the time) the time) farms % (#) farms % (#) farms
Never % (#) farms
Feed colostrum from the dam to their own kid(s)
51.7% (15)
20.7% (6)
6.9% (2)
20.7% (6)
Feed colostrum from 1 dam to kid(s) not their own
51.7% (15)
20.7% (6)
6.9% (2)
20.7% (6)
Pool colostrum from more than 1 dam to feed to kid(s)
6.9% (2)
24.1% (7)
17.2% (5)
51.7% (15)
Feed heat-treated colostrum (56°C to 60°C for 1 h)
17.2% (5)
13.8% (4)
3.4% (1)
65.5% (19)
Feed a commercial colostrum replacement product
3.4% (1)
6.9% (2)
20.7% (6)
70.0% (20)
Feed colostrum sourced from off-farm from the same species
0.0% (0)
3.4% (1)
0.0% (0)
96.6% (28)
Feed colostrum from another species (e.g., cattle)
10.3% (3)
6.9% (2)
17.2% (5)
65.5% (19)
Kids allowed to nurse their dams
51.7% 10.3% (15) (3)
17.2% (5)
20.7% (6)
Feed pooled milk
6.9% 13.8% (2) (4)
10.3% (3)
70.0% (20)
Feed milk replacer
65.5% 17.2% (19) (5)
3.4% (1)
13.8% (4)
Feed pasteurized milk
6.9% 10.3% (2) (3)
3.4% (1)
79.3% (23)
Feed acidified milk
44.8% 10.3% (13) (3)
6.9% (2)
37.9% (11)
Feed milk from other species
24.1% 3.4% (7) (1)
3.4% (1)
70.0% (20)
A large proportion of farms reported that their goats or sheep had had contact with other species of animals in the previous 3 y: 93.1% (27/29) of dairy goat and 100% (18/18) of dairy sheep farms reported their animals had contact with barn cats, 75.8% (22/29) of dairy goat and 72.2% (13/18) of dairy sheep farms had contact with pet dogs, and 58.6% (17/29) of dairy goat and 83.3% (15/18) of dairy sheep farms had contact with cattle. More than half of goat producers (51.7%) and 92.3% of sheep producers did not remove kids and lambs immediately at birth. These producers allowed the kids and lambs to nurse for a mean of 7.7 and 21.5 d, respectively; other colostrum and milk feeding practices are presented in Tables 4 and 5. Animals identified as potential replacements were removed from their dams sooner at 4.9 and 11.6 d on dairy goat and dairy sheep farms, respectively. However, replacements were still exposed to the manure of adult animals on 46.4% (13/28) of dairy goat and 82.4% (14/17) of dairy sheep farms. With respect to manure management, 65.5% (19/29) of dairy goat farms and 70.6% (12/17) of dairy sheep farms spread manure on pastures used for grazing. The average time that fresh manure was added to the manure storage pile prior to spreading was 50.6 d (range: 0 to 365 d; median 7 d) and 105.2 d (range: 0 to 365 d; median 14 d) on dairy goat and dairy sheep farms, respectively. 526
Discussion Many aspects of paratuberculosis control programs for dairy cattle can be applied to dairy goat and dairy sheep programs. However, there are important differences in the disease, testing accuracy, animal value, and management practices in small ruminants. This study found many management practices on Ontario dairy goat and dairy sheep farms to be plausible risk factors for paratuberculosis, although statistical associations could not be evaluated due to insufficient negative farms. Nonetheless, this work identified high-risk management practices that should be targeted for prevention and control of not only PTB, but also other important infectious diseases (CL, CAE, MV), on dairy goat and dairy sheep farms in the province. In this study, there was only 1 closed farm. Closing the herd to purchased/borrowed animals is a challenge for small ruminant producers. A major obstacle to herd/flock closure is the low frequency of use of artificial insemination (AI), evidenced by the high percentage of producers who reported purchasing bucks and rams. Artificial insemination is the best way of assuring new male genetics are low risk for PTB and has been promoted by the goat industry and the Canadian Food Inspection Agency (CFIA) (7) in their goat National Biosecurity Standard and Planning Guide. However, as shown in this study, it is not in common use despite the ease with which AI can be done at a CVJ / VOL 57 / MAY 2016
Table 5. Frequency of colostrum and milk feeding practices on 13 dairy sheep farms in Ontario Never % (#) farms
Feed colostrum from the dam to their own lamb(s)
100% (13)
0.0% (0)
0.0% (0)
0.0% (0)
Feed colostrum from 1 dam to lamb(s) not their own
0.0% (0)
18.2% (2)
54.5% (8)
27.3% (3)
Pool colostrum from more than 1 dam to feed to lamb(s)
0.0% (0)
18.2% (2)
18.2% (2)
63.6% (9)
Feed heat-treated colostrum (56°C to 60°C for 1 h)
0.0% (0)
0.0% (0)
0.0% (0)
100% (13)
Feed a commercial colostrum replacement product
0.0% (0)
0.0% (0)
23.1% (3)
76.9% (10)
Feed colostrum sourced from off-farm from the same species
0.0% (0)
0.0% (0)
0.0% (0)
100% (13)
Feed colostrum from another species (e.g., cattle)
0.0% (0)
0.0% (0)
15.4% (2)
84.6% (11)
Lambs allowed to nurse their dams
92.3% 7.7% (12) (1)
0.0% (0)
0.0% (0)
Feed pooled milk
7.7% 7.7% (1) (1)
15.4% (2)
69.2% (9)
Feed milk replacer
38.5% 7.7% (5) (1)
23.1% (3)
30.8% (4)
Feed pasteurized milk
0.0% 0.0% (0) (0)
0.0% (0)
100% (13)
Feed acidified milk
7.7% 0.0% (1) (0)
7.7% (1)
84.6% (11)
Feed milk from other species
7.7% 0.0% (1) (0)
23.1% (3)
69.2% (9)
relatively moderate cost in goats. The use of AI as a biosecurity practice on sheep farms is less likely to be adopted widely because trans-cervical AI is difficult and expensive. Education of producers with respect to how to source healthy animals for purchase is essential. It has been previously highlighted in 2 sheep studies that animal movement between farms, and high purchased replacement rates, are risk factors for PTB (5,8). In addition, the current study found that most dairy goat and dairy sheep producers purchased animals primarily from other producers without determining the infectious disease status of the farm of purchase. This likely contributed to the high herd-level prevalence found in this study, although we were unable to formally assess this statistically given a lack of variability in the data. Most farms in this study did not practice whole herd testing for PTB, nor appropriate quarantine behaviors to prevent transmission of infectious diseases in general. A suspected contributing factor to this indiscriminate pattern of sourcing animals may have been the rapid growth in the demand for goat and sheep milk over the last decade. This demand elevated the price of milk that producers received for their product and encouraged expansion of existing operations and start-up of new ones. Additionally, breeding animals cannot be easily sourced from outside Canada due to import restrictions designed to support the Canadian government’s goal of eradicating scrapie (9). CVJ / VOL 57 / MAY 2016
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Frequently Infrequently Always (. 50% of (, 50% of % (#) the time) the time) farms % (#) farms % (#) farms
To reduce the risk of introducing PTB to a farm, animals should be purchased only from “low-risk” flocks and herds (10). Currently, “low risk” is not defined by a paratuberculosis control program; however, PTB-introduction risk can be lowered by the practice of producers always requesting, prior to purchase, a vendor declaration of herd/flock health status. This declaration should include information regarding whether any animals have been diagnosed with PTB on the vendor’s farm, the frequency of testing of animals for PTB, and tests used. Information regarding the farm’s policy on animal movements, the measures taken to interrupt potential on-farm transmission of infectious diseases, and the monitoring of animals dying onfarm through the use of veterinary postmortem examinations should also be included in this declaration (11). When farmof-purchase status cannot be determined to be “low risk,” all purchased animals should undergo quarantine until testing for PTB can be performed before introduction to the herd/flock. However, testing of purchased young stock will generally fail to detect infection. MAP-infected goats and sheep generally do not shed enough bacteria to test positive on fecal tests before the age of 9 mo (12), test positive on an antibody-based test before 1 y of age (13), or demonstrate clinical signs of wasting before the age of 18 mo (14). In addition, animals do not shed the bacteria consistently and antibody responses can vary depending on age and lactation stage (15). Given these age 527
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constraints and variability in immune responses, there can be no guarantee that any test-negative animal is free of infection. Testing recommendations will vary depending on the history of the animal and farm-of-origin, but given what we know about PTB test performance, the following should be considered when developing a testing protocol for new purchases. Animals under a year of age can be screened with fecal testing such as PCR. Animals that are purchased when they are 1 year of age or older should be tested using both fecal PCR and an antibody test (e.g., serum ELISA) in parallel to maximize the sensitivity of detecting infected animals (16). Once purchased animals are introduced to the herd they should be monitored closely with semi-annual testing. Written documentation of their contacts and offspring should also be kept. If the introduced animal was to test positive at a later date, these recorded animals should be subsequently tested to identify the extent of the spread of PTB. Current within-farm PTB control measures concentrate on reducing direct and indirect exposure of replacement youngstock to MAP by minimizing their exposure to potentially infected adult animals (17), their manure, and the contaminated environment (18). As observed in this study, some dairy goat producers currently implement some of the following management practices: removal of offspring at birth, feeding safe colostrum and milk replacement products, and rearing young stock separately from the adults. These practices were most often undertaken by goat producers to reduce transmission of the CAE virus. Safe colostrum and milk feeding are not widespread (Tables 4 and 5), which may be due to the labor-intensiveness of these practices. The peri-parturient period in the small ruminant industries is already a labor-intensive period as most producers have seasonal lambing/kidding periods with animals routinely having multiple births. While minimizing contact with infected adult goats and sheep is probably most important, contact from other species is also a risk. Mycobacterium avian subsp. paratuberculosis infects a wide range of ruminant and non-ruminant animals (19) and transmission from other species to goats or sheep is possible (20). In this study, many farms indicated their animals came in contact with barn cats and pet dogs. The MAP bacteria were isolated from feral cats on a dairy cattle farm where paratuberculosis had been previously diagnosed and further analysis of these isolates using restriction fragment length polymorphism supported inter-species transmission between the cattle and the cats (21). This bacterium has also been isolated from pet dogs with gastrointestinal illness (22). Whether cats and dogs are potential sources of infection to ruminants is yet to be determined. A high proportion of small ruminant farms had also housed cattle on their premises within the last 3 y. This indicates that these farms are diverse with multiple species in co-existence, or that producers are new to the dairy small ruminant industry having recently sold their cattle. Cattle are potential reservoirs for new infections either directly through animal interactions or indirectly through environmental contamination (23). In this study, the producers reported that no cases of PTB had been diagnosed in other species of animals on their farms, but we do not know to what extent testing had been performed previously. 528
While MAP requires a host animal to replicate (19) and therefore restricting exposure to the animal reservoir is critical, the bacteria can also survive for long periods of time even in harsh environments — up to 55 wk in naturally infected soil and grass (24). To compensate for this long survivability, PTB-prevention strategies recommend spreading manure only on crop-producing fields, and not those used for grazing (25). Two studies on sheep support the application of this strategy in small ruminants. A study in Portugal identified that not spreading manure on grazing pastures was a preventative factor (26), and a study in Czechoslovakia (27) detected MAP in the green parts and roots of plants growing at sites at which feces had been deposited on pasture. It is generally believed that composting manure prior to spreading will dramatically reduce and potentially eliminate MAP (28,29), other bacterial organisms (30), and gastrointestinal parasite eggs and larvae from manure (31). There is uncertainty regarding the length of time manure should be composted and little research has involved small ruminant feces specifically (28). Overall, producers should be encouraged to compost manure for a minimum of 90 d to reduce all pathogen burdens on their farms, and to spread it on crop yielding fields only, not pastures (32). Small ruminants infected with PTB often do not develop overt diarrhea (11); therefore, the disease can go unrecognized on farms or be mistaken for other wasting disease such as those caused by CAE, CL, gastrointestinal parasites, or dental problems. This is supported by the high number of producers in our study who were unaware the disease was present on their farm. One important benefit of this study is that it raised awareness among producers regarding PTB, its effects, diagnosis and control. Cost of production on small ruminant dairy farms is high and profits are minimal (33); therefore, efficient use of resources is essential. Since all the biosecurity interventions, whether between-farms or on-farm, are time-consuming and expensive (34), producers are unlikely to make the management changes unless the disease has been diagnosed on their farm. Therefore, all producers should be encouraged to determine their herdstatus by herd-level testing (bulk tank milk, random sample of individual animals, or whole herd, and veterinary-performed postmortem examination of adult animals with clinical evidence of disease or wasting). In addition, many of the risk factors and management strategies for PTB also apply to other production-limiting infectious diseases. It may be prudent to not concentrate on control strategies for just one disease, but to expand them to include the others. The dairy goat producers of this study also had a high prevalence of CL on their farms (75.6%). In Quebec, maedi-visna seroprevalence in cull sheep was reported to be 44% (35), and a proportional mortality study of goats in that province (36) indicated that CAE (4.6%) and CL (3.9%) were significant causes of mortality, and that CL lesions were present in 24.3% of submitted animals. It has been speculated that continued uptake of PTB prevention strategies may be more successful if producers see the reduction in transmission of other pathogens as well (34). Norway has adopted this approach with the “Healthier Goat” program (37), in which government and industry have dedicated finances and effort to CVJ / VOL 57 / MAY 2016
Acknowledgments We are grateful to the Ontario Ministry of Agriculture, Food and Rural Affairs-University of Guelph Agreement through the Animal Health Strategic Investment fund (AHSI) managed by the Animal Health Laboratory of the University of Guelph, and to the Ontario Veterinary College for a Fellowship to the primary author. CVJ
References 1. Tiwari A, VanLeeuwen JA, McKenna SLB, Keefe GP, Barkema HW. Johne’s disease in Canada Part I: Clinical symptoms, pathophysiology, diagnosis, and prevalence in dairy herds. Can Vet J 2012;47:874–882. 2. Barker RA, Barkema HW, Fecteau G, Keefe GP, Kelton DF. Johne’s Disease Control in Canada — Coordinated Nationally — Delivered Provincially. Available from: http://manitobaholsteins.ca/my_folders/ pdf/CJDI-_ICP_Australia__12.pdf Last accessed March 9, 2016. 3. Bauman CA, Jones Bitton A, Menzies P, Toft N, Jansen J, Kelton D. Prevalence of paratuberculosis in the dairy goat and dairy sheep industries in Ontario, Canada. Can Vet J 2016;57:169–175. 4. Sorge U, Lissemore K, Godkin A, et al. Risk factors for herds to test positive for Mycobacterium avium ssp. paratuberculosis-antibodies with a commercial milk enzyme-linked immunosorbent assay (ELISA) in Ontario and western Canada. Can Vet J 2012;53:963–970. 5. Dhand NK, Eppleston J, Whittington RJ, Toribio JA. Risk factors for ovine Johne’s disease in infected sheep flocks in Australia. Prev Vet Med 2007;82:51–71. 6. Reviriego FJ, Moreno MA, Domínguez L. Soil type as a putative risk factor of ovine and caprine paratuberculosis seropositivity in Spain. Prev Vet Med 2000;43:43–51. 7. Biosecurity Planning Guide for Canadian Goat Producers. Avail able from: http://www.inspection.gc.ca/animals/terrestrial-animals/ biosecurity/standards-and-principles/producer-guide-goats/eng/ 1375213342187/1375213659306 Last accessed March 9, 2016. 8. Mainar-Jaime RC, Vázquez-Boland JA. Factors associated with sero prevalence to Mycobacterium paratuberculosis in small-ruminant farms in the Madrid region (Spain). Prev Vet Med 1998;34:317–327. 9. General information about non-slaughter goats importation from USA — April 2007. Canadian National Goat Federation. Available from: http://www.cangoats.com/index.php?pageid=470 Last accessed March 9, 2016. 10. Sanderson MW, Dargatz DA, Garry FB. Biosecurity practices of beef cow-calf producers. J Am Vet Med Assoc 2000;217:185–189. 11. Stehman SM, Shulaw WP. Paratuberculosis (Johne’s disease) in sheep and goats. 1996 Committee Proceedings on Sheep and Goats. Available CVJ / VOL 57 / MAY 2016
from: http://goatconnection.com/articles/publish/article_128.shtml Last accessed March 9, 2016. 12. Lybeck KR, Storset AK, Djønne B, Valheim M, Olsen I. Faecal shedding detected earlier than immune responses in goats naturally infected with Mycobacterium avium subsp. paratuberculosis. Res Vet Sci 2011;91:32–39. 13. Stehman S. Q & A: Johne’s Disease (Paratuberculosis). Available from: http://kinne.net/johnesqa.htm Last accessed March 9, 2016. 14. Smith MC, Sherman DM. Goat Medicine. 2nd ed. Ames, Iowa: WileyBlackwell 2009:419–427. 15. Nielsen SS, Grohn YT, Enevoldsen C. Variation of the milk antibody response to paratuberculosis in naturally infected dairy cows. J Dairy Sci 2002;85:2795–2802. 16. Manning EJB, Steinberg H, Krebs V, Collins MT. Diagnostic testing patterns of natural Mycobacterium paratuberculosis infection in pygmy goats. Can J Vet Res 2003;67:213–218. 17. Geraghty T, Graham DA, Mullowney P, More SJ. A review of bovine Johne’s disease control activities in 6 endemically infected countries. Prev Vet Med 2014;116:1–11. 18. Sweeney RW. Transmission of paratuberculosis. Vet Clin North Am Food Anim Pract 1996;12:305–312. 19. Chiodini RJ, van Kruiningen HJ, Merkal RS. Ruminant paratuberculosis (Johne’s disease): The current status and future prospects. Cornell Vet 1984;74:218–262. 20. Moloney BJ, Whittington RJ. Cross species transmission of ovine Johne’s disease from sheep to cattle: An estimate of prevalence in exposed susceptible cattle. Aust Vet J 2008;86:117–123. 21. Palmer MV, Stoffregen WC, Carpenter JG, Stabel JR. Isolation of Mycobacterium avium subsp. paratuberculosis (MAP) from feral cats on a dairy farm with MAP-infected cattle. J Wildl Dis 2005;41:629–635. 22. Glanemann B, Schönenbrücher H, Bridger N, Abdulmawjood A, Neiger R, Bülte M. Detection of Mycobacterium avium subspecies paratuberculosis-specific DNA by PCR in intestinal biopsies of dogs. J Vet Intern Med 2008;22:1090–1094. 23. Moravkova M, Babak V, Kralova A, Pavlik I, Slana I. Culture- and quantitative IS900 real-time PCR-based analysis of the persistence of Mycobacterium avium subsp. paratuberculosis in a controlled dairy cow farm environment. Appl Environ Microbiol 2012;78:6608–6614. 24. Whittington RJ, Marshall DJ, Nicholls PJ, Marsh IB, Reddacliff LA. Survival and dormancy of Mycobacterium avium subsp. paratuberculosis in the environment. Appl Environ Microbiol 2004;70:2989–3004. 25. Baumgartner W. News concerning paratuberculosis in cattle. Bull UASVM Vet Med 2013;70:177–181. 26. Coelho AC, Pinto ML, Coelho AM, Aires A, Rodrigues J. A seroepidemiological survey of Mycobacterium avium subsp. paratuberculosis in sheep from North of Portugal. Pesq Vet Bras 2010;30:903–908. 27. Pribylova R, Slana I, Kaevska M, et al. Soil and plant contamination with Mycobacterium avium subsp. paratuberculosis after exposure to naturally contaminated mouflon feces. Curr Microbiol 2011;62:1405–1410. 28. Gobec I, Dobeic M, Pogačnik M, Pate M, Ocepek M. Influence of different sheep manure treatments on survival of Mycobacterium avium subsp. paratuberculosis. 8th International Colloquium on Paratuberculosis, Copenhagen, Denmark, 2005. 29. Bonhotel J, Schwarz M, Stehman S. How Mycobacterium avium paratuberculosis is affected by the composting process. Trends Anim Vet Sci J 2011;2:5–10. 30. Grewal SK, Rajeev S, Sreevatsan S, Michel FC, Jr. Persistence of Mycobacterium avium subsp. paratuberculosis and other zoonotic pathogens during simulated composting, manure packing, and liquid storage of dairy manure. Appl Environ Microbiol 2006;72:565–574. 31. Duval J. The control of internal parasites in ruminants. Available from: http://eap.mcgill.ca/agrobio/ab370-04e.htm Last accessed March 9, 2016. 32. The Zenith Agribusiness Solutions. Q Fever Risk Management Bulletin. Available from: http://www.thezenith.com/files/rmb/rm-q-feverag-rm186-eng.pdf Last accessed March 9, 2016. 33. Hedrich C. Best Management Practices for Dairy Goat Farmers. 2008. Available from: http://www.milkproduction.com/Global/ PDFs/Bestmanagementpracticesfordairygoatfarmers.pdf Last accessed December 2, 2015. 34. NRC, National Research Council, Committee on Diagnosis and Control of Johne’s disease. Diagnosis and Control of Johne’s Disease. Washington DC: The National Academies Press, 2003:1–14. 35. Arsenault J, Girard C, Dubreuil P, et al. Prevalence of and carcass condemnation from maedi–visna, paratuberculosis and caseous lymphadenitis in culled sheep from Quebec, Canada. Prev Vet Med 2003;59:67–81.
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eradicating CAE, CL, and PTB within the same program. While very labor-intensive, producers have been reported to be satisfied with the results (38); the main benefit for enrolled farms has been overall healthier animals and 63% higher milk yields than farms not enrolled in the program (39). This study has demonstrated that current biosecurity practices — both between-herd and within-herd — on Ontario dairy goat and dairy sheep farms are not conducive to the prevention or control of PTB infection, and likely other infectious diseases as well. A PTB disease control program is needed in these industries. Established dairy cattle PTB control programs to date have concentrated on risk management of PTB alone. As the dairy goat and dairy sheep industries are in the preliminary stages of developing their own species-specific control program, they have an opportunity to consider a “whole herd” approach to disease control similar to the program in Norway. This would have the potential to control/eradicate other production- limiting diseases and consolidate resources, which may contribute to sustained uptake by producers and improved health and productivity.
4QFjAH&url=http%3A%2F%2Fwww.bioforsk.no%2FikbViewer%2 FContent%2F35685%2FGOAT%2520HUSBANDRY%2520NOR WAY.doc&ei=83W1VO7_AtCwyAT6mIGoCw&usg=AFQjCNExcz_ T3J3NvBe2bLLuqPvy8rXqyw Last accessed on March 9, 2016. 39. Nagel-Alne GE, Krontveit R, Bohlin J, Valle PS, Skjerve E, Sølverød LS. The Norwegian Healthier Goats program-Modeling lactation curves using a multilevel cubic spline regression model. J Dairy Sci 2014;97:4166–4173.
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36. Debien E, Hélie P, Buczinski S, Lebœuf A, Bélanger D, Drolet R. Proportional mortality: A study of 152 goats submitted for necropsy from 13 goat herds in Quebec, with a special focus on caseous lymphadenitis. Can Vet J 2013;54:581–587. 37. Disease Eradication in Norwegian Goats. Available from: http://leine. no/htg/sanering/info/english/infengl.htm Last accessed March 9, 2016. 38. Bioforsk. Norwegian Goat Husbandry. Available from: http://www. google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=0CD
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Abstract — A cross-sectional study was undertaken (October 2010 to August 2011) to determine the risk factors for dairy goat herds and dairy sheep flocks testing positive for paratuberculosis (PTB) in Ontario, Canada. A questionnaire was administered to 50 producers during a farm visit in which concurrently, 20 randomly selected, lactating animals over the age of 2 years underwent sampling for paratuberculosis testing. Only 1 of 50 farms (2.0%) was closed to animal movement, whereas 96.6% of dairy goat farms and 94.1% of sheep farms purchased livestock from other producers. Only 10.3% of dairy goat, and no dairy sheep farms used artificial insemination. Manure was spread on grazing pastures by 65.5% and 70.6% of dairy goat and dairy sheep farms, respectively. Because of the high true-prevalence of paratuberculosis infection detected, no risk factor analysis could be performed. This study demonstrates that biosecurity practices conducive to transmission of PTB are highly prevalent in Ontario small ruminant dairy farms. Résumé — La paratuberculose dans les fermes laitières de petits ruminants de l’Ontario, au Canada : enquête sur les pratiques de gestion. Une étude transversale (d’octobre 2010 à août 2011) a été entreprise afin de déterminer les facteurs de risque pour les troupeaux de chèvres laitières et de brebis laitières obtenant des résultats positifs pour la paratuberculose (PTB) en Ontario, au Canada. Un questionnaire a été soumis à 50 producteurs durant une visite à la ferme pendant laquelle, parallèlement, 20 animaux en lactation âgés de plus de 2 ans, qui étaient choisis au hasard, ont subi un prélèvement pour un test de paratuberculose. Seulement 1 des 50 fermes (2,0 %) était fermée au mouvement des animaux, tandis que 96,6 % des fermes de chèvres laitières et 94,1 % des fermes de brebis achetaient des animaux d’autres producteurs. Seulement 10,3 % des fermes de chèvres laitières, et aucune ferme de brebis laitières, avaient eu recours à l’insémination artificielle. Le fumier était épandu dans les pâturages par 65,5 % et 70,6 % des fermes de chèvres laitières et de brebis laitières, respectivement. En raison de la prévalence réelle élevée détectée pour l’infection par la paratuberculose, aucune analyse de facteur de risque n’a pu être réalisée. Cette étude démontre que les pratiques de biosécurité propices à la transmission de la PTB sont hautement prévalentes dans les fermes de petits ruminants de l’Ontario. (Traduit par Isabelle Vallières) Can Vet J 2016;57:523–530
P
Introduction
aratuberculosis (PTB, also known as Johne’s disease) is a well-recognized infectious wasting disease in dairy cattle throughout the world, caused by infection with the bacterium Mycobacterium avium subsp. paratuberculosis (MAP) (1). In Canada, each of the 10 provinces has developed voluntary
control programs aimed at reducing the level of disease in dairy cattle (2). In contrast, there is no paratuberculosis control program for dairy small ruminants in Canada, although there have been published reports of cases of paratuberculosis in goats and sheep. Given our recent report of true PTB herd/flock-level prevalence of 83.0% [95% probability interval (PI): 62.6% to
Department of Population Medicine, University of Guelph, 50 Stone Road, Guelph, Ontario N1G 2W1 (Bauman, Jones-Bitton, Menzies, Kelton); Ontario Ministry of Agriculture, Food and Rural Affairs, 6484 Wellington Road 7, Elora, Ontario N0B 1S0 (Jansen). Address all correspondence to Dr. Cathy Bauman; e-mail: [email protected] Reprints will not be available from the authors. Use of this article is limited to a single copy for personal study. Anyone interested in obtaining reprints should contact the CVMA office ([email protected]) for additional copies or permission to use this material elsewhere. CVJ / VOL 57 / MAY 2016
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98.1%] in dairy goats and 66.8% (95% PI: 41.6% to 91.4%) in dairy sheep (3) the lack of control programs for the small ruminant industry is concerning. Current cattle programs are based on: on-farm risk assessments (RAs), implementation of biosecurity strategies that reduce within-farm and between-farm transmission of the bacteria, and testing for paratuberculosis (individual animal, bulk tank milk, and farm environment) (2). Risk assessments and control strategies were developed from risk factor studies, literature published on methods of transmission of the bacteria, and expert opinion (4). To date, few small ruminant risk factor studies have been published (5) and even fewer include dairy goat or dairy sheep farms, specifically (6). Since dairy animals are managed more intensively (higher indoor-housing times with higher stocking densities) than meat animals, those farms may possess different risk factors. The objectives of the current study were to: i) obtain industry profiles of farm management practices that may serve to increase the risk of paratuberculosis on-farm, and ii) investigate risk factors associated with small ruminant dairy farms testing positive for paratuberculosis, in order to provide a framework for development of future control programs.
Materials and methods The sampling of farms and animals is described in Bauman et al (3). In brief, a cross-sectional study was conducted between October 2010 and August 2011 to determine the prevalence of paratuberculosis in the small ruminant dairy industry in Ontario. A total of 50 farms (29 dairy goat and 21 dairy sheep) were recruited and visited once during this 10-month period. The Ontario Milk Act only licenses dairy goat producers and not dairy sheep producers. Therefore, for the current study, the 29 dairy goat farms were selected from a government list following a randomized, stratified sampling (based on size of the breeding herd). The 21 dairy sheep flocks were selected non-randomly using both contact information obtained from licensed milk processors purchasing their milk and information available from an out-of-date government list from January 26, 2010. During each farm visit, 20 lactating does or ewes (. 2 y old) were randomly selected at milking time. The first animal was selected based on a random number between 1 and 5. Then the size of the milking herd was divided by 20 to give “x” and every “xth” animal afterward was selected. Each selected animal was subsequently sampled for feces from the rectum and for whole blood via jugular venipuncture. At least 20 g of feces were collected into sterile plastic vials using a sterile lubricant (Lubricating Jelly; Healthcare Plus, Canadian Custom Packaging, Toronto) and individual sterile polyethylene gloves for each animal to minimize contamination. Blood was collected into 1 non-additive BD Vacutainer® tube (Becton, Dickinson and Company, Franklin Lakes, New Jersey, USA) and centrifuged for 10 min at 1000 3 g within 12 h of collection. No animals had been vaccinated against paratuberculosis, and the PTB status of each farm and animal was unknown to researchers at the time of the study. Three paratuberculosis tests were all performed according to manufacturer’s instructions: fecal culture (FCUL), direct 524
real-time polymerase chain reaction (FPCR) on feces, and an enzyme-linked immunosorbent assay (ELISA) on serum. Fecal culture was performed using the BD BACTEC TM MGITTM 960 Mycobacterial detection system (Becton Dickinson and Company) and BACTEC TM MGIT TM Para TB medium. Culture-positive samples underwent both acid-fast staining and PCR confirmation with the hspX gene (Culture Confirmation Protocol, MAP Extraction System, Tetracore ®, Rockville, Maryland, USA). The FPCR was performed directly on the feces prior to decontamination using the MAP extraction system by Tetracore® using the cycle threshold (Ct) of # 42.0 as the cut-off for positive selection. The serum samples were processed using the Paracheck® ELISA (Prionics, Schlieren-Zürich, Switzerland) and the positive cut-off of . 0.3 was used. The small ruminant positive cut-off stipulated by the manufacturer is the mean optical density of the negative control 1 0.2. Farm owners/managers received a questionnaire which they completed during the sampling visit or submitted at their earliest convenience (self-addressed, stamped envelope provided). Paratuberculosis test results were not released to the producer until the questionnaire had been received. The questionnaire consisted of 90 questions, took approximately 90 min to complete, collected general herd/flock demographic information, and asked questions regarding management practices. These questions were categorized as follows: animal movements on and off farms, use and handling of replacement livestock, exposure of livestock to other animals, animal housing, feeding of milk and colostrum, manure management, and specific questions related to the farm’s Johne’s disease status. Sixty-two questions were closed-ended: 20 were dichotomous, 38 multiple-choice, 2 were scaling, and 2 were matrix. Fifteen questions were semiclosed-ended as they offered an option to specify an alternative answer to those listed and the remaining 13 questions were open-ended fill-in-the blank and asked for dates or numerical estimates. After development, the questionnaire was pre-tested on 10 goat and sheep producers/industry representatives during the spring of 2010. The individuals were purposively selected to represent different aspects of the small ruminant industries. Any questions considered lengthy or confusing were reworded prior to initiation of the study. Copies of the questionnaire are available upon request from the corresponding author. Questionnaire responses were entered and stored in Excel® (Microsoft, 2007; Redmond, Washington, USA) and all summary descriptive statistics calculated using Stata® 11.2 (StataCorp LP, College Station Texas, USA) and reported at the farm-level. True prevalence was determined using a 3-test Bayesian model constructed separately for each species and is described in detail in Bauman et al (3). In order to statistically determine risk factors from data, infected and non-infected groups of sufficient size are needed. Among the study farms, all of the 29 (100%) goat herds and 18 of the 21 (85.7%) sheep flocks had at least 1 animal test positive on at least 1 test and the true herd-level prevalence (that accounted for imperfect test performance) exceeded 80% and flock-level prevalence exceeded 65% (3). The lack of uninfected farms meant we were not able to determine if any specific practices affected PTB herd/flock CVJ / VOL 57 / MAY 2016
Table 1. Number of Ontario dairy goat and dairy sheep farms that purchased replacement animals in the previous 3 years, categorized by gender and age of animals purchased Males Males Females Females Purchased , 1 year $ 1 year Purchased , 1 year $ 1 year males of age of age females of age of age 28 (96.6%)
26 (92.9%)
15 (53.6%)
11 (37.9%)
9 (81.8%)
9 (81.8%)
Dairy sheep (n = 17 flocks)
17 (100%)
15 (88.2%)
13 (76.4%)
15 (88.2%)
7 (46.7%)
15 (100%)
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Dairy goat (n = 29 herds)
Table 2. Location and number of animals purchased by the 29 Ontario dairy goat and 17 dairy sheep farms that purchased replacements in the last 3 years
Table 3. Quarantine practices of 29 Ontario dairy goat and 17 dairy sheep farms which reported purchasing replacement animals in the last 3 years
Number of replacement animals purchased in last 3 years
Frequency with which purchased Number animals are of farms quarantined # (%)
Mean number of days animals quarantined (range)
Dairy goat Always Sometimes Never
10 (34.5%) 4 (13.8%) 15 (51.7%)
69.7 (2 to 365) 23.3 (7 to 42) 0
Dairy sheep Always Sometimes Never
1 (5.9%) 42 (2 to 180) 1 (5.9%) 21 (2 to 42) 15 (88.2%) 0
Source of purchased animals Other producers Dealer
Dairy goats # 6 15 7 to 20 6 21 to 50 1 $ 51 7 Total 29
1 1 0 2 4
Dairy sheep # 6 3 0 7 to 20 4 0 21 to 50 4 0 $ 51 5 1 Total a
16
Sales barn
Show/ Sale
1 1 0 2 1 0 2 2 4 5 0 0 0 0
0 0 0 0
1 0 0
a Since
animals could be acquired from more than 1 source totals may exceed total number of farms sampled.
status. No statistical modeling was undertaken and no statistical comparisons were made between species.
Results Questionnaires from all 29 goat producers and 18 of the 21 sheep milk producers (85.7%) were returned. All goat producers completed all questions while some questionnaires from sheep producers were incomplete. Overall, there was little variation in the responses to many of the management questions. The questionnaire data were summarized, and a profile was developed of current management practices that possibly contribute to the high prevalence of disease in these industries. Relevant herd and animal summary statistics are presented elsewhere (3). Overall, no goat and only 1 sheep farm were closed to live animal introductions or returns. Animal movements were primarily due to purchase of live animals as all 29 goat herds and 17 of the 18 sheep flocks had purchased animals in the last 3 y. Only 20.7% (6/29) of goat herds and 5.9% of (1/17) sheep flocks had borrowed animals, and 10.3% (3/29) of goat herds and 5.9% (1/17) of sheep flocks had loaned animals out. Since only 3/29 (10.3%) goat herds and no sheep flocks used artificial insemination, 96.6% (28/29) of goat farms and 94.4% (17/18) of sheep farms had purchased male animals for breeding. For the breakdown of age group and genders purchased see Table 1. Producers indicated they had purchased replacement animals from other producers, dealers, sales barns, and from shows or sales in the last 3 y. However, 96.6% (28/29) of goat herds and CVJ / VOL 57 / MAY 2016
94.1% (16/17) of sheep flocks had primarily purchased their animals from other producers. For number of replacements purchased and locations of purchases, see Table 2. Practices for quarantining new introductions are reported in Table 3. Producers who purchased livestock from other producers were asked if they inquired about the disease status of the herd/ flock of origin, specifically history of abortions, Q-fever, PTB, caseous lymphadenitis (CL), and caprine arthritis encephalitis (CAE)/maedi visna (MV). Dairy goat producers were most likely to have asked about CAE (60.7%; 17/28), CL (57.1%; 16/28) and PTB (46.4%; 13/28). Only 2 dairy sheep producers (12.5%) inquired about disease status, and the same 2 producers inquired about the same 5 infectious diseases as mentioned above. No dairy goat producer tested all purchased animals for Johne’s disease; only 1 goat producer (3.6%; 1/28) sometimes tested and the remaining goat producers (96.4%) and all dairy sheep producers never tested. Many (72.4%; 21/29) dairy goat farms reported having 1 or more animal(s) with CL in the last 3 y. Farm-level prevalence of CL was lower on dairy sheep farms (18.8%; 3/16). Despite the high true herd-level prevalence of PTB determined in this study, few producers reported having the disease diagnosed on their farm in the last 10 y [dairy goats: 13.8% (4/29); dairy sheep: 11.1% (2/18)]. However, no farms of either species had any herd-level testing performed, and only 6 of the 29 (20.7%) dairy goat herds and 4 of the 17 (23.5%) dairy sheep flocks had performed some form of individual animal testing. Of the 6 farms reporting previously diagnosed cases, 3 of the 4 dairy goat and both of the dairy sheep farms had purchased the affected animals; on the remaining dairy goat farm, the animal had been born and raised on the farm. No cases of PTB were diagnosed in other species such as cattle, on any farm. 525
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Table 4. Frequency of colostrum and milk feeding practices on 29 dairy goat farms in Ontario Frequently Infrequently Always (. 50% of (, 50% of % (#) the time) the time) farms % (#) farms % (#) farms
Never % (#) farms
Feed colostrum from the dam to their own kid(s)
51.7% (15)
20.7% (6)
6.9% (2)
20.7% (6)
Feed colostrum from 1 dam to kid(s) not their own
51.7% (15)
20.7% (6)
6.9% (2)
20.7% (6)
Pool colostrum from more than 1 dam to feed to kid(s)
6.9% (2)
24.1% (7)
17.2% (5)
51.7% (15)
Feed heat-treated colostrum (56°C to 60°C for 1 h)
17.2% (5)
13.8% (4)
3.4% (1)
65.5% (19)
Feed a commercial colostrum replacement product
3.4% (1)
6.9% (2)
20.7% (6)
70.0% (20)
Feed colostrum sourced from off-farm from the same species
0.0% (0)
3.4% (1)
0.0% (0)
96.6% (28)
Feed colostrum from another species (e.g., cattle)
10.3% (3)
6.9% (2)
17.2% (5)
65.5% (19)
Kids allowed to nurse their dams
51.7% 10.3% (15) (3)
17.2% (5)
20.7% (6)
Feed pooled milk
6.9% 13.8% (2) (4)
10.3% (3)
70.0% (20)
Feed milk replacer
65.5% 17.2% (19) (5)
3.4% (1)
13.8% (4)
Feed pasteurized milk
6.9% 10.3% (2) (3)
3.4% (1)
79.3% (23)
Feed acidified milk
44.8% 10.3% (13) (3)
6.9% (2)
37.9% (11)
Feed milk from other species
24.1% 3.4% (7) (1)
3.4% (1)
70.0% (20)
A large proportion of farms reported that their goats or sheep had had contact with other species of animals in the previous 3 y: 93.1% (27/29) of dairy goat and 100% (18/18) of dairy sheep farms reported their animals had contact with barn cats, 75.8% (22/29) of dairy goat and 72.2% (13/18) of dairy sheep farms had contact with pet dogs, and 58.6% (17/29) of dairy goat and 83.3% (15/18) of dairy sheep farms had contact with cattle. More than half of goat producers (51.7%) and 92.3% of sheep producers did not remove kids and lambs immediately at birth. These producers allowed the kids and lambs to nurse for a mean of 7.7 and 21.5 d, respectively; other colostrum and milk feeding practices are presented in Tables 4 and 5. Animals identified as potential replacements were removed from their dams sooner at 4.9 and 11.6 d on dairy goat and dairy sheep farms, respectively. However, replacements were still exposed to the manure of adult animals on 46.4% (13/28) of dairy goat and 82.4% (14/17) of dairy sheep farms. With respect to manure management, 65.5% (19/29) of dairy goat farms and 70.6% (12/17) of dairy sheep farms spread manure on pastures used for grazing. The average time that fresh manure was added to the manure storage pile prior to spreading was 50.6 d (range: 0 to 365 d; median 7 d) and 105.2 d (range: 0 to 365 d; median 14 d) on dairy goat and dairy sheep farms, respectively. 526
Discussion Many aspects of paratuberculosis control programs for dairy cattle can be applied to dairy goat and dairy sheep programs. However, there are important differences in the disease, testing accuracy, animal value, and management practices in small ruminants. This study found many management practices on Ontario dairy goat and dairy sheep farms to be plausible risk factors for paratuberculosis, although statistical associations could not be evaluated due to insufficient negative farms. Nonetheless, this work identified high-risk management practices that should be targeted for prevention and control of not only PTB, but also other important infectious diseases (CL, CAE, MV), on dairy goat and dairy sheep farms in the province. In this study, there was only 1 closed farm. Closing the herd to purchased/borrowed animals is a challenge for small ruminant producers. A major obstacle to herd/flock closure is the low frequency of use of artificial insemination (AI), evidenced by the high percentage of producers who reported purchasing bucks and rams. Artificial insemination is the best way of assuring new male genetics are low risk for PTB and has been promoted by the goat industry and the Canadian Food Inspection Agency (CFIA) (7) in their goat National Biosecurity Standard and Planning Guide. However, as shown in this study, it is not in common use despite the ease with which AI can be done at a CVJ / VOL 57 / MAY 2016
Table 5. Frequency of colostrum and milk feeding practices on 13 dairy sheep farms in Ontario Never % (#) farms
Feed colostrum from the dam to their own lamb(s)
100% (13)
0.0% (0)
0.0% (0)
0.0% (0)
Feed colostrum from 1 dam to lamb(s) not their own
0.0% (0)
18.2% (2)
54.5% (8)
27.3% (3)
Pool colostrum from more than 1 dam to feed to lamb(s)
0.0% (0)
18.2% (2)
18.2% (2)
63.6% (9)
Feed heat-treated colostrum (56°C to 60°C for 1 h)
0.0% (0)
0.0% (0)
0.0% (0)
100% (13)
Feed a commercial colostrum replacement product
0.0% (0)
0.0% (0)
23.1% (3)
76.9% (10)
Feed colostrum sourced from off-farm from the same species
0.0% (0)
0.0% (0)
0.0% (0)
100% (13)
Feed colostrum from another species (e.g., cattle)
0.0% (0)
0.0% (0)
15.4% (2)
84.6% (11)
Lambs allowed to nurse their dams
92.3% 7.7% (12) (1)
0.0% (0)
0.0% (0)
Feed pooled milk
7.7% 7.7% (1) (1)
15.4% (2)
69.2% (9)
Feed milk replacer
38.5% 7.7% (5) (1)
23.1% (3)
30.8% (4)
Feed pasteurized milk
0.0% 0.0% (0) (0)
0.0% (0)
100% (13)
Feed acidified milk
7.7% 0.0% (1) (0)
7.7% (1)
84.6% (11)
Feed milk from other species
7.7% 0.0% (1) (0)
23.1% (3)
69.2% (9)
relatively moderate cost in goats. The use of AI as a biosecurity practice on sheep farms is less likely to be adopted widely because trans-cervical AI is difficult and expensive. Education of producers with respect to how to source healthy animals for purchase is essential. It has been previously highlighted in 2 sheep studies that animal movement between farms, and high purchased replacement rates, are risk factors for PTB (5,8). In addition, the current study found that most dairy goat and dairy sheep producers purchased animals primarily from other producers without determining the infectious disease status of the farm of purchase. This likely contributed to the high herd-level prevalence found in this study, although we were unable to formally assess this statistically given a lack of variability in the data. Most farms in this study did not practice whole herd testing for PTB, nor appropriate quarantine behaviors to prevent transmission of infectious diseases in general. A suspected contributing factor to this indiscriminate pattern of sourcing animals may have been the rapid growth in the demand for goat and sheep milk over the last decade. This demand elevated the price of milk that producers received for their product and encouraged expansion of existing operations and start-up of new ones. Additionally, breeding animals cannot be easily sourced from outside Canada due to import restrictions designed to support the Canadian government’s goal of eradicating scrapie (9). CVJ / VOL 57 / MAY 2016
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Frequently Infrequently Always (. 50% of (, 50% of % (#) the time) the time) farms % (#) farms % (#) farms
To reduce the risk of introducing PTB to a farm, animals should be purchased only from “low-risk” flocks and herds (10). Currently, “low risk” is not defined by a paratuberculosis control program; however, PTB-introduction risk can be lowered by the practice of producers always requesting, prior to purchase, a vendor declaration of herd/flock health status. This declaration should include information regarding whether any animals have been diagnosed with PTB on the vendor’s farm, the frequency of testing of animals for PTB, and tests used. Information regarding the farm’s policy on animal movements, the measures taken to interrupt potential on-farm transmission of infectious diseases, and the monitoring of animals dying onfarm through the use of veterinary postmortem examinations should also be included in this declaration (11). When farmof-purchase status cannot be determined to be “low risk,” all purchased animals should undergo quarantine until testing for PTB can be performed before introduction to the herd/flock. However, testing of purchased young stock will generally fail to detect infection. MAP-infected goats and sheep generally do not shed enough bacteria to test positive on fecal tests before the age of 9 mo (12), test positive on an antibody-based test before 1 y of age (13), or demonstrate clinical signs of wasting before the age of 18 mo (14). In addition, animals do not shed the bacteria consistently and antibody responses can vary depending on age and lactation stage (15). Given these age 527
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constraints and variability in immune responses, there can be no guarantee that any test-negative animal is free of infection. Testing recommendations will vary depending on the history of the animal and farm-of-origin, but given what we know about PTB test performance, the following should be considered when developing a testing protocol for new purchases. Animals under a year of age can be screened with fecal testing such as PCR. Animals that are purchased when they are 1 year of age or older should be tested using both fecal PCR and an antibody test (e.g., serum ELISA) in parallel to maximize the sensitivity of detecting infected animals (16). Once purchased animals are introduced to the herd they should be monitored closely with semi-annual testing. Written documentation of their contacts and offspring should also be kept. If the introduced animal was to test positive at a later date, these recorded animals should be subsequently tested to identify the extent of the spread of PTB. Current within-farm PTB control measures concentrate on reducing direct and indirect exposure of replacement youngstock to MAP by minimizing their exposure to potentially infected adult animals (17), their manure, and the contaminated environment (18). As observed in this study, some dairy goat producers currently implement some of the following management practices: removal of offspring at birth, feeding safe colostrum and milk replacement products, and rearing young stock separately from the adults. These practices were most often undertaken by goat producers to reduce transmission of the CAE virus. Safe colostrum and milk feeding are not widespread (Tables 4 and 5), which may be due to the labor-intensiveness of these practices. The peri-parturient period in the small ruminant industries is already a labor-intensive period as most producers have seasonal lambing/kidding periods with animals routinely having multiple births. While minimizing contact with infected adult goats and sheep is probably most important, contact from other species is also a risk. Mycobacterium avian subsp. paratuberculosis infects a wide range of ruminant and non-ruminant animals (19) and transmission from other species to goats or sheep is possible (20). In this study, many farms indicated their animals came in contact with barn cats and pet dogs. The MAP bacteria were isolated from feral cats on a dairy cattle farm where paratuberculosis had been previously diagnosed and further analysis of these isolates using restriction fragment length polymorphism supported inter-species transmission between the cattle and the cats (21). This bacterium has also been isolated from pet dogs with gastrointestinal illness (22). Whether cats and dogs are potential sources of infection to ruminants is yet to be determined. A high proportion of small ruminant farms had also housed cattle on their premises within the last 3 y. This indicates that these farms are diverse with multiple species in co-existence, or that producers are new to the dairy small ruminant industry having recently sold their cattle. Cattle are potential reservoirs for new infections either directly through animal interactions or indirectly through environmental contamination (23). In this study, the producers reported that no cases of PTB had been diagnosed in other species of animals on their farms, but we do not know to what extent testing had been performed previously. 528
While MAP requires a host animal to replicate (19) and therefore restricting exposure to the animal reservoir is critical, the bacteria can also survive for long periods of time even in harsh environments — up to 55 wk in naturally infected soil and grass (24). To compensate for this long survivability, PTB-prevention strategies recommend spreading manure only on crop-producing fields, and not those used for grazing (25). Two studies on sheep support the application of this strategy in small ruminants. A study in Portugal identified that not spreading manure on grazing pastures was a preventative factor (26), and a study in Czechoslovakia (27) detected MAP in the green parts and roots of plants growing at sites at which feces had been deposited on pasture. It is generally believed that composting manure prior to spreading will dramatically reduce and potentially eliminate MAP (28,29), other bacterial organisms (30), and gastrointestinal parasite eggs and larvae from manure (31). There is uncertainty regarding the length of time manure should be composted and little research has involved small ruminant feces specifically (28). Overall, producers should be encouraged to compost manure for a minimum of 90 d to reduce all pathogen burdens on their farms, and to spread it on crop yielding fields only, not pastures (32). Small ruminants infected with PTB often do not develop overt diarrhea (11); therefore, the disease can go unrecognized on farms or be mistaken for other wasting disease such as those caused by CAE, CL, gastrointestinal parasites, or dental problems. This is supported by the high number of producers in our study who were unaware the disease was present on their farm. One important benefit of this study is that it raised awareness among producers regarding PTB, its effects, diagnosis and control. Cost of production on small ruminant dairy farms is high and profits are minimal (33); therefore, efficient use of resources is essential. Since all the biosecurity interventions, whether between-farms or on-farm, are time-consuming and expensive (34), producers are unlikely to make the management changes unless the disease has been diagnosed on their farm. Therefore, all producers should be encouraged to determine their herdstatus by herd-level testing (bulk tank milk, random sample of individual animals, or whole herd, and veterinary-performed postmortem examination of adult animals with clinical evidence of disease or wasting). In addition, many of the risk factors and management strategies for PTB also apply to other production-limiting infectious diseases. It may be prudent to not concentrate on control strategies for just one disease, but to expand them to include the others. The dairy goat producers of this study also had a high prevalence of CL on their farms (75.6%). In Quebec, maedi-visna seroprevalence in cull sheep was reported to be 44% (35), and a proportional mortality study of goats in that province (36) indicated that CAE (4.6%) and CL (3.9%) were significant causes of mortality, and that CL lesions were present in 24.3% of submitted animals. It has been speculated that continued uptake of PTB prevention strategies may be more successful if producers see the reduction in transmission of other pathogens as well (34). Norway has adopted this approach with the “Healthier Goat” program (37), in which government and industry have dedicated finances and effort to CVJ / VOL 57 / MAY 2016
Acknowledgments We are grateful to the Ontario Ministry of Agriculture, Food and Rural Affairs-University of Guelph Agreement through the Animal Health Strategic Investment fund (AHSI) managed by the Animal Health Laboratory of the University of Guelph, and to the Ontario Veterinary College for a Fellowship to the primary author. CVJ
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eradicating CAE, CL, and PTB within the same program. While very labor-intensive, producers have been reported to be satisfied with the results (38); the main benefit for enrolled farms has been overall healthier animals and 63% higher milk yields than farms not enrolled in the program (39). This study has demonstrated that current biosecurity practices — both between-herd and within-herd — on Ontario dairy goat and dairy sheep farms are not conducive to the prevention or control of PTB infection, and likely other infectious diseases as well. A PTB disease control program is needed in these industries. Established dairy cattle PTB control programs to date have concentrated on risk management of PTB alone. As the dairy goat and dairy sheep industries are in the preliminary stages of developing their own species-specific control program, they have an opportunity to consider a “whole herd” approach to disease control similar to the program in Norway. This would have the potential to control/eradicate other production- limiting diseases and consolidate resources, which may contribute to sustained uptake by producers and improved health and productivity.
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