Veterinary Parasitology 200 (2014) 295–298
Contents lists available at ScienceDirect
Veterinary Parasitology journal homepage: www.elsevier.com/locate/vetpar
Short Communication
Frequency of intestinal parasites in pet dogs from an urban area (Greater Oporto, northern Portugal) Diogo Neves a,∗ , Luís Lobo a,b,c , Paula Brilhante Simões d , Luís Cardoso e,f a
Hospital Veterinário do Porto, Oporto, Portugal Universidade Lusófona de Humanidades e Tecnologias, Lisbon, Portugal c CECA – Centro de Estudos de Ciência Animal, Universidade do Porto, Portugal d Inno Laboratories – Servic¸os Especializados em Veterinária, Braga, Portugal e Department of Veterinary Sciences, School of Agrarian and Veterinary Sciences, University of Trás-os-Montes e Alto Douro, Vila Real, Portugal f Parasite Disease Group, IBMC – Instituto de Biologia Molecular e Celular, Universidade do Porto, Oporto, Portugal b
a r t i c l e
i n f o
Article history: Received 25 September 2013 Received in revised form 9 November 2013 Accepted 11 November 2013 Keywords: Dogs Gastrointestinal disease Helminths Portugal Protozoa
a b s t r a c t The present study was conducted to evaluate the prevalence of gastrointestinal parasites in dogs with no clinical signs (n = 175; group H) and in dogs with gastrointestinal disease (n = 193; group D) that were admitted to a veterinary hospital. In group H, the overall prevalence of intestinal parasites (i.e. the presence of at least one species) was 20.6%. Cystoisospora canis was the most prevalent protozoon (8.0%) followed by Giardia spp. (7.4%); Toxocara canis (5.1%) was the most frequent helminth, followed by Trichuris vulpis (1.1%) and Toxascaris leonina (0.6%). Among group H, age ≤ 6 months was found to be a risk factor for infection with C. canis and with at least one agent (odds ratio [OR] = 3.4). In group D parasites were found in 33.7% of the dogs, with Giardia spp. (15.5%) being the most prevalent species, followed by C. canis (13.5%), T. canis (7.8%), T. vulpis (2.6%) and T. leonina (0.5%). In group D dogs, age ≤ 6 months was a risk factor for infection with Giardia spp. (OR = 3.2), with C. canis (OR = 32.7) and with at least one agent (OR = 7.2). This study reveals a remarkable number of dogs infected but with no clinical signs. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Gastrointestinal parasites of dogs can cause anorexia, anemia and diarrhea associated with considerable morbidity and mortality rates, particularly in young, old and immunocompromised animals. These parasites can lower resistance to infectious diseases, reduce work efficiency and lead to stunted growth and general malaise in the host (Yacob et al., 2007; Balassiano et al., 2009). Global climate change appears to be influencing the life cycle of helminths with multiple hosts and different
∗ Corresponding author. Tel.: +351 912646304. E-mail address: [email protected] (D. Neves). 0304-4017/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.vetpar.2013.11.005
transmission routes (Traversa, 2012). Nonetheless, protozoa are the group of intestinal parasites that currently assume more importance and that have been found more frequently, which can result from a natural emerging phenomenon or due to significant improvement in diagnostic tests (Villeneuve, 2009). Several studies performed throughout the world have demonstrated that dogs can play an important role in the transmission of zoonotic parasites (Soriano et al., 2010). They represent a potential risk to public health, especially in children, since natural transmission of parasitic infections from dogs to humans may occur, directly or indirectly (Martínez-Moreno et al., 2007; Xhaxhiu et al., 2011). Thus, there is a continuing interest in implementing control measures (Traversa, 2012). The protozoon Giardia and ascarid
296
D. Neves et al. / Veterinary Parasitology 200 (2014) 295–298
Table 1 Prevalence of gastrointestinal parasites in clinically healthy dogs (group H) by age group, gender and breed. Independent variable/category
Age ≤6 months 7–12 months >1 year Gender Male Female Breed Purebred Crossbred Total a b c d
No. of tested dogs (%)
No. of positive dogs (%) Cystoisospora canis
Giardia spp.
Toxocara canis
Trichuris vulpis
≥1 agent(s)d
89 (50.9) 13 (7.4) 73 (41.7)
12 (13.5)a 1 (7.7) 1 (1.4)a
9 (10.1) 1 (7.7) 3 (4.1)
7 (7.9) 0 (0.0) 2 (2.7)
0 (0.0) 0 (0.0) 2 (2.7)
26 (29.2)b 2 (15.4) 8 (11.1)b
98 (56.0) 77 (44.0)
7 (7.1) 7 (9.1)
6 (6.1) 7 (9.1)
2 (2.0)c 7 (9.1)c
0 (0.0) 2 (2.7)
16 (16.3) 20 (26.0)
129 (76.7) 46 (26.3)
12 (9.3) 2 (4.3)
9 (7.0) 4 (8.7)
8 (6.2) 1 (2.2)
1 (0.8) 1 (2.2)
29 (22.5) 7 (15.2)
175 (100)
14 (8.0)
13 (7.4)
9 (5.1)
2 (1.1)
36 (20.6)
p = 0.018. p = 0.005. p = 0.036. Including Toxascaris leonina (n = 1).
nematode Toxocara canis are among the parasites assumed to have most zoonotic potential. Cystoisospora species are also known to infect humans; however, their clinical relevance is thought to be largely limited to immunosuppressed people (Batchelor et al., 2008). The purpose of this study was to determine the frequency of intestinal parasites in pet dogs from Greater Oporto, an urban area in northern Portugal, and to evaluate whether sex, age, breed and clinical status were associated with the prevalence of infection.
The chi-square and Fisher’ exact tests compared proportions of positivity related to categorical dependent variables such as gender, age, breed and clinical status. A probability value (p) < 0.05 was regarded as statistically significant. Independent variables with a significant difference between groups were selected to logistic regression analysis to identify risk factors, calculating odds ratios (OR) and their 95% confidence intervals (CI) (Petrie and Watson, 2006). Analyses were done with SPSS 11.5 software for Windows and StatLib.
2. Materials and methods
3. Results and discussion
The sampled dogs were privately owned animals from the Greater Oporto urban area (North region of Portugal) presented to a veterinary hospital and comprised: 175 clinically healthy (group H) and 193 dogs with gastrointestinal clinical signs (group D). Animals were divided into three age categories; puppies (≤6 months), young dogs (7–12 months) and adults (>1 year). Purebred or pedigree dogs were from 42 different breeds. Dogs without gastrointestinal signs were mainly puppies presented to their first consultation and also adult dogs that were tested in annual check-ups which included a fecal exam. In addition, the veterinary clinicians sampled dogs every time they detected any abnormality on physical examination related to the gastrointestinal tract (i.e. history of diarrhea and mucus or blood on the thermometer). A total of 368 stool samples were collected from April 2008 to March 2010. Each fecal sample consisted of 3–5 g of fresh stool and was collected at home by the owners with a sterile plastic container provided by the hospital. Samples kept at 4 ◦ C were transferred to the hospital and submitted to the laboratory within 24 h. Fecal samples were first macroscopically assessed for the detection of blood, mucus and potential parasitic forms. Afterwards, an efficient separation was accomplished by using a centrifugationflotation technique with a 33% (w/v) zinc sulfate solution (Zajac et al., 2002). After this procedure, samples were microscopically examined in search for eggs, cysts, oocysts and larvae. A dog was classified as positive if at least one of these elements was present in its stool sample.
Table 1 shows the positivity of group H (clinically healthy dogs) to various parasites, including positivity to at least one of the parasitic agents (≥1 agent[s]). A 6-monthold male Labrador Retriever was additionally infected with Toxascaris leonina (0.6%). Among group H, age ≤ 6 months was confirmed to be a risk factor for infection with Cystoisospora canis (OR = 11.2, 95% CI: 1.4–88.5; p = 0.022) and with at least one agent (OR = 3.4, 95% CI: 1.4–8.0; p = 0.006). Table 2 shows positivity levels among group D (dogs with gastrointestinal disease). A 24 month-old male Setter was additionally found infected with T. leonina. In group D dogs, age ≤ 6 months was a risk factor for infection with Giardia spp. (OR = 3.2, 95% CI: 1.3–8.0; p = 0.013), with C. canis (OR = 32.7, 95% CI: 4.3–247.7; p = 0.001) and with at least one agent (OR = 7.2; 95% CI: 3.4–15.1; p < 0.001). No dog was positive for all parasitic agents; and 79.4% of the group H and 66.3% of the group D dogs were negative for all the five agents (Table 3). No statistically significant differences were found among the categories of sex, age and breed in pairwise comparison for positivity to single and mixed parasites. In univariate analysis, positivity to Giardia spp. (OR = 2.3, 95% CI: 1.2–4.6; p = 0.018) and positivity to at least one agent (OR = 2.0, 95% CI: 1.2–3.1; p = 0.005) were risk factors for the presence of gastrointestinal disease. Fig. 1 presents the distribution of the whole canine population which were brought to the veterinary hospital for consultation during the two-year study period, taking into account groups H (n = 175) and D (n = 193), and performing extrapolation for the total number of dogs (n = 3352). Group
D. Neves et al. / Veterinary Parasitology 200 (2014) 295–298
297
Table 2 Prevalence of gastrointestinal parasites in dogs with gastrointestinal disease (group D) by age group, gender and breed. Independent variable/category
Age ≤6 months 7–12 months >1 year Gender Male Female Breed Purebred Crossbred Total a b c d e f
No. of tested dogs (%)
No. of positive dogs (%) Cystoisospora canis
Giardia spp.
Toxocara canis
Trichuris vulpis
≥1 agent(s)f
87 (45.1) 24 (12.4) 82 (42.5
25 (28.7)a,b 0 (0.0)a 1 (1.2)b
20 (23.0)c 3 (12.5) 7 (8.5)c
10 (11.5) 2 (8.3) 3 (3.7)
2 (2.3) 0 (0.0) 3 (3.7)
48 (55.2)d,e 5 (20.8)d 12 (14.6)e
114 (59.1) 79 (40.9)
18 (15.8) 8 (10.1)
21 (18.4) 9 (11.4)
8 (7.0) 7 (8.9)
2 (1.8) 3 (3.8)
42 (36.8) 23 (29.1)
140 (72.5) 53 (27.5)
23 (16.4) 3 (5.7)
24 (17.1) 6 (11.3)
10 (7.1) 5 (9.4)
4 (2.9) 1 (1.9)
53 (37.9) 12 (22.6)
193 (100)
26 (13.5)
30 (15.5)
15 (7.8)
5 (2.6)
65 (33.7)
p = 0.032. p < 0.001. p < 0.001. p = 0.003. p < 0.001. Including Toxascaris leonina (n = 1).
Fig. 1. Percentage distribution of the dog population brought to the veterinary hospital for consultation (n = 3352). (1) Clinically healthy dogs not found infected with gastrointestinal parasites; (2) clinically healthy and infected dogs; (3) dogs with gastrointestinal disease and not found infected; (4) dogs with gastrointestinal disease and infected.
D dogs represented ∼6% (5.8%) of the total canine population and had a 33.7% (65/193) prevalence of infection with gastrointestinal parasites. That way, ∼2.0% (1.9%; 65/3532) of the total population would have gastrointestinal disease and be infected with gastrointestinal parasites, and ∼4.0% (3.8%; 128/3532) of the same population would also have gastrointestinal disease but no detectable infection with such parasites. On the other hand, and by extrapolating to the overall number of clinically healthy dogs (n = 3159), those 20.6% (36/175) group H dogs that were clinically healthy but found to be infected with gastrointestinal parasites would represent ∼19% of the total dogs (19.4%; 651/3352). Finally, the 79.4% (139/175) group H dogs that were clinically healthy and not found infected would represent ∼75% (74.8%; 2508/3352) of the total. Around 20% of the dogs were clinically healthy but infected, which must be highlighted considering that all of them had an owner who periodically (i.e. twice a year, on average) sought veterinary care and parasiticides. The
Table 3 Positivity to single and mixed parasites among 175 clinically healthy (group H) and 193 dogs with gastrointestinal disease (group D). Parasites
Healthy (n)
%
With GI disease (n)
%
Single agents Cystoisospora canis Giardia spp. Toxascaris leonina Toxocara canis Trichuris vulpis Mixed agents C. canis + T. canis C. canis + Giardia spp. Giardia spp. + T. leonina Giardia spp. + T. canis Giardia spp. + T. vulpis T. canis + T. vulpis
33 11 13 1 6 2 3 3 0 0 0 0 0
18.9a , b 6.3 7.4 0.6 3.4 1.1 1.7b , d 1.7 0.0 0.0 0.0 0.0 0.0
53 19 24 0 8 2 12 4 3 1 1 1 2
27.5a , c 9.8 12.4 0.0 4.1 1.0 6.2c , d 2.1 1.6 0.5 0.5 0.5 1.0
Total positive
36
20.6e
65
33.7e
a b c d e
p = 0.051. p < 0.001. p < 0.001. p = 0.029. p = 0.005.
298
D. Neves et al. / Veterinary Parasitology 200 (2014) 295–298
administered parasiticides comprised pyrantel pamoate, pyrantel plus febantel plus praziquantel, fenbendazol plus praziquantel and milbemycin oxime plus prazinquantel (data not shown). Only ∼2% were both clinically suspected of gastrointestinal disease and infected which suggests that if clinicians ask for a fecal exam merely based on the presence of clinical signs, many infected dogs will not be detected. In both groups, protozoa (Giardia spp. and C. canis) were apparently more prevalent than helminthes (T. canis and Trichuris vulpis). Several reasons might explain these results. First of all, they might represent a genuine increase in prevalence, or be due to significant improvement in diagnostic tests (Villeneuve, 2009). For instance, the use of centrifugation plays an important role in improving dramatically both sensitivity and specificity of results regarding to Giardia spp. (Zajac et al., 2002). By not using other diagnostic tests, such as the Giardia antigen test and the polymerase chain reaction (PCR) assay, the true prevalence with regards to Giardia spp. might be underestimated (Tupler et al., 2012). This is also applicable to many other intestinal parasites due to their intermittent shedding. In this study, new diagnostic techniques such as the modified Ziehl–Neelsen technique and the PCR were not used, which might explain the absence of Cryptosporidium (Robertson et al., 2000; Fontanarrosa et al., 2006). Associations were found between puppies and infection with C. canis and at least one agent (groups H and D) and with Giardia spp. (group D). Stress associated with weaning, transportation and re-homing might explain a higher prevalence in this age class. This predisposition may also reflect immunological immaturity, with resistance to the parasite getting stronger over time (Batchelor et al., 2008). Fontanarrosa et al. (2006) described that prevalence of T. canis, Cystoisopora spp. and Giardia spp. infections decreased significantly as age increased, whereas the opposite occurred for infections with T. vulpis. The same trend was exactly found in this study, which explains why prevention and control should be applied to dogs throughout their lifetime (Balassiano et al., 2009). Only two dogs in the present work were found to be infected with T. leonina (one from group H and the other one from group D). This considerably lower level of infection might be partially related with the inability of T. leonina to reach the offspring via placenta or milk, as opposed to T. canis (Traversa, 2012). Infections with a single species were more prevalent than mixed infections (Table 3). Rural areas often sustain heavily infected dogs but urban areas should not be neglected. The results obtained from a survey conducted in the Czech Republic suggest that pets may contribute significantly to the environmental burdens of intestinal parasites in both urban and rural areas (Dubná et al., 2007). Even with periodic veterinary assistance many dogs living in urban areas are also a potential risk for the health of both humans and other animals. A study that took place in Spain reported no differences in protozoon infection between rural and urban dogs (Martínez-Moreno et al., 2007). Infections with Giardia or at least one agent were a risk factor for the presence of gastrointestinal disease. In general, clinical disease caused by gastrointestinal parasites can range from ill thrift
or reduced growth to life-threatening anemia and protein loss, particularly in puppies (Bowman, 2008). Giardia has the ability to cause a small bowel diarrhea in dogs, which may be acute or chronic, and self-limiting, intermittent or continuous in nature (Thompson et al., 2008). The relationship between clinical signs and the presence of Giardia suggests that dogs can be very susceptible to its pathological effects (Paoletti et al., 2008). In conclusion, this study reveals a remarkable number of infected dogs with no clinical signs. This is of paramount importance because intestinal parasites do represent a silent hazard not only for other animals, but also for the general public health. Generated information will provide veterinarians and physicians with real tools to explain people how frequent intestinal parasites are, even in urban areas. References Balassiano, B.C., Campos, M.R., Menezes, R.C., Pereira, M.J., 2009. Factors associated with gastrointestinal parasite infection in dogs in Rio de Janeiro, Brazil. Prev. Vet. Med. 9, 234–240. Batchelor, D.J., Tzannes, S., Graham, P.A., Wastling, J.M., Pinchbeck, G.L., German, A.J., 2008. Detection of endoparasites with zoonotic potencial in dogs with gastrointestinal disease in the UK. Transbound. Emerg. Dis. 55, 99–104. Bowman, D.D. (Ed.), 2008. Georgis Parasitology for Veterinarians. , 9th edition. Saunders, St. Louis, p. 451. Dubná, S., Langrová, I., Nápravník, J., Jankovská, I., Vadlejch, J., Pekár, S., Fechtner, J., 2007. The prevalence of intestinal parasites in dogs from Prague, rural areas, and shelters of the Czech Republic. Vet. Parasitol. 145, 120–128. Fontanarrosa, M.F., Vezzani, D., Basabe, J., Eiras, D.F., 2006. An epidemiological study of gastrointestinal parasites of dogs from Southern Greater Buenos Aires (Argentina): age, gender, breed, mixed infections, and seasonal and spatial patterns. Vet. Parasitol. 136, 283–295. Martínez-Moreno, F.J., Hernández, S., López-Cobos, E., Becerra, C., Acosta, I., Martínez-Moreno, A., 2007. Estimation of canine intestinal parasites in Córdoba (Spain) and their risk to public health. Vet. Parasitol. 143, 7–13. Paoletti, B., Iorio, R., Capelli, G., Sparagano, O.A., Giangaspero, A., 2008. Epidemiological scenario of giardiosis in dogs from central Italy. Ann. N.Y. Acad. Sci. 1149, 371–374. Petrie, A., Watson, P., 2006. Statistics for Veterinary and Animal Science, 2nd edition. Blackwell, Oxford, pp. 299. Robertson, I.D., Irwin, P.J., Lymbery, A.J., Thompson, R.C., 2000. The role of companion animals in the emergence of parasitic zoonoses. Int. J. Parasitol. 30, 1369–1377. Soriano, S.V., Pierangeli, N.B., Roccia, I., Bergagna, H.F., Lazzarini, L.E., Celescinco, A., Saiz, M.S., Kossman, A., Contreras, P.A., Arias, C., Basualdo, J.A., 2010. A wide diversity of zoonotic intestinal parasites infects urban and rural dogs in Neuquén, Patagonia, Argentina. Vet. Parasitol. 167, 81–85. Thompson, R.C., Palmer, C.S., O Handley, R., 2008. The public health and clinical significance of Giardia and Cryptosporidium in domestic animals. Vet. J. 177, 18–25. Traversa, D., 2012. Pet roundworms and hookworms: a continuing need for global worming. Parasit. Vectors 5, 91. Tupler, T., Levy, J.K., Sabshin, S.J., Tucker, S.J., Greiner, E.C., Leutenegger, C.M., 2012. Enteropathogens identified in dogs entering a Florida animal shelter with normal feces or diarrhea. J. Am. Vet. Med. Assoc. 241, 338–343. Villeneuve, A., 2009. Giardia e Cryptosporidium como infecc¸ões emergentes em animais de companhia. Vet. Focus 19, 42–45. Xhaxhiu, D., Kusi, I., Rapti, D., Kondi, E., Postoli, R., Rinaldi, L., Dimitrova, Z., Visser, M., Knaus, M., Rehbein, S., 2011. Principal intestinal parasites of dogs in Tirana, Albania. Parasitol. Res. 108, 341–353. Yacob, H.T., Ayele, T., Fikru, R., Basu, A.K., 2007. Gastrointestinal nemotodes in dogs from Debre Zeit, Ethiopia. Vet. Parasitol. 148, 144–148. Zajac, A.M., Johnson, J., King, S.E., 2002. Evaluation of the importance of centrifugation as a component of zinc sulfate fecal flotation examinations. J. Am. Anim. Hosp. Assoc. 38, 221–224.
Contents lists available at ScienceDirect
Veterinary Parasitology journal homepage: www.elsevier.com/locate/vetpar
Short Communication
Frequency of intestinal parasites in pet dogs from an urban area (Greater Oporto, northern Portugal) Diogo Neves a,∗ , Luís Lobo a,b,c , Paula Brilhante Simões d , Luís Cardoso e,f a
Hospital Veterinário do Porto, Oporto, Portugal Universidade Lusófona de Humanidades e Tecnologias, Lisbon, Portugal c CECA – Centro de Estudos de Ciência Animal, Universidade do Porto, Portugal d Inno Laboratories – Servic¸os Especializados em Veterinária, Braga, Portugal e Department of Veterinary Sciences, School of Agrarian and Veterinary Sciences, University of Trás-os-Montes e Alto Douro, Vila Real, Portugal f Parasite Disease Group, IBMC – Instituto de Biologia Molecular e Celular, Universidade do Porto, Oporto, Portugal b
a r t i c l e
i n f o
Article history: Received 25 September 2013 Received in revised form 9 November 2013 Accepted 11 November 2013 Keywords: Dogs Gastrointestinal disease Helminths Portugal Protozoa
a b s t r a c t The present study was conducted to evaluate the prevalence of gastrointestinal parasites in dogs with no clinical signs (n = 175; group H) and in dogs with gastrointestinal disease (n = 193; group D) that were admitted to a veterinary hospital. In group H, the overall prevalence of intestinal parasites (i.e. the presence of at least one species) was 20.6%. Cystoisospora canis was the most prevalent protozoon (8.0%) followed by Giardia spp. (7.4%); Toxocara canis (5.1%) was the most frequent helminth, followed by Trichuris vulpis (1.1%) and Toxascaris leonina (0.6%). Among group H, age ≤ 6 months was found to be a risk factor for infection with C. canis and with at least one agent (odds ratio [OR] = 3.4). In group D parasites were found in 33.7% of the dogs, with Giardia spp. (15.5%) being the most prevalent species, followed by C. canis (13.5%), T. canis (7.8%), T. vulpis (2.6%) and T. leonina (0.5%). In group D dogs, age ≤ 6 months was a risk factor for infection with Giardia spp. (OR = 3.2), with C. canis (OR = 32.7) and with at least one agent (OR = 7.2). This study reveals a remarkable number of dogs infected but with no clinical signs. © 2014 Elsevier B.V. All rights reserved.
1. Introduction Gastrointestinal parasites of dogs can cause anorexia, anemia and diarrhea associated with considerable morbidity and mortality rates, particularly in young, old and immunocompromised animals. These parasites can lower resistance to infectious diseases, reduce work efficiency and lead to stunted growth and general malaise in the host (Yacob et al., 2007; Balassiano et al., 2009). Global climate change appears to be influencing the life cycle of helminths with multiple hosts and different
∗ Corresponding author. Tel.: +351 912646304. E-mail address: [email protected] (D. Neves). 0304-4017/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.vetpar.2013.11.005
transmission routes (Traversa, 2012). Nonetheless, protozoa are the group of intestinal parasites that currently assume more importance and that have been found more frequently, which can result from a natural emerging phenomenon or due to significant improvement in diagnostic tests (Villeneuve, 2009). Several studies performed throughout the world have demonstrated that dogs can play an important role in the transmission of zoonotic parasites (Soriano et al., 2010). They represent a potential risk to public health, especially in children, since natural transmission of parasitic infections from dogs to humans may occur, directly or indirectly (Martínez-Moreno et al., 2007; Xhaxhiu et al., 2011). Thus, there is a continuing interest in implementing control measures (Traversa, 2012). The protozoon Giardia and ascarid
296
D. Neves et al. / Veterinary Parasitology 200 (2014) 295–298
Table 1 Prevalence of gastrointestinal parasites in clinically healthy dogs (group H) by age group, gender and breed. Independent variable/category
Age ≤6 months 7–12 months >1 year Gender Male Female Breed Purebred Crossbred Total a b c d
No. of tested dogs (%)
No. of positive dogs (%) Cystoisospora canis
Giardia spp.
Toxocara canis
Trichuris vulpis
≥1 agent(s)d
89 (50.9) 13 (7.4) 73 (41.7)
12 (13.5)a 1 (7.7) 1 (1.4)a
9 (10.1) 1 (7.7) 3 (4.1)
7 (7.9) 0 (0.0) 2 (2.7)
0 (0.0) 0 (0.0) 2 (2.7)
26 (29.2)b 2 (15.4) 8 (11.1)b
98 (56.0) 77 (44.0)
7 (7.1) 7 (9.1)
6 (6.1) 7 (9.1)
2 (2.0)c 7 (9.1)c
0 (0.0) 2 (2.7)
16 (16.3) 20 (26.0)
129 (76.7) 46 (26.3)
12 (9.3) 2 (4.3)
9 (7.0) 4 (8.7)
8 (6.2) 1 (2.2)
1 (0.8) 1 (2.2)
29 (22.5) 7 (15.2)
175 (100)
14 (8.0)
13 (7.4)
9 (5.1)
2 (1.1)
36 (20.6)
p = 0.018. p = 0.005. p = 0.036. Including Toxascaris leonina (n = 1).
nematode Toxocara canis are among the parasites assumed to have most zoonotic potential. Cystoisospora species are also known to infect humans; however, their clinical relevance is thought to be largely limited to immunosuppressed people (Batchelor et al., 2008). The purpose of this study was to determine the frequency of intestinal parasites in pet dogs from Greater Oporto, an urban area in northern Portugal, and to evaluate whether sex, age, breed and clinical status were associated with the prevalence of infection.
The chi-square and Fisher’ exact tests compared proportions of positivity related to categorical dependent variables such as gender, age, breed and clinical status. A probability value (p) < 0.05 was regarded as statistically significant. Independent variables with a significant difference between groups were selected to logistic regression analysis to identify risk factors, calculating odds ratios (OR) and their 95% confidence intervals (CI) (Petrie and Watson, 2006). Analyses were done with SPSS 11.5 software for Windows and StatLib.
2. Materials and methods
3. Results and discussion
The sampled dogs were privately owned animals from the Greater Oporto urban area (North region of Portugal) presented to a veterinary hospital and comprised: 175 clinically healthy (group H) and 193 dogs with gastrointestinal clinical signs (group D). Animals were divided into three age categories; puppies (≤6 months), young dogs (7–12 months) and adults (>1 year). Purebred or pedigree dogs were from 42 different breeds. Dogs without gastrointestinal signs were mainly puppies presented to their first consultation and also adult dogs that were tested in annual check-ups which included a fecal exam. In addition, the veterinary clinicians sampled dogs every time they detected any abnormality on physical examination related to the gastrointestinal tract (i.e. history of diarrhea and mucus or blood on the thermometer). A total of 368 stool samples were collected from April 2008 to March 2010. Each fecal sample consisted of 3–5 g of fresh stool and was collected at home by the owners with a sterile plastic container provided by the hospital. Samples kept at 4 ◦ C were transferred to the hospital and submitted to the laboratory within 24 h. Fecal samples were first macroscopically assessed for the detection of blood, mucus and potential parasitic forms. Afterwards, an efficient separation was accomplished by using a centrifugationflotation technique with a 33% (w/v) zinc sulfate solution (Zajac et al., 2002). After this procedure, samples were microscopically examined in search for eggs, cysts, oocysts and larvae. A dog was classified as positive if at least one of these elements was present in its stool sample.
Table 1 shows the positivity of group H (clinically healthy dogs) to various parasites, including positivity to at least one of the parasitic agents (≥1 agent[s]). A 6-monthold male Labrador Retriever was additionally infected with Toxascaris leonina (0.6%). Among group H, age ≤ 6 months was confirmed to be a risk factor for infection with Cystoisospora canis (OR = 11.2, 95% CI: 1.4–88.5; p = 0.022) and with at least one agent (OR = 3.4, 95% CI: 1.4–8.0; p = 0.006). Table 2 shows positivity levels among group D (dogs with gastrointestinal disease). A 24 month-old male Setter was additionally found infected with T. leonina. In group D dogs, age ≤ 6 months was a risk factor for infection with Giardia spp. (OR = 3.2, 95% CI: 1.3–8.0; p = 0.013), with C. canis (OR = 32.7, 95% CI: 4.3–247.7; p = 0.001) and with at least one agent (OR = 7.2; 95% CI: 3.4–15.1; p < 0.001). No dog was positive for all parasitic agents; and 79.4% of the group H and 66.3% of the group D dogs were negative for all the five agents (Table 3). No statistically significant differences were found among the categories of sex, age and breed in pairwise comparison for positivity to single and mixed parasites. In univariate analysis, positivity to Giardia spp. (OR = 2.3, 95% CI: 1.2–4.6; p = 0.018) and positivity to at least one agent (OR = 2.0, 95% CI: 1.2–3.1; p = 0.005) were risk factors for the presence of gastrointestinal disease. Fig. 1 presents the distribution of the whole canine population which were brought to the veterinary hospital for consultation during the two-year study period, taking into account groups H (n = 175) and D (n = 193), and performing extrapolation for the total number of dogs (n = 3352). Group
D. Neves et al. / Veterinary Parasitology 200 (2014) 295–298
297
Table 2 Prevalence of gastrointestinal parasites in dogs with gastrointestinal disease (group D) by age group, gender and breed. Independent variable/category
Age ≤6 months 7–12 months >1 year Gender Male Female Breed Purebred Crossbred Total a b c d e f
No. of tested dogs (%)
No. of positive dogs (%) Cystoisospora canis
Giardia spp.
Toxocara canis
Trichuris vulpis
≥1 agent(s)f
87 (45.1) 24 (12.4) 82 (42.5
25 (28.7)a,b 0 (0.0)a 1 (1.2)b
20 (23.0)c 3 (12.5) 7 (8.5)c
10 (11.5) 2 (8.3) 3 (3.7)
2 (2.3) 0 (0.0) 3 (3.7)
48 (55.2)d,e 5 (20.8)d 12 (14.6)e
114 (59.1) 79 (40.9)
18 (15.8) 8 (10.1)
21 (18.4) 9 (11.4)
8 (7.0) 7 (8.9)
2 (1.8) 3 (3.8)
42 (36.8) 23 (29.1)
140 (72.5) 53 (27.5)
23 (16.4) 3 (5.7)
24 (17.1) 6 (11.3)
10 (7.1) 5 (9.4)
4 (2.9) 1 (1.9)
53 (37.9) 12 (22.6)
193 (100)
26 (13.5)
30 (15.5)
15 (7.8)
5 (2.6)
65 (33.7)
p = 0.032. p < 0.001. p < 0.001. p = 0.003. p < 0.001. Including Toxascaris leonina (n = 1).
Fig. 1. Percentage distribution of the dog population brought to the veterinary hospital for consultation (n = 3352). (1) Clinically healthy dogs not found infected with gastrointestinal parasites; (2) clinically healthy and infected dogs; (3) dogs with gastrointestinal disease and not found infected; (4) dogs with gastrointestinal disease and infected.
D dogs represented ∼6% (5.8%) of the total canine population and had a 33.7% (65/193) prevalence of infection with gastrointestinal parasites. That way, ∼2.0% (1.9%; 65/3532) of the total population would have gastrointestinal disease and be infected with gastrointestinal parasites, and ∼4.0% (3.8%; 128/3532) of the same population would also have gastrointestinal disease but no detectable infection with such parasites. On the other hand, and by extrapolating to the overall number of clinically healthy dogs (n = 3159), those 20.6% (36/175) group H dogs that were clinically healthy but found to be infected with gastrointestinal parasites would represent ∼19% of the total dogs (19.4%; 651/3352). Finally, the 79.4% (139/175) group H dogs that were clinically healthy and not found infected would represent ∼75% (74.8%; 2508/3352) of the total. Around 20% of the dogs were clinically healthy but infected, which must be highlighted considering that all of them had an owner who periodically (i.e. twice a year, on average) sought veterinary care and parasiticides. The
Table 3 Positivity to single and mixed parasites among 175 clinically healthy (group H) and 193 dogs with gastrointestinal disease (group D). Parasites
Healthy (n)
%
With GI disease (n)
%
Single agents Cystoisospora canis Giardia spp. Toxascaris leonina Toxocara canis Trichuris vulpis Mixed agents C. canis + T. canis C. canis + Giardia spp. Giardia spp. + T. leonina Giardia spp. + T. canis Giardia spp. + T. vulpis T. canis + T. vulpis
33 11 13 1 6 2 3 3 0 0 0 0 0
18.9a , b 6.3 7.4 0.6 3.4 1.1 1.7b , d 1.7 0.0 0.0 0.0 0.0 0.0
53 19 24 0 8 2 12 4 3 1 1 1 2
27.5a , c 9.8 12.4 0.0 4.1 1.0 6.2c , d 2.1 1.6 0.5 0.5 0.5 1.0
Total positive
36
20.6e
65
33.7e
a b c d e
p = 0.051. p < 0.001. p < 0.001. p = 0.029. p = 0.005.
298
D. Neves et al. / Veterinary Parasitology 200 (2014) 295–298
administered parasiticides comprised pyrantel pamoate, pyrantel plus febantel plus praziquantel, fenbendazol plus praziquantel and milbemycin oxime plus prazinquantel (data not shown). Only ∼2% were both clinically suspected of gastrointestinal disease and infected which suggests that if clinicians ask for a fecal exam merely based on the presence of clinical signs, many infected dogs will not be detected. In both groups, protozoa (Giardia spp. and C. canis) were apparently more prevalent than helminthes (T. canis and Trichuris vulpis). Several reasons might explain these results. First of all, they might represent a genuine increase in prevalence, or be due to significant improvement in diagnostic tests (Villeneuve, 2009). For instance, the use of centrifugation plays an important role in improving dramatically both sensitivity and specificity of results regarding to Giardia spp. (Zajac et al., 2002). By not using other diagnostic tests, such as the Giardia antigen test and the polymerase chain reaction (PCR) assay, the true prevalence with regards to Giardia spp. might be underestimated (Tupler et al., 2012). This is also applicable to many other intestinal parasites due to their intermittent shedding. In this study, new diagnostic techniques such as the modified Ziehl–Neelsen technique and the PCR were not used, which might explain the absence of Cryptosporidium (Robertson et al., 2000; Fontanarrosa et al., 2006). Associations were found between puppies and infection with C. canis and at least one agent (groups H and D) and with Giardia spp. (group D). Stress associated with weaning, transportation and re-homing might explain a higher prevalence in this age class. This predisposition may also reflect immunological immaturity, with resistance to the parasite getting stronger over time (Batchelor et al., 2008). Fontanarrosa et al. (2006) described that prevalence of T. canis, Cystoisopora spp. and Giardia spp. infections decreased significantly as age increased, whereas the opposite occurred for infections with T. vulpis. The same trend was exactly found in this study, which explains why prevention and control should be applied to dogs throughout their lifetime (Balassiano et al., 2009). Only two dogs in the present work were found to be infected with T. leonina (one from group H and the other one from group D). This considerably lower level of infection might be partially related with the inability of T. leonina to reach the offspring via placenta or milk, as opposed to T. canis (Traversa, 2012). Infections with a single species were more prevalent than mixed infections (Table 3). Rural areas often sustain heavily infected dogs but urban areas should not be neglected. The results obtained from a survey conducted in the Czech Republic suggest that pets may contribute significantly to the environmental burdens of intestinal parasites in both urban and rural areas (Dubná et al., 2007). Even with periodic veterinary assistance many dogs living in urban areas are also a potential risk for the health of both humans and other animals. A study that took place in Spain reported no differences in protozoon infection between rural and urban dogs (Martínez-Moreno et al., 2007). Infections with Giardia or at least one agent were a risk factor for the presence of gastrointestinal disease. In general, clinical disease caused by gastrointestinal parasites can range from ill thrift
or reduced growth to life-threatening anemia and protein loss, particularly in puppies (Bowman, 2008). Giardia has the ability to cause a small bowel diarrhea in dogs, which may be acute or chronic, and self-limiting, intermittent or continuous in nature (Thompson et al., 2008). The relationship between clinical signs and the presence of Giardia suggests that dogs can be very susceptible to its pathological effects (Paoletti et al., 2008). In conclusion, this study reveals a remarkable number of infected dogs with no clinical signs. This is of paramount importance because intestinal parasites do represent a silent hazard not only for other animals, but also for the general public health. Generated information will provide veterinarians and physicians with real tools to explain people how frequent intestinal parasites are, even in urban areas. References Balassiano, B.C., Campos, M.R., Menezes, R.C., Pereira, M.J., 2009. Factors associated with gastrointestinal parasite infection in dogs in Rio de Janeiro, Brazil. Prev. Vet. Med. 9, 234–240. Batchelor, D.J., Tzannes, S., Graham, P.A., Wastling, J.M., Pinchbeck, G.L., German, A.J., 2008. Detection of endoparasites with zoonotic potencial in dogs with gastrointestinal disease in the UK. Transbound. Emerg. Dis. 55, 99–104. Bowman, D.D. (Ed.), 2008. Georgis Parasitology for Veterinarians. , 9th edition. Saunders, St. Louis, p. 451. Dubná, S., Langrová, I., Nápravník, J., Jankovská, I., Vadlejch, J., Pekár, S., Fechtner, J., 2007. The prevalence of intestinal parasites in dogs from Prague, rural areas, and shelters of the Czech Republic. Vet. Parasitol. 145, 120–128. Fontanarrosa, M.F., Vezzani, D., Basabe, J., Eiras, D.F., 2006. An epidemiological study of gastrointestinal parasites of dogs from Southern Greater Buenos Aires (Argentina): age, gender, breed, mixed infections, and seasonal and spatial patterns. Vet. Parasitol. 136, 283–295. Martínez-Moreno, F.J., Hernández, S., López-Cobos, E., Becerra, C., Acosta, I., Martínez-Moreno, A., 2007. Estimation of canine intestinal parasites in Córdoba (Spain) and their risk to public health. Vet. Parasitol. 143, 7–13. Paoletti, B., Iorio, R., Capelli, G., Sparagano, O.A., Giangaspero, A., 2008. Epidemiological scenario of giardiosis in dogs from central Italy. Ann. N.Y. Acad. Sci. 1149, 371–374. Petrie, A., Watson, P., 2006. Statistics for Veterinary and Animal Science, 2nd edition. Blackwell, Oxford, pp. 299. Robertson, I.D., Irwin, P.J., Lymbery, A.J., Thompson, R.C., 2000. The role of companion animals in the emergence of parasitic zoonoses. Int. J. Parasitol. 30, 1369–1377. Soriano, S.V., Pierangeli, N.B., Roccia, I., Bergagna, H.F., Lazzarini, L.E., Celescinco, A., Saiz, M.S., Kossman, A., Contreras, P.A., Arias, C., Basualdo, J.A., 2010. A wide diversity of zoonotic intestinal parasites infects urban and rural dogs in Neuquén, Patagonia, Argentina. Vet. Parasitol. 167, 81–85. Thompson, R.C., Palmer, C.S., O Handley, R., 2008. The public health and clinical significance of Giardia and Cryptosporidium in domestic animals. Vet. J. 177, 18–25. Traversa, D., 2012. Pet roundworms and hookworms: a continuing need for global worming. Parasit. Vectors 5, 91. Tupler, T., Levy, J.K., Sabshin, S.J., Tucker, S.J., Greiner, E.C., Leutenegger, C.M., 2012. Enteropathogens identified in dogs entering a Florida animal shelter with normal feces or diarrhea. J. Am. Vet. Med. Assoc. 241, 338–343. Villeneuve, A., 2009. Giardia e Cryptosporidium como infecc¸ões emergentes em animais de companhia. Vet. Focus 19, 42–45. Xhaxhiu, D., Kusi, I., Rapti, D., Kondi, E., Postoli, R., Rinaldi, L., Dimitrova, Z., Visser, M., Knaus, M., Rehbein, S., 2011. Principal intestinal parasites of dogs in Tirana, Albania. Parasitol. Res. 108, 341–353. Yacob, H.T., Ayele, T., Fikru, R., Basu, A.K., 2007. Gastrointestinal nemotodes in dogs from Debre Zeit, Ethiopia. Vet. Parasitol. 148, 144–148. Zajac, A.M., Johnson, J., King, S.E., 2002. Evaluation of the importance of centrifugation as a component of zinc sulfate fecal flotation examinations. J. Am. Anim. Hosp. Assoc. 38, 221–224.
