in 18 of the farms (Table 1). In 1984 the survey was repeated on the same farms but included more anthelmintics (oxfendazole, levamisole, morantel, closantel, and naphthalophos, all at the manufacturers' recommended dose rate, and TBZ at 66 m a g ) and considered data for T colubriformis and 0 circumcincta as well as H contortus. In these two surveys, resistance was determined by a faecal egg count reduction test (FECRT) in which faecal egg counts (PECs) were done for each of the sheep from treatment and control groups on the day of treatment and again 4 days later. The group arithmetic mean FECs for the trichostrongylid genera under considerationwere obtained by using the percentage of larvae for each genus recorded from faecal cultures. Larvae were routinely identified to species level in the case of Haemonchus, but only to genus level in the case of Trichostrongylusand Ostertagia. In the New England region it is generally recognised that the latter two genera are represented in sheep by T colubriformis and T axei, with T colubriformispredominating, and 0 circumcincta. In the 1984survey, reductions in post-treatment FECs for each genus were calculated only if the pre-treatment group mean exceeded 50 eggs per gram (epg). A minimum acceptable FEC did not apply in the 1977 study. In both surveys, resistance was defined as failure to reduce the FEC by more than 90% after treatment.

Anthelmintic resistance in sheep nematodes in the New England region of New South Wales Regional Veterinary Laboratory, SCJ LOVE NSW Agriculture and Fisheries, WH JOHNS Private Mail Bag, OR COVERDALE University of New England, Armidale 235 1

In Australia, the first report of resistance of nematodes to anthelmintics related to thiabendazole (TBZ) resistant Haemonchus contorius on 3 sheep farms in the Northern Tablelands of the New England region of NSW (Smeal et a1 1968). Reports of resistance in field isolates of Trichostrongylus colubriformis (Hotson et a1 1970; Le Jambre et a1 1978), H confortus(Le Jambre el al1976) and Ostertagia circumcincta (LeJambre e fa1 1977) indicated that such strains may have been widespread. To estimate the prevalenceof strains of anthelmintic resistant H contortus in the Northern Tablelands, Webb et al (1979) conducted a survey of 40randomly selected sheep farms. Inthissurvey, thefirstinAustralia,resistancetoTBZat 66mgkg (1.5 t i e s themanufacturer'srecommendeddoserate) wasfound

TABLE 1 Anthelmintic resistance in nematode parasites of sheep on 40 farms in the NSW Northern Tablelands No. of farms

Parasite

surveyed

genus

Percentage (number) of farms with resistance to anthelmintics' LEV

MOR

TBZ

OFZ

Source

CLOS

NAP

40 (1977)

Haemonchus

N/R

N/R

45( 18)

N/R

N/R

N/R

Webb eta/(1979)

40 (1984

Haemonchus

6(1)

6(1)

65( 13)

5(1)

O(n= 21)

O(n= 18)

Love SCJ(unpub.)

I"

Trichostrongylus

88(29)

90(27)

36( 10)

24(7)

NIR

82(22)

I "

Ostertagia

W14)

J33(15)

39(5)

19(3)

N/R

N/R

" Y

Love SCJ and Chick BF (unpub.)

Percentages are based on the number of farms that provided results for the indicated parasiteand anthelmintic. Anthelmintics: LEV -levamisole, MOR - rnorantel, TBZ - thiabendazole, OFZ -oxfendazole, CLOS - closantel, NAP - naphthalophos All anthelmintics were used at manufacturers' recommended dose rates, except for TBZ which was used at 66 mg/kg. Resistance - < 90% reduction in group arithmetic means. N/R - no result. TABLE 2 Faecal egg count reduction tests, 1987 1991 Regional Veterinary Laboratory, Armidale

-

Parasite genus

Percentage (number) of FECRTs displaying resistance' to: BZ

LEV

BZ or LEV

Dual (62 + LEV)

Multiple (BZ + LEV)

NorVlern tablelands

Allt

83( 135)

83(144)

96(176)

28(41)

44(68)

Trichostrongylus

83(127)

85(130)

95(157)

28(36)

46(62)

93(25) 86(19)

59(16) 70( 16)

16(3) 2544)

3W) 27(94)

Ostertagia Haemonchus

North west slopes and plains All Trichostrongylus

1OO(25) 96(22)

Resistance is defined as being present in ea& case and for each species when the pre-treatment control group mean FEC was 2 150 epg and there was < 95% reduction in the treabnent group mean FEC with the lower 95% confidence limit of the percentage reduction in FEC being < 90%. Dualresistance- resistant to BZ and LEV but susceptible to a BiYLEV cornbination. Multiple resistance (combination resistance) - as for 'dual' but resistant to a BULEV combination also. BZ - benzimidazole, usually oxfendazoie or albendazole. LEV - levamisole. All -combined all trichostrongylid species.

196

Australian Veterinary Journal Vol69, No 8, August 1992

We report here the complete results of the 1984 survey (Table 1) and the results of FECRTs conducted by this laboratory from 1987 to 1991 (Table 2). The later FECRTs were conducted according to industry guidelines (Anon 1989) and differ fmm those of the 1977 and 1984 studies in that FECs were done 10 to 14 days after treatment and resistance was defmed as failure to reduce the FEC by 95%(with the lower 95%confiidence l i t of that estimate being c 90%) and the pre-treatment control group mean FEC for each genus was not less than 150 epg. The flocks included in the FECRTs from 1987 to 1991 were selected on the basis of their response to the recommendation, made as part of the WORMKILL* program,to check a n t h e w tic efficacy or because, for other reasons, anthelminticresistance was suspected. These FECRTs confirmed the finding of the 1984 survey that anthehhic resistance in the important sheep nematode species is very commonin the New England Region Most flocks have resistance in at least one of themore important speciesof internal parasites. The flocks on which these FECRTs were conducted are likely to be a biased sample of the New England population because of the basis of selection. Accordingly, it is difficult to draw conclusions about apparent differences in frequency of resistance between the Northern Tablelands and the North West Slopes and Plains (Table 2). Likewise, the results of these FECRTs cannot be closely compared with those of the 1984 and 1977 surveys. As well as differences in method of selection, the definition of resistance for the FECRTs was differentfrom that which applied to the earlier surveys. Furthermore, a 10 to 14 day post-treatment sampling was used in the 1987 to 1991 FECRTs (to eliminate the effects of a possible temporary depression of egg production) whereas a 4-day interval applied in the 1977 and 1984 surveys. However, opinion is divided on the matter of post-treatment depressionofegg laying. McKenna (199O)presentsevidencethat differences in results between the shorter and longer posttreatment intervals may be of little practical significance. Also, Beveridge et a1 (1990) remark that there is no fm published evidence of a temporag depression of egg production occurring in the field. Scott et al(1991), however, found a reduction in the fecundity of anthelmintic resistant adult H contortus after exposure to ivermectin or benzimidazoles in vivo and concluded that a post-treatment period of at least seven to 10 days should be used in FECRTs. The results of the 1987 to 1991 FECRTs support the finding of the 1984 survey, and subsequentfield experience,that anthelmintic resistance in the important sheep nematodes is very common in the New England region. Very few flocks tested were without resistance (detectable by a FECRT) in at least one of the more important species: H contortus, T colubriformis or 0 circumcincta. The prediction by Dash (1986) that multiple resistance in T cotubriformis and consequent control failures would emerge as a problem in the Northern Tablelands has been confiied by this study and by field experience in recent years. In addition, H contortrcs isolates recovered by this laboratory were recently confiied to be resistant to closantel (Rolfe e f ul 1990). Recognising the importance of anthelmintic resistance in the New England region, the WORMKILL program is undergoing continual revision and development. For example, because the possible emergence of closantel resistance was anticipated, the number of treatments each year with this drug was reduced a few years ago, with some farms using only one annual treatment in late Spring instead of 3 treatments a year as specified in the original program. B m d o n (1980) suggested that parasite control shouldinvolve more complex systems with such components as chemotherapy, grazing and animal management, and the induction of immunity being involved. The WORMKILL

WORMKILL. A strategic drenching program for sheep in summer rainfall areas; NSW Agriculture, Rural Lands Protection Boards and CSIRO

Australian VeterinaryJournal Vol69, No 8, August 1992

program, ernphasising as it does not only strategicdrenching but also grazing management, nutrition and management factors such as time of weaning and periodic monitoring of FECs, has clearly followed this line of development. The technical assistance of Peter Choice and Pennie Glock in our parasitology section, as well as the cooperation of the laboratory's veterinary clients, Rural Lands Protection Board Rangers (particularly H R Officer), and Dr Douglas Gray of the University of New England, is gratefully acknowledged. For their involvement in the 1984 survey, we acknowledge Stephen Sinclair and Kerry Speak, as well as Drs P Andrew, B Chick, R Everett, P Greentree, E Hall and R Maher.

References Anon (1989) Anthelmintic Resistance. Report of the Working Party for the AnimalHealthCommittee ofthe StandingCommittee ondgricultwe,SCA Technical Report Series, No. 28 BeveridgeI, EIIisNJS.RileyMJandBrown TH (1990)Awt Vet J67: 413 Bmsdon RV (1980) Vet Parasitol6: 185 Dash KM (1986)Awt Vet J63: 45 Hotson IK,Campbell NJ and SmealMG (1970)Awt Vet J 4 6 : 356 Le Jambre LF, Southcott WH and Dash KM (1976) Inf J Pararitol 6:217 Le Jambre LF, Southcott WH and Dash KM (1 977) Inf J Parasitol7: 473 Le Jambre LF. Southcott WH and Dash KM (1978)Awt Vet J54:570 McKenna PB (1990)NZ Vet J38: 142 Rolfe PF, Boray JC. Fitzgibbon C. Parsons G,Kemsley P and Sangster N (1990) Aurt Vet 167: 29

ScottEW,BaxterPandArmourJ(1991)ResVetSci500:247 SmealMG, Gough PA, Jackson AR, and Hotson M (1968) Awl Vet J & 108 Webb RF, McCuUy CH, Clarke FL,Greentree P and Honey P (1979) Awt Vet J 55: 422 (Accepted for publication 13 May 1992)

Pasteurella multocida septicaemia in two calves Queensland Department of Primary Industries, Rockhampton Veterinary Laboratories, Rockhampton, Queensland4700 Department of Food and Agriculture, Benalla Agriculture and Veterinary Centre, Benalla, Victoria 3672

BD HILL

RB JOHNSON

Haemorrhagic septicaemia is a specific form of acute pasteurellosis of cattle and water buffaloes, which is caused by Pasteurella multocida capsular antigen types Carter B or E and somatic antigen Heddleston types 2 and 5 (Brogden and Packer 1979; Carter and Chengappa 1981). The disease has a high mortality rate and is one of the most economically important diseases of livestock in South East Asia. It differs from pneumonic pasteurellosis that is associated with infection by P multocida (Carter A serotype) and P haemolytica. Bovine pneumonic pasteurellosis appears as a fibrinous bronchopneumonia (Gourlay et a1 1989) and in contrast to haemonhagic septicaemia, has a longer clinical course and a lower mortality rate (Blood and Radostits 1989). This paper describes cases of P multocida septicaemia in two calves in central Queensland where the pathological findings were suggestive of haemorrhagic septicaemia. In Decembex 1989, two Brahman calves, 3 to 5 days old, died on a farm near Rockhampton. Clinical signs had included depression, excessive salivation, laboured breathing and lameness associated with swollen limbs. One of these calves (calf 1) was submined, 8 h after death, for necropsy. These calva were on what was normally swampy pasturebut prevailing weather at the t h e was dry. 197