7.5 mg/kg. However againsi inhibited H . contortus larvae there was no significant effect of treatment even at twice the recommended dose rate (Table 1). Naphthalophos significantly reduced both adults and inhibited larvae at 9.38 mg/kg or 2/3 the recommended dose rate (Table 1). On the Northern Tablelands of New South Wales haemonchosis is primarily a disease of lambs in their first summer or autumn (Anderson et a1 1978). It has been shown that eggs deposited in spring by previously inhibited H . contorfus in older sheep can be an important source of infection for young sheep that subsequently graze the same pasture (Barger and Le Jambre, personal communication). It is advisable therefore to drench sheep in late winter with an anthelmintic that is effective against inhibited larvae. The present experiment indicates that of the 2 narrow spectrum anthelmintics tested, only naphthalophos is an effective winter drench. Rafoxanide would be best used as a flukicide or if used to control benzimidazole resistant H . contortus it should only be used in the summer months when inhibited larvae are less prevalent.
L.F. LE JAMBRE, I.A. BARGER.
CSIRO, Division of Animal Health, Pastoral Research Laboratory, Armidale, New South Wales 2350
5 March 1979 References Anderson, N., Dash, K.M., Donald, A.D., Southcott, W.H. and Waller, P.J. (1978) - TheEpidemiologyandConfrolof Gastrointestinal Parasites of Sheep in Austrafia. Ed A.D. Donald, W.H. Southcott and J.K. Dineen. CSIRO, Melbourne, p24. Campbell, N.J. and Hotson, I.K. (1971) - Ausl. vet. J. 47: 5. Campbell, N.J., Hall, C.A., Kelly. . J.D. and Martin, I.C.A. (1978) - Aust. vet. J. 54: 23. Egerton, J.R., Yakstis, J.J. and Campbell, W.C. (1970) Res. Vef. Sci. 11: 382. Le Jambre, L.F., Southcott, W.H. and Dash, K.M. (1976) Int. 1.Parasit. 6: 217. Prichard, R.K. (1978) - The Epidemiology and Control of Gastrointestinal Parasites o f Sheep in Australia. Eds. A.D. Donald, W.H. Southcott and J.K. Dineen, CSIRO, Melbourne, p.76. Snijders, A.J., Horak, I.G. and Louw, J.P. (1973) - J. S. Afr. vet. Ass. 44: 25 1.
RESISTANCE OF HAEMONCHUS CONTORTUSTO OXFENDAZOLE Oxfendazole was reported by Averkin et a1 (1975) to be a highly effective anthelmintic against experimental and natural nematode infections in laboratory and domestic animals. Kistner et a1 (1972-1976) demonstrated that the dose level of 5 mg/kg bodyweight removed greater than 90% of natural infections of Haemoncbus confortus in sheep. More recently, oxfendazole was shown to be 100% effective against a laboratory strain (Kistner and Wyse 1978) and field populations (Webb et af 1979a) of H. contortus resistant to other benzimidazole anthelmintics. Following its commercial release in Australia at the end of 1977, oxfendazole has been used widely as a broad spectrum anthelmintic for sheep and cattle. This letter reports evidence of a natural infection of H . contortus in sheep which was resistant to treatment with oxfendazole. A lack of clinical response in a group of naturally parasitised sheep following treatment with oxfendazole was reported to us from a commercial property on the northern tablelands of New South Wales. In an initial investigation, faecal samples were collected from 20 sheep which were then treated with oxfendazole* at the manufacturer’s recommended dose rate of 4.65 mg/kg. Four days later faecal samples were collected from the same sheep. The mean strongyle ova per gram (opg) count for the group before treatment was 2,725 (range 0-11,200) and after treatment was 2,458 (range 200-10,600). Bulk faecal cultures prepared from the group showed that 97% of the ova in the first sampling and 100% in the second were H. contortus. A second trial was undertaken immediately on the property using 10 different sheep which were individually identified and weighed. Faecal samples were collected from each sheep and the latter were assigned to 1 of 2 groups of 5 according to the strongyle ova counts. Sheep in Group 1 were treated with OXfendazole at a dose rate of 4.65 mg/kg according to individual
*Systameu, Cooper AUStralta Lfd, Concord, New South Wales.
Australian VeterinaryJournal, Vol. 55, July, 1979
bodyweight while sheep in Group 2 were left untreated as controls. Four days later all 10 sheep were slaughtered. Strongyle opg counts in faecal samples collected immediately before and after treatment together with total worm counts of all sheep are shown in Table 1. All larvae obtained from individual faecal cultures were H. contortus. Oxfendazole removed 47.8% adult and 48.4% immature H . contortus worms in the treated group when compared with the untreated controls. Four days after treatment, oxfendazole had reduced the output of H . contortus ova in the treated group by 43.4%. Compared with the reported efficiency of oxfendazole (Averkin 1975; Kistner and Wyse 1978; Webb et a1 1979a) this result indicates that individuals within H. contortus populations in sheep on this property are resistant to this anthelmintic. This contrasts with our previous communication (Webb et a1 1979a) in which no evidence of resistance to oxfendazole was found in 4 populations with varying resistance to other benzimidazole anthelmintics. This highlights the sporadic nature of the occurrence of resistance o f H . confortus to members o f the benzimidazole group of anthelmintics in an area where benzimidazole resistance is known to be widespread (Webb et a1 1979b). It further confirms the contention of Le Jambre e t a1 (1979) that members of the benzimidazole group of anthelmintics cannot be relied upon to control outbreaks of clinical naemonchosis in sheep in such areas. We thank Wellcome Australia Ltd for referring this case to us and for the purchase of experimental sheep.
R. F. WEBB, C. H. McCULLY, New South Wales DeDartment of Agriculture, Regional Veterinary Laboratory, Private Mailbag, Armidale, New South Wales, 2350. 7May, 1979 347
TABLE 1
H. contortus (opg) in Faeces and H . contortus Worm Counts in Sheep Treated with 4.65 mgfkg Oxfendazole (Group I ) and Left Untreated (Group 2) H . contortus (opg) Sheep
H . contortus
count Day + 4 Immatures
Day 0
Day + 4
Adults
Group I 1 2 3 4 5 Mean
1600 2900 1800 1700 2600 21 20
2800 300
1320 3 20 160 760
Group 2 6 7 8 9 10 Mean
1700 3500 1600 2400 1900 2220
1800 2800 4400 2300 4900 3240
100 800 2000 1200
References Averkin, E., Beard, C . , Dvorak, C., Edwards, J., Schiltz, R., Kistner, T. P., Drudge, J.H., Lyons, E. T., Sharp, M. L. and Corwin, R. M. (1975)-J. med. Chem. 18: 1164. Kistner, et af (1972-1976) unpublished data cited by Kistner, T. P. and Wyse, D. (1978)-Aust. vet. J . 54: 469.
5 20 616 1600 600 1240 1380 1080 1180
0 80 120 360 80 128 240
40 280 360 320 24 8
Kistner, T. P. and Wyse, D. (1978)-Aust. vet. J . 54: 469. Le Jambre, L., Martin, P . J. and Webb, R. F. (1979)-Aust. vet. J . in press. Webb, R. F., McCully, C. H. and Adams, B. S. (1979a)-Aust. vet. J . in press. Webb, R. F., McCully, C . H., Clark, F. L., Greentree, P . and Honey, P. (1979b)-Aust. vet. J . in press.
EFFICACIES O F ALBENDAZOLE AND FENBENDAZOLE AGAINST CATTLE NEMATODES IN WESTERN VICTORIA Previous work (Callinan and Cummins 1978) has shown that fenbendazole. is effective against cattle nematodes in western Victoria. However, variable efficacies of fenbendazole have been recorded. Duncan et al(1977) suggested that this may be due to stimulation of the oesophageal groove reflex by the anthelmintic. Kelly et al (1977) found that if the anthelmintic bypasses the rumen, as is the case when the oesophageal groove reflex is stimulated, the resultant efficiency of the anthelmintic is lowered. The effect of the oesophageal groove reflex on anthelmintic efficacy was included in this study of the comparative efficacies of albendazolet and fenbendazole. In February 1978, 47 crossbred 10-month-old heifers were randomly allocated by bodyweight into 5 groups of 9 heifers. The remaining 2 were slaughtered to determine whether initial nematode numbers were sufficient to proceed with the experiment. All heifers were maintained in cleaned concrete yards for 14 days prior to treatment, so that reinfection during this time did not occur. 'Hoechst Australia Limited. Melbourne, Victoria tSmith Kline Animal Health Products, Broohbale. Neu South Wales
348
Group 1 remained untreated, group 2 was drenched with albendazole at 7.5 mg active ingredient per kg bodyweight. Group 3 was drenched with 60 ml NaHCO, 30 seconds before drenching with albendazole at the above dose rate. Riek (1954) has shown that NaHCO, effectively stimulates the oesophageal groove reflex. Group 4 was drenched with fenbendazole at 7.5 mg active ingredient per kg liveweight and group 5 was drenched with 60 ml NaHCO, and fenbendazole at the above dose rate. All heifers were slaughtered 12 days later. The abomasums and small intestines were recovered and 10% aliquots of the washings from each and the digested abomasal mucosa were assayed for nematodes. The analysis procedure was initially that used by Callinan and Cummins (1978). Treatment groups were not normally distributed and variances of nematode numbers in treatment groups within nematode groups were not homogeneous, which precluded parametric analysis. Significant differences between treatments were consequently determined by the nonparametric Mann-Whitney test. The geometric mean number of nematodes, range and significant differences (P
L.F. LE JAMBRE, I.A. BARGER.
CSIRO, Division of Animal Health, Pastoral Research Laboratory, Armidale, New South Wales 2350
5 March 1979 References Anderson, N., Dash, K.M., Donald, A.D., Southcott, W.H. and Waller, P.J. (1978) - TheEpidemiologyandConfrolof Gastrointestinal Parasites of Sheep in Austrafia. Ed A.D. Donald, W.H. Southcott and J.K. Dineen. CSIRO, Melbourne, p24. Campbell, N.J. and Hotson, I.K. (1971) - Ausl. vet. J. 47: 5. Campbell, N.J., Hall, C.A., Kelly. . J.D. and Martin, I.C.A. (1978) - Aust. vet. J. 54: 23. Egerton, J.R., Yakstis, J.J. and Campbell, W.C. (1970) Res. Vef. Sci. 11: 382. Le Jambre, L.F., Southcott, W.H. and Dash, K.M. (1976) Int. 1.Parasit. 6: 217. Prichard, R.K. (1978) - The Epidemiology and Control of Gastrointestinal Parasites o f Sheep in Australia. Eds. A.D. Donald, W.H. Southcott and J.K. Dineen, CSIRO, Melbourne, p.76. Snijders, A.J., Horak, I.G. and Louw, J.P. (1973) - J. S. Afr. vet. Ass. 44: 25 1.
RESISTANCE OF HAEMONCHUS CONTORTUSTO OXFENDAZOLE Oxfendazole was reported by Averkin et a1 (1975) to be a highly effective anthelmintic against experimental and natural nematode infections in laboratory and domestic animals. Kistner et a1 (1972-1976) demonstrated that the dose level of 5 mg/kg bodyweight removed greater than 90% of natural infections of Haemoncbus confortus in sheep. More recently, oxfendazole was shown to be 100% effective against a laboratory strain (Kistner and Wyse 1978) and field populations (Webb et af 1979a) of H. contortus resistant to other benzimidazole anthelmintics. Following its commercial release in Australia at the end of 1977, oxfendazole has been used widely as a broad spectrum anthelmintic for sheep and cattle. This letter reports evidence of a natural infection of H . contortus in sheep which was resistant to treatment with oxfendazole. A lack of clinical response in a group of naturally parasitised sheep following treatment with oxfendazole was reported to us from a commercial property on the northern tablelands of New South Wales. In an initial investigation, faecal samples were collected from 20 sheep which were then treated with oxfendazole* at the manufacturer’s recommended dose rate of 4.65 mg/kg. Four days later faecal samples were collected from the same sheep. The mean strongyle ova per gram (opg) count for the group before treatment was 2,725 (range 0-11,200) and after treatment was 2,458 (range 200-10,600). Bulk faecal cultures prepared from the group showed that 97% of the ova in the first sampling and 100% in the second were H. contortus. A second trial was undertaken immediately on the property using 10 different sheep which were individually identified and weighed. Faecal samples were collected from each sheep and the latter were assigned to 1 of 2 groups of 5 according to the strongyle ova counts. Sheep in Group 1 were treated with OXfendazole at a dose rate of 4.65 mg/kg according to individual
*Systameu, Cooper AUStralta Lfd, Concord, New South Wales.
Australian VeterinaryJournal, Vol. 55, July, 1979
bodyweight while sheep in Group 2 were left untreated as controls. Four days later all 10 sheep were slaughtered. Strongyle opg counts in faecal samples collected immediately before and after treatment together with total worm counts of all sheep are shown in Table 1. All larvae obtained from individual faecal cultures were H. contortus. Oxfendazole removed 47.8% adult and 48.4% immature H . contortus worms in the treated group when compared with the untreated controls. Four days after treatment, oxfendazole had reduced the output of H . contortus ova in the treated group by 43.4%. Compared with the reported efficiency of oxfendazole (Averkin 1975; Kistner and Wyse 1978; Webb et a1 1979a) this result indicates that individuals within H. contortus populations in sheep on this property are resistant to this anthelmintic. This contrasts with our previous communication (Webb et a1 1979a) in which no evidence of resistance to oxfendazole was found in 4 populations with varying resistance to other benzimidazole anthelmintics. This highlights the sporadic nature of the occurrence of resistance o f H . confortus to members o f the benzimidazole group of anthelmintics in an area where benzimidazole resistance is known to be widespread (Webb et a1 1979b). It further confirms the contention of Le Jambre e t a1 (1979) that members of the benzimidazole group of anthelmintics cannot be relied upon to control outbreaks of clinical naemonchosis in sheep in such areas. We thank Wellcome Australia Ltd for referring this case to us and for the purchase of experimental sheep.
R. F. WEBB, C. H. McCULLY, New South Wales DeDartment of Agriculture, Regional Veterinary Laboratory, Private Mailbag, Armidale, New South Wales, 2350. 7May, 1979 347
TABLE 1
H. contortus (opg) in Faeces and H . contortus Worm Counts in Sheep Treated with 4.65 mgfkg Oxfendazole (Group I ) and Left Untreated (Group 2) H . contortus (opg) Sheep
H . contortus
count Day + 4 Immatures
Day 0
Day + 4
Adults
Group I 1 2 3 4 5 Mean
1600 2900 1800 1700 2600 21 20
2800 300
1320 3 20 160 760
Group 2 6 7 8 9 10 Mean
1700 3500 1600 2400 1900 2220
1800 2800 4400 2300 4900 3240
100 800 2000 1200
References Averkin, E., Beard, C . , Dvorak, C., Edwards, J., Schiltz, R., Kistner, T. P., Drudge, J.H., Lyons, E. T., Sharp, M. L. and Corwin, R. M. (1975)-J. med. Chem. 18: 1164. Kistner, et af (1972-1976) unpublished data cited by Kistner, T. P. and Wyse, D. (1978)-Aust. vet. J . 54: 469.
5 20 616 1600 600 1240 1380 1080 1180
0 80 120 360 80 128 240
40 280 360 320 24 8
Kistner, T. P. and Wyse, D. (1978)-Aust. vet. J . 54: 469. Le Jambre, L., Martin, P . J. and Webb, R. F. (1979)-Aust. vet. J . in press. Webb, R. F., McCully, C. H. and Adams, B. S. (1979a)-Aust. vet. J . in press. Webb, R. F., McCully, C . H., Clark, F. L., Greentree, P . and Honey, P. (1979b)-Aust. vet. J . in press.
EFFICACIES O F ALBENDAZOLE AND FENBENDAZOLE AGAINST CATTLE NEMATODES IN WESTERN VICTORIA Previous work (Callinan and Cummins 1978) has shown that fenbendazole. is effective against cattle nematodes in western Victoria. However, variable efficacies of fenbendazole have been recorded. Duncan et al(1977) suggested that this may be due to stimulation of the oesophageal groove reflex by the anthelmintic. Kelly et al (1977) found that if the anthelmintic bypasses the rumen, as is the case when the oesophageal groove reflex is stimulated, the resultant efficiency of the anthelmintic is lowered. The effect of the oesophageal groove reflex on anthelmintic efficacy was included in this study of the comparative efficacies of albendazolet and fenbendazole. In February 1978, 47 crossbred 10-month-old heifers were randomly allocated by bodyweight into 5 groups of 9 heifers. The remaining 2 were slaughtered to determine whether initial nematode numbers were sufficient to proceed with the experiment. All heifers were maintained in cleaned concrete yards for 14 days prior to treatment, so that reinfection during this time did not occur. 'Hoechst Australia Limited. Melbourne, Victoria tSmith Kline Animal Health Products, Broohbale. Neu South Wales
348
Group 1 remained untreated, group 2 was drenched with albendazole at 7.5 mg active ingredient per kg bodyweight. Group 3 was drenched with 60 ml NaHCO, 30 seconds before drenching with albendazole at the above dose rate. Riek (1954) has shown that NaHCO, effectively stimulates the oesophageal groove reflex. Group 4 was drenched with fenbendazole at 7.5 mg active ingredient per kg liveweight and group 5 was drenched with 60 ml NaHCO, and fenbendazole at the above dose rate. All heifers were slaughtered 12 days later. The abomasums and small intestines were recovered and 10% aliquots of the washings from each and the digested abomasal mucosa were assayed for nematodes. The analysis procedure was initially that used by Callinan and Cummins (1978). Treatment groups were not normally distributed and variances of nematode numbers in treatment groups within nematode groups were not homogeneous, which precluded parametric analysis. Significant differences between treatments were consequently determined by the nonparametric Mann-Whitney test. The geometric mean number of nematodes, range and significant differences (P
