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Biomedical subjects

W E Pomroy

Publications and source records attributed to W E Pomroy.

At least 55 records · Page 3Linked to original sources
PubMed1995

Evaluation of the efficacy of doramectin against an artificial infection of Dictyocaulus viviparus in calves.

Three groups of eight Friesian calves, reared parasite-free, were experimentally infected with 1000 infective larvae of Dictyocaulus viviparus. Two groups were injected subcutaneously with 1% doramectin at 0.2 mg/kg body weight, one group 5 days after infection and the other 25 days after infection. A third group served as untreated controls. Faecal samples were examined for lungworm larvae on days 28, 32, 33, 34 and 35 after infection; the calves were killed and necropsied 39 or 40 days after infection and any lungworms present recovered and counted. Doramectin proved 100% effective against both 5-day-old and mature D. viviparus infections.

Journal Article↗
PubMed1994

Nematode worm egg output by ewes.

The results from routine monitoring of parasite burdens in ewe flocks from 1980 to 1991 by the Massey University Veterinary Clinic were analysed. Faecal strongylate nematode egg counts from 401 flock samples were analysed according to ewe age (two-tooth, 16-23 month-old vs mixed-age, greater than 2-year-old ewes) and month of the year. Each flock sample contained faeces from ten ewes and nematode egg counts were carried out on each faecal sample. ln the mixed-age ewes, the overall mean faecal egg count per gram of faeces (epg) was lowest during January (82 epg) and rose to a peak during October (539 epg). The overall mean faecal egg count in two-tooth ewes remained constant from January (240 epg) to June (294 epg) and dropped during July (156 epg). Overall, 8% of the mixed-age ewes and 12% of the two-tooth ewe submissions had a mean egg count equal to or greater than 500 epg. It is possible that these data over-estimate the pasture contamination by ewes as farmers are more likely to submit faecal samples and to seek veterinary assistance when parasitism is thought to be a problem. The role of ewes as a source of pasture contamination should be considered when developing parasite control regimes on farms.

Journal Article↗
PubMed1992

Evaluation of moxidectin for the treatment of internal parasites of cattle.

Two groups of eight yearling Hereford cattle were used to assess the efficacy of injectable moxidectin in removing internal parasites. At 0.2 mg/kg liveweight, moxidectin was effective in ridding all eight treated animals of internal parasites in the abomasum, small and large intestines. The difference in worm counts between treated and control animals was highly significant (P<0.001) for all worm species present in sufficient numbers for evaluation. No adverse side-effects were observed in the treated animals.

Journal Article↗
PubMed1992

Multiple resistance in goat-derived Ostertagia and the efficacy of moxidectin and combinations of other anthelmintics.

Faecal egg count reduction tests were used to identify a strain of Ostertagia circumcincta/trifurcata complex in goats which was resistant to: ivermectin (at 0.2 mg/kg and 0.4 mg/kg orally), oxfendazole (at 5 mg/kg orally), levamisole (at 12 mg/kg orally) and fenbendazole (at 5 mg/kg orally) combined with levamisole (at 9.4 mg/kg orally). The percentage reductions achieved in these faecal egg count reduction tests were respectively 27%, 83%, 82%, 79% and 82%. Moxidectin (at 0.2 mg/kg by subcutaneous injection), fenbendazole (at 10 mg/kg orally) combined with levamisole (at 18.8 mg/kg orally), ivermectin (at 0.4 mg/kg orally) combined with oxfendazole (at 10 mg/kg orally) and ivermectin (at 0.4 mg/kg orally) combined with levamisole (at 12 mg/kg orally) were effective in removing these nematodes in goats as determined by faecal egg count reduction tests. These drenches achieved reductions of 100%, 100%, 98% and 100% respectively.

Journal Article↗
PubMed1991

A survey of the prevalence of Toxoplasma infection in goats in New Zealand and a comparison of the latex agglutination and indirect fluorescence tests.

Anti-Toxoplasma antibody titres in 185 sera from clinically normal goats from 14 farms were assayed by both the latex agglutination and the indirect fluorescent antibody tests. The animals were of various breeds including Angora, New Zealand feral, Angora x feral, Saanen and Toggenburg. A high level of agreement between the two tests was obtained with 83.8% of titres corresponding to within one dilution and 96.8% to within two dilutions. In both tests, titres of 1:64 and above were considered positive. A total of 298 goat sera from clinically normal kids (n = 88), yearlings (n = 65) and adults (n = 145) from 17 farms were examined by the latex agglutination test. The prevalence of positive sera was 7% in kids, 23% in yearlings and 37% in adults. There was a significantly higher prevalence of positive sera in dairy than in fibre breeds.

Animals↗
PubMed1990

Anthelmintic usage on goat farms in New Zealand: results of a postal survey.

A nationwide postal survey in New Zealand of about 3850 goat farmers was conducted in 1988 to determine gastrointestinal nematode control practices. The analysis of 848 replies revealed that at least 16.9%, 20.0% and 34.4% were drenching their adults, yearlings and kids respectively 10 or more times per year. During 1987-88, 42.0% used only ivermectin, 9.0% only a benzimidazole and 1.9% only levamisole or morantel; 42.7% used anthelmintics from two different action families and 3.5% used all three action families. In total, 85.8% had used ivermectin at some stage during the preceding 12 months. Ivermectin was used by 46.5% during the 1987-88 season and also for the 3 preceding years. Sixty percent estimated the weight of their goats only by eye. Twenty-seven percent set the dose volume of the drench gun for the average weight of the goats in the mob, not the heaviest. Drenching frequency was positively correlated with the ratio of goat stock units to total stock units and also with the actual stocking rate of kids and yearlings.

Journal Article↗
PubMed1989

Development of resistance to Trichostrongylus colubriformis in goats.

A high level of host resistance to Trichostrongylus colubriformis was established in a group of Saanen goats infected weekly with 10,000 infective larvae for 10 weeks, treated with an anthelmintic and then challenged twice with 50,000 larvae, with a further anthelmintic treatment 28 days after the first challenge. A second group of goats exposed only to the two challenge infections developed worm burdens intermediate between, and significantly different from, the first group and a third control group given only the second challenge infection. Nematode fecundity (eggs per female) and male:female ratios were also significantly decreased in the first two groups. Faecal egg counts and worm counts were highly correlated and this relationship was dominated by the influence of the number of eggs/female nematode. The goats were approximately 9 months old at the start of the experiment.

Analysis of Variance↗
PubMed1989

Failure of young goats to acquire resistance to Haemonchus contortus.

Two experiments were carried out to investigate the acquisition by goats of resistance to Haemonchus contortus. In Experiment 1, five Saanen wethers reared worm-free and averaging 5 1/2 months of age at the start of the experiment, were dosed with 200 H. contortus infective larvae three times per week for 10 weeks (approximately 23 infective larvae/kg mean initial liveweight/week) and then given anthelmintic treatment. Each goat and an equal number of worm-free controls were then challenged with 10,000 infective larvae. Post mortem worm counts were carried out 30 days later. In Experiment 2, eight worm-free Saanen wethers, 14 months old at the start of the experiment, were dosed with 825 infective larvae per week for 14 weeks (approximately 23 infective larvae/kg mean initial liveweight/week) except for one week when only 300 larvae were given and one week when no larvae were given. After anthelmintic treatment, each received, together with seven worm-free control animals, a challenge dose of 15,000 infective larvae. Post-mortem worm counts were carried out 28 days later. There were no significant differences in post-mortem worm counts between previously infected and uninfected groups in either experiment. In both experiments, serum pepsinogen values rose significantly as a result of infection but there was no significant (p>0.5) correlation between worm counts and pepsinogen values on the day of slaughter.

Journal Article↗
PubMed1989

Multigeneric resistance to benzimidazole anthelmintics in four sheep flocks.

Clinical parasitism associated with multigeneric resistance to benzimidazole anthelmintics was investigated in four sheep flocks during February and March 1989. The genera considered resistant were Haemonchus and Nematodirus spp. on all four farms and Trichostrongylus and Ostertagia spp. on three of the four farms. It is suggested that when investigating cases of suspected drench resistance, post-drenching worm counts are useful to help identify the resistant worm species present.

Journal Article↗
PubMed1989

A survey of anthelmintic resistance on ten goat farms in the Manawatu region in 1988.

A survey of anthelmintic resistance on ten goat farms was carried out. The criterion for resistance was a faecal egg count reduction (FECR) of <90 percent based on arithmetic means of 11 to 19 goats per group. It was found that nine of the ten farms harboured nematodes resistant to oxfendazole when used at 5mg/kg although on two of these, the FECR's were 89.2 percent and 89.8 percent. Post treatment larval cultures indicated Haemonchus, Ostertagia and Trichostrongylus were the resistant genera involved. On none of the ten farms was resistance to oral ivermectin at 0.2mg/kg detected.

Journal Article↗
PubMed1988

The efficacy of albendazole against some gastrointestinal nematodes in goats.

On the basis of worm counts in naturally infected Angora-X goats, albendazole at either 3.8 mg/kg repeated after 24 hours or as a single dose at 7.6 mg/kg, was >99% effective in removing adult Ostertagia and Trichostrongylus spp. Small numbers of adult Haemonchus contortus, Cooperia sp. and Chabertia ovina were present in control but not treated animals. The single dose of 7.6 mg/kg removed >99% of adult Oesophagostomum venulosum whereas the repeated dose of 3.8 mg/kg removed only 96%.

Journal Article↗
PubMed1987

The prevalence and identity of Sarcocystis in beef cattle in New Zealand.

Muscle tissue from the oesophagus and diaphragm of 500 beef cattle slaughtered in New Zealand was examined for Sarcocystis infection by microscopic examination of cysts isolated from muscle samples. All cattle were infected with Sarcocystis; based on light microscopy of cysts, 98% had thin-walled Sarcocystis cruzi cysts and 79.8% had thick-walled (Sarcocystis hirsuta/Sarcocystis hominis) cysts. Cysts were also collected for electron microscopy and transmission experiments. Thick-walled cysts could not be distinguished as S. hirsuta or S. hominis by light or electron microscopy. Thick-walled cysts were fed to three cats and one human volunteer; one cat shed sporocysts but not the human volunteer. Electron microscopy of the cysts revealed many features that have not been described previously.

Animals↗
PubMed1987

Prevalence of dog-derived Sarcocystis spp. in some New Zealand lambs.

Pepsin: hydrochloric acid digestion and histological examination of the myocardium of 51 hearts from five to nine month-old lambs from the southern half of the North Island, showed that 47 (92%) were infected with microscopic sarcocysts that are presumed to be dog-derived. Of 157 sarcocysts detected histologically, 32 corresponded morphologically with Sarcocystis ovicanis and 120 with Sarcocystis tenella (Syn. S. arieticanis). The remainder could not be identified as to type.

Journal Article↗
PubMed1987

The relationship of heart-girth to liveweight of female goats in New Zealand.

The correlations between heart-girths (measured as the smallest thoracic circumference) and liveweight were determined for 96 Saanen, 100 Angora and 101 feral female goats all of New Zealand origin. The correlation coefficients were 0.94, 0.94 and 0.90 for Saanens, Angoras and ferals respectively. To facilitate liveweight estimation for calculating doses of non-mineralised anthelmintics and to minimise under-dosing it is suggested that a straight-line equivalent of the upper 95% confidence curve be used. Care should be exercised in using girth measurements in small animals where the error could be high. They are not recommended for use when mineralised drenches or potentially dangerous drugs are being administered.

Journal Article↗