The effects of early-season treatments with doramectin on set-stocked calves naturally exposed to trichostrongyles

A study was carried out to evaluate the effects of strategic early-season treatments with doramectin on first-season grazing calves exposed to trichostronglylid infection on a naturally contaminated pasture. Two groups of cross-bred Limousine/Red Danish calves were turned out in early May on two plots that were similar with respect to size and herbage infectivity. They grazed separately until housing in early October. One of these groups was given doramectin at turnout and 10 weeks later, while the other group served as untreated controls. The results showed that the treatments significantly reduced trichostrongylid loads throughout the season, as evidenced by significant reductions in both their Ostertagia ostertagi burdens and serum pepsinogen levels compared with the controls. Furthermore, the results of herbage larval counts and post-mortem worm counts in tracer animals demonstrated that the treatment had successfully suppressed herbage infectivity on the treated plot.     

Development and survival of infective larvae of gastrointestinal nematodes of cattle on pasture in central Kenya

On a series of pasture plots, 2 kg pats of bovine faeces containing known numbers of strongylid (Haemonchus, Cooperia, Oesophagostomum and Trichostrongylus) eggs were deposited at intervals of 4 weeks from July 1995 to June 1996. The plots were sampled every 2 weeks after contamination and infective larvae were identified and counted. Larvae of all the genera developed throughout the year, but the pats exposed during the rainy season yielded more abundant larvae on the herbage. Irrespective of the season of deposition of the pats, larvae were found in larger numbers from 2 to 6 weeks after deposition and generally declined to below detectable levels within 12 to 16 weeks of contamination. The comparatively short survival times noted in this experiment may present opportunities for manipulation of the population dynamics of the gastrointestinal nematodes in the tropical environment of Kenya.     

A Questionnaire Survey on the Practices Adopted to Control Gastrointestinal Nematode Parasitism in Dairy Goat Farms in France

To evaluate the efficacy with which recommendations of means to avoid the spread of anthelmintic resistance in parasitic nematode populations are communicated to farmers on dairy goat farms in France, a questionnaire survey was undertaken on their use of antiparasitic drugs. Information was collected from 73 farms in two main areas of dairy goat production. The data referred to three years. Anthelmintics were used in 69 farms, the mean number of treatments per year being 2.74. Changing the drug from one year to another was not practised. Moreover, of the 58 farms using two or more treatments per year, only 37% used anthelmintics from different classes in the lactation and drying-off periods. Benzimidazoles and probenzimidazoles were given in all except two farms and these substances represented more than 80% of all the treatments. Levamisole/pyrantel or avermectins were used in 15% and 27% of the farms, respectively. Double the ovine dose, as recommended in goats to ensure efficacy of benzimidazoles, was applied in 55% of the farms. In addition, in all the flocks, the substances were given on the basis of a mean estimated live weight and not by reference to the heaviest animal. These results indicate that errors in the use of anthelmintics are still frequent in dairy goat farms in France, with probable consequences for the spread of anthelmintic resistance in the populations of parasites.     

The significance of the gastrointestinal parasites of Asian buffalo in Sri Lanka

Buffalo aged 3–15 months on institutional farms and in the villages of an irrigation project were monitored for gastrointestinal nematodes by faecal egg counts over two years. Apart from treatment for Toxocara vitulorum at 10–16 days of age, no anthelmintics were used. Half of the strongylid egg counts were zero and 90% were less than 500 epg of faeces on the institutional farms, and 67% were zero and 97% less than 500 epg in the villages. No problems arose during four years without anthelmintics on the institutional farms and during two years in the villages. Autopsies demonstrated that the eggs which were present were produced by mixed infections of small numbers of Haemonchus spp., Mecistocirrus digitatus, Trichostrongylus spp., Bunostomum phlebotomum and Cooperia spp. High egg counts of Strongyloides papillosus occurred in calves up to six months old, but were not pathogenic.