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At least 631 records · Page 35Linked to original sources
PubMed1992

Prevalence of anthelmintic-resistant nematodes in fibre-producing goats in Scotland.

Six cashmere goat herds in Scotland were surveyed to assess the prevalence of anthelmintic resistance and the species of nematode involved. Resistance was determined in vivo by a faecal egg count reduction test and in vitro using an egg hatch assay and specific faecal egg identification techniques. Benzimidazole resistance was present in five of the herds, insufficient eggs were obtained from the other herd to draw firm conclusions. Teladorsagia (Ostertagia) species predominated in four of the five herds in which resistance was detected and Haemonchus contorus was the dominant species in the other.

Animals↗
PubMed1992

Efficacy of moxidectin against gastrointestinal nematodes of cattle.

Three groups of 11 naturally infected crossbred beef calves were injected subcutaneously with moxidectin 1 per cent injectable at 0.2 or 0.3 mg moxidectin/kg bodyweight or with the unmedicated vehicle. Nematode infections had been acquired during grazing from December to April. Based on the faecal egg counts and total worm counts of the control calves at necropsy (11 to 13 days after treatment) most of the calves had heavy parasitic burdens. Ostertagia ostertagi was predominant and the mean numbers of adults, developing fourth stage larvae (L4) and inhibited early L4 were 45,906, 10,061 and 68,918, respectively. Haemonchus placei and Trichostrongylus axei were also present in the abomasa. Three species of Cooperia, Oesophagostomum radiatum L4 and T colubriformis adults were found in the intestinal tract. Both dosages of moxidectin were equally effective (P < 0.05) against all the abomasal nematodes (99.9 to 100 per cent) and the intestinal tract nematodes (99.4 to 100 per cent). No adverse reactions to the moxidectin treatment were observed. Abomasal pathology characteristic of heavy O ostertagi infection was observed in the control calves, but not in the treated calves.

Animals↗
PubMed1993

Demonstration of co-resistance of Haemonchus contortus to ivermectin and moxidectin.

Studies were conducted to determine whether organisms which are resistant to ivermectin are also resistant to moxidectin. The mechanisms of action of moxidectin and ivermectin were compared by measuring the changes in membrane conductance they induced in leg muscle fibres of the common shore crab (Pachygrapsus crassipes) by using standard micro-electrode techniques. Meriones unguiculatus (jirds) were infected with ivermectin-resistant or -susceptible strains of Haemonchus contortus, treated with moxidectin or ivermectin at a dose which routinely clears more than 98 per cent of the susceptible strain, and examined for parasite clearance. The results showed that moxidectin induced a rapid loss of membrane resistance in the muscle preparation, and that the effect was almost 50 per cent reversible with the chloride channel-blocker picrotoxinin; this pattern of activity is qualitatively similar to that of ivermectin. In the jird model, moxidectin achieved a clearance of only < or = 47.2 per cent against ivermectin-resistant H contortus at a dose which invariably clears > or = 98 per cent of an ivermectin-susceptible strain. These results indicate that moxidectin and ivermectin share a common mechanism of action, and that organisms that are resistant to ivermectin are also likely to be resistant to moxidectin.

Animals↗
PubMed1994

Effect of subclinical Eimeria species infections in tropical goats subsequently challenged with caprine Haemonchus contortus.

Fourteen goat kids of the local indigenous breed naturally infected with Eimeria species were divided into two equal groups. The first group was superinfected with 500,000 Eimeria species oocysts and the second group was treated with amprolium. Sixty days later both groups were infected with 5000 third-stage caprine Haemonchus contortus larvae. The goats experimentally superinfected with eimeria shed more H contortus eggs and gained weight more slowly.

Amprolium↗
PubMed1994

Detection of anthelmintic resistant nematodes in sheep in southern England by a faecal egg count reduction test.

On five farms identified by in vitro tests to have benzimidazole resistance, and on one farm with apparent anthelmintic failure, faecal egg count reduction tests were performed using benzimidazoles, levamisole and ivermectin. With benzimidazoles efficacy was less than 70 per cent on all farms, confirming the validity of the in vitro tests to detect benzimidazole resistance. On two farms levamisole had an efficacy of less than 90 per cent but laboratory tests failed to demonstrate levamisole resistance. Ivermectin reduced egg counts by 100 per cent on all farms.

Animals↗
PubMed1995

Efficacy of oral moxidectin against benzimidazole-resistant isolates of gastrointestinal nematodes in sheep.

The efficacy of orally administered moxidectin was determined against four benzimidazole-resistant nematode isolates. At the start of the trial, 30 lambs were each infected experimentally with 20,000 third stage larvae (5000 Haemonchus contortus, 7000 Teladorsagia circumcincta, 3000 Trichostrongylus colubriformis and 5000 Cooperia curticei); 28 days later they were allocated randomly to three groups of 10: one untreated group, one group treated orally with fenbendazole (5 mg/kg bodyweight) and one group treated orally with moxidectin (0.2 mg/kg). Samples of faeces were taken five and 10 days after treatment and the lambs were killed 10 days after treatment. Fenbendazole reduced the average number of nematode eggs in faeces by 95 per cent and the average number of worms by 25 to 45 per cent according to the species. The efficacy of moxidectin against these benzimidazole-resistant isolates was 100 per cent. No adverse reactions to either of the drugs were observed.

Animals↗
PubMed1996

Occurrence of anthelmintic resistant nematodes on sheep farms in England and goat farms in England and Wales.

A survey in 1992 showed that 44 per cent of the sheep farms tested in the south west and 15 per cent of those in the north east of England had parasitic nematode worm burdens which were resistant to benzimidazole anthelmintics, and that 65 per cent of the non-dairy goat farms tested in England and Wales had resistant worms. Ostertagia circumcincta was the main species in sheep and Haemonchus contortus in goats. The resistance to benzimidazoles was diagnosed by a combination of an egg hatch assay and a larval development test. A simplified faecal egg count reduction test was used to investigate sheep and goat farms for signs of ivermectin resistance but no positive cases were detected. The initial identification of levamisole resistance on one farm, both from a faecal egg count reduction test and a positive larval development test, was confirmed by a 'dose and slaughter' trial.

Animals↗