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PubMed1986

Effects of anthelmintics on Haemonchus contortus (Nematoda: Trichostrongylidae).

The review summarizes and evaluates recent information about the effects of anthelmintics on Haemonchus contortus. The topic is discussed under the headings effects of drugs on the absorptive surfaces, effects of drugs on metabolism, effects of drugs on the neuromuscular system, effects of drugs on developmental stages, anthelmintic efficacy, and resistant strains. Possible future lines of work are suggested in the conclusions.

Animals↗
PubMed1984

The effect of transfer factor treatment on two challenge infections of Haemonchus contortus in immuno-competent 7-month-old lambs.

A number of immuno-competent Blackface lambs were infected with 10,000 Haemonchus contortus third stage larvae and were later challenged with a second dose of 10,000 H. contortus third stage larvae. One group of lambs was treated with dialysed transfer factor prior to the second challenge dose. Histological changes in the abomasal wall, reductions in abomasal worm burdens at slaughter and faecal egg counts monitored throughout the experiment suggested the presence in some animals of an innate resistance, a "self curing" effect, an enhancement of this "self curing" effect in the transfer factor treated group and a response in one transfer factor treated animal comparable to "classical self cure".

Abomasum↗
PubMed1983

Pharmacokinetic behaviour and anthelmintic efficacy of 1-n-butyl carbamoyl oxfendazole given by intramuscular injection.

Oxfendazole (OFZ) was chemically modified to 1-n-butyl carbamoyl OFZ (C4-OFZ) in an attempt to improve the solubility of OFZ and enable it to be administered by injection. After intramuscular injection to sheep and cattle, C4-OFZ was metabolised to OFZ which resulted in higher plasma OFZ concentrations that persisted for a considerably longer period than those observed following administration of OFZ orally. The anthelmintic efficacy of injected C4-OFZ was tested, in sheep, against strains of Trichostrongylus colubriformis, Haemonchus contortus and Ostertagia circumcincta, which were highly resistant to benzimidazoles. In all cases, the C4-OFZ treatment showed a significant improvement in efficacy over the conventional oral OFZ drench.

Animals↗
PubMed1983

A comparison of the effects of dialysed and non-dialysed transfer factor preparations on Haemonchus contortus infections in young lambs.

Significant reductions in worm burdens were achieved in lambs treated with dialysed transfer factor and challenged with 10,000 Haemonchus contortus larvae, when compared with challenged control animals. Non-dialysed transfer factor, from the same leucocyte pool, produced no protection, but was successful in reducing worm burdens when given after a primary infection of 1,000 H. contortus larvae with subsequent challenge of 10,000 larvae. While the results confirmed the previously reported inconsistencies of transfer factor activity, the histological abomasal changes in all the dialysed and non-dialysed transfer factor treated groups, irrespective of measurable effects on worm burdens, were consistent and corresponded to immediate type hypersensitivity responses. The similarity of these responses with self cure in haemonchosis and the possibility of genetic factors influencing the quantitative expression of protection to the effects of transfer factor treatments is discussed.

Abomasum↗
PubMed1981

The role of absorbed drug in the efficacy of oxfendazole against gastrointestinal nematodes.

Comparisons were made of the relative efficacy of ozfendazole (OFZ), administered to sheep at 5 mg/kg either as an oral drench, single intravenous injection or 12 and 24 divided intravenous injections over 24 and 48 hours, against benzimidazole-resistant Haemonchus contortus and Trichostrongylus colubriformis. A single intravenous injection was at least equally potent as the oral drench whilst the divided dose intravenous regimes significantly increased OFZ efficacy against both parasite species. These findings demonstrate that (i) absorbed drug is important for the efficacy of OFZ against nematodes in the abomasum and small intestine and may be more important than unabsorbed drug passing down the gastrointestinal tract, and (ii) the maintenance of plasma OFZ levels of approximately 2 micrograms/ml by divided dose regime increased efficacy compared with that achieved with the same total dose given as a single administration.

Administration, Oral↗
PubMed1978

Helminth parasites of beef cattle in the East Kimberley and Victoria River Districts of Northern Australia.

An investigation into the helminth species present in cattle in the East Kimberley and Victoria River Districts of Northern Australia was conducted over a 2-year period based on bi-monthly total and differential worm counts in weaner cattle as well as on a post mortem survey of adult cattle sent for slaughter. The most important species found in young cattle were Haemonchus placei and Cooperia spp. Only small numbers of Bunostomum phlebotomum, Nematodirus spathiger, Oesophagostomum radiatum and Moniezia benedini were present. Calicophoron calicophorum and nodules of Onchocerca spp. and Oe. radiatum were recorded in adult cattle. Seasonal fluctuations in helminth parasite burdens are discussed in relation to temperature and rainfall and the results are interpreted in relation to the effects of helminthosis on present and future beef production in this area.

Animals↗
PubMed1980

Use of disophenol for the control of Haemonchus contortus in sheep in West Java, Indonesia.

The result of a field trial investigating the anthelmintic effect of disophenol against H. contortus in sheep raised under Asian small farming practice is reported. it was clearly shown that a single injection of disophenol suppressed the numbers of H. contortus to very low levels for periods up to 3 months despite the presence of large populations of H. contortus infective larvae available on pasture and herbage grasses.

Animals↗
PubMed1993

Efficacy of closantel against fenbendazole and levamisole resistant Haemonchus contortus in small ruminants.

Sheep infected with a fenbendazole resistant strain of Haemonchus contortus and goats with a levamisole resistant strain of the same parasite were used to evaluate the anthelmintic efficacy of closantel. Closantel at the rate of 10 mg/kg body weight was 100% effective against the 2 resistant strains of the parasite as indicated by faecal egg count and worm reduction. The efficacy of fenbendazole in sheep and of levamisole in goats was 56.68 and 76.90%, respectively.

Animals↗
PubMed1979

The response of Awassi and Merino sheep to primary infection with Haemonchus contortus.

The possible existence of breed differences in the response of sheep to primary infection with Haemonchus contortus was examined by comparing worm establishment and pathogenic effects of the parasite in Awassi and Merino sheep of haemoglobin type B infected with 500 third stage H. contortus larvae per kg body weight. The results showed that the Merino sheep had lower faecal egg counts and worm burdens and suffered less severe clinical disturbances than sheep of the Awassi breed. This suggests that genetic resistance operates primarily at the level of worm establishment.

Animals↗
PubMed1988

Epidemiology of ovine helminthiasis in Haryana, India.

Tracer lambs were used to study the pasture contamination with infective stages of helminth parasites during one annual cycle in a subtropical climate. Post-mortem worm counts indicated that low infections with Haemonchus contortus occurred throughout the year except in June. However, twenty five or more H. contortus per lamb were recorded in January, April, May and August. Trichostrongylus colubriformis infection was detected throughout the year and 150 or more worms per lamb were recorded during January to May and in August. Anoplocephalids were recorded from the lambs throughout the year but had no seasonal pattern. Low infections with Oesophagostomum columbianum and Trichuris ovis were observed. The faecal egg counts from the permanent flock with whom the tracer lambs were grazed revealed heavy to mild worm burdens throughout the year. Coproculture indicated that H. contortus predominated from the second fortnight of May to December except in the second fortnight of July. Infection with T. colubriformis was more severe from January to the first fortnight of May and in the second fortnight of July. Negligible infections with O. columbianum, Bunostomum trigonocephalum, Gaigeria pachyscelis and Dictyocaulus filaria were also observed. Biohythergraphs prepared for H. contortus and T. colubriformis showed differences between observed and expected results. It is suggested that for realistic biohythergraphs related parameters in addition to rainfall and temperature should also be considered.

Animals↗
PubMed1987

Seasonal changes in the prevalence of Haemonchus and Trichostrongylus hypobiotic larvae in tracer goats in Malaysia.

An investigation into the seasonal changes in the population structure of Haemonchus and Trichostrongylus in tracer goats was conducted over 12 months at Serdang, an area in southern West Malaysia with year-round tropical rainfall. Successive groups of parasite-free tracer goats were grazed for a month alongside naturally infected adult goats and necropsied for worm counts 14 days after their removal from pasture. No hypobiotic larvae of Trichostrongylus were recovered. Hypobiotic larvae of Haemonchus were evident during each month of the year but accounted for only a very small proportion of the total Haemonchus burden. Very low levels were encountered from December through to June. Comparatively higher levels of hypobiosis were observed thereafter with a peak of 7.4% in September. The factors responsible for hypobiosis were not clearly defined but the phenomenon was associated with increasing levels of soil moisture storage. Host resistance, adult worm population of tracers and population of ingested L3 were ruled out as possible inducing factors.

Animals↗
PubMed1984

Ovine internal parasitism in the Yemen Arab Republic.

Internal parasitism was studied in five flocks in different regions of the Yemen Arab Republic. Ewes and lambs were faeces sampled from the spring of 1977 to the spring of 1978 and helminth-free tracer lambs were subsequently run with three of the flocks from October 1978 to November 1979. The findings indicated that ovine helminthiasis and fascioliasis may be of importance with the following regional variations: Haemonchosis all the year round in the Tihammah coastal plain. Haemonchosis and trichostrongylosis in the periparturient period in the Southern Uplands and Western Foothills. Fascioliasis and nematodiriasis in the Inter-Montane Plains of the Highlands. Possible control regimes are suggested for further investigation.

Animals↗
PubMed1996

Comparative efficacies of closantel, ivermectin, oxfendazole, thiophanate and levamisole against thiabendazole resistant Haemonchus contortus in sheep.

Forty-nine sheep artificially exposed to a thiabendazole (TBZ) resistant isolate of Haemonchus contortus were assigned to 7 groups of 7 animals each and used to conduct a controlled anthelmintic trial. One group of sheep served as untreated infected controls and 6 groups were treated as follows: closantel, 5.0 mg kg-1; ivermectin, 0.2 mg kg-1; oxfendazole, 5.0 mg kg-1; thiophanate, 50 mg kg-1, levamisole, 7.5 mgkg-1 and thiabendazole, 66 mg kg-1. Eggs per gram of faeces were determined on days 21, 24 and day 34 (10 days post-treatment) after infection and all animals were necropsied for residual worm counts. The calculated efficacies of the treatments against H. contortus as indicated by worm reduction were closantel (100%), ivermectin (99.3%), oxfendazole (35.2%), thiophanate (56.7%), levamisole (98.6%) and thiabendazole (24.3%). The data therefore indicate that the TBZ-resistant isolate of H. contortus used was highly resistant to the 2 benzimidazole (BZ) anthelmintics, oxfendazole and thiophanate. This is the first report in Kenya of a field strain of H. contortus resistant to thiophanate.

Animals↗
PubMed1982

An epidemiological study of helminthiasis in cattle in subtropical Argentina.

Nine farms were each visited regularly for a year in 1979 and 1980 in Salta Province in the subtropics of Argentina. A necropsy was done at each visit and faecal and blood samples were taken from other animals mostly aged between 6 and 18 months. Ninety necropsies were done and nearly 1,500 faecal samples collected. Gastro-intestinal helminthiasis was most general and severe in autumn when calves were about 9 months old and this was followed by a dramatic fall in numbers of worms by the end of winter. Helminths were found in other organs but were not considered important. At peak periods 20% of the animals had worm egg counts of more than 750 epg and contained more than 1,000 Haemonchus worms. This species was considered to be the most important but other frequently encountered species were Oesophagostomum, Cooperia and Trichostrongylus spp. A list is given of all species found. Tracer calves were used to determine the periods of infestation. No hypobiosis was encountered. It was concluded that the sharp fall in numbers of worms after the autumn peak was due to the development of immunity by the majority of the young animals.

Animals↗