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PubMed1976

Efficacy of p-Toluoyl chloride phenylhydrazone against gastrointestinal helminths in ovines.

A new anthelmintic candidate, p-toluoyl chloride phenlylhydrazone, was administered to lambs in a paste formulation. The efficacy of this drug was determined at dose rates of 20, 30, 40, and 50 mg of active ingredient per kilogram of body weight. Helminths expelled by these dosages included Haemonchus contortus, Ostertagia circumcicta, Trichostrongylus colubriformis, T. axei, Nematodirus filicollis, Cooperia curticei, Strongyloides papillosus, Oesophagostomum columbianum, Bunostomum trigoncephalum, Chabertia ovina, Moniezia expansa, and M. benedeni.

Animals↗
PubMed1976

A possible relationship between haemonchosis and haemoglobin polymorphism in Merino sheep in Kenya.

It is known that sheep show polymorphism for haemoglobin in that three phenotypes (HbA, HbB AND HbAB) are normally found. Since it has been suggested, on the basis of haematological values, that HbA type sheep are more able to survive in Haemonchus contortus endemic environments, a preliminary study was conducted on the performance of set-stocked Merino ewes and lambs in relation to their haemoglobin phenotypes. The results provided some evidence that, in Merino sheep at least, those with HbA type show 'self-cure' more frequently and effectively than those with HbB and HbAB types. Examination of the PCV values and total body weights of Merino eres showed a similar trend, ie, the HbA types had the highest haematological parameters and the heaviest body weights, while the HbB types were consistently lowest. It would appear that the practical significance of these results justifies investigation on a larger scale.

Animals↗
PubMed1976

Controlled evaluation of fenbendazole as a bovine anthelmintic.

Calves experimentally infected with Haemonchus, Ostertagia, and Cooperia, and to lesser degrees with Trichostrongylus, Oesophagostomum, Nematodirus, and Bunostomum were used in a controlled experiment to record the anthelmintic efficacy of a benzimidazole compound methyl 5-(phenylthio)-2-benzimidazolecarbamate at dosage levels of 3.5, 5, and 7.5 mg/kg bodyweight. With the 3 dosages, reductions of Haemonchus were 96.7, 99.2, and 99.8%; of Ostertagia, 97.2, 97.2, and 99.5%; and of Cooperia, 99.9, 99.9, and 99.9%. Pronounced reductions were also recorded for Trichostrongylus, Nematodirus, Oesophagostomum, Trichuris, and Capillaria, but these populations were too numerically small or too unevenly distributed within the control groups to be given much emphasis. The experimental parasitic populations which developed in the 10 control calves amounted to 91, 763 worms (total).

Animals↗
PubMed1976

Effect of nematode parasite infection on the performance of stocker cattle at high stocking rates on coastal bermudagrass pastures.

Studies were conducted during the summer of 2 successive years (1971 and 1972) to determine the effects of gastrointestinal nematode parasitism on performance failure of stocker beef steers grazed at high stocking rates on Coastal bermudagrass pastures. During each of the 2 years, 3 groups of steers were rotated at 7- to 10-day intervals on sets of three 1.63-ha pastures from mid-May to late October. (Each group was maintained on a given set of pastures.) In the 1971 program, from mid-May to early August (phase 1) each group consisted of 48 steers for a stocking rate of 29.6 steers/ha. From early August to late October (phase 2) the number of steers per group was reduced to 36 (stocking rate of 22.2 steers/ha) to improve the plane of nutrition. In the 1972 program, 2 groups were stocked at 48 steers per group (29.6 steers/ha) and a 3rd group was temporarily stocked with 58 steers (10 additional steers) to provide 2 animals each month for necropsy evaluation of worm burdens. With exception of the monthly removal of 2 steers from the 3rd group, the stocking rate in 1972 remained intact for the entire grazing season. In 1971, the 3 groups (groups 1, 2, and 3) were treated with thiabendazole (2 doses, 16 days between doses) before grazing. Parasite burdens and levels of pasture contamination were low initially and body weight gains were good during the 1st 3 months of grazing (phase 1). In the 2nd half (phase 2) of the grazing program, 1 group of steers given free-choice supplemental feed (1% of body weight/steer each day) and treated with anthelmintic (thiabendazole; 2 doses, 18 days between doses, during August) and another group, given supplemental feed only, had significantly better weight gains than did the 3rd group, not given supplemental feed nor treated with anthelmintic. There was no weight gain advantage derived from the reduced stocking rate in phase 2. Tracer calves, which were allowed to graze on pastures, developed an increased level of infection after August. Fecal egg counts in the principal steers and recovery of infective larvae from pasture paralleled the infection level in tracer calves. Necropsy evaluation of steers from groups 1, 2, and 3 at the end of the 1971 program indicated a similarity in total worm counts, but in the group not given supplemental feed nor treated with anthelmintic there was more generalized inflammation and a greater number of lesions in the abomasum (Ostertagia) and the caudal portion of the intestine (Oesophagostomum). Steers in the 3rd group also were in poorer condition. Initial worm burdens in the 3 steer groups (groups 4, 5, and 6) were low at the start of the 1972 program. One group was given freechoice supplemental feed (0.5% of body weight/steer each day) and treated with anthelmintics (thiabendazole in the 1st dose, levamisole in the 2nd dose, 12 days between doses, in May and August) and another group was given supplemental feed throughout the summer; the 3rd group was treated with anthelmintics (in May and August)...

Animal Feed↗
PubMed1975

The control of adult parasitic nematodes of cattle with morantel tartrate.

The anthelmintic efficacy of morantel tartrate at 5mg/kg bodymass was investigated in three separate controlled trials comprising 68 calves. High anthelmintic activity was established against adult Haemonchus placei, Ostertagia ostertagi, Cooperia spp. (C.pertinata and C. punctata), Bunostomum phlebotomum and Oesophagostomum radiatum.

Animals↗
PubMed1992

Response to ivermectin treatment of parasitic stages of Haemonchus contortus resistant or susceptible to ivermectin.

Two groups of 33 helminth-naive lambs were infected with 5,000 L3 of an ivermectin-resistant or -susceptible strain of Haemonchus contortus (groups R and S). On days 6, 10, 16, and 21 postinfection, 5 animals from each group were chosen at random and orally treated with 0.2 mg/kg of ivermectin. On each occasion, 2 randomly selected lambs from each group were also killed to determine the number and stage of development of the worms present at the time of treatment. These necropsies revealed that by day 6 early and late fourth-stage larvae were present, whereas on day 10 the early fifth stage had been reached; by days 16 and 21 all worms had reached the adult stage. Necropsies on day 28 postinfection revealed that although animals treated at day 6 had 26.3% fewer worms than the controls, there was no significant difference (P greater than 0.05) between worm burdens from any of the animals infected with the R strain and treated at different times after infection when compared with the untreated controls. With ivermectin significant reductions were obtained in the worm burdens of the animals infected with the susceptible strain; these were reduced by 96% when treatment was given on day 6 against fourth-stage larvae and 98.9% when the drug was given on day 21 against adult stages. From these results it is clear that resistance to ivermectin in this strain of H. contortus is present as early as the fourth larval stage.

Animals↗
PubMed1992

Lymphocyte reactivity to antigens of Haemonchus contortus in antigen-inoculated and H contortus-naive lambs.

Lambs were inoculated during either fetal or early neonatal life with antigens of Haemonchus contortus (HcAg) third-stage larvae, or ovalbumin (OVA), or were left untreated. By the time lambs were 4 weeks old, blood lymphocytes from all of them responded to HcAg. This was evident in all lambs, regardless of the previous inoculation regimen, although higher response was seen in HcAg-inoculated lambs, compared with naive lambs. Only lambs inoculated with OVA had OVA-specific lymphocyte activity. In HcAg-naive lambs, the maximal HcAg lymphocyte response was observed between the ages of 5 and 25 weeks, with gradual decrease thereafter. In vitro detection of HcAg-reactive lymphocytes was affected by antigen concentration and presence of plasma. Plasma inhibited HcAg-reactive lymphocytes from all lambs at high in vitro antigen concentration and completely abrogated the response in H contortus antigen-naive lambs.

Animals↗
PubMed1977

Further controlled evaluations of fenbendazole as a bovine anthelmintic.

The efficacy of fenbendazole (methyl-5-(phenythio)-2-benzimidazole-carbamate) in cattle parasitized by the lungworm Dictyocaulus viviparus and in other cattle parasitized by Haemonchus, Ostertagia, Trichostrongylus, Cooperia, and Oesophagostomum was investigated in 3 controlled critical experiments. A single treatment with 5.0 mg/kg of body weight administered in the feed or in a 10% suspension exceeded 99% efficacy against these helminths. Dosages of 1, 0.5, 0.35, and 0.25 mg/kg of body weight administered for 5 days to individual calves in their feed were 99% efficacious against all helminths, except Haemonchus. The 1.0 mg/kg dose removed 99.5% of the Haemonchus, and the other 3 dosages had efficacies of 91.0, 93.7, and 95.6%, respectively. The small daily dosages were not evaluated against Dictyocaulus.

Animal Feed↗
PubMed1977

Levamisole: anthelmintic activity in calves following dermal application.

A series of seven experiments designed to evaluate the anthelmintic efficacy of levamisole (1-tetramisole) by dermal application is described. This work involved use of 181 artificially infested calves. The drug was formulated at a concentration of 10% m/v levamisole base in a solvent system promoting dermal absorption and was applied to both sides of the spine in the lumber region at a dose rate of 10 mg levamisole base per kg livemass. A consistent performance was achieved in these investigations, the results from all of which were based upon necropsy findings. Efficacy of treatment was assessed against the third and fourth larval stages and fifth stage larvae/adult worms of six nematode species; the respective efficacies obtained were Haemonchus placei 72,0%; 99,3%; and 100%: Ostertagia ostertagi 85,5%; 38,1% and 74,5%: Cooperia spp. 98,9%; 99,9% and 100%: Bunostomum phlebotomum 83,0%; 100% and 98,5%: Oesophagostomum radiatum 47,4%; 94,9% and 99,6% and Dictyocaulus viviparus 79,5%; 94,1%; 90.9% (fifth stage larvae) and 93,8% (adult worms). The anthelmintic efficacy of levamisole in these experiments is of the same order as that achieved by orthodox methods of administration at dose rates between 7,5 and 10,0 mg levamisole HC1 per kg livemass. These findings add a new dimension to the use of levamisole and to anthelmintic therapy in general.

Administration, Topical↗
PubMed1977

Trials with rafoxanide. 8. Efficacy of an injectable solution against trematodes and nematodes in cattle.

Four experiments are described in which the efficacy of an experimental 5% injectable solution of rafoxanide was evaluated against various adult and immature helminths in cattle. Subcutaneous injection at a dosage of 3 mg/kg live mass resulted in the following reductions in mean worm burdens: adult Fasciola hepatica, 82,6%; adult Fasciola gigantica, 99,8% immature Paramphistomum microbothrium, 10,1% adult Haemonchus placei, 99,6%, third stage H. placei, 73,7%; adult Bunostomum phlebotomum, 99,8%; adult Oesophagostomum radiatum, 99,9%; and fourth stage O. radiatum, 76,9%. At 5 mg/kg live mass, rafoxanide solution was 97,5% and 99,2% effective against 8-week old F. gigantica and third stage H. placei respectively and at 7,5 mg/kg, 92,4% against 6-week old F. gigantica.

Animals↗
PubMed1977

Occurrence and seasonal behavior of gastrointestinal nematodes infecting Maine dairy cattle.

Gastrointestinal tracts of 48 yearling Maine dairy cattle were examined (8 animals every 2 months) for 1 year. Adult and immature nematodes were identified and counted. Species recovered were Bunostomum phlebotomum, Cooperia mcmasteri, Cooperia oncophora, Cooperia pectinata, Cooperia punctata, Haemonchus placei, Nematodirus helvetianus, Oesophagostomum radiatum, Ostertagia circumcincta, Ostertagia lyrata, Ostertagia ostertagi, Trichostongylus axei, and Trichuris ovis. Strongyle parasitism was observed during every sampling period and the overall incidence was 93.7%. The most commonly encountered genera were Ostertagia spp (85.4%) and Cooperia spp (81.2%). Seasonal fluctuations in the worm burden of various nematodes were observed, with largest numbers seen in the fall. The incidence and degree of parasitism appeared to be related to environmental conditions. Proportions of adult and immature worms were shown to fluctuate with the time of year. Greatest numbers of immature worms were observed during the fall and winter.

Animals↗
PubMed1977

Parasites of domestic and wild animals in South Africa. IV. Helminths in sheep on irrigated pasture on the Transvall Highveld.

The seasonal incidence of helminth infestation in sheep on newly established irrigated pastures was determined by the slaughter of pairs of tracer lambs exposed for periods of approximately 33 days from October 1968--July 1970 and of sets of 3 lambs from March 1971--May 1973. It took several months for the infestation to become established on the pasture, but thereafter, of the various species present; Haemonchus contortus was most prevalent. In general, peak burdens of this species were recovered from January--May or June, while marked inhibition of larval development was evident from April--August. Ostertagia circumcinta usually occurred in increased numbers from April--October, and larval development was inhibited during July and August. Although the sizes of the burdens varied considerably from year to year, Trichostrongylus spp. were present mainly from April--August. Oesophagostomum columbianum, although present in the lambs slaughtered during the first 5 months of the survey, virtually disappeared until May 1971. After this it reappeared in small numbers in nearly all the sheep, reaching peak burdens during April and May 1972, and May 1973. Moniezia expansa were generally recovered from the lambs slaughtered from November--May.

Agriculture↗
PubMed1992

Fibrinogen-degrading proteins from Haemonchus contortus used to vaccinate sheep.

Sixteen nonsibling sheep, approximately 12 months old, that were raised in a helminth-free environment, were used for 2 protection studies 6 months apart. Sheep were vaccinated weekly for 5 weeks by IM injection of fibrinogen-degrading proteins derived from the intestinal tract of adult Haemonchus contortus. Ten days after the last vaccination, sheep were given 2,500 infective H contortus larvae by intraruminal injection. Vaccinated sheep produced specific antibodies, and were protected from the worm challenge. Significant differences in mean fecal worm egg counts for 56 days after worm challenge, in mean numbers of H contortus worms, and female fecundity ratios at necropsy were detected in vaccinated sheep, compared with those in control sheep. These data suggest that the fibrinogen-degrading proteins have a protective role in vaccination of sheep against H contortus.

Abomasum↗
PubMed1992

Comparison of anthelmintic control programs for sheep in Virginia.

Haemonchus contortus is the most serious parasitic problem encountered by sheep producers in southwestern Virginia. Four anthelmintic control programs for grazing lambs were tested. Group TR received monthly SC injections of ivermectin (200 micrograms/kg of body weight). Group SI received the same dose of ivermectin at 0, 3, 6, 9, and 12 weeks after the start of the grazing season. Group SL was given levamisole (8 mg/kg, PO) 0, 3, 6, 9, and 12 weeks after the start of the grazing season, and group TA received ivermectin (200 micrograms/kg) 0, 8, 16, 20, and 24 weeks after the beginning of grazing. None of the 4 programs provided satisfactory control of parasites as indicated by fecal egg counts and serum pepsinogen concentrations, although group-TR lambs gained significantly more weight than lambs in groups SI and TA. Group-TA lambs developed clinical haemonchosis in early August and required additional treatment at that time. These findings suggest that reliance on anthelmintics alone may not provide the most effective and economic control of parasitic infection.

Abomasum↗
PubMed1992

Controlled tests on activity of contemporary parasiticides on natural infections of helminths in lambs, with emphasis on strains of Haemonchus contortus isolated in 1955.

Ten controlled tests were done between 1972 and 1989, in lambs on pasture, evaluating activity of fenbendazole (FBZ; 5 mg/kg of body weight), oxfendazole (OFZ; 3.5 and 10 mg/kg), oxibendazole (OBZ; 10 mg/kg), pyrantel pamoate (PRT; 25 mg of base/kg), and thiabendazole (TBZ; 44 and 50 mg/kg) against natural infections of helminths, with emphasis on 2 strains (A and B) of Haemonchus contortus. Strain A was phenothiazine-susceptible and strain B was phenothiazine-resistant when isolated in 1955. For approximately 10 years prior to these tests, sheep infected with both strains had been treated periodically each year with several compounds, including thiabendazole, which was used many more times than the other drugs. For this study, 4 (FBZ, OFZ, OBZ, and PRT) of the 5 compounds were evaluated in either 1 or 2 controlled tests. The fifth compound, TBZ, was used for 5 tests. Strain A H contortus was resistant to TBZ for all years tested, but more susceptible to FBZ, OFZ, OBZ, and PRT. Overall, strain B was susceptible to TBZ (with a few exceptions), and also to FBZ, OFZ, OBZ (activity less on immature forms), and PRT. Other abomasal parasites (2 species of Ostertagia and 3 of Trichostrongylus) were found in low numbers, but removal overall was good for the compounds tested. Trichostrongylus axei, found in higher numbers than species of Ostertagia and other species of Trichostrongylus, were effectively removed by all compounds in most cases. Activities of TBZ and PRT were also evaluated against several species of intestinal helminths, most of which were found in low numbers. Cooperia curticei were inconsistently removed by TBZ, but activity of PRT was effective.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2004

[Use of FAMACHA Scoring System as a diagnostic aid for the registration of distinguishing marks in the breeding program for lambs exposed to an experimental Haemonchus contortus infection].

The control of gastro-intestinal nematodes in sheep has almost entirely been based on the use of anthelmintics and pasture management. Therefore anthelmintic resistance escalated in the past. One way of reducing this problem may be the limitation of anthelmintic treatment to those animals with clinical symptoms only. The FAMACHA Eye-colour-chart is based on the principle knowledge that the colour of mucous membranes are correlated with the anaemiae situation of an animal. To monitor anaemic animals they are identified and classified in a 1 to 5-color scale based on the colour of the conjunctiva, and anaemic animals can be selectively treated. It helps to reduce treatments and therefore the development of drug resistance. The objective of this study was to estimate the correlation between FAMACHA-scores, haematocrit values, faecal egg counts, plasma albumin level and worm burden following an experimental infection with Haemonchus contortus in lambs. The estimated correlations have been low. This proofs the limits of the FAMACHA system under a situation of low parasite pressure.

Anemia↗