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. Both compounds were active on mature Nematodirus spathiger, but TBZ had variable activity on immature forms. Strongyloides papillosus were effectively removed by TBZ. Other parasites found in lower numbers than the aforementioned 3 species were Capillaria spp, Trichuris spp, and Oesophagostomum columbianum; removal was variable for both drugs.

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.

<p>The trial was carried out in nine different farms in the State of São Paulo to verify the effect of anthelmintic treatment with oxfendazole, levamisole and ivermectin in gastrointestinal nematode parasites in sheep. In each farm, the sheeps were randomly allocated in four groups: the first group was treated with oxfendazole at 4,5 mg/kg; the second one with levamisole at 7,5 mg/kg; the third one with ivermectin at 0,2 mg/kg and the fourth one was the untreated control. Faecal samples were collected from animals on the day of the treatment and seven days after that. After the treatment with oxfendazole, levamisole and ivermectin, significant reductions in nematode egg counts were verified in two, four and five farms, respectively. Haemonchus spp and Tnchostrongylus spp were the most prevalent parasites in the trial. The results suggest the occurrence of parasites with multiple anthelmintic resistance in the majority of the farms.</p> | O trabalho foi realizado em nove propriedades do Estado de São Paulo, com o objetivo de verificar o efeito da administraçõo de oxfendazol, ivermectina e levamisol sobre os exames coproparasitólogicos de ovinos. Em cada propriedade foram formados aleatóriamente quatro grupos de ovinos: o primeiro foi medicado com oxfendazol, na dose de 4,5 mg/kg, o segundo com levamisol, na dose de 7,5 mg/kg, o terceiro com ivermectina, na dose de 0,2 mg/kg e o quarto grupo foi o controle, não medicado. Colheitas de fezes foram realizadas no dia da vermifugação e novamente sete dias depois para a realização de exames coproparasitológicos. Após a administraçâo de oxfendazol, levamisol e ivermectina, foi verificada redução estatística significativa nas contagens de ovos por grama de fezes (OPG) em duas, quatro e cinco propriedades, respectivamente, sendo Haemonchus e Tnchostrongylus os parasitas com maior ocorrência no experimento. Os resultados sugerem, na maioria das propriedades, a presença de parasitas com resistência múltipla aos anti-helmínticos testados.