The strategic use of single therapeutic doses of
closantel,
tetramisole or sustained low-level administration of
albendazole in feed pellets in controlling naturally acquired parasitic
gastroenteritis in sheep was investigated on a farm in semi-arid Rajasthan, India. A total of 303 5- to 6-month-old sheep were divided into three groups. Two groups were dosed with single therapeutic doses of
closantel and
tetramisole and the third group was given a low-level medication with
albendazole through feed pellets for 30 days. Faecal egg counts revealed significantly lower counts (p<0.001) in the group treated with
closantel compared to the other two groups. The faecal egg counts in the group receiving sustained low-level
albendazole rose after withdrawal of the medication but remained significantly lower than those in the group treated with
tetramisole up to 7 weeks
after treatment (p<0.05). On the other hand, in the group treated with
tetramisole, the mean faecal egg count rose from 3 weeks
after treatment and remained continuously higher than those in any other group up to 12 weeks
after treatment. The
closantel-treated group gained more
body weight but the first six-monthly greasy fleece yield was greater in the group treated with medicated pellets. During the first 3 months of the experiment, three animals in the group treated with
tetramisole died of parasitic
gastroenteritis. Following sustained low-level administration of
albendazole in feed pellets, the plasma disposition curve of both the
sulphoxide and sulphone metabolites reached its plateau level by day 5 and remained almost constant thereafter. The comparative cost-effectiveness of the three treatment regimes during the first 3 months of treatment was best for the group treated with
closantel followed by the group treated with medicated feed pellets.