THE STRATEGIC USE OF CLOSANTEL AND ALBENDAZOLE IN CONTROLLING NATURALLY ACQUIRED GASTROINTESTINAL NEMATODES OF SHEEP IN THE KENYA HIGHLANDS

The strategic use of closantel, a narrow-spectrum salicylanilide anthe lmintic against bloodsucking helminths, and of albendazole, a broad-sp ectrum benzimidazole anthelmintic, in the control of gastrointestinal nematodes of sheep was investigated on a farm in Nyandarua District in the highlands of Kenya. Thirty Corriedale female lambs aged between 9 and 12 months were assigned to three treatment groups of 10 lambs eac h. The three groups were set stocked on separate paddocks for 12 month s. Lambs in group 1 (strategic treatment group) were treated with clos antel and albendazole a? the beginning and towards the end of the long rains (April and June, respectively) and towards the end of the short rains (December). During the intervening dry season, the lambs were t reated with albendazole. Lambs in group 2 (suppressive treatment group ) were kept 'worm free' by regular deworming with albendazole at 3-wee kly intervals for 12 months. The third group of lambs remained untreat ed (control group). Gastrointestinal nematode infections and pasture i nfectivity were well controlled in the case of the strategic treatment group. This resulted in higher weight gains, wool production, packed cell volume, and serum albumin and protein concentrations compared wit h the untreated control lambs. These parameters were comparable betwee n the strategic treatment and the suppressive treatment groups of lamb s. It was concluded that worm control strategies based on the epidemio logy of the parasites and the sustained anthelmintic action of closant el in combination with broad-spectrum anthelmintics can provide effect ive control of gastrointestinal nematodes of sheep in the study area.