The epidemiology and control of gastrointestinal nematode infections of goats in Kathiani division, if Machakos district, Kenya

A survey of gastrointestinal nematode infections of goats reared under extensive grazing conditions was conducted for 18 months on 4 farms in Kathiani Division of Machakos District, Kenya. The survey was based on monthly coproparasitological examination of kids « 6 month), immature (6-12 months) and adult (> 12 month) goats. The effects of season and age on the prevalence and intensity of infection were determined. Faecal egg counts (FEC) revealed that the overall prevalence of strongyles was 52.0% and the wet season prevalence was significantly (p <0.05) higher than for the dry season in the 3 age groups on the 4 farms. Majority of the animals had FEC of below 400 eggs per gram and did not vary significantly (p > 0.05) between the 3 age groups. The FEC followed a typical overdispersed distribution. Haemonchus contortus was the main nematode encountered in coprocultures (75 %) and post mortem total worm counts. Other nematodes encountered included Trichostrongylus axei, T. colubriformis, Bunostomum trigonocephalum, Oesophagostomum columbianum, O. venulosum and Trichuris ovis. Based on these findings, it is now possible to explore the possibility of using strategic treatments for the control of strongylosis in the study area. ii) Control experiments The persistent anthelmintic effect of closantel (CLO) plus albendazole (ABZ) mixture against common gastrointestinal nematodes (GIN) of goats was evaluated in 2 experiments. In the 1st experiment, the suppresion of strongyle egg output in faeces was examined in goats treated orally with either ABZ or CLO plus ABZ liquid suspension. Sixty goats with naturally acquired infections were randomly assigned to 3 groups of 20 goats each. The 1st group served as the untreated controls and the other groups received respectively single doses of 5 mg kg' body weight ABZ or CLO (10 mg kg') plus ABZ (5 mg kg:') orally. Faecal egg counts (FEC) and generic determination of third-stage larvae (Lj) were performed at weekly intervals, from the time of treatment (day 0) until week 7 post treatment. In the 2nd X experiment, a controlled trial was conducted in goats infected experimentally with GIN L, including a benzimidazole (BZ)-resistant isolate of H. contortus. Twenty-one goats were randomly assigned to 3 groups of 7 each and drenched with either ABZ (5 mg kg'), CLO (10 mg kg") plus ABZ (5 mg kg:'), or untreated controls. Ten days post treatment, goats were killed and necropsied for parasite recovery. Results revealed that a single dose of either CLOIABZ mixture or ABZ were highly effective (100 %) in suppressing faecal egg output up to 2 weeks post treatment, and FEC of CLOIABZ treated groups remained significantly lower than those of ABZ treated group up to 4 weeks post treatment (p < 0.05). CLOIABZ mixture was 99-100% effective against H. contortus, T. axei, T. colubriformis and O. columbianum. Efficacy of ABZ was poor for H. contortus (29%) but approached 100% for most of the other parasites. The results demonstrated an advantage of the CLOIABZ mixture over ABZ in that excellent anthelmintic efficacy persisted for 3 weeks after treatment in preventing establishment of GIN of goats and, was highly effective against a BZ-resistant isolate of H. contortus. In conclusion, the results of this study suggest that strongyle infections, especially haemonchosis, are major constraints to the health of goats of the study area. Most of the infections were subclinical and could indirectly cause production losses without attracting the farmer's attention to institute control measures. To increase the productivity of goats, helminthosis control should be based on epidemiological observations of an area before initiating strategic control programmes. Use of anthelmintic mixtures of different classes (i.e., CLOIABZ) is one such programme.