Prevalence and risk factors for Gastrointestinal nematode infection and efficacies of two anthelmintics in cattle in Mukurew-ini and Nakuru districts of Kenya
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This thesis describes a study that was carried out in Nakuru and Mukurweini districts to establish the prevalence of nematode infections in dairy cattle and to compare the efficacies of the anthelmintics, moxidectin and albendazole. In addition, the study identified the risk factors associated with nematode infection in dairy cattle and estimated the loss of milk production attributable to infections among smallholder dairy farms. The study was a cross sectional design (to determine the prevalence, establish the risk factors and to estimate the economic impact of helminth os is) and a field trial design (to establish and compare the efficacies of the anthelmintics). One hundred and twenty eight dairy farms were randomly recruited, 64 from each district. Faecal samples were collected from the rectum of 4] 9 heads of cattle that were above three months of age on the selected farms, refrigerated and delivered to the Department of Veterinary Pathology, Microbiology and Parasitology, Faculty of Veterinary Medicine, University of Nairobi, for nematode faecal egg counts using the McMaster method. On the first visit, questionnaires were administered on every farm to collect individual animal data and the farm management data. The cattle were allocated to three treatments groups (albendazole treated, moxidectin treated and placebo treated groups). This was done using a blocked random allocation method, with the first treatment picked using a simple random technique. A second sampling was done two weeks post treatment, with similar laboratory analysis (nematode egg count, McMaster method). Statistical analyses, using linear logistic regression were conducted to determine differences in prevalence of GIT nematode infections between districts, farm characteristics, animal characteristics, and treatment groups, controlling for clustering of cattle within farms. The prevalence in gastrointestinal tract (GIT) nematode infections in Nakuru and Mukurweini were 19.8% and 8.29%, respectively. The difference between the prevalence rates was significant (p< 0.05). The relative risk of infection was 2.32, showing that the risk ofthe infection was more than twice in Nakuru as compared to Mukurwe-ini District. The factors best explaining GIT nematode infections in dairy cattle in the final logistic regression model were the age of the animal, the duration from last deworming, the frequency of deworming and the kind of dewormer that was used last, source of pastures and availability of housing. The efficacy ofmoxidectin was estimated to be 95.8% while that ofalbendazole was 75%. Average daily milk production in litres of the helminth infected milking cows was 5.4 compared to 7.77 of the non infected cows. Generalized linear regression analysis, that controlled for the effects of breed, animal weight, parity, lactation stage and the amount of concentrates feed to the animals, estimated a difference of 1.4 Kg per cow per day. The difference was statistically significant (p < 0.05). The observed reduction in milk production translated to a daily loss of Ksh 28 per cow per day at a cost of Ksh 20/= per Kg, which was the average farm gate price of milk at study time in the area under study. In conclusion it is recommended that farmers be encouraged to deworm their animals at regular intervals, especially the younger animals which were considered more vulnerable. Improved housing and pasture management is also recommended as it may be cheaper in the long run.