Prevalence of gastrointestinal parasites of sheep in semi-arid Rajasthan: a field study

Epidemiological pattern of a disease in a particular area can provide basis for evolving suitable and sustainable worm management strategy. The present communication describes the prevalence of GI parasites in field flocks reared under semi-arid conditions of Rajasthan. A total of 3964 faecal samples from sheep were examined for endoparasitic infection for the period from June 2004 to March 2010. The overall prevalence of GI parasites was 69.7, 1.6, 1.5, 3.8, 17.2, 0.1, 0.7 and 50.7% for strongyle, Trichuris spp., Strongyloides papillosus, Moneizia spp., amphistomes, Fasciola gigantica, Schistosoma indicum and Eimeria spp., respectively. Among positive cases, majority (55.1%) were found to harbour mixed infection while 29.4, 11.2 and 3.9% harboured single infection of strongyle, Eimeria spp. and amphistomes, respectively. The effect of year was found significant for the prevalence of Eimeria infection only. A significant influence of season (P<0.05) was observed on the prevalence rate of strongyle, amphistomes and Eimeria infection. Higher prevalence rate for strongyle and Eimeria infection was encountered during monsoon and post-monsoon (hot and humid climate) than summer (hot and dry) and winter (cold and humid) season. The monthly prevalence of strongyle infection remained at the lowest (47.0%) in March and in subsequent months rose gradually to reach at peak (84.3%) in October and then declined thereafter. The intensity of strongyle infection suggested existence of over-dispersion phenomenon in degree of infection. The proportion of samples possessing moderate to high level of infection increased significantly (P<0.05) to ~ 20% in monsoon compared to < 5% in winter and summer. The findings clearly indicated that if targeted selective treatment approach using anaemia chart could be applied then even during wormy season only 20 to 30% of animals possessing high level of infection required anthelmintic intervention in contrast to the present prevailing practice of en-mass treatment approach. Thus, there are ample scopes to curtail drench frequency as well as expenditure on worm management in flocks in order to preserve anthelmintic efficacy and maintain equilibrium of refugia in population for future.