Influence of annual rainfall on epidemiology of gastrointestinal parasites in sheep flocks of Rajasthan

Abstract

The translation of exogenous stages of gastrointestinal (GI) parasites varies according to climatic variables like temperature, rainfall and humidity. The present paper describes the influence of quantum of annual rainfall on the prevalence and intensity of GI parasites in field flocks of sheep in Rajasthan. The period of 9 years (2004-13) was divided in 3 categories as years with above normal, normal and below normal annual total rainfall (TRF). Faecal samples (59,398) were subjected to qualitative and quantitative evaluation and data on monthly incidence and intensity were analyzed according to categories of years. The effect of annual TRF was significant on incidence of strongyle worms for all the months except during June in semi-arid and April in arid region. During August to December (favourable season), it was higher in the years with below normal TRF in semi-arid and in the years with normal annual TRF in arid region. The incidence of Trichuris spp, Strongyloides papillosus, Fasciola gigantica and Schistosoma indicum was very low. Incidence of S. papillosus was higher in the years of normal annual TRF in semi-arid region only. The incidence of Amphistomes remained lowest in the years of normal annual TRF. Higher annual TRF resulted in lower monthly incidence of Moneizia infection. The intensity of strongyle infection for all the months was significantly lower in years with above normal annual TRF in semi-arid region however similar influence was noticed only for July and August in arid region. It was inferred that moderate flexibility in single drench schedule according to magnitude of annual rainfall effectively managed the GI nematodes in field flocks of Rajasthan. However, a different strategy is required to formulate for management of flukes depending on quantum of rainfall, availability of water reservoirs and water resources for flocks.