Spatio-temporal distribution of bovine leptospirosis in Tamil Nadu and a risk factor analysis.

Leptospirosis is a bacterial zoonotic disease that causes abortions, infertility and mastitis in cattle. This research was aimed at investigating the temporal and spatial pattern, sex, age, breed wise distribution of leptospirosis in Tamil Nadu. A seroreactivity of 28.2% was noticed among cattle in seven agro-climatic zones. The temporal trend of leptospirosis recorded during the post-monsoon season (30.5%) was significant when compared to the pre-monsoon season (25.8%). The spatial distribution revealed a high proportion of leptospirosis (31.2%) in the North East zone in comparison with the other zones. The serogroups Australis (37.9%), Hebdomadis (30.6%), Hardjo (29.9%), Javanica (28.1%) and Pomona (19.7%) were predominant in all the agro-climatic zones. The observation of 44.2% seroreactivity in buffaloes is most probably associated with the wallowing behaviour. A high seroreactivity of 31.1% in Holstein Friesian than that compared with the native breed discloses a breed susceptibility. A seroreactivity of 30.2% in animals aged above three years shows an age-related susceptibility, but there was no significant difference between the sexes. The seroreactivity among the animals in an organised farm (33.8%) is higher than in individually reared animals (25.5%) indicating the impact of the rearing system. The three Leptospira strains isolated were identified as the serogroup Australis, Canicola and Sejroe. This study depicted the epidemiology of leptospirosis in cattle and emphasises the need of leptospirosis to be included in cattle health surveillance programmes.