Prevalence of anti-leptospiral antibodies and frequency distribution of Leptospira serovars in small ruminants in enzootic South Peninsular India.

Abstract

Background and aim For understanding the epidemiology of leptospirosis, the confined abundance of several species of pathogenic leptospires and knowledge on the serovar(s) prevalent in the reservoir and carrier hosts may be a useful indicator of transmission to incidental or accidental hosts in a geographical niche. The present study was carried out to ascertain the frequency distribution of Leptospira serovars and the prevalence of anti leptospiral antibodies in small ruminants (sheep and goats) in the epidemiological units (villages) in the coastal districts of enzootic regions in South Peninsular India. Materials and methods A total of 1167 serum samples (sheep 299 and goats 868) from apparently healthy animals, randomly collected from various epidemiological units were tested in microscopic agglutination test (MAT) using 18 reference Leptospira serovars antigens. Results The overall seroprevalence of 40% (at 95% confidence intervals 36.82 to 42.43) in small ruminants (44% at 95% confidence interval 40.49 to 52.26) in sheep and 38% (95% confidence interval 34.96 to 41.41) in goats was observed with the predominance of Icterohaemorrhagiae, Javanica, Australis, Hurstbridge, and Pyrogenes serogroup anti leptospiral antibodies in the studied region. The Chi squared test revealed that the presence of anti leptospiral antibodies is significantly not independent (associated) across the administrative division (Chisquare 105.80 p less than 0.05) as well as for sheep (Chisquare 34.67 p less than 0.01) and goats (Chi square 68.78 p less than 0.01). Among seropositive samples (462 reactors), the MAT was positive for more than one serovar in 73% of sheep (95 out of 131) and 53% of goats (177 out of 331), representing an overall 59% cross reactive prevalence in small ruminants. The determined frequency distribution (varied among small ruminants) of the employed serovars representing major reactive serogroup was Icterohaemorrhagiae (29.87), Javanica (20.78), Australis (20.35), Hurstbridge (16.23), Pyrogenes (15.8), Djasmin (15.58), Bataviae (15.37), Autumnalis (14.5), Canicola (14.5), Hebdomadis (14.07), Shermani (13.64), Panama (13.42), Sejroe (12.77), etc. Conclusion: This study indicates alarmingly high seroprevalence of leptospirosis in small ruminants with existing endemicity in the studied region in South Peninsular India. Further, these prevalent serovars in the administrative division may be of use in the reference panels of antigens in the MAT in both humans and animal disease diagnostic laboratories for effective and timely diagnosis of leptospirosis and to combat the challenges in public health.