Prevalence of Bancroftian filariasis in Burdwan District, west Bengal: a comparative study between colliery and non-colliery areas.

The present study reports results of a survey of bancroftian filariasis in Burdwan district West Bengal. 85,974 persons were examined of which 46,221 were inhabitants of the colliery areas of the district and rest 39,753 were from non-Colliery areas, including urban and rural areas of the district. The clinicopositivity, endemicity, microfilaria(mf)-positivity, mf-clinicopositivity, and mf-density were determined. It was found that all these epidemiological and parasitological parameters were significantly higher in the colliery area as compared to non-colliery area. The high vector density in the colliery area may account for such significantly higher prevalence of filariasis in this area. From a differential count of neutrophils, eosinophils and lymphocytes in the mf-positive cases, it was revealed that neutrophil percentage was significantly (P < 0.01) decreased while eosinophils and Lymphocytes increased. The decrease of neutrophils was correlated ((Correlation co-efficient, r = -0.78) with the increase of lymphocytes, indicating an imbalance in the immune-system of the infected persons. The geographical and geological factors resulting in high vector density are considered responsible for the significantly higher rate of bancroftian filariasis in the Colliery area.