Visceral Leishmaniasis in Rural Bihar, India

Epco Hasker¹

, Shri Prakash Singh¹, Paritosh Malaviya, Albert Picado, Kamlesh Gidwani, Rudra Pratap Singh, Joris Menten, Marleen Boelaert, and Shyam Sundar

Author affiliations: Institute of Tropical Medicine, Antwerp, Belgium (E. Hasker, A. Picado, J. Menten, M. Boelaert); and Banaras Hindu University, Varanasi, India (S.P. Singh, P. Malaviya, K. Gidwani, R.P. Singh, S. Sundar)

Abstract

To identify factors associated with incidence of visceral leishmaniasis (VL), we surveyed 13,416 households in Bihar State, India. VL was associated with socioeconomic status, type of housing, and belonging to the Musahar caste. Annual coverage of indoor residual insecticide spraying was 12%. Increasing such spraying can greatly contribute to VL control.

Visceral leishmaniasis (VL), a vector-borne parasitic disease caused by several Leishmania spp., is nearly always fatal if left untreated (1,2). The clinical syndrome is characterized by fever, weight loss, splenomegaly, hepatomegaly, and anemia. The disease is endemic in >60 countries, but 90% of all reported cases occur in just 5 countries: Bangladesh, Brazil, India, Nepal, and Sudan (3). On the Indian subcontinent, the disease is assumed to be an anthroponosis; the vector is a sand fly, Phlebotomus argentipes. Approximately 200 million persons on the Indian subcontinent are at risk for VL, and the annual incidence is ≈420,000 cases (4). The disease affects mainly poor rural communities; ≈80% of all cases in the region are reported from the state of Bihar in India (4).
Earlier studies on the Indian subcontinent have identified several risk factors for VL (5–11). At times, findings between studies have been conflicting, particularly in relation to the role of domestic animals (7). The use of bed nets was found to be protective in some studies (2,5), but this conclusion could not be confirmed in a recent cluster-randomized trial (12). Many of the earlier studies were conducted on fairly small populations, usually 1 or 2 villages (5,6,8,9); confounding by socioeconomic status was controlled to a varying extent. Most studies were conducted in high-incidence villages or in villages in which a recent outbreak had occurred. Because VL has a strongly clustered distribution, understanding the reasons behind widely varying incidence levels among villages and hamlets could also be useful. We therefore studied factors associated with VL in an area made up of villages with variable levels of VL incidence and constructed an asset index to control for confounding by socioeconomic status.