Wuchereria bancrofti infection is associated with progression to clinical visceral leishmaniasis in VL- endemic areas in Muzaffarpur, Bihar, India.

BIHAR (India); INDIA

Background: Co-endemicity of neglected tropical diseases (NTDs) necessitates that these diseases should be considered concomitantly to understand the relationship between pathology and to support disease management and control programs. The aims of the study were to assess the prevalence of filarial infection in asymptomatic Leishmania donovani infected individuals and the correlation of Wuchereria bancrofti infection with progression to clinical visceral leishmaniasis (VL) in Bihar, India. Methodology/Principal findings: Within the Muzaffarpur-TMRC Health and Demographic Surveillance System (HDSS) area, a cohort of Leishmania seropositive (n = 476) or seronegative individuals (n = 1130) were sampled annually for three years for filarial infection and followed for progression to clinical VL. To corroborate the results from the cohort study, we also used a retrospective case-control study of 36 VL cases and 71 controls selected from a subset of the HDSS population to investigate the relationship between progression to clinical VL and the prevalence of filarial infection at baseline. Our findings suggest a higher probability of progression to clinical VL in individuals with a history of filarial infection: in both the cohort and case-control studies, progression to clinical VL was higher among filaria infected individuals (RR = 2.57, p = 0.056, and OR = 2.52, p = 0.046 respectively). Conclusion: This study describes that progression to clinical VL disease is associated with serological evidence of prior infection with W. bancrofti. The integration of disease programs for Leishmania and lymphatic filariasis extend beyond the relationship of sequential or co-infection with disease burden. To ensure elimination targets can be reached and sustained, we suggest areas of co-endemicity would benefit from overlapping vector control activities, health system networks and surveillance infrastructure. Author summary: India has committed to eliminate two neglected tropical diseases (NTDs) as a public health problem: visceral leishmaniasis (VL) and lymphatic filariasis (LF), both of which are transmitted by vectors and are caused by the parasites Leishmania donovani and Wuchereria bancrofti, respectively. Notably, the majority of L. donovani infections do not lead to a clinical event of VL and asymptomatic infections significantly outnumber the clinical cases. While mixed infections with Leishmania parasites and those causing lymphatic filariasis have been reported, the influence of the immune response triggered by filarial infection on the clinical manifestations and progression of both disorders is not well understood. The Muzaffarpur-TMRC Health and Demographic Surveillance System (HDSS) in Bihar is a well-established demographic platform in an area with the highest incidence of L. donovani infections in India which is also co-endemic for lymphatic filariasis. We used both cohort and case-control study designs within the HDSS population to assess the prevalence of filarial infection in blood samples and examine the association between filarial infection and the progression to clinical VL. Our findings strongly suggest there is an increased risk of progression to clinical VL in individuals with a history of infection with W. bancrofti: in both the study designs, progression to clinical VL was higher among filaria-infected individuals. These results highlight that the co-endemicity of these NTDs necessitates an integrated approach in diagnosis and disease management to ensure elimination targets can be achieved and sustained. [ABSTRACT FROM AUTHOR]

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