Challenges and Way Forward for Prevention of Resurgence of Visceral Leishmaniasis: A Four Years Community Based Study in Erstwhile Endemic Districts of West Bengal, India

Objectives The resurgence of Visceral Leishmaniasis (VL) is a natural cyclical phenomenon with an inter‐epidemic period of 10–15 years. It might be due to the persistence of a silent parasite pool amongst post kala‐azar dermal leishmaniasis (PKDL) and asymptomatic leishmanial infection (ALI). The present study targeted to find out the obstacles for unearthing and proper management of the hidden parasite pool for prevention of the resurgence of VL in erstwhile endemic districts of West Bengal, India. Methods Two strategies were employed to identify the latent parasite reservoirs: follow‐up of individuals having a previous history of VL and/or PKDL and limited mass sero‐surveillance within a 500‐m radius of recently treated VL and PKDL. Diagnosed PKDL and VL cases were treated and ALI were followed up. Results A total of 95 new PKDL and 70 relapse PKDL were diagnosed during the entire study period; those remained undiagnosed in spite of ongoing case searching methods recommended by the national VL elimination programme. ‘Relapse PKDL’—a new challenge for VL elimination has been identified. The incidence of PKDL declined steadily during successive study years. Limited mass survey revealed 17 VL, 2 PKDL and 124 ALI. Most of the ALI sero‐reverted during the follow up period and 2 of them converted to disease VL. Conclusions The present work revealed three major obstacles. First, identification of the occult parasite pool may be resolved by applying the searching methods used in this study. Second, case confirmation of ‘relapse PKDL’ may be achieved by examining slit skin samples at the local level by existing staff with proper training. Alternative short duration treatment strategy for the treatment of new and relapse PKDL is needed. Third, considering the long inter‐epidemic period and observed declining trend of incident PKDL, such surveillance should be continued for 10–15 years for the prolonged post‐elimination phase and finally to achieve eradication.