Detection of a case of Brugian Filariasis from Anuradhapura, a non-endemic district of Sri Lanka

Abstract

INTRODUCTION AND OBJECTIVES: In 2016, the WHO declared that lymphatic filariasis was no longer a public health problem in Sri Lanka. However low-grade persistence of bancroftian filariasis continues in all three endemic provinces, while brugian filariasis has re-emerged. The periodicity pattern of the re-emerged Brugia spp. suggests zoonotic origin. A canine survey done in the district of Anuradhapura found a moderately high prevalence (28.2%) of B. malayi infections in the Thirappane MOH area. Objective of the study was to investigate the threat of zoonotic B.malayi infections to humans in the Thirappane MOH area. METHODS: A cross sectional survey was done among all consenting residents of three randomly selected areas representing the three PHI areas of the Thirappane MOH. Residents were screened between 8.00 pm and 12.00 pm using night blood smears (NBS) and Brugia rapid test (BRT) for presence of anti-Brugia IgG4 antibodies. BRT was done selectively. Ethical and administrative clearance was obtained prior to the survey. RESULTS: A total of 752 individuals were screened by NBS; 176 of them were also screened by BRT. 193, 208 and 351 NBSs were done respectively in Thirappane, Galkulama and Mooriyankadawala PHI areas. One individual, a 25-year-old long-term resident of Mooriyankadawala PHI area was positive for Brugia spp. microfilariae by NBS and by BRT. The microfilariae exhibited nocturnal sub-periodicity. CONCLUSION: Transmission of brugian filariasis appears to occur even outside the traditional endemic belt. The presence of canine reservoirs of infection and water bodies with aquatic vegetation probably favour transmission by Mansonia spp. vector mosquitoes in the study area.