Abstract:
Five rounds of Mass Drug Administration (MDA) with Diethylcarbamazine plus
Albendazole were distributed by the Anti Filariasis Campaign (AFC) nearly to ten
million people in eight districts of Sri Lanka between 2002 and 2006. The risk of
lymphatic filariasis (LF) to humans is rapidly changing due to unplanned
urbanization, increased movement of people, environmental changes, and biological
challenges such as vectors resistant to insecticides and evolving strains of pathogens.
This study was aimed to assess the entomological risk factors of LF transmission in
endemic and non-endemic areas in the District of Galle, Sri Lanka. According to the
night blood films records and mosquito Xenomonitoring records, Balapitiya,
Ambalangoda, and Hikkaduwa Medical Officers of Health (MOH) areas were
selected as the main endemic MOH areas and Baddegama and Gonapinuwala were
selected as the non-endemic MOH areas in Galle district. Entomological
surveillances were conducted on a monthly basis for a period of 05 months from
October 2021 to February 2022 in endemic and non-endemic areas using two
standard field collection techniques named Human Landing Catches (HLC) and
Gravid Traps (GT). Collected mosquitoes were morphologically identified using
stranded taxonomic keys. The DNA was extracted from detected nematodes and PCR
was conducted for all positive samples. A total of 4057 mosquitoes were during the
study period. Culex quinquefasciatus (80.7%) was the prominent mosquito species
followed by Armigerus subalbatus (9.9%), Mansonia uniformis (3.3%) Mansonia
annulifera (1.9%) and other 7 mosquito species (4.2%) were detected. Mansonia
uniformis, Mansonia Annulifera, Armigerus sabalbatus, and Culex quinquefasciatus
were positive for microfilaria in very low persistency at 0.156%, 0.026%, 0.0074%,
and 0.00092% respectively, while other mosquito species were negative for any
microfilariae. Brugia malayi was the prominent LF nematode identified from
mosquitoes while Wuchereria bancrofi and Dirofilaria repens were identified from
mosquitoes. Wuchereria bancrofti were identified from Cx. quinquefasciatus and
Brugia malayi microfilaria were detected from Mansonia uniformis and Mansonia
Annulifera. In addition, Dirofilaria repens microfilariae were detected from
Armigerus Subalbatus. The current findings facilitate decision-making in the national
filariasis vector control programmes. Knowledge of the distribution and risk areas of
filariasis vector mosquitoes will be important for controlling filariasis transmission
in the risk areas of the country.
