Assessment of risk factors for transmission of malaria in Ampara and Batticaloa Districts in Sri Lanka

Abstract

Malaria is a major public health concern in the world. Sri Lanka has achieved a significant reduction in malaria incidence since 2000. Anopheles culicifacies (Giles) complex is well established as the predominant vector of malaria in Sri Lanka. Anopheles subpictus is considered as the secondary vector in Sri Lanka. Assessment of the risk factors for transmission of malaria and sibling species complex of An. culicifacies have not been studies in Ampara and Batticaioa district in Sri Lanka due to the situation in the country during the past three decades. The current study was carried out in above two districts from March 2011 to August 2012. Adult mosquito collection using Cattle Baited Hut Trap, Cattle Baited Net Trap, Window Trap, Hand Catch and Larval Surveillance were carried out on a monthly basis in 28 localities of Ampara and Batticaioa Districts while monitoring the climatic factors correlate with the Anopheles density variations. A sociological survey was also carried out in above 28 localities to assess the risk factors for malaria. An. culicifacies samples collected from the study were checked for their sibling species status based on mitochondrial CO II subunits using Polymerase Chain Reaction method. Results showed that even though An. culicifacies recorded was with low density An. subpictus was recorded with a high density in both Districts. Among the climatic factors, rainfall significantly correlated with the anopheline density in both districts. Also it was revealed that the people in the area have been ignoring malaria due to its low transmission. Sibling species status of the An. culicifacies needs to be studied further in order to determine whether there is new sibling species of An. culicifacies. Continuous entomological surveillance should be done in order to monitor the malaria vector prevalence in the area. People in the area should be educated on malaria particularly about the possibility of migrant populations from malarious countries reintroducing parasite to the country. Malaria vector control measures should be implemented based on the rainfall pattern in the area since the vector continues to breed in usual breeding sites which are clear stagnant water collections.