Entomological surveillance and detection of dengue viruses in vector mosquitoes as an early warning tool for the control of dengue in Pakistan

Dengue viruses are transmitted through the bites of female Aedes mosquitoes to human mostly in urban areas of tropical/sub-tropical countries. Dengue epidemics are annually occurring in Pakistan since 2006.  Recently in 2011 dengue became severe epidemic in province Punjab, where >15000 positive cases and >7300 deaths occurred, especially in the highly populated urban city of Lahore. With neither vaccine nor proper treatment for dengue, prevention of the disease depends upon the surveillance and early diagnosis/detection of dengue virus antigens from mosquito vectors which will serves as early warning system for forecasting impending outbreaks. In current study 35 entomological surveys were carried out in various localities of Lahore from March-November, 2011-2012 for the collection of Aedes mosquitoes. Two species Aedes aegypti and Aedes albopictus were found common during this period. However, Aedes aegypti were present throughout these months while Aedes albopictus appeared in the months of July-August, 2011. In addition various types of natural and artificial breeding containers were also observed for immature stages of Aedes mosquitoes in all localities visited during above mentioned period. The most productive containers were automobiles used tyres for larval production with 94% positivity. Collected mosquitoes were screened for dengue viruses using dengue specific monoclonal antibodies (MAB) as antigen capture Enzyme Linked Immunosorbant Assays (ELISAs). Of the 114 pools of Aedes aegypti females (n=570) screened, 31 pools were found positive for dengue viruses indicating 27.19% infection rate (MIR). However, of the 04 pools of Aedes albopictus females (n=20) screened; only 1 pool was found positive with 25% infection rate (MIR). This is the first report of DENV detection from adult females of Ae. aegypti and Ae. albopictus collected from different localities of Lahore, Pakistan.