West nile virus surveillance in humans and mosquitoes and detection of cell fusing agent virus in Vojvodina province (Serbia)

Abstract

After the large 1996 outbreak of West Nile virus (WNV) in Romania and spreading from East (1999) to the West Coast (2002) of USA at a remarkable speed, WNV has, in 2010, reemerged in Europe causing outbreaks in human populations reported from Greece, Hungary, Italy, Romania and Russia. Surveillance of WNV in humans and mosquitoes by enzyme-linked immunosorbent assay, rapid antigen panel assay, virus isolation in Vero cells and real time polymerase chain reaction assay was carried out from 2005 to 2010 in Vojvodina Province, northern Serbia. Human sera samples were collected from 27 persons with viral meningitis or encephalitis disease history or from 18 persons with acute viral meningitis or encephalitis and 406 randomly chosen healthy persons from Vojvodina Province. Mosquitoes were sampled in bird reservoirs and human settlements by dry ice-baited traps. IgG antibodies were found in 18 out of 451 (3.99%) human sera with yearly rates varying between 1.97% and 6.04%. Viral RNA was detected in 6 out of 841 pools made out of 56757 sampled, identified and pooled mosquito specimens. In three pools of Aedes vexans sampled in 2005, RNA sequences related to cell fusing agent virus (CFAV) were detected. Data obtained from serological surveillance in 2009 were used to indicate "hot spots" of possible WNV transmission in urban area of Novi Sad (capital of Vojvodina Province) where mosquito trapping was focused during the next year. In 2010, three out of 50 pools of Culex pipiens sampled in "hot spot" areas were positive for WNV RNA. Both CFAV and WNV detections in mosquitoes are the first records of such type in Serbia.