Twenty years of surveillance for Eastern equine encephalitis virus in mosquitoes in New York State from 1993 to 2012.

backgroundThe year 1971 was the first time in New York State (NYS) that Eastern equine encephalitis virus (EEEV) was identified in mosquitoes, in Culiseta melanura and Culiseta morsitans. At that time, state and county health departments began surveillance for EEEV in mosquitoes.

methodsFrom 1993 to 2012, county health departments continued voluntary participation with the state health department in mosquito and arbovirus surveillance. Adult female mosquitoes were trapped, identified, and pooled. Mosquito pools were tested for EEEV by Vero cell culture each of the twenty years. Beginning in 2000, mosquito extracts and cell culture supernatant were tested by reverse transcriptase-polymerase chain reaction (RT-PCR).

resultsDuring the years 1993 to 2012, EEEV was identified in: Culiseta melanura, Culiseta morsitans, Coquillettidia perturbans, Aedes canadensis (Ochlerotatus canadensis), Aedes vexans, Anopheles punctipennis, Anopheles quadrimaculatus, Psorophora ferox, Culex salinarius, and Culex pipiens-restuans group. EEEV was detected in 427 adult mosquito pools of 107,156 pools tested totaling 3.96 million mosquitoes. Detections of EEEV occurred in three geographical regions of NYS: Sullivan County, Suffolk County, and the contiguous counties of Madison, Oneida, Onondaga and Oswego. Detections of EEEV in mosquitoes occurred every year from 2003 to 2012, inclusive. EEEV was not detected in 1995, and 1998 to 2002, inclusive.

conclusionsThis was the first time in NYS that EEEV was detected in Cx. salinarius, Ps. ferox and An. punctipennis. The detection of EEEV in mosquitoes every year for 10 years was the longest time span since surveillance began in 1971. The calendar date of the earliest annual appearance of EEEV in mosquitoes did not change during surveillance spanning 42 years.