Surveillance for arthropod-borne viral activity in Nebraska, 1994-1995

A 2-yr arbovirus surveillance program was established in Nebraska following the midwest flood of 1993. CDC light traps were used to collect mosquitoes at 11 localities throughout Nebraska. In 1994, we collected 685,582 mosquitoes, and we tested 1,359 pools of Culex mosquitoes for arbovirus infection, with St. Louis encephalitis virus isolated from 2 pools collected in Scotts Bluff County in western Nebraska. In 1995, 1,163,741 mosquitoes were collected and 2,788 pools tested, with 36 positive for western equine encephalomyelitis (WEE) virus. Thirty of the WEE-positive pools were collected in Scotts Bluff County, 4 pools from the city of Norfolk and 2 from the city of Grand Island. All viruses were isolated from Culex tarsalis Coquillett. The highest minimum infection rate of 3.81 per 1,000 mosquitoes was observed in Scotts Bluff County on 13 September 1995. The seasonal minimum infection rate for WEE was 0.52 in Scotts Bluff County. No human or horse disease attributed to arboviral infection was reported in Nebraska during 1994 and 1995.