Eastern Equine Encephalitis Virus in Ohio During 1991

Abstract

During August and September of 1991, an epizootic of eastern equine encephalitis (EEE) virus in horses occurred in Wayne and Holmes countries, OH. This was the first recorded epizootic of EEE virus in the state. Twelve horses were confirmed positive for EEE virus through virus isolation or seroconversion, and seven additional horses with compatible symptoms were in close spatial and temporal proximity to the confirmed cases and were presumed to have died from EEE virus. The outbreak was centered around the Killbuck Wildlife Area, a 2,147-ha tract maintained by the state, half of which consists of wooded swamp and marsh. Mosquitoes were collected in upland areas before the epizootic and in the swamp basin at the end of the epizootic to identify the mosquito species involved in EEE virus transmission. We collected and tested 22,095 specimens for the presence of virus. EEE virus was isolated from one pool of the most likely epizootic vector, Coquillettidia perturbans (Walker). The minimum infection rate for EEE virus in this species was 0.1/1,000. Dense populations of Aedes vexans (Meigen) and Culex salinarius Coquillett occurred in the area, but their densities peaked after the epizootic. It is unlikely that these species were involved in epizootic transmission. IgM antibody to EEE virus was detected in three bird species collected in the swamp.

Predicting seasonal abundance of mosquitoes based on off-season meteorological conditions

“…Aedes sollicitans is an major vector of Eastern equine encephalitis and Venezuelan equine encephalitis (O'Meara 1992) and has shown some potential as a vector for West Nile virus (O'Leary et al 2002, Turell et al 2001b. Culex salinarius is considered a bridge vector for Eastern equine encephalitis, St. Louis encephalitis and West Nile virus (Nayar et al 1986, Nasci et al 1993, Turell et al 2001a. Aedes sollicitans females lays eggs in the fall which enter diapause to endure the winter (O'Meara 1992), while C. salinarius is thought to overwinter as inseminated adult females that may even be periodically active (Slaff 1990).…”

Pre-West Nile Virus Outbreak: Perceptions and Practices to Prevent Mosquito Bites and Viral Encephalitis in the United States

“…These "arboviruses" (arthropod-borne viruses) exist in a intricate natural life cycle that involves nonhuman vertebrate hosts, such as birds, and arthropod vectors, such as a mosquitoes (Gubler 1996;Monath 1989). Female mosquitoes acquire the viruses while taking a bloodmeal (male mosquitoes feed on plant nectar) from vertebrate hosts and then transmit the viruses to other vertebrates, such as birds, horses, and humans, during subsequent blood feeding (Nasci et al, 1993;Nasci and Moore CG 1998). In some mosquito species, transovarial transmission occurs whereby viruses are passed to the female's eggs.…”

“…In some mosquito species, transovarial transmission occurs whereby viruses are passed to the female's eggs. The emergent mosquitoes are then infective without having taken a bloodmeal from a viremic host (Nasci et al 1993;Nasci and Moore 1998).…”

An Epizootic of Eastern Equine Encephalitis Virus, Maine, USA in 2009: Outbreak Description and Entomological Studies

“…Despite the abundance of mosquito vectors 32,33 and the primary habitat associated with EEEv, forested freshwater wetlands such as red maple or cedar swamps, EEEv activity has historically been rare, and when present, very focal. 34 Although the neighboring state of New Hampshire has seen increased EEEv activity in recent years, including several human cases (two of which resulted in death), they have been largely restricted to southern coastal regions. 35 Previously, EEEv activity has also been reported from southeastern Canada, in the provinces of Quebec.…”