Venezuelan Equine Encephalitis Virus Infection of Spiny Rats

Abstract

Enzootic strains of Venezuelan equine encephalitis virus (VEEV) circulate in forested habitats of Mexico, Central, and South America, and spiny rats (Proechimys spp.) are believed to be the principal reservoir hosts in several foci. To better understand the host-pathogen interactions and resistance to disease characteristic of many reservoir hosts, we performed experimental infections of F1 progeny from Proechimys chrysaeolus collected at a Colombian enzootic VEEV focus using sympatric and allopatric virus strains. All animals became viremic with a mean peak titer of 3.3 log10 PFU/mL, and all seroconverted with antibody titers from 1:20 to 1:640, which persisted up to 15 months. No signs of disease were observed, including after intracerebral injections. The lack of detectable disease and limited histopathologic lesions in these animals contrast dramatically with the severe disease and histopathologic findings observed in other laboratory rodents and humans, and support their role as reservoir hosts with a long-term coevolutionary relationship to VEEV.

Venezuelan encephalitis emergence mediated by a phylogenetically predicted viral mutation

“…Additional selective forces on the RNA genome sequence related to genomic or subgenomic RNA replication, secondary structure, and͞or packaging could complicate the selection of such mutations in nature and should be studied further. A population size of 10 4 is exceeded in infected mosquitoes, which generally develop titers of Ϸ10 6 infectious units, including Յ10 4 in the saliva (40,41) and in reservoir hosts such as spiny rats (42,43) and cotton rats (42,44), which develop peak viremia titers exceeding 10 4 infectious units͞ml. This finding suggests that ecological factors including transport of nascent epidemic strains to locations conducive to equine amplification, as well as epidemiologic and ecologic factors including equine herd immunity and mosquito densities, constrain the frequency of VEE epidemics rather than the generation of amplification-competent mutants.…”

Experimental Infection of Potential Reservoir Hosts with Venezuelan Equine Encephalitis Virus, Mexico

“…In this study, 5 of the most commonly captured rodent species in coastal Chiapas, Mexico, were evaluated for their ability to participate in the natural transmission cycle of enzootic VEEV-IE. S. hispidus and O. capito rodents have previously been implicated in amplifi cation of other VEE subtypes, ID, IE, and II (7)(8)(9) Figure 3. Relatedness of 7 wild rodent genera that have been experimentally evaluated for suitability as amplifying hosts in enzootic transmission cycles of Venezuelan equine encephalitis virus.…”

“…These viruses are thought to circulate continuously among mosquitoes and their principal vertebrate amplifying hosts, whereas horses and humans are considered spillover, dead-end hosts not required for maintenance of the natural cycle. Several studies have shown that terrestrial mammals of 5 genera (Didelphis, Oryzomys, Proechimys, Sigmodon, and Zygodontomys) are susceptible to VEEV-IE infection; they develop viremia suffi cient to infect mosquito vectors, yet they usually survive infection (5)(6)(7)(8)(9)(10).…”

Night and crepuscular mosquitoes and risk of vector-borne diseases in areas of piassaba extraction in the middle Negro River basin, state of Amazonas, Brazil

“…Cx. vomerifer was found to be infected with certain arboviruses such as Caraparu (Brazil, Panama), Guama (Colombia, Peru), Itaqui (Brazil, Venezuela), Moju (Venezuela), Murutucu (Belém), Ossa (Panama), Ananindeua, Vinces, Madrid and other types of Bunyaviridae (Shope et al 1988, Walter Reed Report 1998, Carrara et al 2005. Cx.…”