Wednesday, January 13, 2010

West Nile Virus and your cat -- what you need to know

Title: The pathogenesis of West Nile virus in dogs, cats, and house sparrows
Author(s): Austgen, Laura E.
Degree: Ph.D.
Year: 2003
Pages: 00124
Institution: Colorado State University; 0053
Advisor: Adviser Richard A. Bowen
Source: DAI, 64, no. 12B (2003): p. 5911
Abstract: In the 1990s, a more aggressive and neurovirulent form of West Nile virus (WNV, family Flaviviridae, genus Flavivirus, species West Nile virus) emerged that has caused morbidity and mortality in human beings, horses, and most severely, a large number of avian species. This work explores the replication of WNV in three species: dogs and cats, of potential import due to their close association with human beings; and house sparrows, significant avian hosts of WNV. Domestic dogs and cats were infected by mosquito bite. Each of four dogs developed a viremia of low magnitude and short duration, but did not display signs of disease. Twenty-one of 23 cats became viremic, with peak titers from 101.0 –104.2 plaque forming units/ml. Several cats showed mild, non-neurologic signs of disease. WNV was not isolated from saliva of any of the dogs or cats tested. An additional group of four cats were exposed to WNV orally. Two cats consumed an infected mouse on three consecutive days and two cats consumed one infected mouse. All of these cats developed viremia with magnitude and duration similar to that seen in cats infected by mosquito bite, but none showed clinical signs. These results suggest that dogs and cats are readily infected by WNV, and that infected prey animals may serve as an important source of infection to carnivores. The magnitude of viremia measured in dogs and cats indicates that neither species is likely to function as an epidemiologically-significant amplifying host, although the peak viremia observed in some cats may infect mosquitoes at low efficiency.

Passer domesticus, the house sparrow, is thought to have key importance in the amplification and maintenance of WNV. To gain understanding of the pathogenesis of WNV in this host, virus isolation was performed at intervals on a battery of tissues obtained from experimentally infected birds. WNV rapidly established disseminated infection with wide tissue tropism. Skin was the tissue from which virus was most consistently isolated, and was also the first in which WNV was detected—as early as 12 hours postinfection. Other tissues frequently containing virus included blood, heart, lung, liver, kidney, and testis.


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