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Date: Tues, 17 Sept 2002
Posted by: Lois Levitan (lcl3@cornell.edu)

Del Wilmot, Deputy State Veterinarian at the Nebraska Department of Agriculture, Bureau of Animal Industry, posted information about WNV in sheep and goats in Nebraska to ProMed-mail Sept 13 and 16 http://www.promedmail.org.

Dr. Wilmot (delwindw@agr.state.ne.us) reported that the Lincoln Veterinary Diagnostic Laboratory of the University of Nebraska announced Sept 13 2002 that samples from a mountain goat and a sheep were found to be WNV-positive by "the Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) test for WNV. The samples were also positive by immunohistochemistry for WNV. The PCR results were confirmed at National Veterinary Services Laboratory (NVSL) and virus isolation results are pending at NVSL."

The animals were tested because they showed signs of illness:

The 6-year-old Suffolk ewe was located in a small farm flock in NE Nebraska. "When first noticed she was febrile (104 to 106 degrees F), with hind-limb paralysis and progressed to convulsions. She died 2 days after onset of clinical signs and was the only animal in a small farm flock that showed any clinical signs. The Rocky Mountain goat flock is located in [N Central Nebraska]. The flock consisted of 12 head of males and females, that ranged in age from 16 months to 2 years age. During a 2-week period, 7 of the goats showed neurological signs and died. Clinical signs included horizontal nystagmus, ataxia, head tilt, and lateral recumbency. The 5 remaining goats did not show any clinical signs."

Fatal illness in the sheep and mountain goat flock appear to distinguish this incidence of WNV from the serological evidence of WNV detected in NJ in black bears (3 of 51 samples) and white-tailed deer (7 of 689 samples) by a research team from Rutgers University earlier this year. The abbreviated Rutgers report to ArboBytes listserv (reprinted on WestNileVirus-L July 23, 2002) did not imply or report evidence of disease in these animals.*

The ecological and epidemiological significance of detecting WNV infection in wildlife/domestic animals is unclear:

In the East Coast outbreaks of WNV there were very limited reports of illness caused by WNV in mammals other than human beings and horses (e.g., a rabbit in NYS in 2000). A few animals already in distress from other causes have been affected (e.g., a stray cat found in a sewer), but considered anomalies.

Evidence and expert judgement have both suggested that mammals are dead-end hosts of WNV (i.e., unlike some species of birds, mammals are not known to build up sufficient levels of virus in their blood to infect mosquitoes that bite them). This is supported by research reported in the April 2002 issue of "Emerging Infectious Diseases," which concludes that "horses infected with WNV develop viremias of low magnitude and short duration and that infected horses are unlikely to serve as important amplifying hosts for WNV in nature." (full text: http://www.cdc.gov/ncidod/EID/vol8no4/01-0239.htm). However, we are not aware of similar recent research on other species.

News about WNV infection/disease in mountain goat, sheep, deer, black bear, and increasing numbers of game birds--together with the recent evidence that WNV may be transmitted in blood, and with increasing discussion about other animal diseases that can affect people--is likely to raise public concern about risks of consuming meat from WNV-positive livestock and game animals. (I have received a number of inquiries along these lines.)

Does anyone know if there have been research or statements from any of the agencies responsible for food safety/animal industry with regard to these concerns of hunters and others about potential for WNV transmission through food consumption and/or animal handling?

* See: http://www.cfe.cornell.edu/ERAP/WNV/WNV-LArchive/7-23-02c.html

-- 
Lois Levitan, PhD       Program Leader
Environmental Risk Analysis Program
Center for the Environment
213 Rice Hall, Cornell University
Ithaca, New York USA 14853-5601

Phone:   (607) 255-4765     Fax: (607) 255-0238
Email:	LCL3@cornell.edu

Program Email: envrisk@cornell.edu
Web:http://www.cfe.cornell.edu/ERAP

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