Wildlife officials at Spokane are investigating the cause behind the growing number of crow deaths in the area. Residents have been reporting seeing several crows dead or on the verge of in yards and roads for the past week for no visible reason.

"We just (thought) that it was really odd," Christine Cross from Millwood spoke of her experience. She had seen the crows in her backyard and on her way home from taking her son to school last Sept. 16. She is probably among at least a dozen who reported seeing dead crows in the Millwood area. She described that the crows appeared unharmed, but looked like they were seizing with their eyes rolled back.

"The Washington Department of Fish and Wildlife (WDFW) has received about a dozen reports of dead crows this week from residents in the Millwood area," said veterinarian Kristin Mansfield. With the death count running highter than average in the area, investigators are attempting to deduce what is causing them. Mansfield believes that the birds had been infected by a corvid retrovirus, though other experts are also considering the West Nile Virus.

This would not be the first time a high number of corvid viral infections has affected the U.S. Last 2006, an unusual number of crows and other corvids have been found dead in the Sacramento area. According to Center for Vectorborne Disease (CVEC) research epidemiologist William Reisen, the cause was a West Nile Virus epidemic.

"Corvids are more susceptible to the virus than other species of birds," Reisen explained. ""There's an amazing amount of virus in the bloodstream of infected crows, sometimes as much as 10 billion virus particles in one millimeter of blood." This, Reisen concluded, is what makes corvids excellent reservoirs or incubators of the virus.

Corvid retrovirus, from the name itself, is a viral infection that easily affects corvids like crows, ravens and jays but not humans. The West Nile Virus, on the other hand, can infect both humans and crows and is transmitted by an infected mosquito bite. According to the Center for Disease Control (CDC), about one out of five patients infected by the virus may develop flu-like symptoms such as fever, joint paints, body pain and a rash. Less than one percent may end up with serious neurologic illness.

Authorities are still unsure which between the two viruses is causing the crows' deaths. Currently, the WDFW is still in the middle of performing confirmatory tests and is looking for freshly dead crows or other corvids for study.

Image: Thomas Quine | Flickr

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