An interesting new study sheds some light on one of the saddest parts of the invasion of West Nile into the USA–mass death of birds.

“Stable flies are the latest suspect that may be involved in the West Nile virus deaths of hundreds of pelican chicks at the Medicine Lake National Wildlife Refuge in northeast Montana. West Nile virus killed 800 to 1,000 pelican chicks in 2003, averaged 400 in each of the next three summers and more than 600 this year.”

Stable flies are what make this research a surprise –they weren’t known to munch on birds until this study:

“This is the first report of stable flies feeding on wild birds, or pelicans for that matter, and the first report of stable flies infected with West Nile virus,” Johnson said. “These results suggest that stable flies might be involved in amplification and/or transmission of West Nile virus at the pelican colony and possibly could serve as a vector of West Nile virus to other pelicans.”

When I interviewed for my new job a couple of weeks ago, I had a tour of their bird sanctuary. They had a horned owl and a screech owl that were both sick, and had been picked up and brought to the sanctuary to see if they would recover.

The sanctuary folks said most of them do not make it.

Because stable flies are a known horse pest, this could also signal that the transmission of the disease to horses is much more likely. Both horses and birds are used as sentinel species to monitor spread and growth of the disease.

  • More about stable flies
  • An article in Nature about the declines of bird populations due to WNV (Free news site with same info if you don’t have journal access)
  • Details about the Disease from the CDC, including a list of the 317 bird species in which the disease has been reported.

At this time, there is no treatment for birds infected with the disease, other than to put them in a safe place and hope for the best. I haven’t found info on whether they are then immune from further infections, although it does seem that once recovered, the virus is cleared from their blood and they are no longer infective.

Posted by Gwen Pearson

Writer. Nerd. Insect Evangelist. Have you heard the good news? BUGS!