Four-week-old weaned pigs are susceptible to West Nile virus infection from a fairly small dose of virus carried by mosquitoes, says Iowa State University veterinary microbiologist Kenneth Platt.

“There’s enough virus in that blood that I wouldn’t want to cut myself with a knife that just went through there,” he explains. Susceptibility to the virus appears to wane, as the pigs grow older. But more research will be needed to determine the risk to market age hogs and consequently to packing plant workers.

Platt says it doesn’t look like the virus is spread from pig to pig. “In our observations, we’ve had infected and uninfected pigs in the same pen in intimate contact, and we saw no evidence of transmission from pig to pig.”