US scientists turn to chickens to sound the alarm as West Nile cases rise

Chickens - which can test positive for viruses but cannot spread them - an ideal early warning system for mosquito-borne disease

The start of West Nile virus transmission began unusually early in some US states, with the most cases in early summer since 2004, the US Centers for Disease Control and Prevention (CDC) warned in July - so Delaware turned to chickens.

They kind of are the proverbial canary in the coal mine," said Tom Moran, head of the mosquito control section at the Delaware department of natural resources and environmental control.