DELRAY BEACH, Fla. -

A coop of chickens serve as the first line of defense against mosquito-borne diseases.

The Florida Department of Health tests the chickens twice a month for several diseases, including West Nile virus, St. Louis encephalitis virus, and equine virus.

"It's an early detection system," said spokesman Tim O'Connor.

The chickens don't get sick from those virus but they are carriers.

"When another mosquito bites them, they can get it and then pass it on to a person," said O'Connor.

Each chicken has an identification tag and workers carefully gather blood samples from their wings. The samples are then sent to a lab in Tampa for tests.

This year, positives tests were returned for encephalitis, resulting in a public alert to drain standing water, wear long-sleeved clothing, and use insect repellents.

"People really need to be aware these are out there, especially at late summer into the fall when the mosquito population is at its greatest," said O'Connor. "They run a greater risk."

There are six other coops in Palm Beach County. The state builds the coop, supplies the feed, and the chickens' caregivers keep the eggs.

"The people ask about that and they want eggs, so my husband gives somebody if they ask," said Magda Alvarado, who cares for the chickens.

"This is really one of the original programs," said O'Connor. "The chickens have always been like our first indicator and have been used for many, many years."

When a chicken tests positive for a virus, it's removed from the testing population and the caretakers can eat it.