Dormant parasite hit Florida wild deer

BIG PINE KEY, FLA. •The first signs seemed baffling: deer stumbling around in confusion, howling in pain, found with their heads hideously disfigured — as if eaten alive.

What biologists discovered turned out to be even more frightening: the reappearance of a parasite known as the New World screwworm fly that had not been seen in the United States since the 1970s and had been considered eradicated.

State and federal officials are hopeful that the infestation, restricted to Florida’s southernmost Monroe County, is being controlled. Symptoms were first reported in wild deer in July, and laboratory tests in late September confirmed the presence of the screwworm, which is the larva of the screwworm fly.

The infestation has the potential to cause catastrophic damage to livestock and is being seen by some experts as a reminder of the challenges of controlling the spread of diseases and infestations.

“In the very big picture, this is just the latest example of our failure to adequately protect people, agriculture and the environment from consequences of a shrinking world, an interconnected word,” said Adam Putnam, Florida’s commissioner of agriculture. “Millions of cargo containers and millions of passengers arrive every year, entering and exiting Florida and bringing unwelcome pests and disease with them.”

In July, Florida Key deer, the smallest subspecies of the white-tailed deer, started turning up with grotesque wounds. The tiny deer are the last of their kind — only about 875 remain — and live at a federal refuge in the Florida Keys that was established to protect them in 1957.

Eight deer died in July and August, and 11 more died during the September mating season. Refuge managers at first thought the injuries were abscesses caused by males puncturing one another with their antlers during the rut, when they fight for dominance. Employees at the refuge, many of whom were not even born the last time the screwworm was found in the U.S., had never seen anything like it.

In all, about 15 per cent of the existing endangered Key deer herd — 132 animals — have died since July. Infections were also found in two stray cats, a dog and a pet pig. Officials worry that if the screwworm spreads to ranches and farms, it could cause up to US$1 billion in losses.

Native to South America, it first appeared in the U.S. in the 1800s. Screwworms are larvae laid by flies in the open wounds of an animal, where the larvae feed on flesh. The fly is bigger than a common housefly, with orange eyes and a metallic dark blue or grey body with three dark stripes down its back.

An animal quarantine was imposed by officials in Florida in early October, and an agricultural emergency was declared to avoid the spread of the parasite.

An infestation in the southeastern U.S. from the 1930s to the 1950s caused US$20 million a year in livestock losses and took 20 years to eradicate, according to the U.S. Department of Agriculture.