Florida residents should be vigilant for signs of screwworm on livestock and pets, UF experts say

Adult horses grazing in a pasture at the Horse Teaching Unit.
Adult horses grazing in a pasture at the Horse Teaching Unit.

GAINESVILLE, Fla. — Screwworms infecting wild deer in the Florida Keys have captured headlines, and experts with the University of Florida Institute of Food and Agricultural Sciences and UF’s College of Veterinary Medicine say livestock and pet owners in Peninsular Florida should keep a watchful eye for signs of infection in their animals, to aid in the eradication effort.

Florida residents who own cattle, horses, goats, sheep, dogs, cats, poultry, exotic birds or other warm-blooded animals should know the symptoms animals exhibit when infected by the larvae of the New World screwworm fly, said Jack Payne, Ph.D., UF senior vice president for agriculture and natural resources.

“We have every reason to believe that the current outbreak will be contained and eradicated,” Payne said. “Our UF/IFAS Extension Monroe County office is doing a terrific job of informing residents and interfacing with all the key players, there are relatively few livestock animals in the Keys, and the eradication effort uses proven, effective methods. Having said all that, we need state residents to provide an extra measure of protection, just by observing their animals.”

James Lloyd, D.V.M., Ph.D., dean of the UF veterinary college, explained that screwworm infestations occur when an adult female screwworm flies lays eggs on an open wound or mucous membranes in a warm-blooded animal. When the eggs hatch, screwworm larvae burrow into the host animal’s flesh to feed. Infestations can strike otherwise healthy animals, he noted.

“The symptoms of a screwworm infestation might include a festering wound or sore or an unexplained lump under the skin, particularly if there’s a discharge or foul smell associated with it,” Lloyd said. “Also, you may observe fly larvae on the animal or in its quarters.”

Any animal with a suspected screwworm infection should be evaluated by a veterinarian immediately, said Wendy Mandese, a clinical assistant professor with the UF veterinary college’s Department of Small Animal Clinical Sciences.

“Open wounds and unexplained lumps can indicate serious health issues other than screwworm infection, so the key point is to get treatment for the animal as soon as possible,” Mandese said.

Time is of the essence from an entomological perspective as well as a veterinary one, because delayed treatment gives screwworm larvae more time to develop and cause damage to the host animals, said veterinary entomologist Phil Kaufman, an associate professor with the UF/IFAS Entomology and Nematology Department.

“The pest we’re talking about, the New World screwworm fly, Cochliomiya hominivorax, is not something you can ignore, because there’s no such thing as a tolerable infestation,” Kaufman said. “The larvae of this species consume healthy tissue – they create wounds. They are also capable of burrowing deep into the host’s body tissues to reach previously uninfected areas. Untreated cases can lead to death within a matter of weeks, maybe less.”

Clinical treatment of infected animals typically involves application of medication to the animal’s wounds to kill the larvae, larvae removal, administration of antibiotics and general supportive care, Mandese said.

“When caught in time, screwworm infections are treatable,” she said. “Even if it turns out your animal has a different health issue, immediate attention is appropriate for any unusual wound, sore or persistent discomfort you notice in a pet or livestock animal.”



Writer: Tom Nordlie, 352-273-3567, tnordlie@ufl.edu

Sources: For interview requests, please contact Tom Nordlie at 352-273-3567 or after hours at 352-375-1415 or tnordlie@ufl.edu, or contact Sarah Carey at 352-294-4242 or careysk@ufl.edu or after hours at 352-273-5810


Posted: October 5, 2016

Category: Agriculture, Invasive Species, Livestock, Pests & Disease, UF/IFAS
Tags: Entomology And Nematology, Kaufman, Payne, Pest

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