TX Animal Health Commission
Warns Of Screwworm Outbreak

AUSTIN — Texas livestock health officials are asking ranchers to watch for and collect suspicious larvae that may be detected in animal wounds, as an investigation continues into a possible screwworm outbreak near Rocksprings in Edwards County.

"A rancher submitted nine suspicious fly larvae he collected from a wound on an Angora goat October 31," said Dr. Max Coats, deputy executive director for the Texas Animal Health Commission, the state's livestock health regulatory agency. The larvae have been examined by the National Veterinary Services Laboratory in Ames, Iowa.

"On visual inspection, one of the nine fly larvae matched characteristics for the screwworm," said Coats. "Additional investigations are being conducted. However, in an instance where a foreign pest may have been introduced into the state, it is never too early to be watchful for other possible cases."

Coats urged producers to call the TAHC Lampasas office at (800) 658-664S, the TAHC Beeville office at (800) 658-6570, or the Austin TAHC headquarters at (800) 550-8242, if they have detected unusual larvae. Fly larvae should be collected, and the specimen should be placed in rubbing alcohol in a container, such as a glass jar or plastic pill bottle.

"Dr. Thurman Fancher, a TAHC foreign animal disease diagnostician, has made an onsite visit and is conducting a thorough inspection of livestock and investigation of animal movement," said Coats. "Texas and Mexico are considered to be 'screwworm-free,' so, we must determine how a screwworm fly could have entered the state to lay its eggs and hatch into larvae."

The screwworm fly was eradicated in the U.S. in l982, but surveillance continues, as the pest has been reintroduced and quickly stopped on several occasions. In l997, screwworm larvae were detected on a dog shipped to San Antonio from a military base in Panama. A quick-thinking private veterinary practitioner detected and collected the larvae. The TAHC and U.S. Department of Agriculture immediately took appropriate measures to track the dog's movement into the U.S., disinfect sites and prevent the spread of the pest.

Prior to eradicating the screwworm fly, Texas producers spent millions of dollars each year on lost production, medications and manpower to fight the flesh-eating pest. In the early l960s, researchers Dr. Edward Knipling and Dr. Raymond Bushland developed sterile male screwworm flies. These flies mate with fertile females, but produce no offspring, and eventually the population dies out.

The eradication effort has continued through Mexico and into Central America. A sterile screwworm plant is in operation in Tuxtla Gutierrez, Chiapas, Mexico.

The eventual goal of the eradication project is to eliminate all screwworms north of the narrow Isthmus of Panama, where a relatively small and inexpensive sterile fly barrier zone could prevent reinfestation of the entire Northern Hemisphere. A similar program in South America at some point in the future could gradually squeeze the screwworm out of existence in the Americas.

A sterile fly plant in Panama is central to both the Northern Hemisphere plan and any South American effort that might follow. Its importance has been highlighted by social unrest and repeated sabotage in the Chiapas region of Mexico — including incidents at the Tuxtla Gutierrez plant itself — but a decade-long effort to establish such a plant has been hampered by diplomatic problems, political indifference and bureaucratic inertia.