Fire ants have gained a foothold in Tennessee, proving they can survive sub-freezing temperatures. Scientists previously believed the ants could only overwinter in climates similar to their native South America. They are now established on 275 million acres in 11 southern states and Puerto Rico. But in 1992, USDA researchers discovered an isolated, 3,000-acre infestation of the pesky ants about 45 miles northeast of Chattanooga. The ants were thought to have been accidently brought to the state in wood material from a pulp processing factory. In preliminary studies over the last few years, scientists found that eight percent of the Tennessee colony survived the record-breaking cold temperatures of early 1994. One possible explanation: Two species have formed a hybrid ant that may be able to withstand northern winters. Once studies are complete, scientists hope to know more about the ultimate northern range of the fire ant, known for its aggressive behavior and painful stings.
Medical and Veterinary Entomology Research Lab, Gainesville, FL
David F. Williams, (904) 374-5982

Just one Toxoplasma gondii parasite is all it takes to infect a pig. Humans can get T. gondii infection by eating uncooked meat from infected animals or by swallowing food and water contaminated with infected cat feces that contains oocysts, a particularly hardy form of the parasite. Cats can excrete millions of oocysts after eating tissue of T. gondii-infected animals. It's not known how much T. gondii transmission to humans occurs through consumption of infected meat and how much results from direct contact with cat feces. If a woman becomes infected with T. gondii while pregnant, her child may be born mentally retarded or blind. Researchers say pork producers should keep cats away from swine feed supplies.
Parasite Biology and Epidemiology Laboratory, Beltsville, MD
J.P. Dubey, (301) 504-8128

Treating broiler chicks with a blend of bacteria reduced the chicks' salmonella count to only about one-third of one percent of those in untreated chicks. That count was taken in the chicks' intestinal pouches called ceca. ARS scientists made the treatment, called CF3, from intestinal bacteria in mature chickens, which are naturally more resistant to microorganisms such as salmonella. In tests, the scientists dosed 100 broiler chicks at one day of age with CF3, but didn't give the treatment to a second group of 100 chicks. Two days later, all the chicks were given 10,000 Salmonella typhimurium bacteria apiece. When the birds' intestines were checked at four weeks of age, the CF3-treated chicks had less than 10 Salmonella typhimurium bacteria per gram of cecal content, compared with about 3,000 per gram in the untreated birds.
Food Animal Protection Research Laboratory, College Station, TX
Michael E. Hume, (409) 260-9404

A protein from cattle grub larvae is the foundation of a promising new environmental-friendly vaccine against grubs. These grubsthe larvae of heel fliesdamage meat and hides by cutting holes in the animal's skin. Limited availability of larvae had thwarted development of a cost-effective, protein-based vaccine. But ARS researchers and researchers from Berlex Biosciences in Richmond, CA, cloned the grub protein, inserted it into a bacterium and now can grow large quantities of the protein inexpensively. Calves vaccinated with the protein had 50 percent fewer mature grubs than did unprotected calves. Each year grubs cost the cattle industry millions of dollars in damaged meat, hides and chemical controls. A safe, effective vaccine also can help eliminate the use of chemicals that are toxic to the environment. In the spring of 1996, the Canada-Alberta Livestock Research Trust, Inc., will be testing a recombinant vaccine in Canada and Europe.
Livestock Insects Research Laboratory, Kerrville, TX
John H. Pruett, (210) 792-0322

Stripping away the genetic "overcoat" that keeps no-see-um biting midges warm in winter will reduce the spread of bluetongue, a livestock virus. That's what ARS scientists would like to see happen, now that they have found a potential genetic key to altering its cold-weather defense. These midgesofficially known as Culicoides variipennis sonorensisspread bluetongue among domestic sheep and cattle. Bluetongue causes approximately $120 million in losses annually to domestic livestock producers, mainly in export markets lost in countries that do not have the disease. Now, ARS scientists have discovered that the midge produces at least seven proteins to protect itself from freezing temperatures. By learning more about the survival mechanism, scientists may be able to use genetic manipulation to remove this advantage. That would reduce the insect's winter survival chances and its ability to spread the disease to healthy animals when spring arrives.
Arthropod-borne Animal Diseases Research Laboratory, Laramie, WY
Richard A. Nunamaker, (307) 766-3624