A new vaccine against brucellosis in cattle may also protect bison against the contagious disease. Bison and elk are the last major sources of cattle brucellosis in the United States. Brucellosis is caused by the bacterium Brucella abortus and costs U.S. beef and dairy farmers about $30 million annually. In an experimental study, ARS researchers vaccinated 10 bison female calves with the new vaccine, B. abortusstrain RB51. The vaccinated animals' immune response was comparable to that of cattle vaccinated with RB51. Another plus: None of the RB51-vaccinated animals shed the live bacterium into the environment. This is important to protect other wildlife--moose, for instance, which could die if infected with the bacterium. USDA's Animal and Plant Health Inspection Service (APHIS) conditionally approved the new vaccine for use in cattle based on ARS studies demonstrating that RB51 protects cattle against brucellosis but doesn't give false signs of infection in blood tests of vaccinated cattle. ARS and APHIS staff are monitoring bison in Yellowstone National Park to determine how brucellosis is transmitted among free- living bison and elk.
National Animal Disease Center, Ames, IA
Steven C. Olsen, (515) 239-8393

Honey bees fare better against deadly varroa mites if the bees build smaller versions of the six-sided cubbyholes, called cells, in which they rear their young and store honey. Beekeepers pre-determine the cell size bees will make by giving them wax sheets with base cells imprinted on them. From these "starter kits," the bees build layers of cells to make the honeycomb. But ARS scientists learned that when bees built combs from starter kits with a smaller cell size, those bees infested with the mites had a much higher survival rate--40 percent instead of near zero with the standard size cells. Researchers suspect the smaller cells result in lower stress on the bees, increasing the bees' ability to withstand mite infestations. Some beekeepers have lost half their hives to mites in recent years. Honey bees annually pollinate U.S. crops worth $10 billion.
Carl Hayden Bee Research Laboratory, Tucson, AZ
Eric H. Erickson, (520) 670-6481, ehejr@ccit.arizona.edu

Corn treated with ivermectin could prove the solution to cattle tick woes on south Texas ranches. Even when cattle aren't present, tick populations can survive in an area by living on white-tailed deer. In a cooperative study, researchers with ARS and USDA's Animal and Plant Health Inspection Service temporarily removed all cattle from the Caterina Ranch north of Laredo, Texas, where problems with cattle fever ticks have persisted for 50 years. Then the researchers provided ivermectin-treated whole kernel corn to white-tailed deer at feeding stations scattered across 22,000 acres. When all livestock on the ranch were returned and inspected in March 1997, no cattle fever ticks were found. This is the first time the area has been completely free of cattle fever ticks. Ivermectin is used to control several parasites in livestock and botflies on reindeer.
U.S. Livestock Insects Research Lab, Kerrville, TX
John E. George, (210) 792-0338