State Officials Fear Imorted Animals Might Introduce Deadly Tick-Borne Livestock Disease

October 20, 1997

GAINESVILLE—A University of Florida professor and the state veterinarian say large African tortoise ticks found on imported reptiles in Florida could carry and spread heartwater, an exotic disease that kills livestock and wildlife.

To prevent a heartwater epidemic in the United States, they want to improve testing procedures for imported wildlife and develop methods to detect ticks on reptiles.

“Finding African ticks — almost by accident — on imported tortoises is a wake-up call,” said Michael Burridge, professor and veterinarian with the UF’s Institute of Food and Agricultural Sciences. “It shows how easily pests that transmit the disease could get into Florida and the United States.” Sandra Allan, a UF/IFAS assistant scientist who works with Burridge, identified the African ticks, which are twice the size of native ticks, on an injured tortoise brought to the UF College of Veterinary Medicine by a Florida reptile breeder.

Heartwater, which already has spread from Africa to the Caribbean, is considered a serious threat to livestock and wildlife in the United States. Heartwater attacks blood vessels, particularly in the brain, causing fluids to accumulate in the lungs, around the heart and in the chest and abdomen.

There is no practical treatment for heartwater once the disease is evident. Once infected, up to 90 percent of susceptible animals die. The disease does not affect humans, horses or household pets such as dogs and cats, and it cannot be transmitted by eating meat or drinking milk from infected animals.

“Heartwater will devastate the cattle, sheep and goat industries. If it gets into the wild deer population, it would be impossible to eradicate,” Burridge said.

He now is working with Leroy Coffman, the state veterinarian with the Florida Department of Agriculture and Consumer Services, to develop additional measures to keep heartwater-carrying ticks out of the country. They also are working with the Florida Game and Fresh Water Fish Commission, the U.S. Department of Agriculture Animal and Plant Health Inspection Services and other agencies to deal with the problem.

“We must make the message clear,” Coffman said. “This is a List A disease, which means it’s as serious as it gets. From a regulatory standpoint, it’s one of the most important animal diseases in the world. The message here is that we must work together to close the door on this disease.”

Florida Agriculture Commissioner Bob Crawford shares the concerns of Burridge and Coffman about the heartwater threat and said finding ticks on imported tortoises increases the risk the disease will find its way into Florida. He has asked U.S. Secretary of Agriculture Dan Glickman for help in fighting the threat of heartwater disease to the state and nation.

“The department has already formed an interagency team to evaluate and find solutions to this problem in Florida,” Crawford said. “I strongly encourage the formation of a national working group to address heartwater disease.”

Burridge said the problem is driven by a growing market for exotic animals and reptiles imported from other countries. He urged veterinarians and other animal-care professionals, especially those working with imported animals and reptiles, to be on the lookout for ticks and said any unusual ticks should be sent to Allan at UF for identification.

“Fortunately, in this case, the African tortoise ticks have not spread from the original infested site in Florida,” Burridge said. “But, this is just one isolated case in a state where thousands of animals are being imported every year. If we don’t do something right away to prevent the introduction of exotic ticks, it’s only a matter of time before they will become established in this country.”

Another complication, Burridge warned, is the native Gulf Coast tick. New UF/IFAS research shows this tick, common in the southeastern United States, is capable of transmitting heartwater disease under experimental conditions. The tropical bont tick has spread heartwater in the Caribbean.

He said the disease could also enter the country with infected animals imported for zoos or conservation and breeding purposes. The disease is widespread in livestock and wildlife in Africa. Animals may look healthy, but some still can carry the disease.

“We must keep exotic ticks out of the U.S. and make sure imported animals are not infected with heartwater,” Burridge said. “Imported animals can be screened for the disease with a new test we have developed, and I believe the time has come to begin using it.”

Burridge and UF/IFAS researchers are developing two new heartwater vaccines that appear to be effective in preventing the disease. The first is a conventional inactivated vaccine being tested in Africa by Suman Mahan, a UF/IFAS veterinary scientist. The second is a genetically engineered vaccine being tested by Anthony Barbet, a UF/IFAS molecular biologist in Gainesville.

UF/IFAS researchers also have developed a tick decoy, similar to a pet flea collar, to control ticks on livestock. For deer and other wildlife, they have developed a feeding bin that applies pesticide to animals when they brush against the dispenser.

Coffman said the exotic tick is yet another example of how increased commerce and mobility can bring new pests and diseases to the state and nation. He cited the Mediterranean fruit fly, citrus canker, and tomato leaf curl virus as other examples.