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

To prevent a heartwater epidemic in the United States, they want to improvetesting procedures for imported wildlife and develop methods to detect ticks onreptiles.

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

Heartwater, which already has spread from Africa to the Caribbean, is considereda serious threat to livestock and wildlife in the United States. Heartwater attacks bloodvessels, particularly in the brain, causing fluids to accumulate in the lungs, around the heart and in thechest and abdomen.

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

"Heartwater will devastate the cattle, sheep and goat industries. If it getsinto the wild deer population, it would be impossible to eradicate," Burridge said.

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

"We must make the message clear," Coffman said. "This is a List A disease, whichmeans it's as serious as it gets. From a regulatory standpoint, it's one of the most importantanimal diseases in the world. The message here is that we must work together to close the door onthis disease."

Florida Agriculture Commissioner Bob Crawford shares the concerns of Burridgeand Coffman about the heartwater threat and said finding ticks on imported tortoisesincreases the risk the disease will find its way into Florida. He has asked U.S. Secretary ofAgriculture 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 findsolutions to this problem in Florida," Crawford said. "I strongly encourage the formation of anational working group to address heartwater disease."

Burridge said the problem is driven by a growing market for exotic animals andreptiles imported from other countries. He urged veterinarians and other animal-careprofessionals, especially those working with imported animals and reptiles, to be on the lookout for ticksand 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 theoriginal infested site in Florida," Burridge said. "But, this is just one isolated case in a statewhere thousands of animals are being imported every year. If we don't do something right away toprevent the introduction of exotic ticks, it's only a matter of time before they will becomeestablished in this country."

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

He said the disease could also enter the country with infected animals importedfor zoos or conservation and breeding purposes. The disease is widespread in livestock andwildlife 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 arenot infected with heartwater," Burridge said. "Imported animals can be screened for the diseasewith 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 thatappear to be effective in preventing the disease. The first is a conventional inactivatedvaccine 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 inGainesville.

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

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