UF/IFAS Researchers Develop Vaccines To Control Tick-Borne Disease

GAINESVILLE — In breakthrough research that will protect U.S. livestock and wildlife from a deadly African tick-borne disease, University of Florida scientists have developed two new vaccines along with environmentally sound measures to battle ticks and check the health of imported animals.

The target is heartwater disease, which has already spread from Africa to the eastern Caribbean and now threatens the United States.

“Obviously, we’re dealing with something we need to keep out of this country,” said Michael Burridge, professor and veterinarian with the UF’s Institute of Food and Agricultural Sciences. “For many years, this disease has been the most feared — the No. 1 foreign animal disease worry for state and national cattle producers.”

Heartwater disease attacks blood vessels, particularly in the brain. Once infected, up to 90 percent of susceptible animals die. The disease does not affect humans and it cannot be transmitted by eating meat.

He said the tick that spreads the disease — known as the tropical bont tick — would thrive in the Southeast United States where heartwater could decimate cattle, sheep, goat and deer populations. And, he warned, once the disease is established in the wild deer population, it would be impossible to eradicate.

The two new vaccines — described as breakthroughs by UF/IFAS researchers — have been under development for more than 10 years. The first is a conventional inactivated vaccine that has been successfully field tested in Africa by Suman Mahan, a UF/IFAS veterinary scientist based in Harare, Zimbabwe.

“The real breakthrough is that we now have the first safe, affordable vaccine that provides excellent protection from the disease under actual field conditions,” Mahan said.

The second development is a new genetically engineered vaccine being successfully tested by Anthony Barbet, a UF/IFAS molecular biologist in Gainesville. He said the DNA vaccine still requires more testing in Africa and the Caribbean, but it will be much cheaper to produce on a commercial basis than the inactivated vaccine. Patent applications on both vaccines are pending, and UF is seeking commercial partners to market the vaccines.

Of major concern, Mahan explained, are new research findings that the disease could enter the United States on wild animals imported to the country for zoos or conservation and breeding purposes. He said the disease is widespread in livestock and wildlife in Africa. Animals may look healthy but still carry the disease. To check the presence of the disease in animals, particularly those being brought into the United States, UF/IFAS researchers have developed two new diagnostic blood tests that now are being made available for use by producers and laboratories.

“Until now, the only way to detect the disease was by a brain biopsy, which is not practical under field conditions,” Mahan explained.

Burridge, director of the project, said one of their main objectives now is to eradicate the tropical bont tick in Caribbean countries to prevent the disease from spreading to the U.S. mainland. To kill the ticks on livestock, UF/IFAS researchers have developed a new tropical bont tick decoy, described as an inexpensive, environmentally sound tag that’s placed around the neck of cattle, sheep and goats. He said the tag has pheromones to attract ticks and a slow- release pesticide that spreads over the animal’s body and kills ticks for at least three months.

“Since tick collars cannot be placed on wild animals, we have also developed a tick control system for deer and other wildlife. The device is a feeding bin that applies pesticide to animals when they brush against the dispenser,” Burridge said.

The UF/IFAS heartwater research project has been supported by $10 million in grants from the U.S. Agency for International Development (USAID) during the past 10 years. In November, USAID awarded the team a new $5 million grant to continue the research project through 1999.



Posted: December 24, 1996

Category: UF/IFAS

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