UGA researcher closes in on Chagas vaccine for companion animals

Athens, Ga. — A researcher in the University of Georgia's (UGA) Center for Tropical and Emerging Global Diseases says he is closing in on a vaccine for pets that could slow the spread of Chagas disease in people and animals.

Chagas disease is a parasitic disease that can cause cardiomyopathy and heart disease in people, UGA says. Caused by the parasite Trypanosoma cruzi, the disease is often spread through a subspecies of blood-feeding insects called triatomines. These insects, also known as "kissing bugs" because they tend to bite people on the face and lips, feed and defecate on human skin. Triatomine feces containing the parasite are then rubbed into the bite when humans scratch the wound or when humans rub their eyes or mouth, according to UGA.

Although kissing bugs are usually responsible for passing the disease to humans, the bugs that live in people's homes don't normally carry the disease—they become infected when they bite the family pet, UGA notes.

"One of the problems with T. cruzi is that it infects not just humans but many different animals," says Rick Tarleton, distinguished research professor in the Department of Cellular Biology and member of the UGA Center for Tropical and Emerging Global Diseases. "What that means is that it will never be eradicated; you can't kill or vaccinate all the animals that carry this parasite. Humans end up being incidental hosts for this parasite (but) it really circulates much better and at much higher levels in a lot of other animal species."

Dogs, cats, goats or any other animal living in or around homes are likely to become infected from kissing bugs living in shrubs, woods, kennels or barns. These animals then expose kissing bugs already nesting in homes to the T. cruzi parasite. Once the insects in a home carry the parasite, the chances of human infection increase significantly. UGA says an estimated 300,000 people in the United States are infected with T. cruzi, as well as a sizeable number of dogs—mostly in the southern United States.

Using a five-year, $1.8 million grant from the National Institutes of Health, Tarleton says he is now close to developing a vaccine that uses a genetically modified live parasite that is incapable of replicating inside the host.

"We have a parasite that can grow in the insect and can infect an animal, but when it goes inside a cell, it cannot replicate," Tarleton says. "As a result, the immune system controls that infection, but you also get induction of a nice, strong immune response, which is what you need a vaccine to do."

Technology does not exist to create a human vaccine, but Tarleton says be believes the vaccine, when administered to pets, will "significantly reduce the number of human infections."