Bugs’ ‘kiss’ a major threat to dogs
“We had a half-dozen dogs – Labs, pointers – die: They’d just fall over,” Berdon Lawrence said. “Nobody knew what was going on.”
Lawrence, a Houston businessman, recalled one dog in particular that made him determined to discover what was happening to the working canines housed on his South Texas ranch. On a quail hunt, a seemingly perfectly healthy pointer was zigzagging through the brush.
“The pointer was working quail and just fell over, dead,” Lawrence said. “It didn’t make any sense.”
Concerned that something associated with the kennel was causing the sudden deaths, Lawrence sent one of the deceased dogs to Texas A&M Veterinary Diagnostic Lab for a necropsy. The results stunned him.
“The diagnosis came back as a heart attack caused by Chagas disease,” he said. “I said, ‘What’s Chagas disease?’ I’d never heard of it.”
Neither have most Texans.
A growing problem
They should. And they almost certainly will. The parasite-caused disease, which in many cases causes fatal, heart-related problems, potentially is a serious threat to human health in Texas. It already is a threat to the state’s canine population.
“We know we have Chagas disease in Texas, and Texas is emerging as a hot spot,” said Dr. Sarah Hamer, assistant professor and associate wildlife biologist with Texas A&M University’s College of Veterinary Medicine and Biomedical Sciences. “There is a growing crisis of canine Chagas in Texas.”
Hamer was among speakers at a day-long “Chagas Disease in Texas” symposium held Tuesday in Kingsville and hosted by the South Texas Private Property Rights Association and Texas A&M-Kingsville’s Caesar Kleberg Wildlife Research Institute.
While there are no hard data on the number of dogs in Texas that are infected with the parasite causing Chagas disease or the number that die from its effects, anecdotal evidence indicates hundreds and probably thousands of Texas dogs die from its effects each year.
“It is a significant problem,” Dr. Glen Wilkinson, a veterinarian in Premont in Jim Wells County and one of the attendees at the Kingsville gathering, said, noting he has seen “over a hundred dogs in the past couple of years” that have tested positive for the protozoan parasite that causes Chagas disease.
Chagas disease is hardly an unknown malady. The disease long has been a major human health issue in Mexico, Central and South America, where it is estimated to infect as many as 8 million people and annually cause as many 25,000 human deaths.
The disease is caused by a protozoa, Trypanosoma cruzi, that, once in a mammalian host, circulates in the blood until it finds a smooth muscle tissue – usually in the heart – where it takes up residence and begins damaging that tissue. Often, the first clinical signs of the disease in dogs is sudden death from heart failure.
There are currently no vaccines that prevent the disease, treatments are invariably minimally effective and there is no cure for Chagas disease.
The protozoa are transmitted to the host by insects – specifically those of the genus Triatoma. Commonly called “kissing bugs,” the winged insects have a flat, pear-shaped body and an elongated, cone-shaped head with a prominent “beak.” That beak is used to puncture skin and gorge on blood from a mammal.
Higher risk at night
Kissing bugs invariably do their feeding at night, emerging from brush piles, cracks, crevasses, thick grasses and similar habitat. They crawl onto their victims, often drawn by the carbon dioxide the mammal exhales, and take a bite. This bite often occurs near the victim’s mouth – thus the name “kissing bug.”
The protozoan parasite carried by the insect isn’t injected during the bite but is deposited in feces typically loosed after the blood meal. The victim typically scratches the bite, smearing the feces into the wound or otherwise introducing it to the body.
If dogs are bitten by a kissing bug in Texas, odds are high that bug carries the parasite causing Chagas disease. And those bugs are found in much of Texas. Seven species of Triatoma have been identified across the state, with the largest numbers in southern and central Texas.
“In every place we have got the insects, we have found positives,” Dr. Teresa Feria, assistant professor in the biology department of University of Texas-Pan American, told symposium attendees.
The problem is not confined to South Texas. Half of the kissing bugs collected in Kerr County of Central Texas tested positive for the parasite.
With no preventative vaccine and no effective treatment for Chagas disease, the best practice for dog owners is to reduce chances their dogs will encounter a kissing bug.
Owners of dogs kept in kennels should install screening around the runs to help prevent the insects from having an unimpeded path to a sleeping dog, Dr. Greta Schuster, Texas A&M-Kingsville professor of integrated pest management, said at the Chagas symposium.
These are the tactics Berdon Lawrence pursued on his South Texas ranch. They installed screens around the chain-link fence kennels. They cleared vegetation from around the kennel and regularly applied insecticide around the peri-meter.
The result was positive. Since making those changes several years ago, the ranch has lost only one dog to Chagas disease, said Lawrence.
“Chagas disease is a problem,” Lawrence said. “The good news is, if you know about it, you can do something about it.”