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Chagas Disease at the U.S./Mexico Border

Posted on Friday, May 24, 2019

By Dr. Sarah Hamer and Alyssa Meyers

Researchers at the Texas A&M College of Veterinary Medicine & Biomedical Sciences (CVM), in collaboration with the Institute for Infectious Animal Diseases (IIAD) at Texas A&M, have received funding for the third phase of research from the U.S. Department of Homeland Security (DHS) to secure the health of dogs working at the United States and Mexico border.

With this new wave of funding, Dr. Sarah Hamer, an associate professor in the CVM’s Department of Veterinary Integrative Biosciences (VIBS); Alyssa Meyers, one of Hamer’s doctoral students; and a team of researchers are taking an in-depth look at dogs working along the U.S.-Mexico border to further study the impending health implications of Chagas disease and the effect this disease has on the canines’ ability to work.

What is Chagas disease?

Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, is transmitted through kissing bugs, or cone-nose bugs, and can cause acute or chronic heart disease or death in dogs and humans.

While Chagas disease has long been known in Central and South America, there is now increasing awareness for the disease in the southern United States where kissing bugs occur.

Why study Chagas disease in dogs?

In South America dogs serve as both domestic reservoirs and as sentinels for human infection-the extent to which they play these roles in the U.S. is not yet understood and more research is needed.  However, a positive dog without a travel history indicates that transmission is taking place in that environment and there is a potential risk for human exposure. “Though Chagas is an emerging disease that we know is in Texas and know can infect dogs and people, we don’t know the full extent of the impact or spread of the disease,” said IIAD director Melissa Berquist, Ph.D. IIAD is a U.S. Department of Homeland Security (DHS) Science and Technology Center of Excellence and a unit of Texas A&M AgriLife.

“By gaining a better understanding of the geographic areas where dogs are becoming exposed and the prevalence of exposure, we are gaining critical information for health management and vector control programs in order to decrease transmission within the DHS human and canine workforce,” she said.

Why study the DHS dogs?

“The DHS maintains more than 3,000 working dogs across the country, including the security dogs at the airports, customs and border protection dogs, Coast Guard dogs, federal protective service dogs, and secret service dogs,” Meyers explained. “These are highly valuable dogs, often selected for their drive and pedigree, and, unfortunately, our initial research found that up to 18 percent of the working dogs along the Texas-Mexico border were positive for exposure to T. cruzi, the Chagas parasite.”  

The team then expanded their study to look at government working dogs across the U.S., not just on the southern border.  This expanded study found that approximately 7 percent of the dogs were exposed to the parasite that causes Chagas disease. Understanding the epidemiology of T. cruzi infection in the DHS dogs could raise awareness among veterinarians regarding T. cruzi infection throughout the U.S. Furthermore, understanding the distribution and risk factors for zoonotic parasite infection in natural populations of dogs could potentially be informative for public health.

So dogs in the U.S. are widely infected-what’s next?

After this eye-opening discovery, Hamer decided to narrow the research on the long-lasting health implications of Chagas disease in these working dogs.

“It’s pretty exciting work because we’re intercepting these border patrol dogs while they’re working,” Hamer said. “We take a blood sample, monitor their heart, have them run on a treadmill, and we want to put on a Fit Bark—which is like a Fit Bit, but for dogs—all while they’re still working and doing their normal jobs.”

Because there is no vaccination to prevent Chagas disease in humans or animals, and approved treatment is limited, Meyers said the team also plans to use this grant to focus on what can be done to control the kissing bugs and prevent transmission. “There is an incomplete understanding of vector-host interactions that impedes vector control efforts, so if we better understand the behavior and life history of the bug, we can better prevent transmission.”

What type of vector control can be used?

“Vector control includes things like clearing brush where kissing bugs can dwell from around kennels and houses, minimizing the use of light at night because kissing bugs are drawn to light, and securing access to kennels, to prevent bugs from getting in,” Meyers said.

Although securing the kennels may seem like an easy fix, it can be a costly and challenging intervention for these facilities, which house dozens of dogs, according to Hamer.

What about other vector-borne diseases?

Along with studying Chagas disease, Hamer’s team will be using the grant to study other vector-borne disease- including those spread by ticks and mosquitoes- that may impact these working dogs.

“Because these working dogs spend lots of time outside where they may be exposed to vectors, they may provide a sensitive indication of the different vector-borne infections across the landscape that are not only important for dog health, but also human health,” Hamer said. “Our studies will have an increased focus on what we can do to ensure these animals remain healthy. We’re excited that Texas A&M University is really helping secure the health of these important animals that are on the frontlines of security for our country.”