A team of researchers at Texas A&M University and the University of Georgia (UGA) has received more than $4 million from federal and non-governmental organizations to support research on Chagas disease prevalence, diagnostics and treatment to benefit both dogs and humans.
Chagas disease is a tropical illness caused by the parasite Trypanosoma cruzi, which is most commonly spread by the fecal matter of triatomine bugs — also known as “kissing bugs” because they bite their hosts to feed on blood. The disease — common in humans and dogs — often goes unnoticed in early stages, but a chronic infection can lead to serious heart and digestive system problems, making early diagnosis important.
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Dr. Sarah Hamer, a professor in the Texas A&M College of Veterinary Medicine and Biomedical Sciences’ (VMBS) Department of Veterinary Integrative Biosciences; Dr. Ashley Saunders, a professor and cardiologist in the VMBS’ Department of Small Animal Clinical Sciences; and Dr. Rick Tarleton, UGA Regents Professor and UGA Athletic Association Distinguished Professor, are leading the projects.
One Health approach
“These projects will advance Chagas disease research to understand the process of natural infections, disease and effect of treatments,” Hamer said. “These projects combine many aspects of biomedical research. We’re conducting field and laboratory research, treating dogs, measuring clinical outcomes and studying ecological factors. It’s truly a ‘One Health’ approach.”
Both privately owned and working dogs in Texas provide an important source of data for Chagas disease because they often encounter kissing bugs.
“Unfortunately, Texas has emerged as a hotspot of infected kissing bugs, infected wildlife and infected dogs across the landscape,” Hamer said. “We think dogs are getting infected when they eat the insects.”
“Dogs that work in customs and border protection and for the Transportation Security Administration can be exposed to Chagas disease,” Saunders said. “Some of our work will be a continuation of previous studies of the clinical impacts of the disease on canine cardiac health, as well as how the dogs are exposed to the parasite so we can help minimize their risk.”
Hotspot of kissing bugs
Although most human cases of Chagas disease are reported from South and Central America and Mexico, there are established kissing bug populations across the southern United States, including Texas. The infection and disease is notoriously difficult to detect and treat.
To address these issues, one project, funded by the National Institutes of Health, will use innovative diagnostic and treatment strategies to establish optimal protocols for detection and treatment of the infection, so as to optimally prevent the development of cardiac disease.
“There are a number of important questions related to treatment efficacy and the protection that cured subjects have from future infection that cannot be easily addressed in humans, but can be in these dog populations that are under intense transmission pressure in Texas,” Tarleton said.
Test challenges
Currently, diagnosis of Chagas disease is complicated by several factors — some diagnostic tests work by looking for the parasite’s DNA in the host’s blood, but if an individual has very low levels of parasite DNA or the test isn’t sensitive enough to detect the DNA, the test may return a negative result. In addition, T. cruzi’s life cycle includes parasites that are dormant, and thus resistant to treatment.
To address these issues, the new study will track infected individuals using a combination approach with sensitive tests to detect both the parasite DNA and the body’s response to infection, while treating with an antiparasitic drug in a modified regimen.
Because the disease presents similarly in dogs as in humans, dogs are a good model for examining the effectiveness of the treatment, and because the researchers will be working with dogs who already have Chagas disease, owners are highly motivated to support the work.
Dormancy difficulties
“The drug we’re using is an existing treatment for Chagas disease in humans,” Saunders said. “But Dr. Tarleton has shown that the parasites aren’t susceptible to this drug when they’re dormant. By changing the drug delivery protocol to dosing over a longer period of time, when the dormant parasites become active again, they are killed by the drug.”
“The project is unique because we are studying privately owned hunting dogs in large kennel environments that have, unfortunately, become naturally infected with T. cruzi,” Hamer said. “Many of these owners have had other dogs die from the disease, so they want to help us solve the problem.”
Government dogs
In another project, funded by the United States Department of Homeland Security (DHS), the researchers will monitor DHS-owned working dogs that are often trained in areas where Chagas disease is prevalent to understand how they are exposed to the disease as well as the impacts it can have on heart health.
This project also includes Dr. Heather Manley Lillibridge, the executive director of Texas A&M’s Cross-Border Threat Screening and Supply Chain Defense, a Center of Excellence in partnership with the DHS, through which the project is being run.
“One of the reasons that monitoring dogs is so helpful is because Chagas disease can produce so many different subsets of health problems,” Saunders said. “Some dogs end up with a heart abnormality, but a large number continue living and working happily for many years. Others will die quite suddenly, before anyone knew they had the disease.”
Health information
“Recording health information from such a large population of dogs will hopefully help us understand why the disease develops in different ways,” Hamer said.
Government working dogs are commonly trained in Texas to detect things such as explosives or drugs, but they may perform their jobs for customs, border patrol and transportation systems anywhere in the U.S. As such, dogs could acquire an infection in the South — where kissing bugs occur — and later be transported to other regions of the country where the disease hasn’t traditionally occurred and where there is little veterinary awareness.
Targeting pets
In a third project, with continued support from the American Kennel Club Canine Health Foundation, the team will treat and monitor individual pet dogs brought to Texas A&M’s Small Animal Teaching Hospital while developing a staging system for Chagas disease in dogs.
“The staging system we develop will help us to categorize the severity of disease, making it easier to determine which dogs will benefit most from drug treatment,” Saunders said. “This scoring system will work hand-in-hand with our improved diagnostic and treatment plan.”
These projects are among Hamer’s, Saunders’ and Tarleton’s ongoing efforts to better understand, diagnose and treat Chagas disease. One of those, the Kissing Bug Community Science Program, has been accepting and testing kissing bugs submitted from around the U.S. for more than a decade. Kissing bugs are most commonly encountered by people and animals in the southern U.S. in summer months.
For more information on these and Texas A&M’s other Chagas disease-related studies, visit vetmed.tamu.edu/chagas.
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