Last month we learned of two dogs in Austin adopted from Austin Boxer Rescue (ABR) who contracted Chagas disease. The dogs had to have three veterinary visits before a Chagas test was ordered — illustrating the fact that it’s rarely on the radar of vets, much less their patients’ families — and the only way to test for Chagas at this point is to have blood samples sent to Texas A&M. The vet eventually ordered the Chagas disease test because the dogs, both of whom became very ill, had caught an armadillo in their backyard in the weeks before.
Chagas disease in dogs can be a silent killer, but it’s not well known or tested for, as we discovered when we set out to research this article. Unfortunately this disease, which often masquerades as heart disease, is very common in Texas and the Southern U.S. Researchers are finding it nearly as often as heartworm in dogs, but it may not cause any visible symptoms until it’s too late.
What is Chagas disease, though, and how do dogs get infected? What are the symptoms? Can Chagas disease be treated or even cured? In this blog we’ll answer these questions and more, and provide some guidance on how to keep your Boxer safe from Chagas disease.
What Is Chagas Disease?
Chagas disease is also known as American Trypanosomiasis. It was primarily observed in Latin America when first studied. In recent years, however, this disease has been seen throughout the Southern U.S, including Texas, and as far north as New York and Oregon. Chagas disease is spread primarily by insects and can affect humans, horses, cattle, armadillos, possums, and rodents. It’s even been seen in monkeys and in a walrus.
Although it’s certainly not a new disease, most people, including many veterinarians, aren’t familiar with it and the damage it can cause. In humans, it can cause gastrointestinal and heart issues, to the point of heart failure. In dogs, the primary effect is usually heart disease or sudden death. There are no vaccines for it.
How Do Dogs Get Chagas Disease?
Chagas disease is caused by a blood-borne parasite called Trypanosoma cruzi. It’s commonly spread by the Kissing Beetle, also known as the “Kissing Bug,” and other insects that feed on the blood of humans and animals as they sleep. Kissing bugs are the most frequent carriers, and dogs can become infected by eating the feces of infected insects, which is present whenever the insects defecate on the bite wound that the dog may then lick.
Dogs can also become infected by biting or eating another animal that’s infected, such as a possum or armadillo. There have also been cases of infections from food and beverages contaminated with fecal matter. If an infected dog is a blood donor, disease can also be transmitted through blood transfusions, as canine blood isn’t tested for Chagas. And finally, possums can transmit Chagas if they spray a dog or human from their anal glands. Yes, that’s about as disgusting as it sounds, but it’s worth noting that dogs don’t actually have to bite the possum to get sick.
Once the dog is infected, the parasite enters cells throughout the body and multiplies until it reaches a point of high density and effectively “explodes,” releasing a high volume of Trypanosoma cruzi into the bloodstream. This process causes the effects seen with Chagas disease.
What Are the Symptoms of Chagas Disease?
The symptoms of Chagas disease can appear within a few weeks of infection (acute) or take months to years to develop (chronic). Dogs younger than two years old are more likely to develop acute disease. Some of the symptoms that dogs have during the acute phase include swollen lymph nodes, seizures, fever, lethargy, depression, weight loss and diarrhea. The acute phase can last several weeks.
Dogs then often appear to get better, but it’s actually the disease moving from the acute phase into the latent or chronic phase. In the middle or latent phase, which can last anywhere from one to four months, many dogs can be asymptomatic. Some dogs may suddenly die, but most enter the chronic phase.
The chronic phase is the “silent killer” in which the dog’s organs are damaged. In the chronic phase, symptoms may mimic congestive heart failure and can include lethargy, fainting, increased or abnormal heart rates, and fluid buildup. Dogs can also have more subtle or hard-to-diagnose symptoms such as weight loss and decreased appetite or diarrhea and vomiting.
Diagnosing Chagas disease at any phase can be challenging. Lab tests can detect antibody levels after three weeks after infection, but aren’t foolproof. In later phases, vets rely primarily on the presence of other symptoms and clinical signs. If a dog passes away, there are also lab tests which can detect Chagas disease in heart tissue if an autopsy is done.
In the case of the two Austin Boxer Rescue dogs who became ill, a veterinarian in Austin who was informed that the dogs she had seen had later tested positive for Chagas, admitted that whenever she and her colleagues see a young dog who has died suddenly of heart failure, they often suspect that the dog had undiagnosed Chagas disease. Unless a test for Chagas is done post mortem, the cause of death is usually attributed to DCM (Dilated Cardiomyopathy), which is a common cause of death in Boxers.
Can Chagas Disease in Dogs be Treated?
Until recently, Chagas disease in dogs was a death sentence. New treatment options are emerging, though. If detected early, medications such as Benznidazole, Ravuconazole and Albaconazole have been used for treatment with varying success rates. Once infection reaches a later phase, the focus is typically on managing heart failure and arrhythmias.
There are also some promising results from Bulverde-based Vida Pharmacal. The company develops, markets and distributes pharmaceuticals designed to treat Neglected Tropical Diseases (NTDs) for human and veterinary patients, and has developed the first antiparasiticide to cure Chagas disease in dogs. According to Vida Pharmacal, they have successfully treated hundreds of dogs with Chagas, and are waiting for approval for a commercially available formula from the U.S. Food and Drug Administration (FDA) that will be distributed through vets.
Can Dogs Transmit Chagas Disease to Humans?
In a 2014 study conducted by a team at Texas A&M, which tested 205 shelter dogs across Texas for signs of Chagas, about 9 percent of the dogs tested positive. Other studies have shown infection rates as high as 20 percent or more in dogs.
However, the odds of a human getting Chagas disease from an infected dog are very low, experts say. To catch Chagas from a dog, a kissing bug would have to bite the infected dog first, and then bite you after the dog. There haven’t been any cases like this reported in the U.S. Vida Pharmacal experts note that the Kissing Bugs that carry Chagas are frequently found in South and Central Texas, and this remains the most common way to catch Chagas.
If you live in an area where Chagas disease is common, you could be at risk from the insects that carry the disease, but are very unlikely to get it directly from your dog. Although most people with Chagas’ disease don’t have any symptoms, about a third of those infected will experience heart or digestive tract damage.
How Can You Prevent Chagas Disease?
Since there’s no vaccine for Chagas disease, the best way to protect your dog is through insect and animal control. One way to do this is by reducing outdoor lighting at night, which may decrease the number of bugs and vermin in the area, particularly on porches. Another is to reduce or remove any debris and wood piles in your yard that can harbor pests or attract rodents and other wildlife.
If you continue to see unwanted insects, you may also need to get regular treatments from an exterminator. If so, check to see that any chemicals they use are safe for dogs and other pets. Other ways to prevent kissing bugs from entering your home and biting you or your dogs are to securely screen all windows, seal any gaps in doorways, roofs, and windows, and to keep your pets indoors at night.
If your yard is plagued by possums and armadillos, consider installing a protective barrier of additional fencing or a combination of fencing material and concrete at the base of the fence to keep them out, along with repairing any holes or closing any gaps that they might be using to enter your yard. And finally, if you see your dog chasing an armadillo or possum, do everything you safely can to remove the animal quickly before your dog comes into contact with it. If your dog catches and bites the animal, monitor them closely for any potential signs of Chagas disease.
Summary
In the case of the ABR dogs who became ill, we’re relieved to report that one is undergoing treatment for Chagas with help from Vida Pharmacal, and the other appears to have fought it off during the acute phase, which is rare.
If your dog has been exposed to kissing bugs or any animals that may be infected, or is showing symptoms of Chagas disease, contact your veterinarian and have your dog tested with what is known as an Indirect Immunofluorescence Assay (IFA) test. The symptoms of Chagas can easily be mistaken for other illnesses and diseases, and many vets aren’t familiar with it yet, either. Texas A&M is currently the only option for testing for Chagas, and results can take days or even weeks.
Your best option is to try to reduce the odds of infection by reducing or eliminating kissing bugs and other vermin, as well as anything in your yard that might be an attractive home for them. Finally, if your dog is confirmed as being infected, seek expert care immediately from a vet familiar with Chagas disease. The sooner it’s detected, the better the outcome may be.
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