Chagas disease in dogs is a life-threatening infection transmitted by insects known as kissing bugs. Kissing bugs sound like cute little insects, but these nasty critters feed on the blood of animals. They carry the parasite that causes Chagas disease. Although the illness is more prevalent in Mexico, Central America, and South America, it’s a concern for dog owners in the United States, as well. Read on to learn more about Chagas disease in dogs.
In This Article
What Causes Chagas Disease in Dogs?
The parasite that causes Chagas disease, known as Trypanosoma cruzi or sometimes T. cruzi, can infect humans, dogs, and other animals. However, once an infection is present in your dog, the parasite isn’t passed from your dog to you. Similarly, you can’t pass the disease to your dog.
Professor of epidemiology at Texas A&M College of Veterinary Medicine & Biomedical Sciences Dr. Sarah A. Hamer, MS, PhD, DVM, Diplomate ACVPM (epi) says, “The traditional route of transmission to people is when an infected insect defecates on a host, which can happen while it is taking a blood meal from the host. However, we suspect that it’s more common for dogs to get infected if they accidentally or intentionally eat a kissing bug.”
When a dog eats an infected bug, the parasites can enter the dog’s mucous membranes or gastrointestinal tract. But dogs can come across parasite-laced bug feces, too. If they sniff or lick areas contaminated by those feces, then the parasite can get in through the eyes, mouth, nose, or a wound in the skin. Finally, congenital transmission is possible. This is where a mother dog with actively circulating parasites infects her puppies in utero.
Where Are Kissing Bugs Found?
Kissing bugs (Triatomine species), also known as assassin bugs or reduviid bugs, are about one half to one inch long when adults. These dark-colored insects have elongated cone-nose heads with long mouthparts extending between their antennae. Their bodies are shaped like a pumpkin seed and many species have red or orange lines along the sides of their body. They are active mostly at night and prefer to live in dry, sheltered crevices near hosts. According to Dr. Hamer, the bugs are also attracted to outdoor light sources. “Common hiding or breeding spots include outdoor dog housing (kennels, bedding, runs, crates), older wooden or rural buildings, under porches or decks, brush or wood piles, chicken coops, and rodent or other wildlife nests or dens.”
Kissing bugs are mainly found in the southern U.S. So are the T. cruzi parasites. Therefore, infected kissing bugs can be found in Texas, Louisiana, Georgia, Florida, Mississippi, Arizona, and Southern California. They have even been found as far north as Pennsylvania. However, Dr. Hamer says the density of infected bugs seems to decrease with higher latitudes.
Which Dogs Are Most at Risk of Contracting Chagas Disease?
Dogs are at the highest risk in the Southern U.S., particularly in Texas, Louisiana, and adjacent states. But Dr. Hamer advises the level of risk varies by lifestyle as well as region. “Dogs that live outdoors, in rural or wooded areas, or in group housing (kennels or shelters) are at higher risk of encountering infected kissing bugs.”
Professor of cardiology at Texas A&M College of Veterinary Medicine & Biomedical Sciences Dr. Ashley B. Saunders, DVM, PGCertVetEd, Diplomate ACVIM (Cardiology) warns about taking trips to high-risk regions with your dog. “If a dog travels with its owner to Chagas-endemic regions, especially for camping, hunting, field trials, or stays in rural areas, the risk increases. Also, dogs that are from Texas or other southern states and later move to northern states may have acquired an infection in the south.”
Importing a dog from a country where the disease regularly occurs is also risky. Chagas disease has been diagnosed in dogs brought up from Mexico as well as Central and South America. If you purchase or rescue a dog from these areas, be aware of the potential for infection.
What Are the Signs of Chagas Disease in Dogs?
Chagas disease progresses through an acute stage to a chronic stage, and each presents different diagnostic challenges and clinical signs. According to Dr. Saunders, many infections go unnoticed until late-stage heart disease appears. During the acute stage, the parasite rapidly multiplies in the dog’s tissues, especially in their heart muscle. Severe sign of illness can include heart failure and death; however, many dogs show no signs of illness or only mild signs. Look out for the following:
- Lethargy
- Lack of appetite
- Fever
- Pale gums and other mucous membranes
- Enlarged lymph nodes
- Irregular heart rhythm
- Ascites (a build-up of fluid in the abdomen)
Once the dog enters the chronic phase of the disease, the parasite is still present in the tissues, but in lower numbers. Many dogs don’t ever show clinical signs despite being infected. But for some dogs, their immune response causes progressive buildup of scar tissue in the heart over months to years, leading to chronic myocarditis (inflammation of the heart muscle) and cardiomyopathy (disease of the heart muscle). Dr. Saunders says at this stage clinical signs include:
- Exercise intolerance
- Coughing or breathing difficulties
- Ascites
- Fainting
- Sudden death
How Is Chagas Disease in Dogs Treated?
Dr. Saunders says although Chagas disease has long been established in the Southern U.S., it’s still a tricky disease for vets. “Awareness among veterinarians is increasing, but Chagas is still challenging to diagnose due to imperfect diagnostic tests, nonspecific signs (e.g., sudden death, arrhythmias, heart failure), and treatment challenges.”
Dr. Saunders says medical management for the heart issues is used on a case-by-case basis. When given early, antiparasitic treatments are more likely to reduce parasite load or protect from heart damage. “Complete parasitological cure remains challenging. In part because the available diagnostic tests are not sufficient and prognosis is poor in dogs with advanced cardiac disease. Continued research into drug efficacy, dosing strategies, and reinfection prevention is essential.”
Dr. Saunders and Dr. Hamer are currently running a study, funded by the AKC Canine Health Foundation, that’s investigating a modified benznidazole (an antiparasitic) treatment protocol for Chagas disease. As part of their Kissing Bug Community Science Program, you can consider donating any kissing bugs you find. Along with helping their research efforts, the free service will also identify the species and test it for infection with the T. cruzi parasite.
How Is Chagas Disease in Dogs Diagnosed?
During the acute phase of Chagas disease in dogs, diagnosis may be made using a blood test to detect antibodies for the parasite. However, Dr. Saunders says these tests are more likely to be negative within the first month as the dog has yet to develop a detectable immune response. A positive diagnosis can be made if parasites are found in a blood smear or lymph node sample, or if a polymerase chain reaction test (a test of genetic material) of a blood or tissue sample is positive for T. cruzi. However, false negatives are possible if there are no circulating parasites.
In the chronic stage, diagnosis is often made through clinical signs of heart damage. Blood tests for antibodies will be positive and issues with the heart may be detectable, such as an abnormal ECG (electrocardiogram). This is because after the acute phase, the parasite persists in the tissues in low numbers. According to Dr. Saunders, “The immune response causes progressive fibrosis of the heart over months to years, leading to chronic myocarditis and cardiomyopathy in some dogs. Many dogs do not ever demonstrate clinical signs despite chronic infection.”
Can You Prevent Chagas Disease in Dogs?
As Chagas disease in dogs is so difficult to diagnose and treat, Dr. Hamer says preventing the disease is the goal. “Environmental management to control the vectors and behavioral precautions are the most effective tools we have right now, especially since there is no vaccine or consistent treatment to eliminate T. cruzi in dogs.”
There are no insecticides specific for kissing bugs in the U.S., but environmental applications of pyrethrin insecticides may be useful. Dr. Hamer says her research with Dr. Saunders is also showing that some flea and tick control medications have the added benefit of also killing kissing bugs, but additional studies to evaluate their effectiveness are still underway. Other preventive steps she suggests include:
- Keeping kennels well sealed, elevated, and screened
- Using artificial lighting cautiously near kennels
- Inspecting and cleaning dog bedding and crates regularly, especially in summer when bug activity peaks
- Removing woodpiles, brush, and debris near dog areas
- When possible, preventing dogs from sleeping outside overnight
- Reducing exposure to wildlife
This article is intended solely as general guidance, and does not constitute health or other professional advice. Individual situations and applicable laws vary by jurisdiction, and you are encouraged to obtain appropriate advice from qualified professionals in the applicable jurisdictions. We make no representations or warranties concerning any course of action taken by any person following or otherwise using the information offered or provided in this article, including any such information associated with and provided in connection with third-party products, and we will not be liable for any direct, indirect, consequential, special, exemplary or other damages that may result, including but not limited to economic loss, injury, illness or death.