American Trypanosomiasis Parasitic Infection in Dogs
Chagas disease is an illness caused by the protozoan parasite Trypanosoma cruzi, which may infect dogs in several ways, including through blood exposure to the feces of “kissing bugs,” the ingestion of infected kissing-bugs, kissing-bug feces or prey (e.g., rodents), or congenitally from a mother to her offspring.
Once the parasites enter the cells in a dog’s body (often the heart muscle), they multiply and eventually rupture the infected cells. This is why Chagas disease is commonly associated with heart disease in dogs.
Chagas disease is endemic in South and Central America, but it is also found in the United States, typically in in Texas, Louisiana, Oklahoma, South Carolina, and Virginia. But the disease’s range is expanding as our climate warms.
Symptoms and Types of Chagas Disease
Two forms of Chagas disease are observed in dogs: acute and chronic. Some dogs experience an extended asymptomatic period between the two forms, which can last for months to years.
- Loss of appetite
- Swollen lymph nodes
- Enlarged liver or spleen
- Neurologic abnormalities (e.g., seizures)
- Sudden death
These symptoms may not be noticed by owners because they often resolve without treatment.
- Exercise intolerance
- Increased heart rate (tachycardia)
- Abnormal heart rhythms
- Fluid accumulation throughout the body
Causes of Chagas Disease
Although Chagas disease can only be acquired through an infection with the T. cruzi parasite, there are a variety of ways a dog may come in contact with the organism. Illness may occur when a vector—a kissing bug (Triatominae)—bites the dog on the skin or on a mucous membrane (such as the lips) and leaves infected feces in the wound. It can also occur when a dog eats an infected prey animal (e.g., rodent) or ingests the feces from a kissing bug. The parasite can also be passed from a mother to her offspring.
Diagnosis of Chagas Disease
You will need to give a thorough history of your dog’s health to your veterinarian, including the onset and nature of the symptoms and possible incidents that might have precipitated them. He or she will then perform a complete physical examination and may order a blood chemical profile with electrolyte panel, a complete blood count, a urinalysis, X-rays, electrocardiogram and ultrasound of the heart, and specific tests for Chagas disease (e.g., serology).
X-Rays may indicate heart changes associated with Chagas disease, while an echocardiogram can reveal the chamber or wall abnormalities often seen with chronic forms of the disease. An electrocardiogram can exposes heart arrhythmias and other changes that are associated with Chagas disease.
Treatment for Chagas Disease
Although several drugs have resulted in somewhat limited improvement in dogs during the acute stage, none produce a clinical “cure.” Unfortunately, even those dogs that get treatment may progress to the chronic form of the disease. In these cases, supportive treatment of heart complications is of primary importance.
Living and Management
Dogs with Chagas disease and the heart disease that results have a guarded to poor prognosis. Dogs are not thought to directly pass Chagas disease to people, so euthanasia solely for this reason is not necessary.