Chagas Cardiomyopathy in Dogs Infected with Trypanosoma cruzi (by Jan Grebe)
Dr. Ashley Saunders, Professor of Cardiology at Texas A&M, described this deadly disease that is widespread in South and Central America and Mexico, but was formerly found mainly along our southern border. It is now in the entire southern half of the United States, and some cases has spread to northern areas.
Chagas Disease is caused by a protozoa parasite called Trypanosoma cruzi, which is carried by a certain type of insect called a Kissing Bug, Triatomine bug, or Reduvian bug. (There are some look-alike bugs so it is a good idea to become familiar with the Kissing Bugs.) The Trypanosome can infect human beings, and can infect dogs who eat the bodies or feces of infected bugs. It can also be transmitted from a dam to her puppies. Wildlife, like opossums or raccoons, can carry the parasite and act as a reservoir for it, which is a problem near dogs housed outside or in multi-dog kennels.
The trypanosome parasites enter the blood, and eventually invade the heart muscle. There is no standard diagnostic test for T. cruzi infection in dogs, though some lab tests may be able to detect an active infection. In dogs, there are few signs or symptoms until cardiac arrhythmia, heart enlargement, or sudden death occur. It is very hard to treat because antiparasitic drugs tend to have adverse effects in dogs. Also, by the time it becomes symptomatic it has already invaded the heart muscle.
Recent studies in Texas examined 10 different kennels. A total of 64 dogs (about half positive and half negative for Chaga) were tested three times during a one-year study; 29 of the 30 infected dogs remained positive when given blood tests over that year. Ten of the 34 dogs testing negative at the beginning of the year were found to become positive during the year-long monitoring. The results of that study showed that a dog housed in those outdoor kennels had a 30.7% chance of becoming infected within that year although numerous methods had been used to control exposure to kissing bugs.
Until successful prevention and treatment strategies are designed for the T. cruzi parasite, we must focus on controlling the disease vector – kissing bugs. Managing vegetation to keep wildlife away from kennels, use of insecticides, screens, and netting, avoiding outdoor lighting that attracts bugs, and housing dogs indoors are recommended measures to prevent dog and human exposure to infected kissing bugs.