Chagas Disease in dogs, also known as American trypanosomiasis, is a parasitic vector-borne disease caused by Trypanosoma cruzi. The disease is native to Central and South America and in the southern parts of the United States of America.
The protozoan is carried by the vector Triatominae, also known as “Kissing bug” or “Assassin bug.” The disease can infect over 100 species of mammals and can cause heart disease.
Dogs are typically infected by eating the feces of infected insects. While feeding on the dogs, these bugs usually defecate on or near the wound; dogs become infected when they lick the wounds containing the insect’s feces.
Dogs can also become infected by consuming infected insects or rodents that have been infected by the Trypanosoma cruzi parasite.
Upon ingestion, the parasite enters several cells in the body, including the cells lining the blood vessels, the muscle cells in the heart, and other cells in the body.
The Trypanosoma cruzi parasite reproduces in these cells until it reaches sufficient numbers that cause the cell to explode and release large numbers of the parasite into the bloodstream.
When this happens, the effects of the parasite become noticeable in the dog. Chagas disease can also be transmitted via canine blood transfusions where an infected dog is the blood donor.
Stages of Chagas Disease
The signs of Chagas disease vary depending on the dog, and they are non-specific. Subtle signs like decreased appetite, lethargy, and weight loss can be observed in infected dogs.
There may also be noticeable severe signs such as exercise intolerance, fainting, vomiting, and diarrhoea. Upon examination, the vet doctor may discover signs of heart failure, enlarged lymph nodes, and fluid in the abdomen.
The stages of Chagas disease infection are:
There are sometimes no observable symptoms during the acute phase of the infection. When the clinical signs are noted, they usually include enlarged lymph nodes and spleen due to the body’s immune system attempting to fight off the infection.
Other symptoms include:
- Pale gums (due to poor circulation)
- Decrease appetite
Some dogs may die suddenly during this phase of the disease. Most, however, enter the latent phase.
This phase which usually lasts for about 1-4 months, is typically asymptomatic. Some dogs may experience sudden death during this phase of the infection; however, most enter the chronic phase.
It is at this stage that most cases of the infection are diagnosed. As the parasite continues to multiply within the tissues of the hearts, the dog develops signs of heart failure.
Irregular heartbeats (Arrhythmias) may also be observed during examination. Pet owners may even notice signs like coughing, shortness of breath, exercise intolerance. Sudden death may occur due to heart failure.
Diagnosing Chagas disease in dogs can be challenging, especially during the acute phase of the infection. The Trypanosoma cruzi parasite may be discovered in the blood or lymph nodes, but their numbers are usually so low that diagnosis may not be reliable.
Antibodies of the parasite can be detected approximately three weeks after the infection. Although, false positives of the lab tests may also occur.
A diagnosis of the disease during the chronic phase is based mainly on the presence of clinical symptoms. Tissue samples taken from a dog that dies from the infection will reveal the characteristic changes associated with the parasite.
There is no specific treatment of Chagas disease in dogs. Medications such as benznidazole, itraconazole, and nifurtimox that are used to treat trypanosomal infections have some degree of success in treating the condition in the acute phase.
However, these drugs can only suppress the parasite temporarily and have a number of side effects.
There is no treatment for the parasite when it reaches the chronic phase. Treatment of the condition depends on managing heart failure and arrhythmias that may occur.
Prevention of Chagas Disease
It is crucial to control vectors that carry the parasite of the infection. Areas, where the Kissing bugs can be found include brush piles, porches, nests, and wooded areas.
The bugs are most active at night and are attracted to light. They can invade homes and kennels. Control of the vectors can include cleaning up brush and woodpiles that serve as breeding grounds for the insect.
Other methods can consist of turning off outdoor lights, housing animals inside the house, and using insecticide.