Chagas Disease in Dogs

Chagas disease or American Trypanosomiasis is caused by Trypanosoma cruzi. This flagellate is transmitted by insects like the Mexican kissing bug that infest bedding. They feed on people and dogs while they sleep.  When the bug defecates, the immature form of T. cruzi is released into the environment. If the dog or human has defects in their skin, the immature form called a trypomastigote  can gain access. It likes to migrate into the reticuloendothelial system as well as the striated muscle of the heart. The trypomastigote mature into intracellular amastigotes. Eventually, the amastigotes form pseudo cysts that will destroy the cell. When the cell membrane ruptures, T. cruzi invades other cells causing massive destruction.

Clinical signs start with weight loss, lethargy and anorexia. As time passes, infected dogs may faint, have respiratory problems, heart problems, vomiting, diarrhea and paralysis. Sudden death may also occur.

There are three phases of infection:

  1. Acute – Dogs can be asymptomatic during the initial stages. Others will have an enlarged spleen, liver and lymph nodes. Their gums are often pale and many have diarrhea. As the disease progresses, some dogs become paralyzed. Sudden death is also possible from abnormal heart rhythms.
  2. Latent – This phase lasts one to four months. Most dogs show  clinical signs in this phase.
  3. Chronic – This phase is characterized by slow progression of heart disease to heart failure. The heart dilates and has trouble contracting. The right side of the heart is usually affected first. Fluid backs up on the abdomen causing distention. Eventually, the left side of the heart is also affected causing fluid to accumulate in the lungs and respiratory problems.

Currently, there are no effective treatments for Chagas disease. Strict hygiene and pest control are the key to prevention.

Source: Snell, Linda. American Trypanosomiasis (Zoonotic), Associate 12/22/2010.