American Trypanosomiasis Parasitic Infection in Dogs

 

Chagas disease is an illness caused by the zoonotic protozoan parasite Trypanosoma cruzi, which may be contracted through a variety of manners including a blood transfusion. Once the parasite becomes intracellular, it multiplies and eventually ruptures out into the blood circulation, spreading to various organs but mainly the brain and heart. This is also why Chagas disease is commonly associated with sudden inflammation of the heart muscle.

 

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. Other areas where you may find vectors and reservoir hosts for the parasite include the west (California, New Mexico), south (Florida, Georgia, North Carolina), and east (Maryland).

 

Symptoms and Types

 

Two forms of Chagas disease are observed in dogs: acute and chronic. Some dogs enter an extended asymptomatic period (where no symptoms develop), which can last from months to years. During that time, however, there is a progressive and insidious development of the parasite, leading to the degeneration and inflammation of the heart, which can eventually cause heart failure and death.

 

Acute (typically dogs younger than 2)

• Diarrhea
• Depression
• Lethargy
• Exercise intolerance
• Walking difficulties
• Rapid body jerks, seizures
• Swollen lymph nodes
• Increased heart rate (tachycardia)
• Congestive heart failure (left and right-sided)

 

Chronic (typically older dogs)

• Weakness
• Fainting
• Exercise intolerance
• Increased heart rate (tachycardia)                  

 

Causes

 

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. It may occur when a vector, such as 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 feces from an infected host (opossum, raccoon, and armadillo), or through a blood transfusion.

 

Diagnosis

 

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 the complications. He or she will then perform a complete physical examination as well as order a blood chemical profile, a complete blood count, a urinalysis, serology and an electrolyte panel -- all of which may demonstrate results common with parasitic infections.

 

X-Rays may indicate heart and pulmonary diseases associated with Chagas disease, while an echocardiogram may show chamber or wall abnormalities, often seen in sudden or chronic forms of the disease. For example, atrioventricular block and right bundle branch block are seen in dogs with acute forms of the disease, whereas ventricular arrhythmias (which can then degenerate into various forms of ventricular tachycardia) are associated with chronic Chagas disease.

 

 

Treatment

 

Although several drugs have shown somewhat limited improvement in dogs during the acute stage, none produce a clinical “cure.” Unfortunately, even those that get treatment may progress to the chronic form of the disease. In these cases, supportive treatment of heart complications (e.g., heart arrythmias) is primary.

 

Living and Management

 

Dogs with Chagas disease and sudden heart complication have a guarded prognosis, while those with chronic forms of the disease typically have a more dismal outcome. In addition, due to the zoonotic nature of the disease, your veterinarian may recommend euthanizing the dog.