What is Chagas Disease?
Chagas disease is a parasitic infection that begins with an insect in the triatominae family consuming the blood of an infected person or animal. The parasite is then excreted through the feces of the insect, which are small and easily overlooked. Accidental ingestion of these feces is the primary route of infection, and curious pets who decide to eat a passing insect will also be at risk. Unlike other insect-transmitted infections, Chagas disease is not known to be passed through the bite of the insect.
This illness poses a serious threat to the health of your pet because it may go undetected, but damage to heart and lymphatic tissue can dramatically shorten a dog’s life. Although historically restricted to South America, the disease now appears over much of the American Southwest. If you notice behavioral changes, fever, or lethargy in your dog, make an appointment with an veterinarian right away.Chagas disease is a zoonotic illness (capable of being passed from pets to humans) transmitted through bugs in the triatominae family (assassin bugs). Caused by the protozoan Trypanosoma cruzi, Chagas disease infects the heart and smooth muscles, but may be found throughout the blood and body. This infection is chronic and if untreated may last for years until the animal’s death.
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Symptoms of Chagas Disease in Dogs
- Swelling of lymph nodes
- Enlarged liver
- Enlarged spleen
- Muscle weakness
- Refusal of food/weight loss
- Heart arrhythmia
- Congestive heart failure
- Sudden unexpected death
Note that the symptoms of Chagas disease are highly variable and may appear only minimally. Always see a veterinarian if your dog appears unwell, for a minor symptom may indicate a deeper, serious illness.
Causes of Chagas Disease in Dogs
- Contact with feces of triatominae
- Contact with fluids of infected animal
- Contact with feces of infected animal
Diagnosis of Chagas Disease in Dogs
Chagas disease has two phases, acute and chronic. During the acute phase the owner’s observation of their pet often leads to a successful diagnosis, where behavioral changes and fever are important clues. During this stage, a veterinarian may diagnose the disease by simply viewing a blood sample under a microscope. The parasite appears as a C-shaped cell with a single, whiplike flagellum on one end.
However, as the disease progresses, the parasite enters the cells of target tissues such as the heart, brain, lungs, and GI tract, no longer being detectable in the blood. At this stage, histologic tests such as ELISA and antibody detection are often used to diagnose the disease. Additionally, tissue samples from affected organs can be analyzed by PCR to detect the DNA of the parasite.
Heart problems such as right-side congestive heart failure, myocarditis and arrhythmia often result as an effect of Chagas disease, and may be detected with a cardiac echo or an electrocardiogram (EKG). Occasionally pneumonia may also result, detectable with a chest x-ray.
Treatment of Chagas Disease in Dogs
Unfortunately, there is no easily-available treatment for Chagas disease, and no vaccine. Treatment usually focuses on managing the symptoms of the disease, such as administering medication for the heart or lungs as their respective conditions require, and keeping the infected animal away from others.
Recovery of Chagas Disease in Dogs
Routine follow-up appointments will be needed to monitor your pet’s condition and treat any new ailments that arise as a result of the disease. Proper disposal of feces, and disinfection of any potentially-contaminated surfaces with 10% bleach solution is essential, as this disease is highly transmissible and capable of infecting humans. Human Chagas disease is an equally serious condition and owners should take every precaution to minimize their risk.
Preventative measures to avoid Chagas disease include turning off outside lights at night, which minimizes the attraction of the insects, cleaning up any insect feces with bleach, and keeping one’s pet indoors at night.
Chagas Disease Questions and Advice from Veterinary Professionals
How soon after being (potentially) infected with Chagas parasite would my dog begin showing signs of the acute phase? I have a 5-yr old Chihuahua who may have been bitten by or exposed to feces of t.Gerstaekeri during first week of July 2017. My vet says we can test around Sept 1. Given her small size, I'm wondering if the parasite could be detected sooner. She is showing signs of lethargy, could be anything, but I'm very worried.
The incubation period for acute Trypanosomiasis in dogs may range from 5-42 days, although some dogs may be asymptomatic for a longer period of time. Diagnosis may be performed by taking a small blood sample and checking it under a microscope as Trypanosoma cruzi is normally visible using this method as the link to the image below. Treatment is with benznidazole, but I do not believe that this is approved in the USA for use. Regards Dr Callum Turner DVM
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