Guess The Probable Parasitic Diagnosis (Part 2)

This was a case of a chronic Trypanosoma cruzi infection or Chaga’s disease.

The clinical history was significant for immigration from an endemic area in Guatemala and the history of past bites with what she called “vinchucas”. Vinchucas are the local name given to a nocturnal blood feeding Triatomine bug more commonly known as the Raduvid, Kissing or Assassin bug. The Triatomine bug is the known vector of the Trypanosoma cruzi hemoflagellate. Also of note is the past family history of Vinchucas bites, and the illness and early deaths of her brothers in their twenties. The disease due to Trypanosoma cruzi is called Chaga’s disease, named after the Brazilian physician Carlos Chagas who discovered it in 1909.

The patients history and the physical presentation of hepatomegaly with symmetrical distention of the abdomen, and most importantly the abnormal ECG consistent with conduction disturbances, point to a strong suspicion of a case of chronic Trypanosoma cruzi infection.

Trypanosoma cruzi îs one of three pathogenic hemoflagellate. The others being Trypanosoma brucei gambiense (western/Central African Sleeping Sickness) and Trypanosoma brucei rhodesiense (East African sleeping sickness). Trypanosoma cruzi is found predominantly in South America,Central America and Mexico. Besides the geographical difference in distribution, the Trypanosoma gambiense have a different vector in the Tsetse fly (Glossina spp.). With recent border migrations and global warming the incidence of Trypanosoma cruzi has by inching upward geographically into the Southern United States border states. This is especially disconcerting as blood transfusions are a possible mode of transmission.

The disease is most commonly seen in the Central and South American continent, especially in rural areas where the population is poor and live in poorly constructed houses that provide excellent dwellings for the vectors within cracks in the walls. During the day they lay hidden in these cracks only to move out for feeding in the night, attracted to their prey by the detection of CO2. As a result the bites of the nocturnal Triatomine bug are almost exclusively around the facial area. As the Triatomine bug feeds on the blood of the host the bug defecates/urinates. The ensuing allergic reaction to the site of the bite produces itching that introduces the bug’s contaminated feces/urine into the bite site. The feces/urine contains the infective developmental metacyclic trypomastigote form of Trypanosoma cruzi. Lymphadenitis around or under the eyelid (Romana’s Sign) is a result of the host immune reaction to the invading metacylic trypomastigote forms.

Chaga’s disease can present to two forms. An acute and a chronic form. The acute form usually has a duration of two months where there are a high number of parasites circulating in the blood. The acute form can present with a lymphadenopathy around the eyes that is called Romana’s Sign. Other than that, symptoms are either absent or mild in presentation and can run the gamut (headache, fever, muscle pain, shortness of breath, abdominal and chest pain).

It is the chronic phase that is most disconcerting. In this phase the parasite becomes hidden preferentially in the muscles of the heart and digestive tract. The manifestations of the chronic infection may not become apparent for decades where 30% of individuals will suddenly present with cardiac abnormalities and/or 10% will present with digestive abnormalities such as megacolon and/or megaesophagus. Neurological or mixed alterations are possible. Many of these chronic infections will progress to irreversible nervous system damage, difficulty swallowing, digestive problems, heart damage, progressive heart failure and eventual sudden death.

Early treatment of the disease is paramount. It is only in the treatment of the disease in its early stages that cure is possible. Once in the chronic phase, especially in the advanced chronic stage, there is no cure. Therapy is directed at attempting to slow the progression of the disease.

The disease has various ways in which it can be transmitted which is a very important consideration when trying to elucidate the potential for disease in a patient being assessed. The consumption of foods contaminated with the feces/urine of infected Triatomine bugs can be a source of infection. Organ transplants and blood transfusions can be a source of infection. The passage of the parasites to newborn babies is possible. And lastly, though rare, laboratory accidents can be a source of transmission.

As Trypanosoma cruzi continues its upward geographical migration from Central America to the Southern United States, we must increase our vigilance in detecting this disease. The importance of screening for the presence of Trypanosoma cruzi in blood and organs for transplant will need to be incorporated with other already disease screens.

Diagnosis can be made by detecting the trypomastigotes in the peripheral smear as seen below, testing for specific parasite antibodies, and a good clinical history of the patient. Trypomastigotes are not commonly seen in patients with long chronic disease and therefore antibody testing along with a clinical history are going to be diagnostic.

High Oil Immersion photo image of a Trypanosoma cruzi trypomastigote in a peripheral smear preparation. Of note is the large kinetoplast characteristic to T. cruzi. Trypanosoma gambiense spp. do not have a prominent kinetoplast.

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