What parasite does the physician suspect the patient having based on the clinical history, family history, and clinical presentation?
Trypanosoma cruzi, the cause of Chaga’s Disease.
What is a “vinchucas” and what is its significance?
Vinchucas is a name given to the Triatomine or Raduvid bug in various South American geographic locations. There are other names given depending on the geographic location ( “Barbeiros” in Brazil; “Pitos” in Colombia; “Chinche besucón”, “Chipos” “Chiramacas”, “Chinches aladas”, “vampire bugs”, cone-nosed bugs”, and “assassin bugs”), depending on the region, but Vinchucas is the most common name used in Latin American countries. The significance of the Vinchucas is that it is the vector for Trypanosoma cruzi, a parasitic hemoflagellate endemic to Central and South America.
This is a case study where the clinical presentation and history would strongly point to Chaga’s disease. An insidious parasitic infection that can cause a chronic parasitosis with unfortunate cardiac complications that can prove to be fatal.
Chagas’ disease is an infection with the trypanosome parasite, Trypanosoma cruzi , a hemoflagellate. Trypanosoma cruzi is endemic in most Latin American countries where the vector, the Triatomine bug, can be found. The Triatomine are a large group of bugs consisting of over 100 species in the New World, that feed on blood from a variety of mammals including humans. Eurasia and Africa also have species but have been found to be insignificant epidemiologically. Triatomine bugs feeding on humans are most prevalent in areas where dwellings are made of adobe, straw, palm thatch or mud. These types of dwellings create environments which the bugs can hide in during the day, and come out from at night to feed on their unsuspecting prey.
Attracted by the CO2 production of the sleeping human, most Triatomine bug bites are located in the facial area. Swelling of the eyelid can occur as a reaction to the trypanosome entering the eyelid. This swelling around/under the eye is called “Romaña’s sign”. Interestingly the trypanosome is not transmitted by the bite of the Triatomine bug but instead is transmitted by the introduction of the metacyclic trypomastigote form of Trypanosoma cruzi infected feces, excreted while the Triatomine feeds on the host. The allergic reaction to the saliva of the bug, causing itching at the site of the bite, results in an enhanced opportunity for the entry of the metacyclic trypomastigote into the host. The metacyclic trypomastigotes are most likely to be introduced into the eyes or a break in the skin.
Once these metacyclic trypomastigotes enter the host they will invade cells and transform into the amastigote form. Amastigote forms are described as the proliferative form of the parasite. Within the infected cell they will multiply and differentiate into trypomastigotes until a critical mass is achieved whereupon the cell will burst and release the trypomastigotes. Trypomastiogote forms are described as the infective form of the parasite. The released trypomastigotes will go on to infect other cells and differentiate into amastigotes to continue the cycle within the host. The host will also act as a source of trypomastigotes to uninfected triatomine bugs which will then eventually be a source of infection to uninfected hosts. Triatomine bugs that ingest trypomastigotes will have these trypomastigotes transform into epimastigotes (described as the proliferative vector form) in the midgut and divide to eventually develop into the infective metacyclic trypomastigote in the hindgut. Thus the epimastigote form of the trypanosome is only seen in the Triatomine bug vector.
Chaga’s disease can present in two forms. One form is an acute myocarditis that presents soon after infection with the parasite. The other is a chronic disease that can last for a lifetime. Generally the acute form is less dangerous of an infection then the chronic form.
The acute disease can be asymptomatic or cause mild symptoms that can present with lymphadenopathy, fever, and other non-specific symptoms that can prove to be diagnostically confusing without a completely obtained clinical history. In very rare cases an acute infection can present as acute myocarditis or as meningoencephalitis. Both of which are associated with a high risk of mortality.
Chronic Chaga’s disease is an insidious parasitosis that over the years of infection will result in mycotic degeneration, inflammatory infiltration, and fibrosis. The myocardial damage is microfocal and disseminated throughout the heart. This disseminated damage is evident in the patient’s ECG abnormalities which are representative of widespread cardiac involvement. Abnormalities in cardiac function due to Chaga’s disease typically do not produce pulmonary edema in patients and orthopnea is uncommon. Patients with chronic Chaga’s disease more commonly will eventually have systemic complications, pulmonary embolisms, and sudden death from a fatal dysrhythmia. The fatal dysrhythmia can be due to ventricular fibrillation, third-degree heart block, or an embolism. Advanced chronic cases can also lead to a deadly aneurism.
What is the suggested treatment for this parasitic infection at this stage?
Acute forms can be treated successfully and usually benznidazole or nifurtimox are used to kill the parasite. These two drugs are highly effective in curing the disease in the acute form and early chronic forms of the disease. The later the delay in the treatment the less chance there is for a cure. Chronic forms will require life-long supportive treatments due to the extensive damage of the parasitosis to affected organ systems. The extent of the life-long supportive treatments will be determined by the organ systems affected.
As global warming continues, so does the spread of Trypanosoma cruzi and its Triatomine bug vector into the southern border areas of the United States. These areas have over the years become vigilant of this parasite. One of the worries has been the blood supply and or organs for transplantation as sources for infection. Screening measures have been initiated to detect Trypanosoma cruzi in the United States as standard practice in blood banks.
What tests should should the physician order? Why are these tests necessary to confirm an infection with the suspected parasite.
The detection of Trypanosoma cruzi infections in the peripheral blood is only practical in acute infections where the trypanosomes can be found in good numbers. These trypanosomes have a characteristically large prominent kinetoplast when compared to other pathogenic trypanosomes. PCR techniques are also best at detecting acute infections. Chronic infections are detected by the use of serological tests that detect the antibodies to the parasite. PCR techniques are less useful in detecting the organisms due to low parasite loads. The screening for Trypanosoma cruzi infections is not routinely performed in the general population, however it is highly recommended for individuals with a history of living in or having traveled to an endemic area of Central and South America.
I hope this has been an informative clinical case study. And as always, please feel free to use this any or any of my other blogs as teaching tools. All the best!
