Disease history/statistics, etiology, and symptoms

            Chagas disease, also known as American Trypanosomiasis, is a parasitic disease caused by the parasite Trypanosoma cruzi.  Chagas disease occurs primarily in endemic regions of Latin America, but has spread to other places of the world, such as the U.S. and Europe.  It is estimated that 6 to 7 million people worldwide have the disease (WHO, 2015).  The parasite T. cruzi usually infects hosts through the vector triatominae, an insect also known as the ‘kissing bug’ because it commonly bites victims on or near their face.

An example of Romaña’s sign.

            Once the parasites have infected a host, they invade host cells and begin to multiply by binary fission (CDC, 2013).  At the end of this incubation period, infected cells burst, releasing more parasites into the bloodstream where they can travel to and infect other parts of the body.  This lytic phase and secondary infection characterize the acute phase of the disease.  The acute phase lasts for about two months after infection.  Often, the acute phase is asymptomatic, or only presents as generic cold symptoms such as fever, headache, swollen lymph nodes, etc.  This, in conjunction with the fact that this disease is most common in areas where access to healthcare is limited, makes it very difficult to detect and document cases of the disease (Kirchhoff, 2014).  One sign unique to the acute phase of Chagas disease is known as Romaña’s sign, which is the swelling of the eyelid caused by the entry of the parasite through the conjunctiva of the eye.

Life cycle of T. cruzi and the progression of Chagas disease

            Once the acute phase subsides, parasites are no longer found in high quantities in the blood.  Instead, they essentially lay dormant in tissues of the heart and digestive muscles.  This characterizes the chronic phase.  The prolonged asymptomatic form of infection is termed ‘chronic indeterminate.’ Many people go the remainder of their lives in the phase, never experiencing any symptoms (CDC, 2013).  However, 20-30% of infected people do experience symptoms later on in life, during the ‘chronic determinate’ phase.  Symptoms include cardiac disorders, such as arrhythmias that can result in sudden death.  Patients may also suffer from gastrointestinal problems, such as enlargement of the esophagus or colon causing difficulty swallowing and passing stool.  Additionally, a small percentage of patients suffer from neurological dysfunction that contributes to the severity of other previously mentioned symptoms (WHO, 2015).

            As mentioned previously, Chagas disease is often asymptomatic, making detection and diagnosis difficult.  If infection is suspected, blood samples can be analyzed in order to identify the presence of T. cruzi parasites.  Thick and thin blood smears are made and stained to help visualize the parasites.  Microscopic identification is only possible in the acute phase when parasites are circulating in the blood at high numbers.  If the patient is in the chronic phase, diagnosis can be accomplished through serological testing for specific antibodies to T. cruzi (Kirchhoff, 2014).

References:

American Trypanosomiasis (also known as Chagas Disease). (2013). Centers for Disease Control and Prevention.  Retrieved June 18, 2015, from http://www.cdc.gov/parasites/chagas/.

Chagas disease (American trypanosomiasis). (2015). World Health Organization. Retrieved June 18, 2015, from http://www.who.int/mediacentre/factsheets/fs340/en/.

Kirchhoff, L. (2014). Chagas Disease (American Trypanosomiasis).  Medscape. Retrieved June 18, 2015, from http://emedicine.medscape.com/article/214581-overview.