Chagas Disease: The Intersection of Infectious Pathogens and Chronic Illness

Cardiovascular diseases (CVDs) are often addressed from the perspective of chronic disease management because of their prevalence in developed countries, where common CVD conditions include coronary and peripheral artery disease, congestive heart failure, and ischemic stroke. In developed countries, these CVDs often develop over many years and are due to chronic conditions like obesity, high blood pressure, diabetes, and cholesterol- and fat-filled plaques in the arteries. However, CVDs can also manifest as the product of communicable diseases. One example is Chagas disease, in which infected individuals can develop long term and potentially fatal complications such as heart rhythm abnormalities. In order to substantially reduce the impact of CVD on a global scale, it is critical that prevention and screening initiatives address both the pathogens that transmit the disease, and the chronic lifestyle behaviors that perpetuate the condition. 

The vector insect of Chagas disease is the triatomine bug, or the kissing bug.  A vector is an organism that carries pathogens and makes transmission of a disease from one population to another more feasible. Chagas disease is not caused by the insect itself, but develops when a human host becomes infected with the Trypanosoma cruzi (T. cruzi) parasite found in the feces of triatomine bugs.1 Infection with the T. cruzi parasite occurs when triatomine bugs feed on humans and defecate on the host’s skin. The initial bite triggers an inflammatory response in the host who then responds by scratching the inflamed area surrounding the bite. Scratching breaks the skin and allows the parasites found in the bug’s stool to enter the host’s bloodstream, which results in initial infection.

Symptoms of Chagas disease can be divided into acute and chronic stages. Acute phase symptoms include fever, headache, loss of appetite, aches, and rash around the site of the initial bug bite. The acute stage of Chagas disease is often treatable with antibiotics such as antiparasitic agents that attack the parasite directly. If left untreated, this illness can transition into its chronic stage. Initially, the chronic phase is asymptomatic and people can theoretically live the remainder of their lives in this stage with no additional issues. However, for others the parasite will eventually travel to the cardiac muscle where it can produce heart arrhythmias or weaken heart muscles. Muscle weakening is caused by enlargement of the heart, which makes it harder to pump blood effectively. Additionally, muscle atrophy can lead to progressive heart complications and possibly heart failure.

Aside from vector transmission there are many other situations during which the parasite can be passed to a new host, including maternal-fetal transmission during pregnancy, organ transplants, and blood transfusions. As a result, it is very important to identify multiple avenues for implementing disease prevention interventions. The most common approach in areas where Chagas disease is prevalent is vector control. This involves the use of large scale insecticide campaigns to deplete insect populations and reduce the probability that a bug bite will be infectious. Other prevention efforts include screening blood donations for parasites and other viral pathogens to prevent hospital-acquired infections.

Chagas disease is found infrequently in some regions of the northern United States. The parasite is endemic in the Southern US, Central America, and South America. Chagas disease is responsible for 8000 deaths and 6.6 million infections annually.2 Currently, there are very limited Chagas disease screening efforts, resulting in millions of acute Chagas infections that transition into the chronic state each year. While the majority of these chronic infections will remain asymptomatic, over 30-40% of them will result in long term cardiac complications.3 This means that despite healthcare advances in other areas of medicine that improve global life expectancy, the number of cardiac disease cases attributable to Chagas disease will continue to increase. Furthermore, the currently limited number of prevention interventions and screening efforts for the T. cruzi parasite means that the rising number of acute cases will lead to a corresponding increase in chronic cases. This will create an especially heavy disease and economic burden on low income communities of color with limited or no access to medical insurance and/or healthcare facilities. The case of Chagas disease demonstrates that while CVDs rooted in chronic lifestyle behaviors are important, a growing number of CVD cases are attributable to transmissible pathogens. Thus, accurate, impactful, and equitable treatment of CVD should encompass funding initiatives that target not just lifestyle behaviors, but also pathogen transmission and prevalence of communicable diseases such as Chagas.

References
  1. Malik, Lindsey H., et al. “The Epidemiology, Clinical Manifestations, and Management of Chagas Heart Disease.” Clinical Cardiology, vol. 38, no. 9, 2015, pp. 565–569., doi:10.1002/clc.22421.
  2. Yager, Jessica E., et al. “Prevalence of Chagas Heart Disease in a Region Endemic for Trypanosoma Cruzi.” Global Heart, vol. 10, no. 3, 2015, pp. 145–150., doi:10.1016/j.gheart.2015.07.002.
  3. “Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990–2015: a systematic analysis for the Global Burden of Disease Study 2015,” The Lancet, Volume 388, Issue 10053, 8–14 October 2016, Pages 1545-1602.

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