If you have read my blogposts you may be aware that I study the ecology and evolution of infectious disease systems. I am particularly interested in understanding more about the abundance and distribution of pathogens and parasites that cause disease, how they interact with other organisms and their environment, and the history behind the observed patterns of their abundance and distribution. Many of the infectious diseases that I assist in research with are vector borne, or transmitted from host to host through another organism. One of the disease-causing parasites we are currently studying causes Chagas Disease. This is an extremely important disease, and as people migrate from regions where it occurs naturally it is becoming more important that people in other parts of the world are aware of it as well.
Chagas disease is caused by a protozoan parasite known as Trypanosoma cruzi. This is a single-celled organism that can cause acute and/or chronic disease in humans. It is transmitted from one host to another through a bug most commonly known as the “kissing bug” in the United States. Kissing bugs are in the family Triatominae and are most commonly found throughout South America, but some species occur as far north as the southern United States.
The most common route of transmission that many people are aware of from a vector is through bites, but that is not how this parasite is transmitted. Instead, Trypanosoma cruzi is transmitted through the feces of the kissing bug. The bug defecates as it’s feeding, and because the bite is itchy, the host will scratch the area and rub feces into the wound.
Currently, this disease is not commonly known about in the United States because the species of kissing bugs that live in the southern United States rarely transmit the disease. There are a few reasons for this: one is that there are only 2 species that occur in the United States that we know transmit the disease. Another is that timing of defecation is extremely important when considering transmission. Species in the United States normally do not defecate while feeding; therefore, it is extremely uncommon to be infected this way in the United States. Also, it is important that the vector species not be detected by the host from whom they are obtaining a meal. Many of the species of kissing bug in the United States are too large and, they usually feed with half of their body off of the host. Therefore, if they do defecate while feeding, they are not defecating on the host.
However, there are other ways to become infected. If someone who is infected donates blood, and that blood is not tested for this parasite, whoever receives that blood may become infected. This can also happen with organ transplants. Also, mothers can pass the infection onto their children, and consuming contaminated food can lead to infection. Chagas disease is becoming more commonly known in the United States and all over the world because of migration of chronically infected individuals from Mexico and South and Central American Countries. Because of this, countries that were previously Chagas disease free have needed to start testing blood and organ’s for infection. However, with taking these precautions, there is no need to worry, just be aware of Chagas disease.
As of 2012, Chagas disease is being referred to as the new HIV/AIDS of the Americas because it is has a long incubation period and is difficult to detect. Although this disease can only be transmitted by the vector in South America, Central America, and Mexico, it can be transmitted in other areas of the world through the other methods described above.
Bern, Caryn, Sonia Kjos, Micheal J. Yabsley, and Susan P. Montgomery. 2011. Trypanosoma cruzi and Chagas’ Disease in the United States. Clinical Microbiology Reviews 24: 665-681.