Question

In the US there are ~300,000 cases of Chagas Disease, as well as several triatomine vectors capable of cruzi transmission. What aspect of kissing bug behavior in species found in the US is one of the major reasons for the absence of Chagas transmission? Name at least two other reasons that lead to an absence of Chagas transmission in the US. Why do kissing bug bites still result in hospitalizations in the US?

Answer 1

Chagas disease:

Chagas disease is a life-threatening infection caused by a protozoan parasite - Trypanosoma cruzi. It is also known as American trypanosomiasis and is most prevalent in 21 Latin American countries, mostly in the south and central America.

Disease transmission:

It is mainly transmitted by an insect vector called Triatomine bug. These bugs often attack humans and other vertebrate hosts like dogs and other pets during night time. The bugs bite exposed areas of the body during sleep, usually face ( also near eyes and lips), hence got the name ‘kissing bug’. When they defecate at the bitten area, the parasite enters the skin/mucus and causes swelling and redness (called as Chagoma) called as acute inflammatory skin alterations and spread to other body tissues, heart and intestinal tract particularly. Sometimes, the parasites pass through mucosal cells of the mouth or airway when inhaled.

The disease can be divided into three phases:

1. Acute: with mild or no symptoms – lasts for few weeks to two months
2. Intermediate/indeterminate phase: with few symptoms – lasts for 10-20 years
3. Chronic phase: severe symptoms of organ damage especially heart and the intestine.

Chagas disease is not contagious. But, T. cruzi can be transferred to humans through blood transfusions, organ transplantation, mother to child during pregnancy (through the placenta) etc. However, these modes of Chagas disease transmission is very rare.

Low risk of Chagas transmission via kissing bugs in the US:

Studies report that there is a very low risk of Chagas disease transmission to humans through kissing bugs in the US.

Reasons include:

Delayed defecation by the bugs after biting the hosts (especially humans).

Kissing bugs endemic to the US usually prefer animal hosts to bite rather than humans is the key reason behind the low prevalence of the disease in humans.

Improved sanitary and housing conditions led to low bug colonization.

Reasons behind hospitalization due to kissing bug bite:

US endemic kissing bugs (like Triatomia rubida, native to Arizona and Triatoma protracta of California) possess salivary antigens that cause allergic reactions in sensitized persons, which include local reactions like angioedema at the bitten area and more systemic infections like mild to severe anaphylaxis. Triatoma rubrofasciata, a rare species s also known to cause allergic reactions.

Prevention of the disease:

Most common and useful method of Chagas disease is “vector control”. Initial screening and diagnosis through blood screening in pregnant women can help to control the disease in their children.