The kissing bug spreads Chagas disease through its droppings, not its bite
Triatomine insects, nicknamed kissing bugs, feed at night and favour moist skin near the eyes or mouth. The bite itself does not deliver the parasite behind Chagas disease. The bug defecates as it feeds, and the parasites in its droppings slip into the bite wound or nearby tissue.
The culprit is a single-celled parasite, Trypanosoma cruzi. Once inside, it invades host cells, multiplies in a form called the amastigote, then bursts out as swimming trypomastigotes that spread through the bloodstream to other tissues. The bugs go by many local names: vinchuca in Argentina, Bolivia, Chile and Paraguay, barbeiro, or the barber, in Brazil, and chipo in Venezuela. The species that matter most for people are those that live inside homes.
Brazilian physician Carlos Chagas described the disease in 1909. It unfolds slowly. An early phase, one to two weeks after infection, is often symptom-free or mild; sometimes a swollen eyelid, known as Romana's sign, marks where the parasite entered. Most people then carry the infection silently for years, but over decades about 30 to 40 percent develop organ damage, most often to the heart, where repeated rounds of parasite growth and immune attack gradually replace muscle with scar tissue and fat. Around 10 to 21 percent suffer damage to the gut, typically an enlarged oesophagus or colon.
Bugs are not the only route. Fruit juice contaminated with a crushed insect is the most common source of food-borne outbreaks, and these tend to be unusually severe, perhaps because one bug can hold around 600,000 infective parasites. The parasite can also pass through transfused blood, transplanted organs, and from mother to baby; a heart from an infected donor transmits it 75 to 100 percent of the time.
An estimated 6.5 million people had the disease as of 2019, mostly in Mexico and Central and South America, and it caused roughly 9,490 deaths a year. Most are poor and unaware of their infection. Migration has carried it to Europe and the United States, where 29 locally acquired cases in eight states between 2000 and 2018 prompted calls to treat it as endemic there.
Source: Chagas disease
