You're right, it's not a fly larva, it is the parasite that lives in the fly, that causes sleeping sickness, or in the case of Trypanosoma cruzi, it causes Chaga disease: https://en.wikipedia.org/wiki/Chagas_disease Sorry about wiki link, but it is often a good place to start. It can be off tho. The symptoms are: "Fever, swollen lymph nodes, headaches, or swelling at the site of the bite. After four to eight weeks, untreated individuals enter the chronic phase of disease, which in most cases does not result in further symptoms. Up to 45% of people with chronic infection develop heart disease 10–30 years after the initial illness, which can lead to heart failure. Digestive complications, including an enlarged esophagus or an enlarged colon, may also occur in up to 21% of people, and up to 10% of people may experience nerve damage." LAter in the article, it says that 30-40% of individuals develop fluid around the heart and enlargement.