Tropical sprue is a digestive problem that occurs in the tropics and subtropics. People with tropical sprue do not absorb nutrients properly, especially vitamin B12 and folic acid.
Normal small intestines have fingerlike projections called villi that provide more surface area for nutrients to be absorbed. In people with tropical sprue, these villi are flattened, making absorption difficult.
Tropical sprue is rare except in a specific geographical zone. It occurs from about 30 degrees north of the equator to 30 degrees south of it. It is more common in certain countries within this tropical area, including India, Southeast Asian countries, Haiti, Cuba, Puerto Rico and the Dominican Republic. The condition afflicts residents of the affected countries as well as travelers, though usually it affects only travelers who stay for a month or longer.
The cause of tropical sprue has not been identified, but many experts suspect that an intestinal infection is to blame. When tropical sprue occurs, the lining of the small intestine is damaged so that it is unable to absorb nutrients efficiently.