Strongyloides

Strongyloidiasis is a parasitic disease caused by the roundworm Strongyloides stercoralis. The roundworm is found in soil contaminated by feces containing the worm, which then burrow through the skin and enter the bloodstream. They then enter the lungs and burrow through the tissue separating the airways from the esophagus and enter the digestive tract, where they lay eggs and reproduce.
Many people who are infected with the roundworm have no symptoms of the disease. However, in patients who are taking proton-pump inhibitors, steroids, or are otherwise immunosuppressed, the worm can often diffuse throughout the body, causing symptoms throughout the digestive tract, in the lungs, and in the nervous system, often leading to shock.
Diagnosis is difficult as the roundworm is not always present in feces. It is always found in the duodenum, but getting a sample from there requires an intrusive procedure.
Treatment is with ivermectin. However, ivermectin does not kill the larvae and as a result a course of treatment is required until all the adult worms are killed and no eggs or larvae remain. Luckily, treatment is low risk and can be used on any patient who might have the disease.
Strongyloidiasis at Wikipedia