Antibiotics provide a treatment regimen, and a vaccine is available. Shistosomiasis is ranked second only to malaria among diseases caused by human parasites. Also called bilharziasis, shistosomiasis infects 200,000,000 people world-wide every year and is endemic to 74 developing countries, including Costa Rica. The diseases are caused by five species of waterborne flatworms, or blood flukes, also called shistosomes. Of the five types of shistosomes, only Shistosoma mansoni occurs in the New World, and it causes a disease called intestinal shistosomiasis.
Infection results from penetration of the skin by the water-borne flatworms.
This requires contact with water, such as swimming in otherwise pristine tropical ponds, lagoons, and slow-moving rivers. Fast-moving streams are free of this parasite. Symptoms vary widely from the lack of symptoms altogether to skin eruptions, fever, back or abdominal pain, bloody stools or urine, and enlargement of the liver and spleen. Complications may include kidney failure and cirrhosis. Praziquantel and oxamniquine are the drugs of choice for killing these parasitic worms.