Final answer:
Heterobilharzia americanum is a parasite that causes schistosomiasis, residing in the mesenteric veins and liver portal system after entering through the skin. The disease affects millions globally and can cause major organ damage.
Step-by-step explanation:
Heterobilharzia americanum is a type of blood fluke associated with schistosomiasis (also known as bilharzia), which is particularly endemic in the Americas. These parasites are known for their life cycle that involves certain species of freshwater snails and human hosts. The disease is caused by parasitic flatworms called schistosomes, and Heterobilharzia americanum is a species native to North America.
After schistosome larvae enter the human body through the skin, they develop into adult worms in the host's blood vessels. The adult worms reside particularly in the mesenteric veins of the intestines and the portal venous system of the liver. Infection may lead to the release of eggs that can become trapped in body tissues, prompting immune reactions and potentially leading to damage to internal organs such as the liver and intestines.
Schistosomiasis is a significant global health concern, affecting an estimated 200 million people. It is considered a neglected tropical disease that primarily affects socioeconomically disadvantaged communities in developing countries. Its impact on human populations is the second only to that of malaria.