infectious diseases
Approach to Parasitic Infections
Helminths
Helminths are multicellular and have complex organ systems. Helminths can be further divided into Roundworms (nematodes) Flatworms (platyhelminthes), which include tapeworms ( Overview of Tapeworm Infections ) and flukes ( , can increase in number because of autoinfection (offspring reinfect the same host rather than being shed to infect another host). In Strongyloidiasis , autoinfection can result in life-threatening, disseminated hyperinfection in immunosuppressed people, particularly those taking corticosteroids. The severity of helminthic infections usually correlates with the worm burden, but there are exceptions as when a single Ascariasis causes life-threatening ( Ascariasis ), ( Overview of Tapeworm Infections ) as adults are multisegmented flatworms that lack a digestive tract and absorb nutrients directly from the host’s small bowel. In the host’s digestive tract, adult tapeworms can become large, up to 40 m for one species. Tapeworms that infect humans include the ( Introduction to Trematodes (Flukes) ) are nonsegmented flatworms that infect the blood vessels, liver, lungs, or gastrointestinal tract. They are usually no more than a few centimeters in length; however, some are only 1 mm, and some are as large as 7 cm. In humans, most fluke infections are caused by 