Parasitic infections often cause intestinal illness, with symptoms like diarrhea and vomiting. But they can also give itchy skin rashes or infect other parts of human body, like brain or lungs.
There are three main classes of parasites that can cause disease in humans: protozoa, helminths, and ectoparasites. Protozoa are microscopic unicellular eukaryotes that have a relatively complex internal structure and carry out complex metabolic activities. Some protozoa have structures for propulsion or other types of movement.
The helminths are worm-like parasites. The clinically relevant groups are separated according to their general external shape and the host organ they inhabit. There are both hermaphroditic and bisexual species.
While ectoparasite is generally used more narrowly to refer to pathogens such as ticks, fleas, lice, parasitic flies and mites that attach or burrow into the skin and remain there for relatively long periods of time.
Parasitic organisms are the causative agents of some of the world’s most devastating and prevalent infections. This group of pathogens includes members such as the protozoans Trypanosoma (Chagas disease and African sleeping sickness), Leishmania (leishmaniasis), Plasmodium (malaria), and the helminths such as Schistosoma (schistosomiasis), Wuchereria (filariasis), and Echinococcus (echinococcosis), among others.
Some parasitic infections, like pinworms, are common all over the world. Many other parasitic infections are more common in rural areas of the world without developed sanitation systems. People who are at higher risk for parasitic infections include:
*Young children and their parents or caregivers.
*People with compromised immune systems.
Parasitic infections
