Parasite Classification

Human-infecting parasites are predominantly classified as ectoparasites, helminths, and protozoa. Protozoa are single-celled parasites that can infect the gastrointestinal tract, blood, and other tissues. Helminths are multicellular parasitic worms that mainly infect the gastrointestinal tract. Ectoparasites live on the exterior surface of the host and include fleas, lice, mites, ticks, and scabies. Protozoa can replicate rapidly within the host, unlike helminths. Most helminths cannot replicate inside the host and can only lay eggs there.