Introduction to Parasites and Their Classification

Parasites Introduction & Classification

• Parasites are organisms that live in or on another organism (the host) and benefit from the relationship, while the host is harmed.
• Parasites are classified into different groups.
• Classification includes Trematodes, Cestodes, Nematodes, and Protozoa.

Trematodes

• Trematodes are a type of flatworm. They are often leaf-like in shape.
• Some Trematodes include Fasciola, Schistosoma spp..
• Fasciola: Adults have a leaf-like structure, are hermaphrodites, and have an intermediate host.
• Schistosoma spp.: Adults have separate sexes; the female is long, cylindrical, and smooth; the male's anterior portion is cylindrical and the posterior flattened and has a gynaecophoric canal.
• Schistosoma mansoni: Includes both the adult and cercaria forms.

Cestodes

• Cestodes are segmented flatworms. They are attached to the lining of the intestine.
• Examples include Diphyllobothrium latum and Taenia saginata.
• Diphyllobothrium latum: Segmented and hermaphrodites.
• Taenia saginata: Segmented and hermaphrodites.

Nematodes (Roundworms)

• Nematodes are unsegmented roundworms.
• Examples include Ascaris lumbricoides, Trichuris trichura, Enterobius vermicularis, Ancylostoma duodenale, and Wuchereria bancrofti.
• Ascaris lumbricoides: A type of roundworm.
• Trichuris trichura: Whip-like shape, males have a coiled posterior end with a long spicule; females have a simple posterior end.
• Enterobius vermicularis: Fusiform shape with thin pointed tail at the posterior ⅓.
• Ancylostoma duodenale: A parasitic nematode found in the small intestine.
• Wuchereria bancrofti: A filarial worm that causes lymphatic filariasis, a parasitic roundworm.

Protozoa

• Protozoa are single-celled eukaryotic organisms.
• Examples include Giardia, Leishmania, Entameoba, and Plasmodium.
• Giardia: Differentiated into cyst and trophozoite.
• Leishmania: Differentiated into amastigote and promastigotes.
• Entameoba: Includes cyst and trophozoite forms.
• Plasmodium: Has ring-stage, schizont, merozoites, and gametocytes forms.

Arthropods with Medical Importance

• Anopheles mosquito: A vector for malaria (Class Insecta). Has 3 pairs of legs, one pair of wings, and an elongated mouth part.
• Sandfly: A vector for Leishmania (Class Insecta). Characterized by a hairy body and wings, and sandy yellow color.
• Flea: A vector for Hymenolepis nana and the plague (Class Insecta). They have no wings with long legs to jump, and are blood-sucking.
• Lice: A vector for some bacterial infections (Class Insecta). They have three pairs of legs, are wingless, and attach to hair.
• Mites: Sarcoptes scabiei (itch mite) causes Scabies.
• Cyclops: A type of copepod, a small crustacean. A vector for some parasitic worms.