Parasitic Helminths & Protozoa Summary & Study Notes

🪱 Trematoda (Flukes)

Clonorchis sinensis — disease: clonorchiasis. Transmission: ingestion of undercooked infected fish. In the lab, observe eggs/larvae at total magnifications around 400X to 1000X as needed.

Schistosoma mansoni — disease: schistosomiasis. Transmission: skin penetration by cercariae in contaminated water. Observe eggs/larvae at the same magnifications as other flukes.

🪲 Cestoda (Tapeworms)

Dipylidium caninum — disease: dipylidiasis. Transmission: ingestion of eggs from contaminated fleas; dogs or cats are typical hosts. Eggs/larvae observed under light microscopy at 400X.

Echinococcus granulosus — disease: hydatid disease. Transmission: ingestion of eggs from contaminated food/water or contact with dog feces. Observe eggs/larvae at 400X when preparing micrographs.

Taenia spp. — diseases: taeniasis. Species include Taenia saginata (beef) and Taenia solium (pork). Transmission: ingestion of undercooked beef or pork containing cysticerci. Egg morphology is similar across Taenia spp.; use proglottid morphology for speciation when possible.

Taenia eggs note

Important: Eggs of all Taenia species look the same under routine light microscopy; differentiating species relies on the morphology of the mature proglottids or scolex.

🪰 Nematoda (Roundworms)

Ascaris lumbricoides — disease: ascariasis. Transmission: ingestion of eggs via fecal-oral route. Observe eggs/larvae at 400X.

Enterobius vermicularis — disease: enterobiasis (pinworm infection). Transmission: ingestion of eggs from contaminated surfaces; common in children. Observe eggs/larvae at 400X.

Necator americanus / Ancylostoma duodenale — disease: hookworm infection. Transmission: larval skin penetration from contaminated soil. Observe eggs at 400X.

Strongyloides stercoralis — disease: strongyloidiasis. Transmission: larvae in soil penetrate skin. Observe larvae/eggs at 400X.

Dirofilaria immitis — disease: canine heartworm disease (zoonotic potential in humans). Transmission: mosquito bite introducing larvae. Observe microfilariae/larval stages at appropriate magnification in blood smears or tissue impressions at 400X–1000X.

🧫 Protozoans of Medical Importance (Exercise 6)

Entamoeba histolytica — disease: amebiasis. Transmission: ingestion of cysts (fecal–oral). Observe trophozoites and cysts at suitable magnification; cysts are typically observed in stool concentrates.

Balantidium coli — disease: balantidiasis. Transmission: ingestion of cysts from contaminated water/food. Observe trophozoites and cysts; characteristic cilia-bearing trophozoites aid identification.

Giardia lamblia — disease: giardiasis. Transmission: ingestion of cysts via contaminated water or food. Observe trophozoites with a distinctive pear-shaped body and adhesive disk, or cysts in stool concentrates.

Trichomonas vaginalis — disease: trichomoniasis. Transmission: sexual contact. Trophozoites observed in urogenital secretions.

Trypanosoma spp. — disease: trypanosomiasis (e.g., African sleeping sickness). Transmission: vector (tsetse fly) for T. brucei; reduviid bug for T. cruzi. Observe kinetoplast-containing forms in blood or tissue.

Plasmodium spp. — disease: malaria. Transmission: bite of infected Anopheles mosquito. Observe ring stages in red blood cells and other stages in stained smears.

Toxoplasma gondii — disease: toxoplasmosis. Transmission: ingestion of oocysts from cat feces or tissue cysts in undercooked meat. Observe intracellular tachyzoites and tissue cysts in stained tissue samples.

Notes on stages and transmission are summarized for quick recall.