Protozoan

Plasmodium spp.

• Causes malaria

• transmitted by Anopheles mosquito

• produces periodic fever and chills due to RBC life cycle

• sporozoites infect humans and merozoites develop in RBCs

• treated with quinine derivatives

• vaccine effectiveness varies

Plasmodium spp. identification

• Seen in blood smears under oil immersion

• parasites located inside RBCs

• ring forms

• schizonts

• gametocytes

Giardia lamblia

• Causes giardiasis

• transmitted by fecal oral route

• cysts convert to trophozoites in the small intestine

• may disrupt nutrient absorption

• often self limiting

Giardia lamblia identification

• Cysts are oval with visible internal structures

• trophozoites are pear shaped with two nuclei that appear as eyes

Trichomonas vaginalis

• Causes trichomoniasis

• sexually transmitted

• men often asymptomatic

• causes leukocyte induced vaginal discharge

• treated with metronidazole

• condoms prevent transmission

Trichomonas vaginalis identification

• Motile trophozoites only

• pear shaped

• flagellated

• no cyst form

Trypanosoma cruzi

• Causes Chagas disease

• transmitted by reduviid kissing bugs

• causes anemia

• lethargy

• heart and brain damage

• treatable early

Trypanosoma brucei

• Causes African sleeping sickness

• transmitted by the tsetse fly

• causes anemia and neurological decline

• multiple antiparasitic drugs available

Trypanosome identification

• Long thin spiral shaped protozoa found outside RBCs

• visible undulating membrane and flagellum

Entamoeba histolytica

• Causes amoebic dysentery

• bloody diarrhea from intestinal ulceration

• transmitted via contaminated food or water

• cysts are resistant and infectious

Entamoeba histolytica cyst identification

• Trophozoites may contain ingested RBCs

• cysts are round with one to four nuclei

• cysts shed in feces

Entamoeba histolytica Trophozoites identification

• Trophozoites may contain ingested RBCs