The two diagnostic forms of Giardia are cysts and trophozoites.

The two diagnostic forms of Giardia are cysts and trophozoites.

• A. Cysts and trophozoites
• B. Oocysts and sporocysts
• C. Merozoites and schizonts
• D. Ova and L3 larvae

Answer: (A)

Giardia diagnosis hinges on detecting the two forms the parasite produces in life: cysts and trophozoites. Cysts are the durable, infective form shed in feces and are what labs often look for in stool samples, since they survive well outside the host. Trophozoites are the active, feeding form inside the intestine and can appear in fresh or diarrheal stool, indicating an ongoing infection. Because Giardia alternates between these two forms, stool microscopic exams (often with concentration or special stains) target either form to diagnoseGiardia. The other options refer to life stages of different parasites (oocysts/sporocysts in coccidia; merozoites/schizonts in malaria-related organisms; ova and L3 larvae in helminths), not Giardia.

Giardia diagnosis hinges on detecting the two forms the parasite produces in life: cysts and trophozoites. Cysts are the durable, infective form shed in feces and are what labs often look for in stool samples, since they survive well outside the host. Trophozoites are the active, feeding form inside the intestine and can appear in fresh or diarrheal stool, indicating an ongoing infection. Because Giardia alternates between these two forms, stool microscopic exams (often with concentration or special stains) target either form to diagnoseGiardia. The other options refer to life stages of different parasites (oocysts/sporocysts in coccidia; merozoites/schizonts in malaria-related organisms; ova and L3 larvae in helminths), not Giardia.