Which parasite typically causes watery diarrhea and is especially problematic in patients with HIV/AIDS due to infection by sporozoites that attach to the intestinal wall?

Which parasite typically causes watery diarrhea and is especially problematic in patients with HIV/AIDS due to infection by sporozoites that attach to the intestinal wall?

• A. Giardia lamblia
• B. Entamoeba histolytica
• C. Cryptosporidium
• D. Toxoplasma gondii

Answer: (C)

Watery diarrhea in immunocompromised patients, especially with HIV/AIDS, is a classic presentation of Cryptosporidium infection. This parasite is a sporozoan that infects the small intestine by releasing sporozoites from ingested oocysts, which then attach to and invade the tips of enterocytes on the intestinal wall. The damage causes a secretory, non-bloody watery diarrhea that can become chronic in people with severe immunosuppression. The oocysts are highly resistant and are transmitted through contaminated water, making outbreaks common in settings with poor water sanitation. In AIDS patients, the reduced CD4 count allows the infection to persist, leading to significant dehydration and weight loss unless the immune system is reconstituted. Understanding how this differs from the other parasites helps solidify the concept. Giardia lamblia typically causes foul-smelling, greasy diarrhea due to malabsorption and attaches to the small intestine with a ventral adhesive disk, but it’s not driven by sporozoites attaching to the intestinal wall. Entamoeba histolytica can cause dysentery with blood and mucus due to invasive trophozoites that ulcer the intestinal mucosa. Toxoplasma gondii mainly causes systemic disease such as encephalitis or chorioretinitis in AIDS, rather than a primary syndrome of watery diarrhea from intestinal wall attachment.

Watery diarrhea in immunocompromised patients, especially with HIV/AIDS, is a classic presentation of Cryptosporidium infection. This parasite is a sporozoan that infects the small intestine by releasing sporozoites from ingested oocysts, which then attach to and invade the tips of enterocytes on the intestinal wall. The damage causes a secretory, non-bloody watery diarrhea that can become chronic in people with severe immunosuppression. The oocysts are highly resistant and are transmitted through contaminated water, making outbreaks common in settings with poor water sanitation. In AIDS patients, the reduced CD4 count allows the infection to persist, leading to significant dehydration and weight loss unless the immune system is reconstituted.

Understanding how this differs from the other parasites helps solidify the concept. Giardia lamblia typically causes foul-smelling, greasy diarrhea due to malabsorption and attaches to the small intestine with a ventral adhesive disk, but it’s not driven by sporozoites attaching to the intestinal wall. Entamoeba histolytica can cause dysentery with blood and mucus due to invasive trophozoites that ulcer the intestinal mucosa. Toxoplasma gondii mainly causes systemic disease such as encephalitis or chorioretinitis in AIDS, rather than a primary syndrome of watery diarrhea from intestinal wall attachment.