HIV and parasitic disease spectrum: Which parasitic infections are frequently observed among people living with HIV, especially at lower CD4 cell counts?

Introduction / Context:
Opportunistic parasitic infections contribute substantially to morbidity in advanced HIV disease. Understanding which parasites are common helps guide prophylaxis, diagnostic testing, and empiric therapy.

Given Data / Assumptions:

• Cryptosporidium parvum can cause chronic, severe diarrhea in immunocompromised hosts.
• Toxoplasma gondii can reactivate as cerebral toxoplasmosis at CD4 counts typically <100 cells/µL.
• Cystoisospora (Isospora) belli causes prolonged watery diarrhea and weight loss in advanced HIV.

Concept / Approach:
The listed parasitic infections are classic opportunistic conditions in people with advanced HIV. Their risk rises as cellular immunity wanes, and some are preventable or treatable when recognized early (e.g., toxoplasma prophylaxis in seropositive patients with low CD4 counts).

Step-by-Step Solution:
Map each parasite to its core clinical syndrome in HIV (diarrhea or encephalitis).Recognize that all are well-documented in HIV literature.Select ‘‘all of these’’ to reflect the complete, correct set.

Verification / Alternative check:
Standard opportunistic infection tables enumerate these infections and their CD4 thresholds for highest risk.

Why Other Options Are Wrong:
Isolated selections omit other equally frequent infections; ‘‘none’’ is contradicted by clinical experience.

Common Pitfalls:
Confusing isosporiasis with other coccidian infections; forgetting that toxoplasmosis usually represents reactivation in seropositive patients.

Final Answer:
all of these.