MI9.1-3 | Zoonotic & Opportunistic Infections — Summary & Reflection

REFLECT

A 28-year-old woman living with HIV, CD4 count 90 cells/µL, presents to your clinic with 2 weeks of progressive headache and mild confusion. Her ART was recently started. What OI is most likely? What single investigation would you order first? If you are in a district hospital with limited resources, what is the minimum investigation you need to confirm the diagnosis and start treatment?

KEY TAKEAWAYS

Zoonoses are infections transmitted from vertebrate animals to humans; 75% of EIDs are zoonotic. In India, the high-priority bacterial zoonoses are leptospirosis (flooding season, MAT/IgM ELISA), brucellosis (livestock contact/unpasteurised dairy, SAT + 2-ME test) and plague (flea bite, bipolar staining, F1 antigen). Major viral zoonoses: rabies (dog bite, Negri bodies, PEP with wound wash + vaccine + HRIG), KFD (Karnataka tick fever), Nipah (bat/palm sap). Opportunistic infections are triggered by immune deficiency — OI spectrum tracks with CD4 count. Cryptococcal meningitis (India ink, CrAg LFA), Toxoplasma encephalitis, PCP and CMV retinitis are AIDS-defining illnesses. Choosing the right investigation requires an epidemiological framework: rapid RDT for bedside → microscopy → serology → culture/PCR, interpreting in context of host immune status and timeline of illness.