## Epidemiology of Malaria in India **Key Point:** Plasmodium vivax is the most common cause of malaria in India, accounting for approximately 50–60% of all malaria cases, followed by P. falciparum (30–40%). ## Geographic Distribution | Plasmodium Species | Prevalence in India | Geographic Focus | Clinical Severity | | --- | --- | --- | --- | | P. vivax | 50–60% | Pan-India, especially plains | Moderate | | P. falciparum | 30–40% | Central & Eastern India | High (severe malaria) | | P. malariae | <5% | Sporadic, endemic pockets | Low (quartan fever) | | P. ovale | <1% | Rare, imported cases | Mild | ## Diagnostic Features of P. vivax **High-Yield:** The clinical vignette describes key morphologic findings: - **Ring forms** (trophozoites) in RBCs - **Schüffner's stippling** — characteristic cytoplasmic dots visible on Romanowsky staining; pathognomonic for P. vivax and P. ovale - **Tertian fever pattern** — fever every 48 hours (fever on days 1, 3, 5, etc.) - **Preference for young RBCs** — causes higher parasitemia (up to 1–2%) **Clinical Pearl:** P. vivax causes relapsing malaria due to hypnozoites in the liver. Patients may have relapses weeks to months after the initial attack if not treated with primaquine (which eliminates hypnozoites). ## Why P. vivax Dominates in India 1. **Anopheles vector adaptation** — *Anopheles culicifacies* and *A. stephensi* (urban vector) are highly efficient transmitters of P. vivax 2. **Duffy antigen expression** — Most Indian populations express Duffy antigen (unlike many African populations), allowing P. vivax RBC invasion 3. **Ecological factors** — Tropical and subtropical climate favors year-round transmission **Mnemonic:** **VIVAX = VIral-like, VAriation (relapse), AXes (fever every other day)** — captures the tertian pattern and relapsing nature.
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