A 28-year-old woman from Jharkhand presents with a 3-week history of intermittent fever, headache, and myalgia. She reports a fever every third day (fever on days 1, 4, 7, 10). Temperature today is 38.5°C, HR 88/min, BP 110/68 mmHg. Spleen is palpable 2 cm below the costal margin. Peripheral blood smear shows schizonts with 8–12 merozoites and stippling in RBCs. Haemoglobin 10.8 g/dL, WBC 3,200/μL, platelets 95,000/μL. What is the most likely diagnosis and the appropriate treatment regimen?

Explanation

## Diagnosis: Plasmodium vivax (Benign Tertian Malaria) ### Fever Pattern Recognition **Key Point:** The fever pattern described — fever every **third day** (days 1, 4, 7, 10) — represents a **72-hour interval between fevers**, which is the classic **quartan** pattern. However, in standard malaria nomenclature, "fever every third day" with days counted inclusively (day 1 → day 4 = 3-day gap) actually describes a **72-hour cycle**, consistent with *P. malariae*. BUT the smear findings here are decisive and override the fever-pattern interpretation. **High-Yield — Smear Morphology is Diagnostic:** | Feature | P. vivax | P. malariae | P. ovale | |---------|----------|-------------|---------| | Schizont merozoites | **12–24** | 6–12 (rosette) | 8–12 | | RBC stippling | **Schüffner's dots** (prominent) | Ziemann's stippling (fine, rare) | Schüffner's dots | | RBC size | **Enlarged** | Normal/small | Slightly enlarged, oval | | Fever cycle | Tertian (48h) | Quartan (72h) | Tertian (48h) | | Hypnozoites | **Yes** | No | Yes | **Clinical Pearl:** The stem states **8–12 merozoites with stippling in RBCs**. Stippling (Schüffner's dots) is characteristic of *P. vivax* and *P. ovale*, NOT *P. malariae* (which shows Ziemann's stippling, rarely seen). Combined with the endemic region (Jharkhand, India — where *P. vivax* is the predominant species), the diagnosis is **P. vivax malaria**. ### Why Not P. malariae (Option D)? - *P. malariae* schizonts form a characteristic **rosette/daisy-head** pattern with 6–12 merozoites and do **not** show prominent stippling. - Chloroquine 600 mg base **weekly for 8 weeks** is not a standard WHO or NVBDCP regimen for any malaria species; the standard chloroquine course is a 3-day acute regimen. - *P. malariae* is rare in India; *P. vivax* accounts for ~50% of malaria cases in Jharkhand. ### Treatment Regimen for P. vivax (India / NVBDCP Guidelines) **Acute Attack (Blood-stage):** - **Artemether-Lumefantrine (AL)** — now preferred first-line in India (NVBDCP 2023), OR - **Chloroquine** 600 mg base on day 1, 300 mg base on days 2 and 3 (total 1500 mg base over 3 days) **Radical Cure (Hypnozoite eradication):** - **Primaquine 0.25 mg/kg/day for 14 days** (15 mg base daily for adults) - Screen for G6PD deficiency before primaquine; if deficient, use weekly primaquine 0.75 mg/kg for 8 weeks **Mnemonic: VIVAX = Very Important to eradicaVAX hypnozoites with Primaquine** **High-Yield:** Failure to add primaquine in *P. vivax* leads to **relapse** from dormant liver hypnozoites — a key distinction from *P. malariae* recrudescence. [cite: Harrison's Principles of Internal Medicine 21e, Ch. 219; NVBDCP National Drug Policy on Malaria 2023; Manson's Tropical Diseases 23e]