Malaria
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Direct answer
The female Anopheles mosquito transmits malaria, and in India Plasmodium vivax and Plasmodium falciparum cause nearly all cases. Diagnosis rests on the peripheral smear — thick for sensitivity, thin for species — or on rapid diagnostic tests detecting HRP-2 or parasite lactate dehydrogenase. Uncomplicated falciparum malaria is treated with artemisinin-based combination therapy, artemether-lumefantrine being the first-line ACT in India, plus a single gametocytocidal dose of primaquine; vivax malaria receives chloroquine followed by 14 days of primaquine; severe malaria is treated with intravenous artesunate.
What you must remember
- Morphology: vivax infects enlarged red cells with amoeboid trophozoites and Schuffner's dots; falciparum shows multiple fine rings, applique or accolé forms and crescent gametocytes; malariae has band forms with 72-hour quartan fever.
- Falciparum is malignant because cytoadherence and sequestration cause microvascular obstruction — cerebral malaria, severe anaemia, renal failure and ARDS.
- Diagnosis: thick smear for sensitivity, thin smear for species and parasite density; rapid tests detect falciparum HRP-2 (persists after treatment, cannot monitor response) or parasite LDH.
- Uncomplicated falciparum: artemether-lumefantrine, the first-line ACT in current national guidelines, plus a single primaquine dose of 0.25 mg per kg for gametocytes; treatment failure is switched to the recommended second-line combination.
- Uncomplicated vivax: chloroquine over three days plus primaquine 0.25 mg per kg daily for 14 days to eradicate hypnozoites; primaquine is contraindicated in pregnancy and G6PD deficiency.
- Severe malaria: intravenous artesunate 2.4 mg per kg at 0, 12 and 24 hours, then daily — superior to quinine — followed by a full oral ACT; features include coma, seizures, severe anaemia, hypoglycaemia (worsened by quinine), jaundice, acute kidney injury, ARDS and hyperparasitaemia.
- Pregnancy: artesunate is the drug of choice for severe malaria in all trimesters; for uncomplicated falciparum, quinine is preferred in the first trimester and ACTs later.
From smear to prescription
A 30-year-old from a construction site in Mumbai returns with four days of fever with chills and rigors; the thin smear shows fine ring forms, two per red cell, an accolé form and one crescent-shaped gametocyte in normal-sized cells. The smear itself has made the species call: Because falciparum cytoadheres and sequesters, check urgently for severity — coma, seizures, severe anaemia, jaundice, hypoglycaemia, oliguria, ARDS, hyperparasitaemia — any of which changes the prescription from tablets to intravenous artesunate 2.4 mg per kg at 0, 12 and 24 hours, then daily, superior to quinine and safe in all trimesters, followed by a full oral ACT once the patient tolerates medicines. This patient has none of those, so give oral artemether-lumefantrine and, after excluding G6PD deficiency where feasible, a single primaquine dose of 0.25 mg per kg to cut transmission. Had the smear shown vivax instead, the plan would be chloroquine over three days plus primaquine 0.25 mg per kg daily for 14 days to eradicate hepatic hypnozoites — withheld in pregnancy and in G6PD deficiency. If the rapid test had been used instead, remember it detects falciparum HRP-2, which persists for weeks after cure, so it diagnoses infection but cannot monitor response; only the parasite count on smear does that.
How the exam frames malaria
Species identification from a smear description is the guaranteed question, and the crescent gametocyte versus the enlarged stippled red cell is the pairing to answer first. Drug-to-species matching follows: ACT for falciparum, chloroquine plus 14-day primaquine for vivax — and the stem offering chloroquine for falciparum is testing both knowledge and the resistance argument. The severe-malaria stem (coma plus anaemia in an endemic area, blackwater fever, quinine-induced hypoglycaemia) asks for artesunate and its dose. Two traps recur: relapse versus recrudescence — vivax relapses from hypnozoites, falciparum recrudesces from surviving blood forms — and the negative rapid test, which lowers but does not extinguish suspicion when the clinical picture is strong.
Frequently asked questions
How do you identify falciparum on a smear?
Multiple delicate rings per red cell, accolé or applique forms, and the crescent-shaped gametocyte in normal-sized red cells.
What is the first-line treatment of uncomplicated falciparum malaria in India?
Artemether-lumefantrine, with a single low primaquine dose (0.25 mg per kg) to cut transmission, after excluding G6PD deficiency where possible.
Why does vivax malaria need 14 days of primaquine?
Primaquine eradicates hepatic hypnozoites responsible for relapse; chloroquine alone clears blood stages but cannot prevent relapse.
What is the drug and dose for severe malaria?
Intravenous artesunate 2.4 mg per kg at 0, 12 and 24 hours, then daily until oral therapy is tolerated, followed by a complete ACT course.
What is blackwater fever?
Intravascular haemolysis with haemoglobinuria and acute kidney injury in severe malaria, classically associated with quinine sensitivity.
Can a negative rapid test exclude malaria?
It makes falciparum unlikely with a good sample, but strong clinical suspicion warrants a repeat test and smear examination.