Microbiology for NEET-PG
Malaria for NEET-PG
Malaria is a protozoan infection caused by Plasmodium species transmitted by the bite of the female Anopheles mosquito. Five species infect humans: P. falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi. For NEET-PG, P. falciparum is the most lethal because it causes high parasitaemia, sequestration in cerebral and placental vessels, and complications such as cerebral malaria, severe anaemia, and blackwater fever. P. vivax and P. ovale form dormant liver hypnozoites that cause relapse, which is why radical cure with primaquine is needed after checking G6PD status. The classic clinical picture is cyclical fever with rigor followed by sweating, corresponding to synchronous erythrocytic schizont rupture: tertian for vivax, ovale, and falciparum, and quartan for malariae. Diagnosis rests on peripheral blood smear examination, thick smear for detection and thin smear for species identification, supported by rapid diagnostic tests detecting HRP-2 or pLDH antigens. Ring forms and banana-shaped gametocytes point to falciparum, while Schuffner dots and amoeboid trophozoites suggest vivax. In India the National Vector Borne Disease Control Programme guides treatment: artemisinin combination therapy for falciparum and chloroquine plus primaquine for vivax where sensitivity persists. Severe malaria is treated with intravenous artesunate. Recognising danger signs, the life cycle stages, and species-specific features are recurrent exam anchors.
MedNext Academy | 3 min read
Malaria for NEET-PG
Malaria is a protozoan infection caused by Plasmodium species transmitted by the bite of the female Anopheles mosquito. Five species infect humans: P. falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi. For NEET-PG, P. falciparum is the most lethal because it causes high parasitaemia, sequestration in cerebral and placental vessels, and complications such as cerebral malaria, severe anaemia, and blackwater fever. P. vivax and P. ovale form dormant liver hypnozoites that cause relapse, which is why radical cure with primaquine is needed after checking G6PD status. The classic clinical picture is cyclical fever with rigor followed by sweating, corresponding to synchronous erythrocytic schizont rupture: tertian for vivax, ovale, and falciparum, and quartan for malariae. Diagnosis rests on peripheral blood smear examination, thick smear for detection and thin smear for species identification, supported by rapid diagnostic tests detecting HRP-2 or pLDH antigens. Ring forms and banana-shaped gametocytes point to falciparum, while Schuffner dots and amoeboid trophozoites suggest vivax. In India the National Vector Borne Disease Control Programme guides treatment: artemisinin combination therapy for falciparum and chloroquine plus primaquine for vivax where sensitivity persists. Severe malaria is treated with intravenous artesunate. Recognising danger signs, the life cycle stages, and species-specific features are recurrent exam anchors.
Malaria is a protozoan infection caused by Plasmodium species transmitted by the bite of the female Anopheles mosquito. Five species infect humans: P. falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi. For NEET-PG, P. falciparum is the most lethal because it causes high parasitaemia, sequestration in cerebral and placental vessels, and complications such as cerebral malaria, severe anaemia, and blackwater fever. P. vivax and P. ovale form dormant liver hypnozoites that cause relapse, which is why radical cure with primaquine is needed after checking G6PD status. The classic clinical picture is cyclical fever with rigor followed by sweating, corresponding to synchronous erythrocytic schizont rupture: tertian for vivax, ovale, and falciparum, and quartan for malariae. Diagnosis rests on peripheral blood smear examination, thick smear for detection and thin smear for species identification, supported by rapid diagnostic tests detecting HRP-2 or pLDH antigens. Ring forms and banana-shaped gametocytes point to falciparum, while Schuffner dots and amoeboid trophozoites suggest vivax. In India the National Vector Borne Disease Control Programme guides treatment: artemisinin combination therapy for falciparum and chloroquine plus primaquine for vivax where sensitivity persists. Severe malaria is treated with intravenous artesunate. Recognising danger signs, the life cycle stages, and species-specific features are recurrent exam anchors.
Key points
- **Vector and species:** Female Anopheles mosquito transmits five Plasmodium species. P. falciparum is the deadliest and P. vivax the most common in India.
- **Life cycle:** Sporozoites infect liver (exoerythrocytic schizogony), then invade red cells (erythrocytic schizogony). Sexual stage occurs in the mosquito gut.
- **Hypnozoites:** P. vivax and P. ovale form dormant liver hypnozoites causing relapses. Radical cure needs primaquine after G6PD testing.
- **Fever periodicity:** Tertian fever every 48 hours in vivax, ovale, falciparum. Quartan fever every 72 hours in malariae. Knowlesi shows daily quotidian fever.
- **Falciparum severity:** Causes cerebral malaria, severe anaemia, blackwater fever, and placental sequestration through knob-mediated cytoadherence and rosetting.
- **Smear diagnosis:** Thick smear detects parasites, thin smear identifies species. Banana-shaped gametocytes and multiple ring forms indicate falciparum.
- **Species markers:** Schuffner dots and enlarged red cells favour vivax and ovale. Maurer clefts and normal-sized cells favour falciparum.
- **Rapid tests:** RDTs detect HRP-2 (falciparum-specific) and pan-species pLDH or aldolase antigens for rapid field diagnosis.
- **Severe malaria drug:** Intravenous artesunate is the first-line treatment for severe malaria, replacing quinine, followed by a full ACT course.
- **Falciparum treatment:** In India, artemisinin combination therapy is standard for uncomplicated falciparum malaria under the national programme.
- **Primaquine caution:** Primaquine causes haemolysis in G6PD deficiency and is contraindicated in pregnancy, so screening precedes radical cure.
Frequently Asked Questions
Which malaria species is most dangerous?
P. falciparum is the most lethal because of high parasitaemia and sequestration, causing cerebral malaria, severe anaemia, and multi-organ failure.
Why do vivax and ovale malaria relapse?
They form dormant liver stages called hypnozoites. These reactivate weeks to months later, so radical cure with primaquine is required to prevent relapse.
What is the gold standard for malaria diagnosis?
Microscopy of peripheral blood smears remains the reference standard. Thick smear detects the parasite and thin smear identifies the species.
How is severe malaria treated?
Intravenous artesunate is the drug of choice for severe malaria, followed by a complete oral artemisinin combination therapy course once the patient stabilises.
Why is G6PD status checked before primaquine?
Primaquine triggers oxidative haemolysis in G6PD-deficient patients, so screening prevents a serious haemolytic crisis during radical cure.
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