Malaria Overview and Life Cycle

Study Notes

Malaria Overview

Malaria is the leading protozoal infection affecting humans.
Four life cycle stages of malaria: sporozoites, schizonts, merozoites, and gametocytes.

Malaria Life Cycle

Transmission occurs when an infected mosquito injects Plasmodium sporozoites into the bloodstream.
Sporozoites migrate to the liver, forming cyst-like structures with thousands of merozoites.
Merozoites invade red blood cells (RBCs), transforming into trophozoites, which use hemoglobin for growth.
Trophozoites multiply into new merozoites, causing RBC rupture and release that can infect other RBCs.
Some merozoites develop into gametocytes, which are ingested by mosquitoes, continuing the cycle.
Diagnosis relies on identifying parasites in peripheral blood smears.

Plasmodium falciparum

Known for malignant tertian malaria (high fevers on days 1 and 3).
Most prevalent and lethal form, responsible for 95% of malaria deaths with a 1-3% mortality rate.
Causes severe symptoms such as hypoglycemia, hemolysis, and potential multi-organ failure.

Plasmodium vivax

Causes benign tertian malaria, characterized by milder symptoms.
Low mortality in untreated adults.

Plasmodium ovale

A rare form of malaria with even less severe symptoms.

Plasmodium malariae

Produces quartan malaria, with high fevers on days 1 and 4.
Clinical symptoms can appear years after initial infection.

Plasmodium knowlesi

Primarily infects monkeys but has increasingly been reported in humans in Asia.

Antimalarial Agents Classification

Antimalarial drugs are classified based on their action at different life cycle stages of the malaria parasite:
- Tissue Schizonticides: Target liver stages of plasmodia, used for relapse prevention.
- Blood Schizonticides: Treat the asexual erythrocytic stage; utilized for clinical and suppressive cure.
- Gametocides: Act against sexual erythrocytic forms, preventing transmission to mosquitoes.
- Sporontocides: Inhibit oocyst and sporozoite formation in infected mosquitoes.

Chloroquine Mechanism of Action

Inhibits heme polymerase, causing toxic heme buildup, resulting in the lysis of malaria and RBCs.
Specifically targets erythrocytic forms (blood schizonticide) for all four species of Plasmodium.
Functions as a gametocide for P. vivax, P. ovale, and P. malariae.

Chloroquine Indications

Used for treatment and prevention of malaria caused by non-resistant P. falciparum.
Also utilized for autoimmune conditions like rheumatoid arthritis.

Chloroquine Pharmacokinetics

Administered orally.

Chloroquine Resistance

Increasing resistance observed in P. falciparum and P. vivax, linked to:
- Reduced intracellular drug accumulation due to the pfcrt gene.
- Changes in transport systems potentially reversible by verapamil and desipramine.

Chloroquine Adverse Effects

Common effects include gastrointestinal disturbances, severe itching (particularly in darker-skinned individuals), and retinopathy.
Can cause acute hemolytic anemia in G6PD-deficient patients but is generally safe during pregnancy.
Additional possible side effects: rash, headache, neuropathies, auditory impairment, myocardial depression, and toxic psychosis.

Description

Explore the critical stages of malaria, a leading protozoal infection. This quiz covers the life cycle of Plasmodium, including its transmission, development, and the significance of Plasmodium falciparum. Test your knowledge on symptoms, diagnosis, and the impact of this disease.