Lecture on Malaria

Introduction

• Malaria affects about half of the global population and causes approximately 500,000 deaths per year.
• Children make up about half of these deaths.

Transmission

• Transmitted by the Anopheles mosquito.
• Different from the Aedes aegypti mosquito, which transmits Zika, chicken gunya, yellow fever, and dengue fever.

Cause

• Caused by a protozoan parasite of the genus Plasmodium.
• Several species: Plasmodium vivax, Plasmodium ovale, and the most lethal, Plasmodium falciparum.

Life Cycle of Plasmodium

1. Sporozoite Stage
   • Mosquito bites human, injecting sporozoites.
   • Sporozoites travel to the liver, reproducing asexually to turn into merozoites.
2. Merozoite Stage
   • Merozoites infect red blood cells, causing them to rupture.
   • Cycle repeats every 2-3 days, leading to symptoms.
   • Some merozoites develop into gametocytes.
3. Gametocyte Stage
   • Male and female gametes are formed.
   • Taken up by a new mosquito, continuing the life cycle.

Symptoms

• Cycles of extreme fever and chills, headache, muscle aches, nausea, vomiting.
• Followed by sweating and fatigue due to synchronous red blood cell rupture.
• Tertian (2-day cycle) and quartan (3-day cycle) malaria.
• Repeated cycles can lead to serious consequences like anemia and exhaustion.

Complications

• Plasmodium falciparum can cause encephalopathy or cerebral malaria.
• High mortality rate (15-25%).
• Immune response can result in organ failure and death.

Treatment and Prevention

• Artemisinin is the first-line drug, used in combination to prevent resistance.
• Resistance to drugs is developing, prolonging treatment duration.
• Vaccine: Approved for children under two, moderate efficacy (~40%) with four injections over 18 months.

Prevention Strategies

• Multimodal methods include insecticides, bed nets, and vaccines to reduce transmission.

Next Topic

• Discussion on another protozoan parasite, Trypanosoma cruzi, which causes Chagas disease.