Geography – Pathogenic diseases, their spread and impacts | e-Consult

Malaria transmission is a complex process involving both biological and environmental factors. The parasite, Plasmodium, has a complex life cycle that is crucial to understanding transmission. The cycle begins when a female Anopheles mosquito bites an infected human, ingesting gametocytes (sexual forms of the parasite). Inside the mosquito, sexual reproduction occurs, leading to the development of sporozoites. These sporozoites migrate to the mosquito's salivary glands.

When the infected mosquito bites a new human, it injects sporozoites into the bloodstream. These sporozoites travel to the liver, where they undergo asexual reproduction, forming merozoites. Merozoites are released from the liver and infect red blood cells. Within the red blood cells, merozoites multiply, causing the characteristic symptoms of malaria. Some merozoites develop into gametocytes, which are taken up by another mosquito during a subsequent blood meal, completing the cycle.

Biological factors include the specific interaction between the parasite and its hosts. The parasite's ability to adapt to different host immune systems and its complex life cycle are key. The Anopheles mosquito is a critical vector, with specific species being more efficient at transmitting malaria than others. The human host's immune response also plays a role; individuals with pre-existing immunity are less susceptible to severe malaria.

Environmental factors are equally important. Anopheles mosquitoes require specific environmental conditions for breeding, including stagnant water sources. Temperature, humidity, rainfall, and vegetation cover all influence mosquito populations and, therefore, malaria transmission. Human activities, such as deforestation and irrigation, can create new breeding sites for mosquitoes, increasing the risk of malaria. Climate change is also altering the distribution of both mosquitoes and the human populations at risk.