“Malaria” as we know it is a parasite that can only be spread from one organism to another. More specifically, this parasite thrives in two types of hosts – humans and mosquitoes.

Out of the 3,500 species and 41 genera of mosquitoes, the female mosquito of the Anopheles genus is the only population that can transmit the malaria parasite. Within this genus, less than 10% of the species are vectors.

Figure 1. This maps shows the distribution of the mosquito Anopheles genus by species.

It is important to understand the life cycle of the mosquito to combat the transmission of malaria. The first three stages – the egg, larvae, and pupa – develop in an aqueous environment between 5 and 14 days. The final stage, the adult, is the only stage that can act as a malaria vector and lives between one to two weeks in nature.

Some important facts to note: eggs are not resistant to drying; larvae feed on algae, bacteria and other microorganisms, most preferring habitats with vegetation, and can be found in either fresh or salt-water environments.

The female Anopheles feed on sugar sources for survival and then blood meals for egg development. After a blood meal the female rests for a few days to allow digestion and egg development – usually 2 to 3 days. Following this period, the female lays her eggs and this feeding cycle repeats. While most species prefer to feed on both humans and cattle, the most efficient vectors of malaria are A. gambiae and A. funestus because they strongly prefer human blood.

The malaria parasite must develop within the mosquito between 10 to 21 days before they become infectious; therefore, if the mosquito cannot survive past this incubation period, she cannot trasmit the malaria parasite. Studies have suggested that less than 10% of female An. Gambiae can survive this period. Certain control measures can make a greater impact upon malaria transmission by effecting mosquito longevity than through their effect on the population of adult mosquitoes.

Malaria Parasite:

There are four malaria parasites that can affect the human condition: Plasmodium falciparum, P. vivax, P. ovale, P. Malariae, the first two causing the most infections worldwide.

Plasmodium falciparum is the most fatal, causing 700,000 to 2.7 million deaths a year and

also the most prevalent in Africa. It’s unique characteristic is that it multiples rapidly in blood and can cause swift blood loss – anemia. Additionally, these parasite can clog narrow blood vessels. If this happens in the brain, a potentially fatal complication called cerebral malaria may persist.

Plasmodium Ovale

P.vivax and P. ovale have dormant stages, incurring a chance of relapse, and causing malaria months or years after moment of transmission. Most of the time, these parasites only cause incapacitating symptoms rather than death; therefore, they are the species most responsible for the economic and social burdens of malaria. The difference between the two is that P. ovale can infect people who are negative for the Duffy blood group ( a population seen frequently in sub Saharan Africa).

Blood cells infected with P. vivax

P. malariae acts in long-term infections, persisting asympotomaticaly for years and potentially a lifetime.

The Interaction between Parasite, Human, and Host:

** Citation: www.cdc.gov