The Malarial Parasite

There are four different species of the malarial parasite, (P standing for Plasmodium) – P.Vivax, P.falciparum, P.malariae and P.ovale.

In India, P.vivax is the parasite that commonly causes malaria followed by P falciparum, P.malariae and P.ovale. The largest focus of P.malariae in India is reported to be in Tumkur and Hassan districts in Karnataka. P.ovale is a very rare parasite of man, mostly confined to tropical Africa. The malaria parasite undergoes two cycles of development – one in humans (asexual cycle i.e. the parasite does not reproduce) and the second in the mosquito cycle (sexual cycle i.e. the parasite reproduces).

The Anopheles Mosquito This is the mosquito that is the vector for the transmission for malaria. Although 45 different species of the anopheles exist, only a few are involved in the transmission of malaria. The breeding habits of each species is different. Knowledge of the breeding habits is essential for anti–larval measures to be taken.

Some breed in moving water, some in wells, cisterns, fountains and overhead tanks. A knowledge of the breeding habits is required for conducting anti–larval operations.

After a blood meal some mosquitoes rest indoors on the walls for quite sometime. This behavior pattern is known as “Endophily”. But there are some species which rest outdoors (exophily). A knowledge of the resting habits (which must be under constant surveillance) is the basis for organizing rational anti–adult measures.

The mosquito feeds on a person who harbors the malarial parasite. Subsequently, the parasite undergoes reproduction within the mosquito which usually takes 10 to 12 days. Thus, the mosquito must live for at least 10 to 12 days after an infective blood meal to become infective. The strategy in malaria eradication is to shorten the life span of mosquitoes to less than 10 days by insecticides.