The parasite that causes most malaria infections in humans is called Plasmodium falciparum. The parasite always has two hosts in its life cycle: a mosquito vector and a vertebrate host. Malaria is a serious tropical disease, caused by a parasite, and spread by mosquitoes. If malaria is not diagnosed and treated promptly, it can be fatal. P. falciparum is found worldwide in tropical and subtropical areas. It is estimated that every year just over 1 million people are killed by P. falciparum, particularly in Africa
One of the aims of international health agencies is to drive this form of malaria to extinction (something of growing priority given the risks of increased resistance by the parasite to anti-malarial drugs.)
An associated concern is if the primary cause of malaria in people is eliminated, will another type of malaria, such as one known to infect animals, make the species jump and begin infecting humans? This is known as zoonotic malaria in humans. A new study suggests that this is unlikely.
Globally, more than 200 Plasmodium species have been identified. This means some 200 different types of malaria, many of which are associated with different mammals. Of these, 10 different species are capable of infecting people, although Plasmodium falciparum remains the primary infectious agent. With primates, there are 29 species that can cause infection.
To consider the possibility, researchers have been looking into types of malaria that infect apes, birds and reptiles. By using genetic techniques, the researchers can find no evidence that the parasitic organisms causing these types of malaria have evolved. Thousands of genes from the 200-plus species were examined. On this basis, the researchers conclude that there is little chance of subsequent evolution.
The research project was performed by staff at the University of Maryland School of Medicine. The new study has been published in the journal Molecular Biology and Evolution. The research paper is titled “A new method for estimating species age supports the co-existence of malaria parasites and their mammalian hosts.”
