Malaria Host Range

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QUESTION

What are the Host range?

ANSWER

Malaria is caused by a parasite,  of the genus Plasmodium, which requires two organisms for the completion of its life cycle—an insect, which is usually referred to as the “vector,” in which sexual reproduction occurs, and a vertebrate “host,” in which asexual multiplication occurs.

Different species of Plasmodium infects a large range of vertebrate hosts, including many birds, reptiles, and dozens of different mammals, specifically primates (including humans) and rodents. These different types of Plasmodium are found all over the world; Plasmodium species that infect birds, for example, are found in much colder climates than human malaria.

The five species of Plasmodium that infect humans are found mainly in the tropics, and seasonally in the sub-tropics. Four of the species mainly infect humans only, but can also be found occasionally in other primates, such as chimpanzees and gorillas; the fifth species, P. knowlesi, is mainly considered a malaria of macaque monkeys in south-east Asia, but can also infect humans. As such, the host range of these malaria species extends wherever humans live throughout the world. However, in reality, the distribution of malaria is constrained to warmer, wetter climates based on the developmental needs of the parasite and also the vector.

For mammalian malaria, these vectors are all mosquitoes of the genus Anopheles, which breed in stagnant freshwater and also have temperature requirements, above or below which they will not develop. However, these mosquitoes are still found in many parts of the world, from far northern latitudes of Canada and Siberia in the summer to similar latitudes in the southern hemisphere and also throughout the tropics.

Three Stages of Malaria

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QUESTION

What are the three stages of malaria?

ANSWER

The three parts of the malaria life cycle are known as the exo-erythrocytic cycle, the erythrocytic cycle and the sporogonic cycle. The first two of these take place in the human (or other mammal) host, while the third occurs in the mosquito vector. The below diagram, courtesy of the CDC, shows the complete life cycle of malaria in more detail.

malaria life cycle CDC

Schematic of the malaria life cycle, courtesy of the CDC (www.cdc.gov)

What is a Malaria Parasite?

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QUESTION

What is a malaria parasite?

ANSWER

A malaria parasite is a single-celled protozoan of the genus Plasmodium. These parasites have a complex life-cycle, which involves sexual reproduction in a mosquito vector, plus cycles of asexual reproduction and multiplication in a human host (or other animal – other primates, rodents, birds and reptiles can also be infected with Plasmodium parasites). A diagram of the life cycle is below, courtesy of CDC.