Mosquitoes complete the complex life cycle of the sporozoan that causes malaria.
Sporozoa are parasitic microorganisms that live at the expense of another organism known as the host. Sporozoa generally have very complex life cycles that require one or more intermediate hosts before they enter their reproductive phase, according to the Oracle Think Ques science website. Some sporozoans cause diseases in their hosts. For example, the sporozoan known as plasmodium vivax is one of four sporozoan species that cause malaria.
Malaria Life Cycle
The complex life cycle of plasmodium vivax is typical of sporozoa, according to Think Quest. This organism requires mosquitoes and primates like human beings to complete its life cycle. Plasmodium grow inside a mosquito's stomach until they reach maturity. At maturity, plasmodium migrate to the mosquito's salivary glands, where they release tiny spore-like reproductive cells called sporozoites. When the mosquito bites a person, it transfers sporozoites to the human bloodstream. They find their way to the liver, where they invade red blood cells.
Away They Grow
The sporozoites grow in the red blood cells, transforming themselves into sexual cells called gametes. When mature, the gametes burst out of the red cells, destroying the cells. Fever and chills are some of the symptoms associated with malaria, according to Think Quest.
The Mosquito Bites
If a mosquito bites the person while malaria symptoms are manifesting, it will suck in plasmodium gametes that unite in the mosquito's stomach to form new plasmodium organisms that start the life cycle all over again. The mosquito phase of the life cycle takes about two weeks, followed by about a two-week incubation phase in the human before symptoms appear.
Sporozoa Are Protists
Sporozoa are one of 14 phylums in the animal kingdom of the protista, better known as the protozoans, said the Snow College biology website. Certain members of the phylums zoomastigina and sarcodina cause other diseases in humans. For instance, the zoomastiginans known as Giardia and Trypanosomes are insect-spread parasites that cause African sleeping sickness and the closely related Chagas disease. Radiolarians from the sarcodina phylum cause amoebic dysentery, and are spread through contaminated water.
Vast Diversity
The vast majority of the 65,000 identified species of protozoans are harmless to humans, according to Kennesaw University's science website. The sporozoa alone comprise 5,500 species. The malaria-causing sporozoa occur throughout the world's tropics and subtropical areas, said Kennesaw U., and kill roughly 2.5 million people a year. Malaria cases have been in an upsurge since 1970 because of drug and insecticide resistance, mosquito control cutbacks due to expense, and increased global travel.
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