<P> The genus Plasmodium was first described in 1885 . It now contains about 200 species, which are spread across the world where both the insect and vertebrate hosts are present . Five species regularly infect humans, while many others infect birds, reptiles, rodents, and various primates . </P> <P> Plasmodium was first identified when Charles Louis Alphonse Laveran described parasites in the blood of malaria patients in 1880 . He named the parasite Oscillaria malariae . The fact that several species may be involved in causing different forms of malaria was first recognized by Camillo Golgi in 1886 . Soon thereafter, Giovanni Batista Grassi and Raimondo Filetti named the parasites causing two different types of human malaria Plasmodium vivax and Plasmodium malariae . In 1897, William Welch identified and named Plasmodium falciparum . This was followed by the recognition of the other two species of Plasmodium which infect humans: Plasmodium ovale (1922) and Plasmodium knowlesi (identified in long - tailed macaques in 1931; in humans in 1965). The contribution of insect hosts to the Plasmodium life cycle was described in 1897 by Ronald Ross and in 1899 by Giovanni Batista Grassi, Amico Bignami and Giuseppe Bastianelli . </P> <P> The life cycle of Plasmodium involves several distinct stages in the insect and vertebrate hosts . In infected mosquitoes, parasites in the salivary gland are called sporozoites . When the mosquito bites a vertebrate host, sporozoites are injected into the host with the saliva . From there, the sporozoites enter the bloodstream and are transported to the liver, where they invade and replicate within hepatocytes . At this point, some species of Plasmodium can form a long - lived dormant stage called a hypnozoite which can remain in the liver for many years . The parasites that emerge from infected hepatocytes are called merozoites, and these return to the blood to infect red blood cells . </P> <P> Within the red blood cells, the merozoites grow first to a ring - shaped form and then to a larger form called a trophozoite . Trophozoites then mature to schizonts which divide several times to produce new merozoites . The infected red blood cell eventually bursts, allowing the new merozoites to travel within the bloodstream to infect new red blood cells . Most merozoites continue this replicative cycle, however some merozoites upon infecting red blood cells differentiate into male or female sexual forms called gametocytes . These gametocytes circulate in the blood until they are taken up when a mosquito feeds on the infected vertebrate host, taking up blood which includes the gametocytes . </P>

The infective stage of malarial parasite plasmodium that enters human body is