The Prevalence Of Malaria Seropositive And Seronegative Population Among Kwara State University
[A CASE STUDY OF MALETE STUDENTS.]

2.1.2.1 Life cycle of malaria
Malaria parasites are obligate intracellular parasites with a complex life cycle involving both a vertebrate (e.g. man) and an invertebrate host (mosquito vector), where they undergo different developmental stages (Ekpenyong and Eyo, 2006). Generally, the life cycle of Plasmodium can be divided into three phases; the exoerythrocytic or pre-erythrocytic phase which occurs in the liver, the erythrocytic phase which occurs in the erythrocyte and the sexual phase which occurs in the mosquito (Ekpenyong and Eyo, 2006). The life cycle of P. falciparum (and other plasmodia) commences when Plasmodium sporozoites enter the mammalian host through the bite of an infected female Anopheles mosquito (Prudencio et al., 2006). Sporozoites enter the blood vessel at the site of the bite and travel through the blood stream to the liver where they develop into merozoites (Prescott et al., 2005). For two of the five human species (P. vivax, P. ovale), dormant hypnozoite forms can develop in the liver leading to delayed clinical attacks months or years later, but for P. falciparum, there are no dormant forms (Prescott et al., 2005). In the liver, merozoites replicate within the hepatocytes and several thousands of merozoites are released into the circulation (Ezeigbo, 2005). Merozoite will invade erythrocytes, initiating a replication cycle of 48 hours, during which a single invaded merozoite develops into “ring” trophozoite, mature trophozoite, and finally a schizont (Sargeant et al., 2006).
 Each erythrocytic schizont, depending on the species, releases approximately 6 to 32 merozoites, which then in turn initiate a new asexual cycle by infecting other RBCs (Ekpenyong and Eyo, 2008). This phase of the life cycle constitutes the erythrocytic cycle, and it is the phase of the parasite’s life cycle that gives rise to all of the clinical symptoms and mortality due to malaria (Ekpenyong and Eyo, 2008). At this stage, the parasite is known to cause a number of changes on the red cell membrane including the insertion or binding of parasite-encoded molecules to the red cell surface, which are important in host parasite interactions (Kirk 2001). At about this time, parasitized RBCs are detectable microscopically, and symptoms of disease occur, which are characterized by fever, chills, headache, lassitude, and gastro-intestinal symptoms (Sargeant et al., 2006). The Plasmodium life cycle continues when some merozoites develop into the sexual parasite stages, the male and female gametocytes, which can be taken up by mosquitoes during subsequent blood meals (Good et al., 2005). The gametocytes undergo fertilization and maturation in the mosquito midgut, forming an infective ookinete form, which migrates through the mosquito midgut into the hemocele, developing into an oocyst in which sporozoites are formed (Good et al., 2005). When fully matured, the oocysts burst and release sporozoites, which migrate into the mosquito's salivary glands, ready for the next transmission step (Kirk 2001; Prudencio et al., 2006).