**5. Life cycle**

The life cycle of *Plasmodium* while complex is similar to several other species in the Haemosporidia.

All the *Plasmodium* species causing malaria in humans are transmitted by mosquito species of the genus *Anopheles.* Species of the mosquito genera *Aedes, Culex, Mansonia* and *Theobaldia* can also transmitted malaria but not to humans. Bird malaria is commonly carried by species belonging to the genus *Culex.* The life cycle of *Plasmodium* was discovered by Ross who worked with species from the genus *Culex.[6]*

Both sexes of mosquito live on nectar. Because nectar's protein content alone is insufficient for oogenesis (egg production) one or more blood meals is needed by the female. Only female mosquito bite.

Sporozoites from the saliva of a biting female mosquito are transmitted to either the blood or the lymphatic system of the recipient. It has been known for some time now that parasites block the salivary ducts of the mosquito and as a consequence the insect normally requires multiple attempts to obtain blood. The reason for this has not been clear. It is not known that the multiple attempts by the mosquito may contribute to immunological tolerance of the parasite.[4] The majority of sporozoites appear to be injected into the subcutaneous tissue from which they migrate into the capillaries. A proportion is ingested by macrophages and still others are taken up by the lymphatic system where they are presumably destroyed. 10% of the parasites inoculated by the mosquitoes may remain in the skin where they may develop into infective merozoites.[5,7,8]

#### **6. Hepatic stages**

The majority of sporozoites migrate to the liver and invade hepatocytes. For reasons that is currently unclear sporozoites typically penetrate several hepatocytes before choosing one to reside within.[9] The sporozoite then matures in the hepatocyte to a schizont containing many merozoites in it. In some *Plasmodium* species, such as *Plasmodium* vivax and *Plasmoduim ovale*, the parasite in the hepatocyte may not achieve maturation to a schizont immediately but remain as a latent or dormant form and called a hypnozoite. Although *Plasmodium falciparum* is not considered to have a hypnozoite form. This may not be entirely correct . This stage may be as short as 48 hours in the rodent parasite and as long as 15 days in *P. malaria* in humans.[10,11]

• Merozites, schizonts or gametocytes can be seen within erythrocytes and may displace

• Merzoites have a "signet-ring" appearance due to a large vacuole that forces the

• Gametocytes are "halter-shaped" similar *Haemoproteus* but the pigment granules are

The life cycle of *Plasmodium* while complex is similar to several other species in the

All the *Plasmodium* species causing malaria in humans are transmitted by mosquito species of the genus *Anopheles.* Species of the mosquito genera *Aedes, Culex, Mansonia* and *Theobaldia* can also transmitted malaria but not to humans. Bird malaria is commonly carried by species belonging to the genus *Culex.* The life cycle of *Plasmodium* was discovered by Ross

Both sexes of mosquito live on nectar. Because nectar's protein content alone is insufficient for oogenesis (egg production) one or more blood meals is needed by the female. Only

Sporozoites from the saliva of a biting female mosquito are transmitted to either the blood or the lymphatic system of the recipient. It has been known for some time now that parasites block the salivary ducts of the mosquito and as a consequence the insect normally requires multiple attempts to obtain blood. The reason for this has not been clear. It is not known that the multiple attempts by the mosquito may contribute to immunological tolerance of the parasite.[4] The majority of sporozoites appear to be injected into the subcutaneous tissue from which they migrate into the capillaries. A proportion is ingested by macrophages and still others are taken up by the lymphatic system where they are presumably destroyed. 10% of the parasites inoculated by the mosquitoes may remain in the skin where they may

The majority of sporozoites migrate to the liver and invade hepatocytes. For reasons that is currently unclear sporozoites typically penetrate several hepatocytes before choosing one to reside within.[9] The sporozoite then matures in the hepatocyte to a schizont containing many merozoites in it. In some *Plasmodium* species, such as *Plasmodium* vivax and *Plasmoduim ovale*, the parasite in the hepatocyte may not achieve maturation to a schizont immediately but remain as a latent or dormant form and called a hypnozoite. Although *Plasmodium falciparum* is not considered to have a hypnozoite form. This may not be entirely correct . This stage may be as short as 48 hours in the rodent parasite and as long as 15 days

• Schizonts are round to oval inclusions that contain the deeply staining merozoites

the host nucleus

more confined • Hemozoin is present

**5. Life cycle** 

Haemosporidia.

female mosquito bite.

**6. Hepatic stages** 

in *P. malaria* in humans.[10,11]

parasite's nucleus to one pole

• Vectors are either mosquito's or sand flies

who worked with species from the genus *Culex.[6]*

develop into infective merozoites.[5,7,8]

• Vertebrate hosts include mammals, bird and reptiles

• Forms gamonts in erythrocytes

There is considerable variation in the appearance of the blood between individuals experimentally inoculated at the same time. Even within a single experimental individual there may be considerable variation in the maturity of the hepatic forms seen on liver biopsy.[12]

A proportion of the hepatic stages may remain within the liver for considerable time – a form known as hypnozoites. Reactivation of the hynozoites have been reported for up to 30 years after the initial infection in humans. The factors precipitating this reactivation are not known. In the species *Plasmodium ovale* and *Plasmodium vivax*. It is not yet known if hypnozoite reactivation occurs with any of the remaining species that infect humans but this is presumed to be the case.[13,14]

The development from the hepatic stages to the erythrocyte stages have, until very recently, been obscure. In 2006 it was showed that the parasite buds off the hepatocytes in merosomes containing hundreds of thousand of merozoties. These merosomes lodge in the pulmonary capillaries and slowly disintegrate there over 48 – 72 hours releasing merozoites. Erythrocyte invasion is enhanced when blood flow is slow and the cells tightly packed: both of these conditions are found in the alveolar capillaries.[15,16]
