Do Sporozoites in blood signal the end of prepatent period?

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QUESTION

Will the appearance of sporozoites in blood mark the end of prepatent period in malaria?

ANSWER

Actually, no. The presence of sporozoites indicates the start of the infection. Sporozoites are introduced into the bloodstream via the bite of an infected mosquit0. The sporozoites then have to make their way to the liver and infect hepatocyte cells, where they undergo pre-erythrocytic schizogony. This is where the malaria parasites produce multiple copies of their nucleus without dividing the cytoplasm of the cell; new copies of the cell are produced by budding. These new cells are called merozoites, and they are released back into the blood, where they search for erythrocytes (red blood cells) to infect.

This is the end of the pre-patent period in malaria, as the symptoms of disease will start once the merozoites infect and rupture the host’s red blood cells, and parasitaemia may also be detected at this stage through observation of peripheral blood samples.

Malaria and Blood Cells

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QUESTION

What effect does malaria have on blood cells?

ANSWER

Malaria survives by invading red blood cells (erythrocytes), then replicating within them several times (the exact number and timing of replication depends on the species of malaria), then, once done with replication, bursts from inside the red blood cells, destroying it in the process. As such, malaria infection decreases the number of red blood cells in a patient’s blood, which can lead to anaemia. Moreover, the most severe species of malaria, Plasmodium falciparum, forces red blood cells to stick to the insides of tiny blood vessels deep within major organs such as the kidneys and even brain. This process is called sequestration.

Infection with malaria is also often associated with a decrease in the overall number of white blood cells, but elevated numbers of monocytes can sometimes be observed.