Describe the developmental stages of the malarial parasite during sporogamy and schizogony?

Answer 1

Sporogony

• The Anopheles mosquito ingests malarial parasites when it feeds on an infected human. In the mosquito's stomach, the parasites move to the gut wall, where they reproduce asexually through the process of sporogony, and produce an oocyst, or spore. These oocysts eventually burst, releasing sporozoites that travel through the mosquito's body to its salivary glands, and finally to its central salivary duct.

Sporozoites

• When a carrier mosquito drinks human blood, the malarial sporozoites travel through its saliva to the host's blood stream, and quickly make their way to the liver's functional cells. The parasites can also infect red blood cells, causing fever, anemia and -- in some cases -- death.

Schizogony

• Schizogony is a form of asexual reproduction in which the multiple fission of sporozoites produces merozoites that can reproduce sexually or asexually. This process often begins as soon as the parasites enter their vertebrate host. For example, Plasmodium falciparum and P. malariae begin reproducing immediately. However, P. ovale and P. vivax may delay reproduction, by forming hypnozoites that remain dormant in the liver cells. P. vivax hypnozoites can have a dormancy of up to 10 months, whereas P. falciparum and P. malariae do not create hypnozoites at all.

Merozoites

• Pre-erythrocytic schizogony occurs in the host's liver cells before the parasite invades red blood cells (erythrocytes). During this phase, each sporozoite produces multiple merozoites, which consist of a single nucleus encased in a narrow cytoplasmic ring. Each P. ovale sporozoite produces 15,000 merozoites. P. vivax produces 10,000, P. falciparum produces 40,000 and P. malariae produces 2,000. Merozoites typically invade red blood cells within two minutes of life.

Answer 2

During sporogamy, the malarial parasite undergoes sexual reproduction in the mosquito gut to form ookinetes, which later develop into oocysts. Oocysts then release sporozoites that migrate to the salivary glands. In schizogony, sporozoites are injected into the human host, invade liver cells, replicate as merozoites, and then infect red blood cells to multiply and cause symptoms.