Asexual reproduction by multiplicity of malaria parasites in human liver cells is called hepatic zygogy. In 1948 scientists Shortt and Garnham described the hepatic schizogony of malaria parasites in the human liver. This cycle takes place through two phases. Pre-erythrocytic schizogony and Ex-erythrocytic schizogony.
1. Pre-erythrocytic schizophrenia
(i) Sporozoite: Sporozoites are mobile, very small, slightly curved and both ends of the body are smooth. Their bodies are covered with elastic membranes. When an Anopheles mosquito, which carries malaria, bites a healthy person, the sporozoites enter the human body through the saliva of the mosquito. Sporozoites penetrate human liver cells within 30-45 minutes. Due to chemotaxis, it is carried by the blood and enters the liver and grows.
(ii) Cryptozoite: The sporozoites take food and become swollen and spherical. It is called cryptozoite.
(iii) Schizont: The nucleus of the cryptozoite divides repeatedly to form numerous (about 1200) tiny nuclei. This multinucleated condition is called zygote.
(iv) Cryptomerozoite: Cytoplasm accumulates around each nucleus of the zygote to form new cells. These are called cryptomerozoites. Cryptomerozoites break through the liver cell wall and come out and lodge in the sinusoids. It then invades the new liver cells causing recurrence of hepatic schizophrenia. A total of 8000-20,000 merozoites are produced.
2. Ex-erythrocytic schizophrenia
(i) Schizont: Cryptomerozoites invade new liver cells. Grows in size by consuming food and divides repeatedly to form numerous nuclei. This multinucleated condition is called zygote.
(ii) Metacryptomerozoite: Cytoplasm accumulates around each nucleus of the zygote to form new cells. The cells are called metacryptomerozites. Metacryptomerozites are of two types. Micrometacryptomerozites and macrometacryptomerozites. Micrometacryptomerozotes are small in size and have large nuclei. Macrometacryptomerozotes are large in size and have small nuclei. Macrometacryptomerozites invade new liver cells. Micrometacryptomerozoites enter the bloodstream and invade red blood cells. From sporozoite to metacryptomerozote takes 7-10 days. Merozoites can undergo zygogy in liver cells for years without showing any symptoms of malaria.