Merozoites of the malaria parasite are released from the liver and enter the bloodstream. It disrupts the normal environment of the blood. White blood cells release pyrogens to destroy them. The hypothalamus of the brain is stimulated due to excess pyrogens in the blood. Because of this, chemical substances like prostaglandin, monoamine etc. are secreted from the brain. This message or stimulus reaches the peripheral regions of the body through vasomotor nerves. Peripheral blood vessels are narrowed. Therefore excess heat cannot escape from the body. As a result, body temperature rises more than normal and fever occurs.