Hypnozoite

Dormant form of malaria parasites found in liver cells. Hypnozoites occur only with Plasmodium vivax and P. ovale. After sporozoites (inoculated by the mosquito) invade liver cells, some sporozoites develop into dormant forms (the hypnozoites), which do not cause any symptoms. Hypnozoites can become activated months or years after the initial infection, producing a relapse.