Training Module for Medical Officer - NVBDCP

or when it may be slowed down by the immune response of the host. Theduration of each erythrocytic cycle varies between species – 48 hours for P.falciparum, P.vivax and P. ovale; and 72 hours for P. malariae.1.4.1.3 GametogonySome of the erythrocytic forms of plasmodia do not divide further but develop intomale and female gametocytes. Not all infected persons are infectious (caninfect anopheline mosquitoes). The blood of the person has to have mature maleand female gametocytes and the density should be minimum 12/ cumm of bloodto be infective. These gametocytes take over a week to appear in the blood.Gametocytes do not cause any symptoms in humans. Most drugs likechloroquine kill the asexual forms that cause the fever but leave intact the sexualforms that are infective especially in case of P falciparum. Thus an apparentlynormal person may harbour the disease and contribute to its spread.Figure 1. Life Cycle of Plasmodium species in man and the mosquito1.5 Spread of malaria4