ABSTRACT
T he disease m alaria is caused by d ie p ro tozoan parasites belonging to genus Plasmodium. T here are four species o f m alaria tha t infect hum ans: P. fa lc iparum , P. malariae , P. ovale and P. vivax; and all are in tracellu lar parasites. A part from the initial m ultip lication stages in the hepatocytes, these parasites are entire ly confined to infecting the e ry th ro cytes in the circulating b lood . To survive they replicate w ith in the e ry th rocy te , the progeny escape from the red b lood cell and each new individual invades a new e ry th ro cyte. Each tim e this even t occurs, parasite antigens in the form o f m etabolic w aste p ro d ucts o r secretions etc are released in to the circulation . The m ajor aspects o f the epidem iology o f m alaria are:
■ C hildren up to the age o f six living in the ru ra l areas in the trop ics m ay have had m alaria fever m ore than once. O ld e r children often have the parasites in the ir system b u t do n o t have fever o r any o f the o th e r sym ptom s o f malaria: a condition re fe rred to as ‘clinical to le ran ce ’ o r ‘an titox ic im m u n ity ’.
