98 



ONE-CELLED ANIMALS— PHYLUM PROTOZOA 



weakened cell then bursts approximately 48 hours from the time it 

 was first invaded and liberates the merozoites into the blood plasma. 

 Each of these spores then finds another red cell and the cycle will be 

 repeated until literally billions of red cells are being destroyed every 

 48 hours. 



The first symptoms of the disease appear within about two or three 

 weeks after infection. When the many red cells burst at about the 

 same time, liberating the spores and the accumulated wastes of the 

 parasites, the body reacts to this poison with a chill. This is followed 



8 hours 



Feve 



24- hours 



\£) ® Merozoiies 



48 hours ® ®:'y®-X^/'^ 



® ''■'&' u ••'&.' ■«.-. 



36 hours 



Fig. 7.8. The cycle of tertian malaria in human blood cells. At the extreme left a 

 merozoite is shown entering a red blood cell. This then forms the signet ring stage, 

 followed by the amoeboid form and the appearance of pigment granules in the red 

 blood cell. This is followed by the presegmenter stage where there are many nuclei 

 in the parasite. Then, in the segmenter stage, the parasite breaks up into merozoites. 

 Finally, the blood cell breaks open liberating the merozoites and the cycle begins again. 

 The hours indicated represent the approximate time from the beginning of the chill. 



by a rather high fever as the body speeds up metabolism to counteract 

 the chill. Then, as the fever subsides the person will feel better, but 

 will be weakened and anemic due to the loss of red blood cells. With- 

 out treatment, the same cycle will be repeated 48 hours later, and so 

 on, until the person dies, or his natural body resistance brings the 

 disease under control. There are many malarial carriers that harbor 

 the parasites and serve as a reservoir of infection, yet do not show 

 serious symptoms themselves. 



This cycle spreads the parasites within the body ; yet, if the parasite 

 is to survive, it must have some means of spread to other persons, 



