PLASMODIUM, HAEMOPROTEUS AND LEUCOCYTOZOON 



263 



in a grape-like cluster. The macrogametes 

 and microgametocytes are rounded, occupy 

 3/4 of the host cell and have coarse, black 

 evenly distributed pigment granules. 



A vivax-type Plasmodium, P. cyno- 

 molgi, occurs in macaques. Eyles, Coat- 

 ney and Getz (1960) recently described 

 accidental laboratory infections of 2 hu- 

 mans with P. c. bastianellii originally 

 isolated from Macaca iriis from Malaya. 

 They were able to infect 2 other humans 

 experimentally by allowing them to be 

 bitten by infected Anopheles freeborni 

 mosquitoes. This finding and the presence 

 of P. malariae in chimpanzees suggest 

 that more than one of the human malarias 

 may be zoonoses. 



Pathogenesis : The malarial paroxysm 

 is highly characteristic. It begins with a 

 severe chill. The patient shivers uncon- 

 trollably, his teeth chatter, and he has 

 gooseflesh, altho his temperature is actu- 

 ally above normal. The chill is followed 

 by a burning fever, headache and sweating. 

 This gradually subsides, the temperature 

 falls, and after 6 to 10 hours the patient 

 feels much better--UDtil his next paroxysm. 

 The destruction of erythrocytes causes 

 anemia. 



After a certain number of paroxysms, 

 the attack of malaria subsides. Relapses 

 may occur over a period of years in vivax 

 and malariae malaria, but this is rarely 

 the case in falciparum malaria. 



In general, mortality from malaria is 

 higher in children than in adults in endemic 

 areas, because by the time the people be- 

 come adult they have had repeated attacks, 

 and those who have survived have devel- 

 oped a good deal of immunity. For this 

 reason, if one wants to determine the in- 

 cidence of malaria in an area, it is better 

 to examine children than adults. 



A highly fatal, cerebral form of ma- 

 laria may occur in falciparum infections. 

 It is due to clogging of the capillaries of 

 the brain by agglutinated, infected ery- 

 throcytes. If enough clogging takes place 

 in the viscera, a severe gastro-intestinal 

 disease resembling typhoid, cholera or 



dysentery may occur. Another complica- 

 tion of falciparum malaria is blackwater 

 fever, which gets its name from the color 

 of the urine. There is tremendous des- 

 truction of the erythrocytes- -60 to 80% 

 may be destroyed in 24 hours--accompanied 

 by fever, intense jaundice and hemoglobi- 

 nuria. Severe attacks are usually fatal. 

 The cause of blackwater fever is not known, 

 but it may involve some sort of immuno- 

 logical reaction which hemolyzes the ery- 

 throcytes. 



Epidemiology : Malaria is transmitted 

 by Anopheles mosquitoes. There are about 

 200 species of this genus, but not all are 

 equally good vectors, and the epidemiology 

 of the disease in any particular locality 

 depends not only upon the terrain and cli- 

 matic conditions, but also upon the partic- 

 ular vectors present, their breeding habits, 

 food preferences, susceptibility to infec- 

 tion, etc. The subject is an extremely 

 complex one and cannot be discussed in de- 

 tail here. Three examples will suffice. 



The principal malaria vector in south- 

 eastern United States is Anopheles quadri- 

 maculatus . This species breeds best in 

 clean, open water with dense aquatic veg- 

 etation and abundant flotage. It prefers 

 bovine to human blood, however, so that 

 the ratio of livestock to men in an area is 

 an important factor in the transmission 

 rate. 



The principal malaria vector in the 

 Solomon Islands is Anopheles farauti. It 

 breeds in small ponds and puddles. During 

 the Guadalcanal campaign of World War U, 

 the profusion of shell holes, fox holes, 

 road ruts, etc. provided ideal conditions 

 for its propagation, and the result was an 

 explosive outbreak of malaria. It was con- 

 trolled by eliminating or draining the breed- 

 ing places or spraying them with fuel oil. 



These measures would not work in the 

 Philippines, where the principal vector is 

 Anopheles minimus flavirostris. This 

 species breeds at the edges of slow-moving 

 streams in the plains, hence quite different 

 measures, such as stream clearing, 

 straightening and flushing, must be used 

 to prevent its breeding. 



