572 HEMOSPORIDIA 



HEMOSPORIDIA. 



The hemosporidia include some of the most important pathogenic 

 protozoa, causing disease in man and domestic animals, namely, 

 the plasmodium which causes malaria in man and monkeys; hemo- 

 proteus, the cause of malaria in birds; piroplasma, or Babesia, the 

 cause of piroplasmoses, or hemoglobinurias, in several species of 

 domestic animals. To the piroplasmoses also belongs Texas fever of 

 cattle. This group of diseases will be considered separately in the 

 next chapter. 



Malaria. Probably no other disease is so widely prevalent among 

 human beings throughout the world, except in the most northern 

 and southern latitudes, as malaria. It is spread from the infected to 

 the non-infected by mosquitoes of the genus anopheles. 



Malarial parasites were first seen in the blood of patients and 

 considered to be the cause of the disease by Laveran in 1880. Mar- 

 ciafava and Celli in 1885 gave a more detailed description of the 

 microorganisms, and proposed for them the name of Plasmodium 

 malariae, under the erroneous impression that they were dealing with 

 a vegetable microorganism. This name is still retained, though the 

 malarial organisms are now properly classified among the subphylum 

 sporozoa, order hemosporidia. Schaudinn divides the species into 

 three varieties, namely, Plasmodium vivax (the parasite of tertian 

 malaria), Plasmodium malaria (the cause of quartan malaria), and 

 Plasmodium falciparum (the organism of quotidian or estivo-autumnal 

 malaria). 



The malarial fevers are characterized by a very definite recurrence 

 of elevations of temperature after different periods of time. The 

 fever curve may rise daily, and reach its maximum at an almost con- 

 stant time of each day; this is the so-called quotidian type. Or the 

 apex of the fever curve, generally ushered in by a chill, may occur 

 and re-occur after forty-eight hours; this is the tertian type. Or it 

 may occur always after seventy- two hours, this is the quartan type. 

 These febrile and afebrile periods depend upon the natural life 

 history of different varieties of malarial parasites. If a person is 

 infected by the bite of a mosquito which carries the parasites as the 

 intermediate host the plasmodia get into that person's blood and 

 there multiply. For a certain time the number of parasites is com- 

 paratively small, no symptoms develop, and the patient is then in 

 the period of incubation. Then an outbreak occurs, characterized 

 by chills, followed by fever. This is repeated after twenty-four, forty- 

 eight, or seventy- two hours, according to the variety of infecting 

 plasmodium. It can be easily shown that these outbreaks always 

 occur shortly after the time when the intracorpuscular parasites 

 break up into merozoites, or asexually produced spores. As soon as 

 these are liberated from the corpuscle which they have flestroyed 



