462 VETERINARY BACTERIOLOGY 



Transmission. At least three species of tick, and probably one 

 species of flea, have been found to act as carriers of the organism. 



Piroplasma gibsoni 



Patton has described an organism causing piroplasmosis in 

 hounds in the Madras Hunt in India. Later, it was discovered 

 also in the blood of a native jackal. Its relationship to the P. 

 canis has not been satisfactorily determined. 



Piroplasma commune 



Phillips and McCampbell have described a new species of 

 Piroplasma as the cause of an epizootic of dogs at Columbus, 

 Ohio. The organisms found were similar to the P. cam's, but these 

 investigators were able to demonstrate the organism in the blood 

 of guinea-pigs injected with virulent blood. The cat was also 

 infected, but not the horse, cow, rat, or rabbit. This fact of 



Fig. 203. Piroplasma commune, organisms in the red blood-cells (adapted 

 from Phillips and McCampbell). 



transmissibility led to the tentative adoption of a new specific 

 name, as the true P. canis is not known to be transmissible to 

 any other animals. The organisms found were round or pear- 

 shaped. The round type were from 0.5 to 1.5 u in diameter, and 

 the piriform 1.5 by 2.3 ^. Considerable pleomorphism was 

 evident. 



THE GENUS PLASMODIUM 



Malaria in man has been found to be due to three species of 

 protozoa, usually placed in the genus Plasmodium. The organ- 

 isms pass certain parts of their life-cycle in the blood-corpuscles 

 in man, and the remainder in the gut and tissues of the mosquito. 

 The organisms of malaria were first noted by Laveran in 1880, 

 and the various types have been differentiated since that time. 



