ETIOLOGY 273 



described the disease under the name of malignant jaundice 

 and pointed out its transmission by the dog tick {Haemaphy- 

 salis leachi). In 1902, Nocard and Motas reported an experi- 

 mental study of the specific parasite. More recently Nuttall, 

 and Graham-Smith have investigated this affection. 



§ 290. Geographical distribution. This disease has 

 been found in several places in Africa, in Italy and in Europe. 



§ 291. Etiology. The Piroplasma cams is the cause of 

 this affection. Like Piroplasma bigenmium it appears in two 

 forms, round and pear-shaped. They nearly always occur in 

 the red blood corpuscles. It varies in its morphology. Ac- 

 cording to Marchoux Piroplasma canis in France is larger than 

 Piroplasma bigeminum and single parasites occur more fre- 

 quently. They vary in size from 2 to \jjl. At the beginning 

 of the disease usually single large round forms appear. It is 

 said by Nocard and Motas not to be pathogenic for other 

 species of animals. The parasite is said to be transmitted by 

 means of certain insects. L,ounsbury has demonstrated that 

 Pulex serra liceps, which is very abundant in certain localities, 

 piays a role in its transmission. In Italy Piroplasma canis 

 is supposed to be transmitted by Ixodes reduvius. In France 

 it is supposed to be conveyed by Dermacentor reticulatus. In 

 South Africa it is conveyed by Haemaphysalis leachi. The 

 parasite appears in the blood in from two to four days after 

 artificial infection. 



Graham-Smith did not find the parasites in films from the 

 peripheral circulation when stained by L,eishman's method 

 until several days after infection. The earliest day on which 

 they appeared was the sixth day and the latest the thirty- 

 sixth day. In most cases they were observed between the 

 eighth and twelfth days after infection. In a few cases he 

 worked out the percentage of red blood corpuscles that were 

 infected. He found that it vai-ied from .3 to i.\%. Free 

 parasites were seldom encountered in the earlier stages but 

 later they became more numerous. The day before death he 

 found one free parasite to 23 infected corpuscles, and the day 



Digitized by Microsoft® 



