INSECT ENEMIES OF LIVE STOCK 165 



ate a disease. The march of civilisation has probably in 

 many cases well-nigh exterminated the ticks' natural hosts, 

 with the result that they have turned their attention to 

 domestic animals, giving them these blood parasites and, 

 in many cases, setting up disease. Ticks are absolutely 

 essential to the blood parasites, for in some, and probably 

 in all, the sexual stages in the life-history of the organism 

 can only be completed within the tick. On this account 

 alone, all ticks must be looked upon with suspicion, for 

 they may, at any time, change from a wild to a domestic 

 host, and in doing so set up a new disease. 



PlROPLASMOSIS 



In our chapter on human diseases conveyed by insects, 

 a considerable space was devoted to malaria, for it is one 

 of the greatest scourges of mankind in many parts of the 

 world. To state that animals, as well as man, suffer 

 from the disease would be hardly accurate ; still, the cattle 

 disease we are about to describe has been termed bovine 

 malaria, and certainly the two diseases are comparable in 

 many ways. There is a group or series of diseases, 

 technically known as piroplasmosis or babesiasis, and 

 caused by a micro-organism, known as a piroplasma or 

 babesia. There are four distinct diseases of cattle, sheep, 

 dogs, and horses, transmitted by a round dozen of ticks, 

 and named respectively, Babesia bovis, or piroplasmosis of 

 cattle; Babesia ovis, or piroplasmosis of sheep; Babesia 

 canis, or piroplasmosis of dogs, and Babesia equi, or equine 

 piroplasmosis. All these diseases are transmitted by ticks, 

 twelve at least being implicated in the work, and, as they 

 resemble one another very closely, we will rest content 

 with a description of bovine piroplasmosis and the method 

 of its transmission, pointing out, as we proceed, when the 

 allied diseases vary from our type. 



Piroplasmosis in cattle is a very wide-spread disease, and 

 has received various popular names in different countries. 



