5iS6 THE TICK FEVER PARASITE, 



There are two varieties of the disease, the acute and the chronic 

 forjn. In the former, tlie destruction of the red corpuscles is 

 very rapid, while in the latter it is much slower. The acute form 

 is marked by the general symptom of rapid oxidation, \'iz., acute 

 fever, and in the organs of affected animals all known forms of 

 the parasite can be found. In the chronic disease only the 

 supposed younger forms are to be seen. The i^resence of the 

 parasite in an animal does not necessarily indicate the presence 

 of disease, since it appears to exist latent, (5, e) becoming evident 

 when the system is weakened from some other disease, just as the 

 cause of rheumatism, influenza, or even the common cold ma}^ 

 presumably remain latent in man to become evident when the 

 system is temporarily weakened as by a sudden chill. 



Cattle are the most susceptible of all animals, and although it 

 may be said that tick fever is a bovine disease, it should not be 

 forgotten that other animals succumb to the action of parasites 

 which ma}' be identical with Ajnosoma bigeminum. There is a 

 canine disease of Lombardy and a sheep disease, carceag or 

 parasitic ictero-haematuria, in both of which the organisms 

 characteristic of tick fever have been observed. Furthermore, 

 according to some authors, rabl>its and guinea-pigs succumb when 

 inoculated with blood containing the parasite. 



Infection occurs l)y means of the cattle tick (Ixodes hovis) in 

 cases of Texas fever, tick fever and haemoglobinuria. In the 

 bovine malaria of the Roman Compagna (3) and of Turkey (e) 

 there is no record of ticks associated with the disease 



The parasite is found in the blood serum and within the red 

 coi-puscles. When invaded l)y the parasite the corpuscle loses its 

 elasticity and is retained in the capillaries and the body organs. 

 Consequentl}' comparatively few in^•aded corpuscles are to be 

 found in the cii-culating blood, the percentage varying from 1 to 

 2 except during the height of the fever, when it may rise to from 

 5 to 10 in a few cases. The blood of the organs, as for example 

 the heart-substance, ■has about 80 per cent, of the corpuscles 

 invaded. 



The typical form of tlie parasite is pear-shaped, and although a 

 single organism may occupy the corpuscle, yet commonly the}- 



