Diseases, Ticks, and their Eraeication. 143 



and we in South Africa have repeated the experiment on imported 

 stock and with ticks sent to Paris and London. It is the blue lick 

 which carries the disease, although subsequent experiments have 

 shown that the brown and the red ticks can also act as hosts of 

 Babesia bigemina. These two form the exception rather than the 

 rule, whereas practically every one of the blue ticks can transmit the 

 infection. 



We can also show from experiments that blue ticks collected from 

 horses can occasionally transmit redwater to cattle, a fact previously 

 noticed in the transmission of human tick fever, wliere the prog-eny of 

 an infected tick remained infective for several generations. 



We have stated that the animal born and bred in Soutli Africa 

 is immune, and what we have said about immunity in biliary fever 

 of the horse applies to redwater in cattle. The immune animal 

 retains the infection in its blood. This has been proved by tapping 

 an animal born on the veld and injecting an imported susceptible 

 one. An animal which recovered from redwater in 1902 proved still 

 to possess virulent blood in 1909. American investigators have even 

 proved that the blood of a cow which had recovered from Texas fever, 

 and had remained for twelve years out of the infected area, still 

 produced the disease. This observation does not, however, apply to 

 all recovered animals which are subsequently stabled ; it has been 

 experienced that blood of immune cattle, when used for inoculation, 

 is not always virulent, at least when used in quantities of 5 c.c. per 

 dose. 



The incubation period of this disease, when naturally contracted 

 by ticks, is about seventeen or eighteen days. 



The progeny of blue ticks collected from cattle recovered from 

 redwater, and of ticks collected at random from any full-grown cattle 

 born in the infected veld of South Africa transmit redwater when 

 placed on susceptible imported cattle. 



Redwater is a curable disease, and an injection of 100-150 c.c. of 

 a 1 per cent, solution of trypan blue in the early stage of the disease 

 is most effective. 



Gall- SICKNESS in Cattle. 



Gall-sickness is a term for a disease in cattle, the chief symptoms 

 of which, on post-mortem, are an abnormal bile, usually of a viscid, 

 thick crimson and yellow to dark green colour, and a jaundiced 

 condition of the body. This jaundiced condition can frequently be 

 recognized during life in examining non-pigmented parts of the skin, 

 particularly the ears. In other cases jaundice is absent and an acute 

 anaemia is noted, revealing itself by white mucous membranes, par- 

 ticularly a white tongue. In addition to these symptoms a dis- 

 turbance of the digestive organs is present. During life, symptoms 

 indicating such a disturbance are frequently found. In the absence 

 of other changes they are interpreted as those of gall-sickness. 

 Accordingly, under the term " gall-sickness " a number of ailments 

 are understood. Many conditions caused by plant poisons are 

 included under the same term. The disease very frequently taken for 

 gall-sickness is redwater, or rather the sequel to redwater, when the 

 urine is no longer noted to be coloured red. In this sequel the lesions 

 of jaundice during life and on post-mortem may be very pronounced, 

 and if the disease is of some standing the causative micro-organism 



