Dtreases, Ticks, and their Eradication. ];l.'i 



v\^ill increase, and under such conditions may become so troublesome 

 tbat, apart from their role as carriers of disease, they do an enormous 

 amount of damao-e by tlie withdrawal of blood from the stor^k nnd by 

 the irritation tliey cause, f?enerally known, ns " tick worry." Indeed, 

 the ticks can kill an animal without even transmitting- a disease. 

 Tliis \A e have ^een in an experiment in wiiicli a lioise was infested 

 Avith 1.1 ue ticks. It died from acute nnaemia as a result of this 

 infestation owino" to the withdrawal of blood. Witliin three days 

 14 lb. weig-ht of blue ticks were collected which had dropped off this 

 horse, and this amount only represented about half of the ticks which 

 eno'orged themselve-; on it. A similar observation was made on a 

 heifer ihat died of acute anaemia, being- bled M'hile bv licks. 



Influence of Climate. ■ 



"We liave stated that ticks are unequally distributed over high 

 and low veld, and it may be expected that this fact finds an explana- 

 tion in the unequal temperature to which ticks are exposed. It is 

 g'enerally thoug-ht that cold kills the ticks. This is to a certain 

 extent true. Ticks which thrive best in the low veld, when brought 

 to the higdi veld by the removal of animals, will not develop there. 

 Expeiience has proved that the cold in itself is not a liarrier for the 

 development of the lilue and red ticks in the hig'h veld. At freezing 

 point the moulting of the red nymphae into adults is only retarded, 

 but the ticks are not killed. This temperature did not affect the blue 

 larvae at all; these latter only died when exposed for some 

 time to a temperature considerably below freezing point. A drougdity 

 condition is probablv the inhibiting- factor for the development of 

 some species of ticks. 



Eradication of Ticks and Disease. 



From a practical ijoint of A'iew we shall consider the two points 

 separately, the eradication of ticks and consequently the eradication 

 of disease. 



The eradication of ticks can be attempted in several ways:-- 

 1. Bulging of Grass. — XTp to the present time the burning of 

 grassS has always been considered to be of great help for the destruc- 

 tion of ticks. Farmers have always distinguished burning of gTass 

 in season and out of season. If burning is not carried out at the 

 proper time the farmers hold this fact to be responsible for various 

 diseases, such as redwater and gall-sickness. These observations have 

 probably a certain foundation. Nevertheless the great importance 

 attached to it from the point of view of tick destruction is generally 

 exaggerated. Burning of grass, undertaken at a time when most of 

 the ticks have hatched and moulted and are sitting on the top of the 

 grass, must undoubtedly destroy them. We note that the principal 

 tick season is the summer, and with the cold tick-life is more or less 

 at a standstill. The ticks which up to the end of the summer iiave 

 moulted and are. sitting on the top of the grass will still fasten 

 themselves on to a passing host, and they are responsible for the tick- 

 life which we notice during the winter months. During the cold 

 weather the laying of eggs and hatching- are retarded, or 

 even absent. If. therefore, burning is undertaken at the beginning 

 of the cold weather we would onlv reach tliose ticks sitting on the 



