177 



organism maintaining its existence in these insects for any length of 

 time. 



The eggs of 0. moubata are deposited in the sand, for preference on 

 the loose sandy floors of native huts ; from 100 to 300 eggs are laid 

 by each female, in batches at short intervals, the young ticks appearing 

 after an interval of about 16 days. On an average, about 30 per cent, 

 of ticks examined from various localities were found to harbour 

 S. duttoni. The incubation period of the disease is not definitely 

 known, but appears to be frequently shorter than the generally 

 accepted period of 10 days. The clinical aspect of the disease is dis- 

 cussed, and malaria as a complication of relapsing fever is considered. 

 The two sometimes exist simultaneously without any relationship 

 to one another ; in other cases they bear a definite relationship, 

 malarial rises of temperature only occurring during or immediately 

 following a spirillum relapse. 



Prophylaxis is best considered from two points of view, namely, 

 for the European and for the native. For the European in permanent 

 quarters the risk of infection in East Africa is practically nil, the 

 possibility of 0. mouhata gaining access to such quarters undetected 

 being very small. It is while traveUing about the country that the 

 majority of cases occur. Precautions against this means of infection 

 include the avoidance of native houses, especially at night, and of 

 camping grounds that have been used in the past by natives. As the 

 tick has been known to survive for as long as four years without food, 

 the sites of old camps remain infected for a very considerable tune. 

 If the necessity for sleeping on such ground should arise, a mosquito 

 net should invariably be used ; as the ticks have a marked antipathy to 

 light, the presence of a lamp by the bedside will assist in warding 

 them off. Blankets that have been carried by native porters should 

 always be searched for ticks before being used. 



The prevention of the disease among natives is a much greater 

 problem, largely owing to their apparent indifference to the presence 

 of ticks, although they are aware of their noxiousness. Examination 

 of native huts showed that ticks were usually hiding in the loose sand 

 of the flooring during the day-time, especially around the supporting 

 poles where the sand is particularly loose ; the ticks were never 

 found at a depth of more than six inches. The provision of a hard 

 floor, impermeable to the tick, is obviously the first essential. Concrete 

 being impossible, a good substitute was found in ant-heap earth 

 beaten hard to a depth of about four inches and then covered with 

 cow-dung spread over the surface in a liquid condition to the depth 

 of half an inch, the surface afterwards being treated once weekly 

 with a watery solution of cow-dung. This gives a hard, even surface 

 and can be brushed over very cleanly every day. Only a few of the 

 ticks thus driven from their usual hiding place took shelter in the 

 roofing, and in no case seemed to oviposit there. The question of 

 eggs is important, since ticks infected with S. duttoni remain infective 

 throughout several generations. A reward of about one-sixth of a 

 penny for each example of 0. mouhata resulted in the production of 

 over 30,000 ticks from a single camp in one month. By strict enforce- 

 ment of simple measures the incidence of relapsing fever was very 

 markedly reduced, and in several smaller camps the disease disappeared 

 entirely. 



