106 TRYPANOSOMES AND SLEEPING SICKNESS 



in treating trypanosome fever to give both drugs either to- 

 gether or alternately. 



When the disease has reached the sleeping sickness stage 

 and the parasites have penetrated the cerebrospinal fluid, a 

 cure has so far never been accomplished. The arsenic and anti- 

 mony compounds which are so destructive to trypanosomes 

 will not permeate the nervous tissue and diffuse into the cerebro- 

 spinal fluid, and they are too poisonous to be injected into the 

 spinal canal. The success that has been attained in the use of 

 salvarsanized serum (see p. 57) against spirochaetes in the cere- 

 brospinal canal gives hope that a similar mode of treatment may 

 be used in the case of sleeping sickness. All that can be done 

 for sleeping sickness now is to alleviate the suffering and postpone 

 the inevitable end. 



Although the use of immune serum from animals which have 

 recovered has been very successful in curing and immunizing 

 various lower animals against certain trypanosome diseases, this 

 has not yet been accomplished for man. 



The Rhodesian trypanosome consistently resists both arsenic 

 and antimony treatment, and no successful drug has been found 

 for combating this parasite. 



Prevention. Since the tsetse flies, Glossina palpalis and G. 

 morsitans, are by all odds the most important means of trans- 

 mitting the Gambian and Rhodesian trypanosomes respec- 

 tively, the prevention of the diseases resolves itself into the prob- 

 lem of avoiding or exterminating these insects. Methods for 

 controlling and destroying tsetse flies are discussed in the chap- 

 ter on Biting Flies, p. 501. 



In places where tsetse fly extermination has not or cannot be 

 accomplished the best safeguard is the avoidance of the " fly- 

 belts." In the case of G. palpalis these belts consist of narrow 

 strips along the brushy edges of water, but with G. morsitans 

 they are not so closely limited, the flies being sometimes found 

 at considerable distances from water. Villages or camps should 

 always be removed from fly-belts, and travel through the belts, 

 when absolutely necessary, should be done on dark nights when 

 the flies seldom bite. Occupations carried on in fly-infested 

 areas should be discouraged or prohibited. In Uganda fishing 

 along the fly-infested streams and lake shores is one of the chief 

 occupations indulged in by the natives, who go naked and are 



