186 JAS. J. SIMPSON — ENTOMOLOGICAL 



VI. Insect-borne Diseases in Man and other Animals. 

 Malaria. 



As in all West African Colonies, this is by far the most prevalent insect-borne 

 disease. Sub-tertian infections are most frequent, but benign tertian and quartan 

 are far from uncommon. Of recent years, however, the number of cases has 

 been gradually diminishing, owing in great part to the almost universal use of 

 quinine as a prophylactic, the more prevalent use of mosquito nets and mosquito- 

 proof rooms, the segregation of European quarters, and the sanitary measures 

 adopted for the diminution of the number of mosquitos. 



Practically nothing is known with regard to the species of mosquitos which 

 are implicated in the transmission of the disease, but it is more than probable 

 that Anopheles fane stus and A. costalis are the principal culprits. 



The number of recorded deaths from malaria from 1906-1909 are as follows : — 

 1906, 118; 1907, 202; 1908, 150 ; 1909, 119. 



The malarial index has been worked out for a number of towns in the colony, 

 and the following are the percentages found : — Kent, 80 ; Tombo, 76 ; Waterloo, 

 69 ; Hastings, 64 ; York, 60 ; Dublin, 50 ; Ricketts, 41. 



These figures taken in conjunction with the recorded number of deaths (which, 

 of course, represents only a small proportion of the actual number) shows that 

 malaria is still a factor to be reckoned with in the economic and social 

 development of West Africa. 



Yellow Fever. 



In 1910, 13 diagnosed cases of this disease occurred in Freetown ; these were not 

 confined to one locality but were distributed over the town, some in the European 

 part, some in the quarter where the Syrians congregate, and some in the purely 

 native quarter. Ten deaths were recorded ; these were as follows : — Europeans 5, 

 Syrians 3, natives 2. In addition to these there were 11 suspicious cases, with 

 one death. As has already been pointed out, Stegomyia fasciata is ubiquitous in 

 Freetown, but stringent measures are being adopted for its diminution. A 

 special Commission is also studying this disease in Freetown, as well as in all the 

 other large coast towns. 



Sleeping Sickness. 



Only one diagnosed case of this disease has been recorded from the Protector- 

 ate, for though several other suspicious cases have been examined, no trypano- 

 somes were found. During my tour in the Protectorate I came across two natives, 

 a man and a woman, at Kamatoto, in the Kaballa district, both showing symptoms 

 which seemed to indicate trypanosomiasis. Blood films were taken from each, 

 but no trypanosomes could be detected. 



The Principal Medical Officer in his annual report for 1910 says : " From the 

 reports of Medical Officers I am inclined to think that human trypanosomiasis is 

 at least not on the increase in Sierra Leone." 



