No. 480] EXTINCTION OF MA MM. ifJA 



831 



active means of introducing and spreading fatal diseases over 

 great geographical areas and on a vast scale. 



Moisture Favoring the Spread of Diseases Carried by Flies. — 

 The presence of the blood protozoan parasites known as trypaiio- 

 somes, combined with certain flies which act as disease carriers^ 

 is in many countries correlated with moist conditions. This is 

 especially true of the disease known in India as 'surra,' ^ the history 

 of which was first suspected by Surgeon Major Lewis in 1888. 



Extermination of the Equida;. Surra. — The wide geographical 

 range of surra and related diseases is significant with reference 

 to former periods in the history of the Equidae. All authors now 

 agree with Lewis that the disease is carried by flies and coincide 

 with moist conditions occurring chiefly during or immediately 

 after heavy rainfalls, though sporadic cases may occur at otlior 

 seasons of the year. In the "Emergency Report on Surra" by 

 D. E. Salmon and C. W. Stiles ' this is described as chiefly a wet- 

 weather disease, invariably fatal to horses and mules, occurring 

 in other animals, such as camels and elephants, more rarely in 

 ruminants, and transmissible to goats, sheep, and other mammals. 

 In India it is said to att'ect horses, camels, and elephants (p. 18). 

 It occurs in Burma, Persia, Tonquin, and Korea. In Africa 

 there is the similar nagana or tse-tse fly disease, more accurately 

 described below by Bruce ^ (p. 833). In Algiers, France, and 

 Spain, the dourine or maladie de coit attacks the horse and ass in 

 particular, and may be transmitted to certain other animals; it 

 is attributed to a t rypanosome. T. ((jh/ pml inn . In the Philippines 



intermediary is a fly, Sfomu.vys calcifraii.s. It was also reported 

 (Curry, 1902) as affecting the carabao {lias {Biihalus) kerahau), 

 but according to Lingard ruminants are not particularly suscepti- 

 ble. An interesting note which may bear upon the origin of colors 

 in certain quadrupeds is the advice to those in charge of horses 

 in the Philippines (p. '.•7): "Avoid light colored animals as much 



Biological and Patholof/i' ' • / , ,/;,,/ I{ichoril.<t Lru'/.s-, 



* U. S. Dept. of Agrir.. • i /. IjuU. 4_'. 



