194 INSECTS AND MAN 



AN INTERNAL PARASITE OF SWINE 



A curious disease of swine must be mentioned en 

 passant, not because an insect is the actual cause of the 

 disease, or even the carrier of infection, in the usually 

 accepted sense, but because the manner in which the 

 organism producing the disease enters the bodies of the 

 swine is so peculiar as to merit attention. The disease in 

 question is common in France towards the end of winter, 

 and it is also well known in Germany, Austria, Sicily, 

 Australia, and the United States. Affected swine become 

 uneasy and show loss of appetite; sometimes convulsions 

 ensue, and, to young animals at any rate, the attacks are 

 often fatal. Although swine are usually affected, wild 

 boar, and even man, may fall victims. 



The cause of the disease is a parasitic worm, known 

 as Giganthorhynchus hirundaceus, whitish in colour and 

 cylindrical in contour, with a retractile head provided with 

 recurved hooks (see A, B, fig. 56). By means of these 

 hooks it becomes affixed to the membrane lining the 

 intestine of its host, much in the same way as the horse 

 bot-fly larva is attached to the stomach of the horse, and 

 the points of attachment appear as nodules on the exterior 

 wall of the intestine. Into the further progress in the life 

 of the worm and the serious damage it causes it is beyond 

 our sphere to enter ; we are only concerned with the part 

 played by insects in the spread of the parasite. 



In course of time the worm produces eggs within the 

 intestine of its host, and these pass to the ground with its 

 excrement; there some of the eggs may be swallowed, 

 either by the larvae of the common cockchafer (Melolontha 

 vulgaris) (see C, fig. 56), or of the rose beetle (Cetonia 

 aurata). Within these intermediate hosts the embryo 

 worms can exist for some time ; but such larvae are eagerly 

 sought by swine, and the eating of them serves to complete 

 the parasitic life-cycle, for, once within the mammalian 



