CO>'TKOL OF ANIMAL PARASITES 



2til 



Man 



pass them uninjured or may carry them to liuman foods 

 as dust on their feet — eggs of eighteen worm parasites 

 have been found on or in flies. It is estimated that a tape- 

 worm produces 12,000,000 eggs a year, and the flukes may 

 l)e equallv prolitic Such powers of reprochiction demand a 

 number of different liosts, or host and parasite would (he 

 toefether. One authority 

 states the })roblem thus : 



It" a liver fiuko were to de- 

 posit its million or so of eggs 

 in the bile ducts of the sheeji, 

 and these were to devplop in 

 situ, the host could not with- 

 stand the increased drain upon 

 its vital resources, and host 

 and parasites would perish to- 

 gether. Hence it is clear that 

 the infection of a second host by 

 trematodes is hiuhlv necessary. 



Egg 



Bovine 

 ^cysticercus\ 



Kk.. 118. Life cycle of human tape- 

 wunii : infection from raw beef 



So, while many of the 

 bacterial parasites " don't 

 know any bettier" than to 

 kill their hosts outright, 

 these animal parasites, as a rule, sap and drain slowly and 

 are the cause of prolonged misery rather than of death. 

 Reasonal)le cleanliness in i-earing of farm animals, proper in- 

 spection of meats, and, above all, j)ruper cooking of meats 

 on tlie part of everyone will iinally relieve us from these 

 disagreeable pests. Tlu' life history of one or two types 

 should be generally known, and any of the following that 

 may be of local interest should l)e worked out to practical 

 conclusions in nature and in the books. 



Liverfluke — Fasciola hepatica. The adult is most commonly fouuil 

 in the liver of tlie sheep, l)ut may occur in the horse, deer, camel, ante- 

 lope, goat, pig, rabbit, kangaroo, beaver, s(|uirrel, and, rarely, in man. 



