EIGHTH ANNUAL YEAR BOOK— PART VI. 241 



are the sexualized parasites or their embryos. Most frequently pigs are 

 infected by eating the bodies of rats or mice which have been feeding 

 upon the feces or scraps of meat of infected pigs. It is thus seen that a 

 very important factor in the eradication of trichinosis is the extermina- 

 tion of the rodents. 



Unless a large quantity of trichina are taken into the system there is 

 not much to be seen in the line of symptoms, in fact what symptoms are 

 manifested are not at all characteristic, as they are analogous to those 

 manifested in simple enteritis or peritonitis. If the infection is extensive 

 however there is great muscular pain manfested, the limbs, especially 

 the posterior, are stiff and movements are halting and uncertain. 



Pigs will nearly always gradually recover and although they con- 

 tinually carry in their muscles the encysted trichinae, this fact does 

 not seem to interfere with their quality to lay on fat; in fact, they may 

 fatten to an extreme degree. 



The parasitic affection of the bronchi and lungs is not uncommon in 

 young and growing pigs, although almost unknown in the adult animal. 

 It is caused by a very fine worm known as the strongylus paradoxus. 

 The parasite is white or brownish in color. The male is from one-half to 

 three-quarters of an inch and the female from one to one and one-fourth 

 of an inch in length. They produce their young through the medium of 

 eggs. The development of the parasite is probably similar to the one 

 that causes lung disease in sheep. The eggs may be thrown out with mu- 

 cous, and if they pass into water or moist earth they may remain in a 

 dormant condition for months. Under certain favorable conditions the 

 embryos, if dried up after moulting, can be preserved for a long time and 

 revivified when again subjected to moisture. This is important as ex- 

 plaining the destructive actions of these parasites in dry seasons, or in 

 and around the di'y and dusty pens and feed lots, as it is then possible 

 for the worm to enter the body in dust by inhalation, although the in- 

 festation usually takes place through the medium of vegetation, earth or 

 water. 



In preventing this disease two things must be kept in mind. First, 

 to prevent the worms from gaining access to the system, and, second, to 

 keep the pigs in a condition unfavorable to the destructive work of the 

 parasite. The most important of the prophylactic measures under the 

 first division is to prevent the animals from drinking the polluted water 

 in infested ponds or mud holes, and contaminated food where the pens 

 and feed lots have not been properly cleaned. If they are watered from 

 a flowing stream, fence out all but the part where they drink, and this 

 should be where there is a decided current, and do not water from shal- 

 low wells that receive surface drainage. Change of pens or pasture for 

 the young pigs is advisable. Constant access to salt is a means of de- 

 stroying the young woi-ms as they are taken in, or the animals may be 

 ffd liberal quantities of salt, copperas and wood ashes. The medicinal 

 treatment does not give satisfactory results except in so far as it prevents 

 the introduction of viable embryos. 



Of the parasites that affect the intestines, besides the ones already 

 named, the echinorrhynchus gigas (or thorn headed worm) and the ascaris 

 16 



