PREVENTION OF ROUNDWORMS IN PIGS 3 



human beings, especially children, in some localities. It is still a 

 debatable point whether swine ascarids can develop to maturity in 

 man, or vice versa, either regularly or occasionally, but both go 

 through the lung-invading stage in man and swine. 



From the foregoing it is evident that the soil of places occupied by 

 hogs is likely to be heavily laden with the eggs of intestinal worms, 

 and it is readily understood, in view of their food habits, how pigs 

 kept in such places may become infested with large numbers of the 

 worms. Worm-infested places (fig. 2) are especially dangerous for 

 young pigs. It is largely on account of worm infestations that so 

 many young pigs are lost or fail to grow properly when reared 

 under ordinary methods of hog management. Unthnftiness usually 

 is caused by poor breeding, poor feeding, or parasites, and if the 

 first two factors can be ruled xmt, the trouble is probably caused by 

 parasites. (Fig. 3.) 



* ? •/ - 



Pig. 2.— A dirty hog lot, a paradise for worms and a source from which susceptible 

 little pigs may pick up worm eggs directly or by transfer from the skins and udders 

 of the sows 



Development of a System for Preventing Infection 



On the basis of the results obtained from laboratory study and 

 experiments on a small scale a system of raising pigs to avoid worm 

 infestation, or at least to reduce the infestation to a point at which 

 it will cause little or no damage, has been worked out by the Bureau 

 of Animal Industry. Through the cooperation of the farm bureau 

 and public-spirited hog raisers of McLean County, 111., this system 

 was carefulty tested on a considerable number of farms in that 

 county for seven years. The results of these tests were so successful 

 from the start that the use of this system has spread rapidly and con- 

 tinues to spread. It is now widely used, especially in the Middle 

 West. Because it was first developed in McLean County it has 

 been called the McLean County system of swine sanitation. The 

 system not only prevents losses from worms, but also more or less 

 completely prevents various diseases that may be termed filth dis- 

 eases, such as bullnose, sore mouth, and certain forms of diarrhea. 



