FEED AND CAEE OF SWINE 705 



invade the lungs at the same time, the results are likely to be serious. 

 The pigs often shows the symptoms known as thumps and may die of 

 pneumonia. Those that survive frequently are stunted. 



Pigs become infected by swallowing the eggs of the parasite, which are 

 of microscopic size and are found in the manure of infected hogs or in 

 the soil of lots contaminated by the droppings from infected hogs. It 

 has been estimated that one full-grown female worm in the intestine of 

 a hog may produce as many as 80,000,000 eggs. The eggs as they are 

 passed out of the body of the hog in the droppings are not at first in- 

 fectious, but in a few weeks or months, depending upon the weather 

 and various other conditions, the egg reaches a stage of development at 

 which it contains a tiny worm within its shell, and it is then infectious, 

 if swallowed. The eggs are long-lived and very resistant to cold weather 

 and drought. Also they are not killed by most chemical disinfectants. 

 Commonly the parasites may be found in one out of three hogs of breed- 

 ing age. 



As pigs are most susceptible to infection and suffer most seriously 

 from the worms during the first few weeks of life, the United States 

 Department of Agriculture has worked out what is known as the 

 "McLean County System" of prevention, because first tried on a 

 large scale in that county of Illinois. According to Ransom, in this 

 system the farrowing pens are cleaned thoroly prior to the farrowing 

 season and then scrubbed with boiling water and lye. Before a sow is 

 placed in a farrowing pen she is cleaned carefully of mud and dirt and 

 her udder is washed with soap and water, to get rid of as many worm 

 eggs as possible. After farrowing the sows and pigs are not allowed 

 to go out of the farrowing pen until they are taken by wagon to a clean 

 pasture, on which there have been no pigs that season. No other hogs 

 should have access to this pasture, and the young pigs must not be 

 allowed to run back to the hog lots or barn. The pigs are kept in this 

 pasture until they have reached a weight of 100 Ibs., after which they 

 are not likely to suffer from worm infestation, even if exposed. 



Pigs infested with worms should be treated with a reliable worm 

 remedy. Combinations including santonin have been widely used with 

 good results, but this drug is now high in price, and oil of chenopodium 

 (American wormseed) is being commonly substituted for it. Before 

 administering a worm remedy, feed should be withheld from the pigs for 

 24 hours. 



In sections of the country where hog cholera is common the only safe 

 plan is to immunize all animals by the double method of vaccination. 

 Where this dreaded disease is rare, one must be on guard at all times, and 

 protect his swine by vaccination if there is an outbreak of cholera in the 

 vicinity. Breeders of pure-bred swine usually keep their herds always 

 immunized by the double method of vaccination. 



1040. Shipment to market. WTiere a farmer ships his fat hogs direct 

 to a central market he naturally wishes to reduce the shrinkage in weight 



