BUREAU OF ANIMAL INDUSTRY, 249 



work at the end of the fiscal year. This work well supports the 

 conclusions reached in prior experiments. All of the cooperating 

 owners are highly pleased with the noticeably beneficial results to 

 their flocks. 



ROUNDWORMS OF HOGS. 



The work in McLean County, 111., consisting of observations on a 

 working system of swine sanitation devised in the Zoological Divi- 

 sion for the control of roundworms, has been continued with excellent 

 results. Approximately 9,000 pigs, the property of 31 farmers, were 

 under observation during the year. 



Developments of late years have emphasized the great suscepti- 

 bility of young animals to parasitism and the seriousness of para- 

 sitism among young livestock. The bureau has taken the initial steps 

 in bringing these facts to the attention of veterinarians and live- 

 stock owners and is planning to obtain wider lecognition of the 

 great importance of preventing the widespread losses from infant 

 mortality among livestock. The possibility of preventing some of 

 these losses by sanitary measures has been effectively demonstrated 

 in the use of a sanitary s^'stem for raising swine. 



Experiments to determine the length of time that infective ascarid 

 eggs Avill persist in soil have been carried out at Chicago, where it 

 was found that live, active worm embryos were present in eggs buried 

 in soil for 375 days, indicating that soil infection will persist for 

 more than a year. This experiment is being continued. 



Experiments to determine the value of certain substances as disin- 

 fectants indicate that ascarid eggs immersed in heavy mineral oil at 

 room temperatures (22° to 25° C.) for 125 daj'S do not undergo divi- 

 sion and can not become infective under such condition. Eggs im- 

 mersed for 2 hours in 10 per cent and 20 per cent commercial lye 

 solutions, however, developed to the infective stage wdien subse- 

 quently incubated, indicating that even very strong lye solution 

 brought into intimate contact with eggs for 2 hours does not destroy 

 them or inhibit development. 



Experiments were made to obtain additional information as to the 

 identity of the ascarid of man with that of swine. The results point 

 to the conclusion that the human ascarid may develop in pigs, al- 

 though additional work is desirable to support this belief. 



TREATMENT AND CONTROL OF EXTERNAL PARASITES. 



Tests of substances intended to prevent infestation with ox warbles 

 were continued, the substances tested including processed crude 

 petroleum or fuel oil. pine-tar emulsions, and coal-tar creosote placed 

 in wading tanks. The fuel oils and pine tar did not prevent infesta- 

 tion, but a 2 per cent solution of coal-tar creosote prevented infesta- 

 tion of 12 treated animals in all cases where part of a herd was 

 treated and the remainder left untreated as check animals. Of the 12 

 check animals 8 became infested. 



Animals grossly infested with warbles were treated with sulphur 

 dioxid gas in a gas chamber to determine the efficacy of this form of 

 treatment. The experiments were made in January, when the open- 

 ings in the skin were full sized and before the warbles had begun 

 to emerge. About 90 per cent of the warbles were killed by exposure 



