426 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1939 



made. Three days after infection, the pigs developed diarrhea. 

 These host animals showed pale or slightly injected mucous mem- 

 branes at various times. About 18 days after infection, some evidence 

 of poor physical condition began to manifest itself and, 4 days later, 

 the pigs appeared to be "off color" with indefinite symptoms; there 

 was evidence of a slight edema of the eyelids and vulva. Five weeks 

 after infection the pigs appeared normal. 



The temperatures of the pigs remained normal except in the case 

 of the pig receiving 75,000 larvae and developing the heaviest infec- 

 tion, as determined later by the number of larvae per gram of mixed 

 muscle tissue. This animal showed a temperature of 105 °F., or 

 slightly above or below this on the eighth, eleventh, fifteenth, and 

 forty-first days after infection; occasionally this animal showed a 

 rapid pulse. When these three pigs were killed, 79 days after infec- 

 tion, they were found to contain 840, 1,535, and 1,215 larvae, respec- 

 tively, per gram of mixed muscle tissue. The weights of these pigs 

 immediately before they were killed were 31.7, 23.41, and 22.04 kilo- 

 grams (69.75, 51.5, and 48.5 pounds), respectively, indicating a failure 

 to gain weight at a normal rate. It is evident from these data that 

 even careful observations of pigs following experimental infection 

 with large doses of trichinae failed to reveal any s^Tiiptoms that were 

 definitely suggestive of trichinosis or any other specific disease. 



CONTROL OF TBICHINAE IN SWINE 



It is evident from the data on the prevalence of trichinae in grain- 

 fed swine that the persistence of these parasites in nearly 1 percent 

 of these host animals is conclusive proof that much still remains to 

 be done to reduce, if not to eliminate altogether, the small residuum 

 of these parasites which, under certain conditions, may be distinctly 

 pathogenic to their porcine hosts. Without minimizing the impor- 

 tance of trichinae to the livestock industry of the United States from 

 the viewpoint of their injuriousness to hogs, the chief importance 

 that attaches to these parasites is their bearing on human health. 

 In the United States, human beings acquire trichinae as a result of 

 eating raw or inadequately cooked pork, the only conclusive excep- 

 tions to this statement being a small outbreak of trichinosis in Cali- 

 fornia which was traced to the consumption of jerked bear meat 

 (Meyer, 12), and several sporadic cases traced to bear meat. 



Although the evidence presented in this paper shows that the 

 vast majority of the infested swine examined by the digestion 

 method had light or practically negligible infections, the data in- 

 dicate conclusively that sources of trichina infection exist on farms 

 in the Atlantic seaboard States, the north central States, the Middle 

 West and elsewhere. Among the possible sources of trichina in- 



