422 a:nnual report Smithsonian institution, 1939 



larly if the patient can recall having eaten, prior to the onset of 

 symptoms, raw or insufficiently cooked pork, or an inadequately proc- 

 essed or cooked meat food product containing pork muscle tissue. In 

 the final analysis, however, a definite diagnosis of trichinosis involves 

 the finding in the patient of the parasites at some stage of their 

 development. 



The clinical manifestations of trichinosis in swine have been estab- 

 lished only as a result of observations following experimental feeding 

 of trichinous meat to these animals. The severity of the symptoms 

 in swine, as in human beings, is related to the number of encysted 

 larvae ingested. This accounts for the somewhat conflicting reports 

 relative to the seriousness of trichinosis in swine, as recorded by dif- 

 ferent investigators. In general the work of the early investigators 

 showed that swine manifest symptoms following the ingestion of 

 relatively large numbers of trichinae, and that indefinite or no symp- 

 toms are shown by these host animals following the ingestion of rela- 

 tively small numbers of these worms. 



Thus, Leuckart (6) concluded that only about 50 percent of hogs that 

 had been infected experimentally showed visible symptoms. Accord- 

 ing to Leuckart, the hogs that were seriously affected showed intestinal 

 disturbances 3 to 4 days after eating trichinous meat. In the severest 

 cases, Leuckart noted intestinal irritation, fever and pain, and on the 

 eleventh day after infection, he observed a sharp increase in tempera- 

 ture with evidence of muscular inflammation, stiffness, difficulty in 

 masticating and breathing, and severe emaciation. Leuckart found 

 that about 50 percent of the hogs showing severe symptoms succumbed 

 to trichinosis. In recovered cases, this investigator observed the sub- 

 sidence of the symptoms beginning about 6 weeks after infection ; re- 

 covery was complete, the recovered animals taking on good weight. 



In the course of experimental investigations on trichinae in hogs 

 carried out during the past few years by Lloyd A. Spindler, of the 

 Zoological Division of the Bureau of Animal Industry, under the 

 direction of the writer, observations were made on the reactions of 

 these host animals to various doses of larvae administered. Although 

 these observations were incidental to other objectives, they are of 

 value in showing the varying degree of susceptibility of pigs to dif- 

 ferent-sized doses of trichinae. When the pigs in question were killed, 

 an estimate was made of the number of larvae per gram of diaphragm 

 muscle tissue by the digestion method proposed by Ransom (10). 

 The results of these observations, together with other pertinent data, 

 are given in table 1. 



An examination of the data presented in table 1 shows that pigs 1 

 to 6 weighing from 100 to 150 pounds, showed no readily observable 

 symptoms following the ingestion of trichinous meat containing vary- 



