TRICHINOSIS — SCHWARTZ 421 



In general, the incidence of trichinae involved in the series of hogs 

 in question is low. Data to be presented in another section of this 

 paper show that hogs that developed infections with trichinae pro- 

 duced by the experimental feeding of trichinous meat did not show 

 clinical sjanptoms when the resulting infection was characterized by 

 less than 800 to 900 larvae per gram of diaphragm muscle tissue. In 

 the entire series of over 15,000 hogs involved in the digestion tests to 

 determine the presence of trichinae, only one contained as many as 

 805 larvae per gram of diaphragm muscle tissue. With the possible 

 exception of this particular hog, not one of the other infested animals 

 under consideration would have been diagnosed as suffering from 

 trichinosis even if all of these hogs had been under the careful scrutiny 

 of a competent veterinary clinician during the period of active infec- 

 tion. The trichina infections in the 357 positive hogs, with the pos- 

 sible exception of the one hog already mentioned, were evidently of the 

 nonclinical type, as far as can be judged by the number of larvae 

 present in the diaphragms of these individual host animals. 



Data obtained by the writer and his associates in the Zoological Divi- 

 sion showed that when the infection with trichinae in the pillars of the 

 diaphragm of hogs was such that less than 1 larva was present per 

 gram of muscle tissue, only 1 out of 11 positive samples, examined 

 microscopically three times, actually showed trichinae. "Wlien the 

 infection was characterized by as many as 3 larvae per gram of 

 diaphragm muscle tissue, only approximately 50 percent of the known 

 positives showed trichinae on miscroscopic examination. Out of a 

 total of 319 diaphragm samples from as many trichina-infested hogs 

 found to be positive by the digestion technique, only 67 (21 percent) 

 were found to be positive by the press preparation method when three 

 preparations, each containing between 100 and 150 milligrams of 

 muscle tissue, were examined. Assuming these findings to have gen- 

 eral application, the positive samples in the series under discussion 

 would have been sharply reduced, had these samples been examined 

 only microscopically. 



TRICHINOSIS IN SWINE 



Considering the fact that a positive diagnosis of trichinosis in human 

 beings can be made with certainty only when the parasites are actually 

 fomid in the patient, usually following a biopsy, it is not surprising 

 that Hutyra and Marek (11) state that trichinosis has not been diag- 

 nosed in living swine. In a human being a tentative diagnosis of 

 trichinosis is made on the basis of a chain of clinical symptoms, not a 

 single one of which, or even several taken together, can be regarded as 

 pathognomonic of this disease. However, when all the symptoms are 

 considered together, a presumptive diagnosis is warranted, particu- 



