Trichinella skin tests in an orphanage and prison; comparison with serologic tests for trichinosis and with the tuberculin reaction.

The possibility that an unrelated disease process may alter the reaction to the trichinella skin test was uncovered in the course of an investigation on the incidence of trichinosis. A higher percentage of positive skin reactions to trichinella antigen (18.3 per cent) was obtained in 674 patients with active tuberculosis confined in 3 sanatoria, than was found in 335 patients without tuberculosis (7.2 per cent) studied in 2 general hospitals for shorter periods of time (1). On the other hand, the incidence (18.4 per cent) in 825 patients without active tuberculosis confined in 3 hospitals for mental diseases was almost identical with that found in the sanatoria. This finding suggested that some factor connected with residence in an institution might account for the high incidence. An analysis of positive reactors according to the duration of stay in an institution revealed that the incidence of positive reactions reached a peak at 18 to 29 months; no history suggesting subclinical institutional epidemics was elicited (1). Experiments were undertaken to determine whether positive trichinella skin tests could be produced in the absence of infection by the ingestion of killed trichinae, as in meat rendered noninfectious by cooking inadequate to denature the protein of the parasite. Sensitization was not induced in the animals used for these experiments (2). The possibility of a biologic cross reaction, detectable by skin test, between Mycobacterium tuberculosis and Trichinella spiralis was investigated in rabbits infected with trichinae and a bovine strain of tubercle bacilli simultaneously. No cross reaction was detected in these rabbits by skin tests (3). The present experiments were undertaken to determine whether a biologic cross reaction de-