Ill tlic soil due to Iieavy rainfall or protection by dense vege- 

 tation. Later epidemiologic investigations elsewhere in the 

 United States supported this view by showing that in other 

 areas where the incidence of ascaiis was much higher than 

 trichuris, infections with the latter were largely limited to 

 households where dense vegetation or poor drainage produced 

 moist areas around the dwellings where the eggs were deposited 

 (Otto, Cort, and Keller, 1931; Otto, 1932); Cort and Otto, 

 1937). 



Certain field studies in the United States (Cort and Otto, 

 1937; Otto, 1932; Caldwell, Caldwell, and Davis, 1930) were 

 made of situations where the incidence of trichuris was higher 

 than ascaris. In these places the soil where the eggs were de- 

 posited was moist and appeared very favorable for develop- 

 ment. The soil pollution in the yards and close to the houses, 

 however, seemed to be considcrabl.v less than that found asso- 

 ciated witli heavy ascaris infections. It was suggested, there- 

 fore, that given favorable conditions for the development of 

 the eggs the advantage in dissemination would be in favor 

 of trichuris on account of its longer life and greater stability 

 in the host. Undoubtedly, other differences in the life cycle, 

 host relations, and general environmental relations of these 

 two parasites also produce differences in their distribution. 



Finally, since the human habits responsible for the spread of 

 trichuris and ascaris appear to be the same, control measures 

 would be the same for both. 



Trichinella spiralis 

 E. B. C. 



The old Mosaic law against eating pork is perhaps traceable 

 to suspicions regarding the casual relationship between pork 

 and the disease later called trichinosis. From very earlj' days 

 epidemics were recorded with symptoms strikingly similar to 

 those of trichinosis; Glazier (1881) refers to such a disease 

 among the Carthaginians sent (B. C. 427) to subjugate Sicily; 

 descriptions of outbreaks from the l.^ith century on, in Ger- 

 many, France, the British Isles, and America correspond so 

 closely with those of trichinosis that there is now no doubt 

 as to the etiology. However, it was not until the 19th century 

 that evidence was produced as to the cause of the disease. 



The principal hosts of TrichineUa spiralis are swine, rat and 

 man. In addition, however, the following other animals either 

 have lipen fmiiid naturally infected or have been experimentally 



infected. Naturally infected: mice, rabbits, beaver (coypu),. 

 domestic eat, palm civet, dog, wolf, coyote, fox, pole cat, martin, 

 ferret, European and American badgers, raccoon, polar bear, 

 common bear {Ursiis sp.), and mongoose. Experimentally in- 

 fected: guinea pig, monkeys, sheep, cattle, horse, young chick- 

 ens, pigeons, magpies, and rooks. In young chickens the larvae 

 in the muscles soon die (Augustine, 1933; Matoff, 1938). Lar- 

 vae developed to the infective stage in very young [ligeon.s 

 (Matoff, 1936; 1938) and in adult pigeons affected by avita- 

 niinosis (Pavlov, 1940). In the latter case infectivity was 

 demonstrated 32 days after the feeding of trichinous meat to 

 tlie pigeons (personal communication). Coldblooded animals 

 are apparently immune (Pavlov, 1937). 



DIAGNOSIS 



During life, diagnosis of trichinosis may l>e made from the 

 clinical history, the differential blood picture, and immunologi- 

 cal tests. Other tests, sometimes used but less reliable, are 

 the following. Stool examination: the evidence indicates it is 

 of little or no value. Biopsy: a bit of muscle excised usually 

 from the deltoid, biceps or gastrocnemius is examined as a 

 fresh press preparation and by digestion, as the trichinae are 

 thus more easily detected than in sections. This method has 

 the limitation of being not deiiendable until the end of the third 

 week after infection and in addition a negative biopsy does 

 not exclude trichinosis. Examinatinn of blood and cerebrospinal 

 fluid for larvae: For a period of about 3 weeks, beginning 

 about 1 week after infection, the larvae may be present but 

 are not always easy to find. 



Immunological reactions, consisting of intradermal and pre- 

 cipitin tests, are more reliable when properly used and inter- 

 ]>reted. Bachman (1928) initiated both tests; they have been 

 somewhat modified by Augustine and Theiler (1932) and other 

 workers. Bozicevich (1939) developed an improved antigen, 

 sujierior in having larvae with a miniinum of debris and in 

 being extracted with neutral O.S.'i percent solution of sodium 

 chloride, without preservatives; the result is much greater speci- 

 ficity and impioved maintenance of potency. With the im- 

 proved antigen a positive skin test in ralibits may be obtained 

 8 or 9 days after infection; however, in man positive reactions 

 are seldom obtained until after the second week of infection. 

 Both skin and precipitin tests should be used for diagnosis, 

 even though the skin test is negative. Positive precipitin re- 



Tablb 9. Findings of trichinae in local stirveys in the United States 



Author Date 



Whelpley 1891 



Thornbury 1897 



Williams 1901 



Queen 1931 



1937* 



Riley and Scheifley .. 1934 



Hinman 1936 



McNaught and Anderson 1936 



Magath 1937 



Sawitz 1937 



Pote 1937 



Scheitiey 1938 



Walker and Breckenridge . 1938 



Evans 1938 



Hood and Olson 1939 



Sawitz - - 1939 



Butt and Lapeyre .. 1939 



Gould 1939 



Gould - 1939 



Harrell and Johnston 1939 



Oosting 1940 



Catron 1940 



Totals 



•Reported by Scheifley, 1938. 



Place 



St. Louis, Mo. 



Buffalo, N. Y. 



Buffalo, N. Y. 



Philadelphia, Pa. 



Baltimore, Md. 



1 >enver, Colo. 



Rochester, N. Y. 



Boston, Mass. 



Denver, Colo. 



Minneapolis, Minn. 



New Orleans, La. 



San Francisco, Cal. 



Rochester, Minn. 



New Orleans, La. 



St. Louis, Mo. 



Minneapolis & St. Paul, Minn. 



Birmingham & Tuscaloosa, Ala. 



Cleveland, Ohio 



Chicago, 111. 



New Orleans, La. 

 Los Angeles, Cal. 

 Eloise, Mich. 

 Eloise, Mich. 

 Durham, N. C. 



Dayton, Ohio 

 Ann Arbor, Mich. 



300 



.-,.-.31 



44 



774 



14.7 



13.9 



Method 



Microscopic 



Microscopic 



Microscopic 



Microscopic 



Microscopic 



Microscopic 



Digestion 



Digestion 



Digestion 



Microscopic 



Digestion 



Digestion 



Microscopic 



Micros. & digestion 



Sections 



Microscopic 



Micros. & digestion 



Micros. & digestion 



Digestion 



Digestion & micros. 



Micros. & digestion 



Digestion 



Digestion 



Micros. & digestion 



Digestion 



Microscopic 



Micros. & digestion 



% Digestion ; % 



Micros. & digest. 

 Digestion and 270 



microscopic 



316 



