134 ANNUAL REPORTS OP DEPARTMENT OF AGRICULTURE. 



THE ZOOLOGICAL DIVISION. 



The Zoological Division, under Dr. B. H. Ransom, chief, has con- 

 tinued the investigation of parasitic diseases of animals and the 

 study, collection, and determination of animal parasites. 



TRICHINOSIS. MEASLES, ETC. 



Further investigations on the effect of cold upon trichinae have 

 conclusively demonstrated that trichinous pork may be rendered 

 innocuous l3y exposure to low temperatures. Slight infections have 

 been produced experimentally by meat exposed to a temperature of 

 10° to 13° F. for 19 days, and heavy infections by meat exposed to 

 a temperature of about 15° F. for 20 days, but the infectiousness of 

 trichinae has not persisted longer than the tenth day in meat refrig- 

 erated at a temperature of 5° F. 



The discovery that the vitality of trichinae may be destroyed by 

 refrigeration has obviated the necessity of considering further the 

 question of undertaking a necessarily expensive microscopic inspec- 

 tion of pork products prepared customarily to be eaten without 

 cooking. Such products may be rendered safe by refrigerating the 

 pork from which they are manufactured at a temperature of not 

 higher than 5° F. for a period of 20 days. It seems advisable to 

 adopt 20 days as a proper length of time for refrigeration rather 

 than a shorter period in order that there may be an ample margin of 

 safety. 



Investigations have also been made of the effects of curing proc- 

 esses upon trichinae, and it has been found that sausage and hams of 

 kinds prepared customarily to be eaten without cooking may be ren- 

 dered safe if certain methods are followed in their preparation. It 

 is expected that provision will be made whereby establishments op- 

 erating under Federal inspection may be enabled to employ these 

 methods in the preparation of such products, as an alternative to 

 refrigeration. 



In the course of a trip of investigation to Alaska, some live cysti- 

 cerci, the cause of measles in reindeer, were procured and fed to dogs, 

 in which adult tapeworms (presumably Tcenia krdbhei) developed 

 as a result. Egg-bearing segments of these tapeworms fed to sheep 

 and calves failed to produce tapeworm cysts, from which it may be 

 concluded that the parasite is not readily transmissible (if at all) to 

 either sheep or cattle, and that there is little likelihood of live stock 

 in the United States becoming infested with reindeer measles through 

 the importation of reindeer meat from Alaska. Dogs in Alaska were 

 found to harbor, in addition to the reindeer measle tapeworm, the 

 dangerous hydatid tapeworm. The prevalence of these two tape- 

 worms in Alaska calls for the adoption of certain prophylactic 

 measures with reference to dogs associated with the reindeer herds 

 in order to prevent damage to the meat from measles in the one case 

 and the spread of hydatid disease among human beings in the other. 



ROUNDWORMS OF SHEEP. 



In order to continue the investigations upon stomach worms and 

 other internal parasites of sheep a farm of about 160 acres near 

 Vienna, Ya., has been rented. During the first year of occupancy 



