122 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



MISCELLANEOUS INVESTIGATIONS OF ANIMAL PARASITES. 



Experiments have been carried out on the effects of injecting into 

 animals material obtained from various species of metazoan para- 

 sites, such as body fluids and aqueous extracts or suspensions of their 

 tissues, either fresh or dried and pulverized. These experiments were 

 suggested by the recent work of Hadwen, of the Canadian Depart- 

 ment of Agriculture, to whom the bureau is indebted for his collabo- 

 ration during several weeks which he spent in the laboratories of the 

 Zoological Division. In the experiments in this division the host 

 animals used were cattle, horses, sheep, hogs, dogs, cats, rabbits, rats, 

 guinea pigs, turkeys, and chickens, and the parasites included nema- 

 todes and tapeworms of various species, ticks, lice, warbles, and bots. 

 Few experiments were made on the ophthalmic and intradermal re- 

 actions, and the injections in most cases were given subcutaneously, 

 occasionally intravenously. The conclusions reached in some re- 

 spects are slightly different from those first expressed by Hadwen. 

 Some of the more important are as follows : 



Reactions of an anaphylactic type may be produced in catrtle, sheep, 

 and hogs by single injections of antigens prepared from various 

 metazoan animal parasites. 



In some cases the reaction may possibly be specific and dependent 

 upon the existence of infestation with the species of parasite from 

 which the antigen is obtained. 



In other cases there is no relation between the reaction and the 

 presence or absence of parasites of the species from which the antigen 

 is obtained, and animals may react to parasites of species with which 

 they are not liable to infestation. 



Sheep are very susceptible to injections of crushed material, fluids, 

 or extracts from certain metazoan parasites, irrespective of the pres- 

 ence of infestation with these parasites, and small quantities, which 

 have no apparent effect upon guinea pigs and rabbits when injected 

 intraperitoneally or subcutaneously, may, when injected subcutane-. 

 ously, produce severe reactions in sheep, frequently terminating in 

 death. 



Sheep may respond repeatedly to subcutaneous injections, at inter- 

 vals of a few days, of material from the same species of parasite, so 

 that the reaction in sheep apparently differs from the ordinary ana- 

 phylactic reaction not only in the fact that a sensitizing injection is 

 not required, but in that sheep recovering from one reaction arc not 

 thereafter for a considerable period of time insusceptible to further 

 injections. 



This work is believed to have an important bearing upon the many 

 problems relating to the phenomena of anaphylaxis, and as Hadwen's 

 reaction (that is, the response of animals to antigens prepared from 

 metazoan parasites) in some cases appears to be specific, it may prove 

 of practical utility in diagnosis. 



In investigations of the gapeworm {Syngamtis trachealis) exami- 

 nation of 635 chickens sold for food on the market at Washington 

 during December, January, and February showed that none was in- 

 fested with this parasite. On the other hand, examinations of 386 

 turkeys from the same market during the same period showed that 

 92, or 23.6 per cent, were infested. This indicates that compared to 



