6 BULLETIN 939, U. S. DEPARTMENT OF AGRICULTURE. 



which the worms succeed in developing to maturity in adult chickens 

 and the failure to find any gapeworms among a large number of 

 adult chickens obtained from a certain market, though the parasites 

 were of common occurrence in adult turkeys from the same market, 

 it seems evident that adult chickens are not likely to be of great im- 

 portance as carriers of gapeworms. On the other hand it is certain 

 that sometimes they may harbor gapeworms for brief periods at least. 



Besides the fact that adult chickens occasionally may be infected ex- 

 perimentally may be cited the following instance of infestation follow- 

 ing exposure to infested ground. A chicken at least 22 months old and 

 probably considerably more than 2 years old died at the Bureau of 

 Animal Industry Experiment Station with a history indicating that 

 it had been kept at least a year in a pen that had previously been 

 used in gapeworm experiments. This hen was in poor condition, 

 greatly emaciated, and devoid of the usual subcutaneous and visceral 

 fat. Besides nematodes and tapeworms in the intestine there were 

 found in the trachea a female gapeworm 21 mm. long with a male 

 5 mm. long, and another female about 10 mm. long, with a male 

 4.6 mm. long. The smaller female contained eggs, but well-developed 

 eggs were not found in the larger female. 



This case perhaps should be taken as an indication of the possibility 

 that as chickens become old and debilitated their susceptibility to 

 gapeworms tends to increase again after having diminished as they 

 approached maturity. Such an explanation would be in harmony 

 with the frequently observed fact that certain parasites are more 

 common in young and very old animals than in those of middle age. 

 No definite conclusion, however, is possible from a single case. 



In marked contrast to adult or nearly adult chickens, adult turkeys 

 can easily be infected experimentally with gapeworms, as would be 

 expected from the fact that the worms have been found to be 

 naturally common among adult turkeys. The following experiment 

 shows the results of attempts to infect chickens approaching ma- 

 turity, young chickens, and adult turkeys, respectively, using in- 

 fective material from the same source. 



Three chickens 21 weeks old at the beginning of the experiment 

 were fed portions of gapeworm cultures November 29, December 18, 

 20, 27, January 3, 31, February 28, and March 31. Beginning Febru- 

 ary 28 the chickens were kept on ground that was contaminated with 

 gapeworms. The feces of these three chickens were examined Janu- 

 ary 3, 13, 17, 25, 31, February 8, 15, 22, 28, and March 28, and the 

 feces of two of them also on April 22, always with negative results. 

 One of the chickens was killed on April 8 and was free from gape- 

 worms, as were also the other two, killed on May 24. 



Some of the culture fed on January 31 was fed on February 7 to 

 three chicks 8 weeks old, and these chicks when killed 14 days later 



