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



From the data shown in the table it seems evident that as chickens 

 grow older they tend to become less susceptible to infection with gape- 

 worms. Apparently, therefore, the most likely reason no gapeworms 

 were found among the 635 chickens from the Washington market was 

 that these chickens when examined had reached an age at which they 

 were no longer favorable hosts for gapeworms. Probably some of 

 them had been infested earlier in life but had afterwards lost their 

 parasites. How long gapeworms will persist in youhg chickens that 

 do not succumb to the infestation is uncertain. That adult chickens, 

 however, in those unusual cases in which they become infested with 

 gapeworms, are likely to harbor the parasites only temporarily is 

 indicated by some of the findings in the following experiments : 



Twelve adult chickens a year old or more were fed gapeworm 

 material from cultures on April 26, 28, 30, May 2, 4, 7, 9, and 11, 

 altogether receiving 8 feedings, except one which was killed May 7, 

 before feeding time, and hence received only 5 feedings. Material 

 from the same cultures was fed to 12 1-week-old chicks April 24, 

 28, 30, May 2, and 4. All the young chickens died of gapes in 11 

 to 27 days after the first feeding, and all were found infested with 

 gapeworms. Except the one killed May 7, 11 days after the first feed- 

 ing, the adult chickens were killed 16 to 29 days after the first 

 feeding and 1 to 14 days after the last feeding. Gapeworms 

 were found in only 3 out of the 12. The lungs of one killed 1 6 days 

 after the first feeding and 1 day after the last feeding contained an 

 unpaired female 2.5 mm. long, and in the trachea were two pairs, 

 the females being 6.5 mm. and 10 mm. long, respectively. The 10 

 mm. female was producing eggs. Another chicken that was killed 

 18 days after the first feeding and 3 days after the last feeding har- 

 bored in the trachea a single pair of worms. The female of this pair 

 measured 13 mm. in length and was depositing eggs. In the trachea 

 of the third chicken, killed 29 days after the first feeding and 14 days 

 after the last feeding, there were 7 dead males without females, 4 

 living males without females, 3 living females with dead males, 1 

 living female with a living male, and 1 living female without a male. 

 The last two females contained apparently viable eggs, but in the 

 other three females the eggs were apparently nonfertile, dark, and 

 unnatural in appearance. All the worms, alive and dead, were firmly 

 attached to the trachea. The living worms were enveloped in a thick 

 layer of mucus. 



On another occasion 6 adult chickens probably a little less than a 

 year old were fed with a gapeworm culture. Seven days later one 

 was killed. No worms were found. A second chicken, killed 8 days 

 after feeding, had one unpaired worm, one pair of coupled worms in 

 the lungs, and 14 pairs of coupled worms in the trachea, all imma- 



