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



gapeworms. There is little question, however, that the turkey is more 

 important than any other bird as a reservoir of infection, and it 

 is essential, if losses from gapes are to be avoided, that the part 

 j>layed by the turkey in spreading and perpetuating gapeworms 

 should be borne in mind by the poultry raiser. The relation of the 

 turkey to gapes in chickens is commonly overlooked, largely, no 

 doubt, because young turkeys are usually less seriously affected 

 by gapeworms than young chickens, and because old turkeys har- 

 boring the parasites rarely show any visible evidence of infestation, 

 so that they are not likely to be suspected as a source of the disease 

 that plays havoc among the young chickens. 



Whether, in the absence of turkeys from a farm, gapeworm dis- 

 ease among chickens will regularly disappear has not been definitely 

 established, but it seems probable that it may often do so. Though 

 it is certain that contaminated soil will remain infectious for a long 

 time and that infection in the soil may persist from one year to the 

 next, nevertheless it may be that, as a rule, chickens alone will not 

 perpetuate the infection. A large proportion of the young chickens 

 that become infested die of gapes before there has been much oppor- 

 tunity for scattering the eggs of the gapeworms, and since chickens 

 as they grow older tend to become not only less susceptible to infec- 

 tion but also more and more unfavorable as hosts of the gapeworms 

 acquired at an earlier age, the infested chickens that do not die of 

 gapes probably do not continue long to harbor the worms and so are 

 unlikely to spread much infection. In view of these apparent limita- 

 tions to the reinfection of the soil by chickens it seems not unlikely 

 that gapes will be found to have a tendency to disappear from places 

 where no turkeys are kept. 



INVESTIGATIONS ON MARYLAND FARMS. 



Evidence gathered from inquiries by Dr. Lawrence Avery and 

 the writer among poultry raisers in several localities in Mary- 

 land is insufficient to show that gapes will usually die out on farms 

 where there are no possible hosts other than chickens, but it is cor- 

 roborative of the statements that have been made as to the great im- 

 portance of the turkey as a source of infection. In fact, it was found 

 that in the absence of turkeys either no gapes occurred among the 

 chickens or the trouble from this cause was practically always slight. 

 On the other hand, where turkeys were present considerable losses 

 among the chickens as a result of gapes were almost always reported. 

 Inquiries were made on 41 farms. On 16 farms where there was 

 no history of the association of turkeys with the chickens, gapes 

 was reported in eight instances, no gapes in the other eight. On 

 one farm where there were said to be numerous cases of gapes 

 among a flock of 500 chickens, turkeys were kept the preceding 



