BUREAU OF ANIMAL INDUSTRY. 123 



turkeys adult chickens are relatively unimportant as carriers of the 

 gapeworm. 



The infectious larval stage of the parasite has been kept alive in 

 moist media in the laboratory over a year, which shows that ground 

 on which infested chickens or turkeys have been kept may retain its 

 infectiousness for long periods of time. 



It has been found that about two weeks are required for gapeworms 

 to reach maturity and begin producing eggs after the larva3 have 

 been swallow^ed by a chicken. In experiments chickens 10 days old 

 when fed gapeworm larvae all died within a month. They began to 

 show symptoms of disease 8 to 10 days after infection, most of them 

 dying between the tenth and fifteenth days, and all w^ere found in- 

 fested when examined post-mortem. Chicks 6 to 10 w^eeks old became 

 infested, but not invariably, and, unlike the younger chicks, did not 

 show marked symptoms. Whether any would have died as a result 

 of infestation was not determined, as they were killed for examina- 

 tion two weeks after feeding gapeworm larvae to them. In the case 

 of adult chickens fed repeatedly with large numbers of gapeworm 

 larvae, less than one-fourth became infested, and usually only a very 

 few worms were recovered. 



With reference to the practical application of these results in the 

 prevention of losses from this parasite, it is evidently very important 

 that young chickens for the first few weeks of life be kept on clean 

 ground ; that is, ground free from gapeworm infection. Brood hens 

 may be associated with them, but other chickens and turkeys should 

 be rigidly excluded from places occupied or to be occupied by the 

 young chicks. So far as known, ground once occupied by infested 

 chickens or turkeys may remain infectious for several years. When 

 chickens have reached an age of a month or six weeks they may be 

 removed from the places reserved for their first occupancy, and 

 thereafter it is unlikely that they will suffer seriously from gape- 

 worms. 



Claims recently made (Salzer, 1916) with reference to the action 

 of serum from animals convalescent from an attack of trichinosis 

 have been investigated and no evidence discovered that such serum 

 has any effect in either preventing or curing the disease. 



Eecent experiments of Stewart, of the British Army, have been 

 repeated in this division, and it has been found, as he found, that 

 the eggs of the common roundworm of hogs {Ascaris suum) when 

 fed to mice and rats hatch out, and that the larvae undergo consider- 

 able development in these hosts, migrating to the liver, lungs, esopha- 

 gus, and intestine, apparently in the order named. The larvae were 

 found also in other organs and locations. It seems likely that the 

 development in rats and mice is simply an expression of the ability of 

 the parasite to live for a limited period in another than its usual 

 host, and that these animals do not in any w\ay act as intermediate 

 hosts as Stewart was inclined to believe. In the light of Stewart's 

 investigations and those of this division it is probable that the larvae 

 which hatch from the eggs of these and similar parasites migrate 

 rather extensively in their normal hosts, as they do in rats and mice, 

 before they finally establish themselves in the intestine to continue 

 their development to maturity. How much damage they may do 

 in the course of their migrations is a question for future determina- 



