88 EXPERIMENT STATION EECOED. 



iu tlie omentum covering the wall of the second stomach, sis or seven Hwmon- 

 clius ( 8ti-onij!i1us) contortus and a whipworm (TricJioccplKtlus affinis) were 

 found in the abomasum, and a few larvjie of (Estrus ovis in the frontal sinuses. 

 A tapeworm (Twiiia cocnurus) developed in a dog to which an infested brain 

 was fed. 



The prevention of losses among sheep from stomach worms {Hcemonchiis 

 contortus), B. H. Ransom {U. S. Dcpt. Agr., Bur. Aii'nn. Indus, Rpt. 1908, pi). 

 269-278; Circ. iJ7, pi). 10). — The behavior, life history and means of control of 

 these parasites as brought out by Investigation and experiment are discussed. 



The older sheep as well as the lambs are more or less heavily infested with 

 stomach worms, but due to a greater resistance are not so much affected. The 

 injurious action of stomach worms is attributed to two things: First, the loss 

 of blood abstracted by the parasites and the loss of nutritive materials which 

 may be absorbed by the parasites from the alimentary fluids, and, second, the 

 destruction of red corpuscles by a poisonous substance secreted by the parasites 

 which is absorbed into the blood. It is suggested that a substance may be 

 present in the blood of adult sheep tending to neutralize the poisonous matter 

 produced by parasites, which is absent from the blood of lambs, or if present 

 occui-s iu small c]uantities. 



While the maximum longevity of the larva? is not definitely known, pastures 

 have been found to remain infectious after a lapse of nearly S months, namely 

 from October 2.") to June 10. Cultures made on September 14, lOOG, from the 

 feces of infected sheeii and kept in the labor.itory contained live larvie on June 

 5, 1907. " Cultures iu which the embryos were allowed to develop to the final 

 larval stage, after which they were kept in cold storage at temperatures below 

 freezing, in some cases as low as 12° F., still contained some living embryos 

 after two or three months, while in other cultures eggs and embryos not yet 

 developed to the final larval stage were killed within a few hours when exiiosed 

 to temperatures below freezing." ExperimiMits have shown that the eml)ry<)n:c 

 stomach worms, when contained in liquids, pass through oi-dinary filter paper. 



It is stated that the only method of handling lambs born of infested ewes 

 which can be guarantied to keep the lambs free from stomach worms is so 

 impracticable that it is not likely to come into general use. Experiments made 

 in the District of Columbia in 190S demonstrated the fact that during the 

 sunmier lambs can not be entirely protected from infection if kept with infested 

 ewes, even though the flock be placed on fresh pastures at intervals much 

 shorter than would be possiI)le under jiractical conditions. The plan of having 

 a special suckling pen has also failed to prevent entirely stomach worm 

 infection in lambs from infested mothers. The failure of the method is con- 

 sidered as due to the more or less common occurrence of larval stomach worms 

 njion the skin and wool of the ewes from whence they may sometimes be taken 

 into the mouth of the lambs while suckling and be swallowed. 



A plan for the combination of pasture rotation and medicinal treatment is 

 described which it is thought should prevent all losses after the first year or 

 two in operation. In following this plan, all the sheep except the lambs should 

 be given a preliminary treatment with bluestone, coal-tar creosote, or gasoline 

 as directed in the circular previously noted (E. S. li., 18, p. 9S7). Rotation 

 should then be practised as follows: "Pasture No. 1 until July, pasture No. 2 

 until winter begins, then to pasture No. 3 (the winter pasture), then at the end 

 of winter to pasture No. 4, then in July to pasture No. 1, then to the winter 

 liasture (No. 3), then to pasture No. 2, etc." If placed upon an infected 

 I)asture, a second mediciusjl ti'eatment should be administered during the sum- 

 mer. Before moving to pasture No. 3, another treatment for stomach worms 

 is recommended. After the first year's treatment the medicine is given only iu 



