Evening Republican, Volume 20, Number 228, Rensselaer, Jasper County, 22 September 1916 — THREADWORMS [ARTICLE]

THREADWORMS

Parasite* Infecting the Gullete of Sheep and Cattle Caused by Swallowing Insects Sheep and cattle very frequently have threadworms In the gullet. These worms are seen in the lining of the gullet beneath the surface in a rather striking wavy pattern similar to that formed by a snake as it travels over a smooth surface. The wqrms are slender and threadlike, but as they measure from over an inch to £ Inches in length and raise up the surface of the lining of the gullet to form Blender wavy ridges, they are readily located an infested gullet is slit open and examined.. So far as known, the damage occasioned by the presence of these parasites in sheep and cattle is rather slight, though it has been determined that a closely related parasite is intimately associated with if not the casual agent of cancer in the stomach of rats. It has been shown by investigatiors and experiments in the Zoological division of the Bureau of Animal Industry that various species of dung beetles are the source from which sheep and cattle become infested with the gullet worm. These dung beetles may be found in almost any manure deposit, except during the winter in cold climates. The beetles usually crawl under the manure deposit, enter from the bottom, and feed on the inner portion of the deposit as long as it remains moist. When the beetles eat the manure they swallow the gullet worm eggs which have passed down the esophagus through the stomach and intestine and out in the manure of the infested sheep or cow. As soon as the manure becomes too dry and hard to work the dung beetles abandon it and crawl into the ground or fly to other and fresher deposits. In about a month the eggs which were eaten by the beetles have hatched and developed into an encysted stage in the body of the beetle, ready to continue thei: development when the infested beetle is swallowed by a cow or sheep. The opportunity for sheep and cattle to swallow these beetles ?omes when the beetles fly from one manure deposit to another. The flight usually ends by the beetles landing on the pasture somewhere near a manure deposit, and as they crawl about through the grass toward the manure, attracted by the odor, they are commonly swallowed by grazing animals. The beetles are no doubt eaten unconsciously as a rule, but as sheep and cattle eat large numbers of insects, since practically every plant is the permanent home or temporary resting place of a number of insects, it is perhaps a matter of more or less indifference to them if they are conscious of the presence of insects in a mouthful of food. This is especially true of cattle, since cattle are noted for eating foreign objects, such as nails, wire, bolts, knives, rubbers, etc. Among the various kinds of insects picked up by sheep and cattle during the course of a day, dung beetles are likely to be more or less numerous, and of these some are likely to harbor larval stages of the gullet worm, now ready for the next step in development. In the digestive tract of the cow or sheep the beetles undergo partial digestion, releasing the larval worms, which make their way to the gullet and burrow into its lining. Here the worms become mature and in time the female deposits eggs which pass down the gullet and out in the manure to carry on the life cycle. It was found that under experimental conditions the eggs of the gullet worm would develop to an infective larva in croton bugs as well as in dung beetles; but since croton bugs do not breed in manure and are house dwellers, it is evident that they do not play any part in the natural transmission of the parasite. It is interesting to note, however, that Danish scientists have found a worm, similar to the gullet worm of sheep and cattle which develops as a larva in croton bugs, cockroaches, and mealworm, and which occurs in nature in the gullet, mouth, tongue, and first portion of the stomach of rats. This worm is extremely interesting from the fact already mentioned that its development In the rat is followed by the appearance of cancer of the stomach, a fact of great impo tance from a scientific and medical standpoint. While there is now a general recog nition of the importance of biting insects as carriers of such diseases as malaria and yellow fever, and of such insects of the fly as carriers of the germs of typhoid- fever and other bacterial diseases, the facts cited above show that insects haye an importance not yet generally recognized as carriers of parasi.es. From §uch parasitic infection man himself ’is not immune. It has long been knowp that infestation with a certain kind of tapeworm only occurs as the result of eating the fleas or life of dogs, and the list of cases of the occurrence of this tapeworm in man, and especially in children, indicates only too well that dog fleas and llcfe are swallowed by human beings not altogether rarely. Tn the case of sheep and cattle the swallowing of insects is practically unavoidable, but man can guard himself against swallowing dog fleas and lice and its rather unpleasant as well as dangerous consequences by observing greater care in his relations with pet animals, particularly by excluding them from his household, which Is the only certain way of preventing the scattering of their external parasites - tn places from which children and evfin grown persons are liable to swalIpw them.