116. Trichostrongylus capricola. Spicule and gubernaculum of male. Lateral view........... 117. Trichostrongylus capricola. Posterior end of body of female, viewed from left side..... 98 118. Strongylus ventricosus. Posterior end of body of male, showing bursa spread out and spicules.............. 99 119. Gongylonema scutatum. Anterior end of body. Dorsal view... 101 101 121. Gongylonema scutatum. Posterior end of body of male. Ventral view. 123. Gongylonema verrucosum. Anterior end of body. Dorsal view 101 101 102 obliquely..... 102 129. Spiroptera verrucosa. Posterior end of body of male. Ventral view.. 130. Strongyloides papillosus. Parasitic adult...... 103 106 131. Strongyloides papillosus. Portion of body of parasitic adult in region of vulva, viewed from right side............ 106 132. Strongyloides papillosus. Posterior end of body of parasitic adult, viewed from right side.. 106 133. Strongyloides papillosus. Female of free living generation, viewed from left side.... 106 134. Strongyloides ovocinctus. Parasitic adult.. 109 135. Strongyloides ovocinctus. Portion of body of parasitic adult in region of vulva, viewed from left side...... 109 136. Strongyloides ovocinctus. Posterior end of body of parasitic adult, viewed from left side...... THE NEMATODES PARASITIC IN THE ALIMENTARY TRACT OF CATTLE, SHEEP, AND OTHER RUMINANTS. INTRODUCTION. Parasites belonging to the group known to zoologists as Nematoda a are so common in the alimentary tract of cattle, sheep, and other ruminants, and in many instances are so injurious, that the proper identification of the various species is a matter of considerable importance. Obviously, one of the first steps in the study of parasitic diseases is to determine the particular parasites concerned to be able to recognize the different species and to distinguish them from one another. In the present paper an attempt has been made to describe the various species of nematodes occurring in the alimentary tract of ruminants in sufficient detail so that any nematodes belonging to known species which may be found in that location can be identified by comparing the specimens with the descriptions herein. For com-. plete references to the literature cited the reader may consult Bureau of Animal Industry Bulletion 39, Index-Catalogue of Medical and Veterinary Zoology. LIST OF NEMATODES OCCURRING IN THE ALIMENTARY TRACT OF RUMINANTS. The following list contains about 50 species of nematodes which have been reported as parasitic in the alimentary tract of ruminants, and not less than 30 of these are known to occur in this country. The portion of the alimentary canal in which each species is most commonly located (so far as it has been possible to determine) is mentioned, and if a species has been reported as a parasite of domestic cattle, sheep, or goats the fact is stated. Family Ascaridæ: Genus Ascaris Ascaris vitulorum.-Small intestine; cattle. All parasitic worms with unjointed elongated cylindrical bodies, with a more or less firm cuticle composed of chitin, and with a terminal mouth at one end of the body and an anal opening terminal or subterminal at the other end, belong in the order Nematoda. b Gaigeria pachyscelis should be added to this list. See Addendum, p. 124. c The asterisk (*) denotes that specimens of the species indicated (collected in the United States) were examined by the author. Family Strongylidæ: Subfamily Strongylinæ Genus Agriostomum— Agriostomum vryburgi.—Small intestine; cattle (Bos indicus). a Genus Monodontus * Monodontus trigonocephalus.-Small intestine; sheep, goat. *Esophagostomum columbianum.-Large intestine; sheep, goat, ?cattle. *Esophagostomum radiatum.-Large intestine; cattle. *Esophagostomum venulosum.-Large intestine; goat, sheep. Subfamily Metastrongylina Genus Hæmonchus— *Hæmonchus contortus.-Fourth stomach; cattle, sheep, goat. (? Hamonchus) bispinosus.—Stomach. Genus Ostertagia *Ostertagia ostertagi.-Fourth stomach; cattle. *Ostertagia circumcincta. Fourth stomach; sheep, goat. *Ostertagia trifurcata.—Fourth stomach; sheep, goat. *Ostertagia marshalli.—Fourth stomach; sheep. *Ostertagia occidentalis.-Fourth stomach; sheep. *Ostertagia mentulata.-Fourth stomach. Ostertagia brigantiaca.-Small intestine. Genus Cooperia— *Cooperia curticei.-Small intestine; sheep, goat. *Cooperia punctata.-Small intestine; cattle. *Cooperia oncophora.-Small intestine; cattle, sheep, goat. Genus Nematodirus— *Nematodirus filicollis.-Small intestine; cattle, sheep, goat. Nematodirus digitatus.—Stomach; cattle (Bos indicus). *Trichostrongylus instabilis.-Small intestine; sheep, goat. *Trichostrongylus vitrinus.-Small intestine; sheep, goat. *Trichostrongylus extenuatus.-Fourth stomach; cattle, sheep, goat. * Trichostrongylus capricola.-Small intestine or fourth stomach; sheep, goat. Species of uncertain generic position- Strongylus ventricosus.-Small intestine. Strongylus fordii.-Stomach or intestine; cattle. Family Filariidæ: Genus Gongylonema— *Gongylonema scutatum.-Mucous lining of esophagus; cattle, sheep, goat. Gongylonema verrucosum.-Stomach; sheep, cattle (Bos indicus). Genus Spiroptera— Spiroptera verrucosa.-Stomach. a See Addendum, p. 124. Family Angiostomidæ: Genus Strongyloides— *Strongyloides papillosus.-Small intestine; sheep, goat. Family Trichinellida: Subfamily Trichurina Genus Trichuris *Trichuris ovis.-Large intestine; cattle, sheep, goat. Trichuris globulosa.-?Large intestine. Trichuris cameli.-Large intestine. Trichuris giraffe.-Small intestine. *Capillaria brevipes.-Small intestine; sheep. Subfamily Trichinellina Genus Trichinella Trichinella spiralis.-Small intestine; accidental in ruminants. METHODS OF COLLECTING AND PREPARING SPECIMENS. Though some species of nematodes infesting ruminants may be recognized at a glance with a fair degree of certainty, for example such forms as Hæmonchus contortus and Chabertia ovina, other species require careful microscopical examination for their identification, either because of their small size or because in their grosser characters several species may look so much alike that they can only be distinguished from each other by means of the finer details of their structure. For the purpose of identification freshly collected specimens may be examined alive in physiological salt solution (about 6 grams of salt to a liter of water) on a glass slide under the microscope, but when time is lacking and if it is desired to retain specimens for future reference it is necessary that they be preserved for later examination. Owing to the tedious nature of the task of picking out specimens one by one from the viscera of animals examined for parasites and the difficulty of finding nematodes, even those of considerable size, amid the ingesta of the alimentary tract, a more rapid and certain method of collection is desirable. A very satisfactory method consists in taking the various portions of the alimentary canal, opening them with an enterotome or other scissors of convenient size, and evacuating their contents into tall jars of water, washing and scraping their mucous lining in order to detach any adherent parasites. The contents of the jars are stirred up and then allowed to settle for a few minutes, during which time the worms, if any be present, settle toward the bottom together with the heavier ingesta. Then the contents of the jars except a few inches at the bottom are carefully decanted off, more water is added, and the same procedure repeated. This operation is continued until the liquid no longer becomes turbid when the contents of the jars are stirred. The water is poured off as before and physiological salt solution added. In this solution the worms may remain for several hours without being damaged. Poured out into a shallow dish the worms thus treated are readily seen and may be picked out with comparative ease from the ingesta. The most satisfactory method of preservation for general purposes is that recommended by Looss (1901a). The worms are killed in hot, nearly boiling, 70 per cent alcohol, to which may be added, if desired, 5 per cent of glycerin, or 10 per cent if the worms are small and readily permeated by the killing fluid. To prepare them for study the specimens may then be placed in a mixture of 20 parts of absolute alcohol and 80 parts of carbolic acid, which renders them sufficiently transparent for examination in temporary mounts under the microscope. As an alternative the specimens, if not already in glycerinated alcohol, may be placed in 5 to 10 per cent glycerin in alcohol and left uncovered in a warm, dry place, free from dust, until the alcohol has evaporated, after which more glycerin may be added, if necessary, to cover the specimens. This gradual change by evaporation from alcohol to glycerin prevents the ruinous shrinkage which would result by more abrupt changes from a medium of one specific gravity to one of another, and which commonly results when the usual technical methods are followed. The specimens may then be mounted in glycerin or in glycerin jelly for microscopical examination. As Looss (1901a) has pointed out, glycerin jelly or glycerin is, as a rule, a better mounting medium for nematodes than balsam, which renders specimens so transparent that many details of structure are not visible, or only difficultly so. STRUCTURE OF NEMATODES PARASITIC IN THE ALIMENTARY TRACT OF RUMINANTS. In the following brief review of the anatomy of nematodes parasitic in the alimentary tract of ruminants those details of structure which are of practical importance in determining species are discussed in a general way. FORM. As indicated by their name, the nematodes are more or less threadlike in form. They are elongated, cylindrical, usually attenuated toward one or both extremities. In the genus Trichuris the anterior portion of the body is much more slender than the posterior portion, and from their fancied resemblance to a whip the worms of that genus are commonly known as whip-worms. a The references are to the Index-Catalogue of Medical and Veterinary Zoology, published as Bulletin 39, Bureau of Animal Industry, Department of Agriculture. |