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Total body water turnover and total body water volume in normal and severely parasitized cattle were studied with tritium labeled water. The parasitized cattle were all Hereford feeders which had acquired infections with Ostertagia ostertagi , Trichostrongylus axei , and Cooperia spp. while on permanent pasture. During the water turnover studies all animals had free access to feed and water. In one group of parasitized animals, an anthelmintic was used in order to determine the turnover rate of body water during convalescence. Analysis of results revealed the following: (1) The mean total body water volume in parasitized animals was 78 ± 1.08 per cent of the body weight. This represents an increase of 8 to 15 per cent over that found in normal animals of similar age. (2) The mean turnover rate (pool fraction per day) of body water in normal animals was 0.223 ± 0.043, while that of parasitized cattle was 0.110 ± 0.005. (3) After therapy the turnover rate in parasitized cattle began to increase within two to five days. Between 20 and 30 days after treatment the mean turnover rate was 0.158 ± 0.011. The reduced turnover rate of body water, assuming a steady state, reveals that in one group of parasitized animals the mean daily water flux was only 13.4 liters, whereas in normal animals having a comparable total body water volume the mean daily flux would have been 27.2 liters.

Female New Zealand White rabbits were inoculated with increasing numbers of infective Obeliscoides cuniculi larvae. The results of the experiment indicate that many similarities exist between the infection produced by this gastric nematode of rabbits and Trichostrongylus or Ostertagia infections of cattle and sheep. An acute postinoculation phase produced by larval activity was the most striking clinical effect. Length of the prepatent period and severity of the acute phase were directly related to the size of the larval inoculum. Egg production and the percentage of inoculum recovered at autopsy were inversely proportional to the number of larvae administered. The number of adult parasites present in the stomach was constant irrespective of the number of infective larvae given. Dysproteinemia, anemia, diarrhea, or peripheral edema were not produced. The associated pathological changes were primarily those of a gastritis, the main lesion being a coarsely granular mucosa overlying thickened, edematous fundic rugae. Ulceration (often with hemorrhage into the lumen of the stomach), petechiation, and the appearance of small white foci in the mucosa were noted. Uses for the model in the laboratory study of ruminant trichostrongylidosis are suggested.

Diagnostic methods which reveal only the presence or absence of Ostertagia in grazing animals are of little importance since all will acquire some degree of infection when grazed in the temperate regions of the world. Ostertagia infections may be (1) light--no disease or performance losses occur; (2) moderate--disease may or may not be overtly visible but performance losses occur or (3) heavy--disease is overt with or without death loss. The differentiation of these levels of infection is a quantitative matter insofar as the number of parasites correlates with the degree of pathology and is much less certain than is the presence or absence of infection. Historically, the quantitative parasite egg count in feces (eggs per gram (e.p.g.)), combined with the usual subjective and objective information obtained in clinical examinations has been the procedure used to obtain a quantitative estimate of the level of infection. More recently, the use of plasma pepsinogen levels as an indication of gastric pathology has been adopted by some laboratories. Neither of these methods have met with the desired level of accuracy, but they do have considerable value when their limitations are recognized. In the present era of emphasis on epidemiologically based control programs we are faced with yet another aspect of diagnosis, namely that of a quantitative estimate of numbers of infective stages (L3) on herbage. Methods to assess the number of L3 on forage are not satisfactory for routine clinical use. This paper evaluates the primary objectives of diagnosis as applied to the herd and flock. It briefly evaluates current methodology insofar as the diagnosis of parasitic gastroenteritis is concerned. The use of e.p.g. counts in clinical practice is discussed. Examples applicable to herds of weaner and stocker cattle are presented.

Serum IgE concentration has been considered a valuable measurement in parasitic infections, yet little has been reported regarding cattle. This study examines the association of IgE levels of nematode-naive Holstein steer calves and the level of gastrointestinal parasitism acquired by grazing irrigated pasture for 30 days. Total IgE levels were determined by enzyme-linked immunosorbent assay (ELISA) specific for bovine IgE on serum collected both before and after exposure to parasite-infested pastures. Following necropsy, parasite loads were determined by direct count from the contents of the abomasum, small intestine, cecum and large intestine; species of Ostertagia and Cooperia being the most common helminths found. Significant increases of IgE in the serum of calves with light infestations were seen, whereas calves with moderate to heavy infestations showed only mild IgE increases. With increased parasite burden, the frequency of increased IgE levels was reduced. Additionally, there appeared to be a seasonal correlation relating the level of serum IgE detected to the number of worms counted and to the course of parasite development.

Four-month-old female New Zealand White rabbits were divided into 12 groups, each consisting of two inoculated animals and one control. All experimental rabbits were given 100,000 third-stage Obeliscoides cuniculi larvae by stomach tube, after which groups were necropsied during the next 22 days. Between postinoculation days 1 and 9, acute gastritis accompanied by weight loss attributable to a marked reduction in food and water consumption developed in experimental rabbits. During subsequent chronic stages of the disease, inoculated rabbits improved rapidly and clinically became essentially normal. Many gross and histopathologic changes similar to those of bovine ostertagiosis occurred in experimental rabbits. There were folding and thickening of the gastric mucosa caused by mucosal and submucosal edema, mononuclear and eosinophilic infiltrates of the lamina propria and submucosa, and extensive mucous-cell hyperplasia. The latter change resulted in the replacement of glandular epithelium and a subsequent rise in gastric pH. Primary nodules and epithelial cytolysis, two common lesions of bovine ostertagiosis, were not observed. Failure of the latter lesion to develop in rabbits may limit the usefulness of Obeliscoides cuniculi parasitism as a model of ostertagiosis, despite its many similarities to the bovine disorder.

Infection of 30-day old mice with 400 larvae of N. dubius resulted in the development of a hypocythemic, microcytic, and hyperchromic anemia. The anemia was largely prevented by an iron supplement and was believed to be due to the following conditions: (1) the high physiological requirements for iron in recently weaned and rapidly growing mice; (2) reduced intestinal absorption of iron and/or other essential nutrients; and (3) chronic hemorrhage. Later in the course of the disease the anemia became hypercythemic, microcytic, and hypochromic. This was attributed to compensatory hemoconcentration, improved function of the small intestine, and lessened requirements for an increase in blood volume. Splenomegaly was a prominent pathlogical change and it appeared to result from the combined effects of anemia and an unidentified factor, possibly a secretion or an excretion of the parasite. It was demonstrated by using splenectomized mice that under the conditions of the present experiments, the spleen was not an essential part of the resistance mechanism.