Seasonal occurrence of infective nematode larvae in California Sierra foothill pastures grazed by cattle.

Worm-free Holstein tracer calves were used to assess the seasonal variation in number and course of development of nematode parasites of cattle on an irrigated pasture located in the California Sierra foothills. The most common genera of nematodes found in the abomasum and small intestine were Ostertagia and Cooperia, respectively. The infective Ostertagia larvae on herbage were most numerous in early spring and lowest in summer months. Arrested development of Ostertagia occurred in mid-to-late spring. The percentage of the population of Ostertagia found to be arrested larvae was constant (73% to 95%) over 4 years, even though the total number of nematodes in the genus was markedly different. Levels of infection with Ostertagia and Cooperia were found to correlate with pasture contamination occurring in the preceding fall and concurrent winter months. In the cecum and large intestine, Oesophagostomum venulosum was found to be the most common nematode. It is suggested that this species may replace Os radiatum as the cattle nodular worm in regions where climate is similar to that of the southwestern coast of North America. Evidence of seasonal hypobiotic development of Oe venulosum was found. Other genera of nematodes observed in tracer calves were Trichostrongylus, Haemonchus, Bunostomum, Trichuris, and Dictyocaulus.

Phenotypic differences in female Ostertagia circumcincta as demonstrated by isozymes hydrolyzing alpha-naphthyl acetate.

According to results of disc gel electrophoresis of homogenates prepared from individual female nematodes of the species Ostertagia circumcincta and subsequent staining of gel preparations, a maximum of 5 isozymes, hydrolyzing alpha-naphthyl acetate, were present. On the basis of resolution and mobility, these isozymes could be classified as 2 slow and 3 fast bands. Phenotypic differences were observed in the intensity of individual bands, as well as in the presence (or absence) of bands.

Anthelmintic efficiency of oxfendazole in California lambs.

Oxfendazole, methyl 5(6)-phenylsulfinyl-2-benzimidazole carbamate, was given by oral drench (5 mg/kg) to California lambs harboring natural infections of gastrointestinal nematodes. Ninety-nine percent of adult Ostertagia circumcincta, Ostertagia trifurcata, Trichostrongylus axei, Trichostrongylus vitrinus, Trichostrongylus colubriformis, Nematodirus filicollis, and Nematodirus spathiger were removed by the anthelmintic.

Influence of plasma A esterase on anthelmintic action of haloxon in sheep.

Controlled trials were conducted to evaluate the anthelmintic action of haloxon in 2 phenotypes of lambs, 1 having an A esterase in plasma which rapidly hydrolyzes di-(2-chloroethyl)aryl phosphates and the other without this enzyme. A total of 116 lambs, 57 with and 59 without the plasma A esterase, 6 to 9 months old, harboring naturally acquired nematode infections were used in 3 trials. Haloxon was administered orally at 20, 25, and 35 mg/kg of body weight. Nematodes against which haloxon was evaluated in the abomasum were Ostertagia circumcincta and Trichostrongylus axei and in the small intestine were T vitrinus, T colubriformis, Nematodirus spathiger, and N filicollis. The anthelmintic efficiency of haloxon did not differ in the 2 phenotypes of sheep.

Acute oral median lethal dose of haloxon and coumaphos in sheep as influenced by plasma A esterase.

Determination of the acute oral medial lethal dose (LD50) of haloxon for lambs classified as to the presence or absence of plasma esterases (A esterase; EsA) rapidly hydrolyzing haloxon revealed markedly different values for the 2 phenotypes of sheep. The LD50 for EsA- lambs was 763 mg/kg of body weight with 95% confidence limits of 543 to 1,072 mg/kg. The acute oral LD50 for EsA+ lambs remains undetermined but was demonstrated to be in excess of 11,392 mg/kg. The acute oral LD50 for a closely related organophosphate (coumaphos) was not different in the 2 phenotypes of sheep.

Seasonal occurrence of infective nematode larvae in California high Sierra pastures grazed by cattle.

Worm-free Holstein calves were used to assess the seasonal variation in numbers of nematode infective larvae on herbage at 2 commercial cow-calf ranches in the Sierra Nevada mountains. Both ranches used Herefords as their basic breed. One ranch near Sattley, California, is at an elevation of approximately 1,500 m above sea level, whereas the study area on the 2nd ranch near Susanville is at an elevation of approximately 1,250 m above sea level. Worm-free tracer calves were allowed to graze for approximately 30 days and were then kept free of further nematode infection until euthanasia and necropsy approximately 30 days after removal from the pastures. At necropsy, the number, species, and stages of development of nematodes in the gastrointestinal tract were determined. The most common species of nematode in the abomasum was Ostertagia ostertagi and in the small intestine Cooperia oncophora. Infection levels decreased during early summer and were low in midsummer to early fall. In late fall and winter, infection levels began to increase, and highest infection levels were obtained during the spring. A low level of inhibited development (up to 18%) of 4th-stage O ostertagi occurred in November and December. Considerably higher levels of inhibition (up to 61%) were observed in March, April, and May. Inhibition of development in Cooperia spp was not noticed. Other nematodes seen were O lyrata, C mcmasteri, C punctata, Trichostrongylus axei, Haemonchus sp, and Nematodirus helvetianus.

Enzyme polymorphism in Fasciola hepatica L.: esterases.

Homogenates of individual adult Fasciola hepatica, collected from bile ducts of sheep, were subjected to isoelectric focusing in polyacrylamide flat-bed gels after which zymograms were made by enzymatic and staining reactions. Seven identifiable isozymes that hydrolyzed alpha-naphthyl acetate were found. These 7 isozymes were identified by their isoelectric points as 5.10, 5.15, 5.25, 5.40, 5.55, 5.65, and 5.75. None of these isozymes was common to all F hepatica examined. Combinations of these isozymes in individual flukes revealed 7 distinct phenotypes, the frequency of which varied between local populations, i.e., populations of flukes obtained from individual sheep of different origin. In addition to these 7 isozymes, there were weak staining bands of enzyme activity, between pH 5.8 and the cathode end of the gels, which could not be accurately identified. The method of isoelectric focusing and zymogram preparation used in the present study did not reveal cholinesterase activity, even though the presence of activity in homogenates was demonstrated by polyacrylamide disc-gel electrophoresis. Strong activity of acid phosphatase between pH 5 and 6 was found, but poor resolution prevented obtaining accurate identification of isozymes. Weak activity with poor resolution of isozymes of alkaline phosphatase was observed between pH 4.4 and 5.75.

Anthelmintic efficacy of oxfendazole in calves.

Oxfendazole, methyl [5-(Phenylsulfinyl)-1H-benzimidazol-2-yl]carbamate given to calves at dose level of 2.5 mg/kg as a paste, as a bolus, or as a drench resulted in excellent (97 to 100%) anthelmintic efficacy against mature Ostertagia ostertagi, Trichostrongylus axei, Cooperia oncophora, C mcmasteri, C pectinata, C punctata, Nematodirus helvetianus, Trichostrongylus longispicularis, Chabertia ovina, and Oesophagostomum radiatum. Against the early 4th stage larvage of O ostertagia and N helvetianus, these formulations had anthelmintic efficacies of 71% to 87% and 21% to 65%, respectively. As the result of differences in drug intake by individual calves, a pelleted feed additive given as top dress on chopped alfalfa hay gave an unsatisfactory mean anthelmintic response. Anthelmintic action in individual calves ranged from none to 98--100%.

Seasonal occurence of infective nematode larvae on irrigated pasture grazed by cattle in California.

During the period extending from Dec 1, 1975, to Dec 22, 1976, 3 distinct peaks in the concentration of infective nematode larvae on pasture forage were detected by use of helminth-free tracer calves. Two of these peaks, 1 occurring in the spring and 1 in the fall, consisted mainly of Ostertagia ostertagi and Cooperia sp. It is concluded that these 2 peaks can be anticipated annually and constitute unsafe periods of grazing. The 3rd peak was comprised largely of Haemonchus placei and Cooperia sp. It is concluded that this peak occurred as the result of unusual rainfall and reduced evaporation in August. Arrested developed (24% to 30%) of O ostertagi larvae occurred only during the spring peak. This finding indicates that on irrigated pastures in California, type I ostertagiasis can be expected to occur as the result of infection during the spring and/or fall peaks, whereas type II ostertagiasis can be expected to occur in the fall as a result of infection obtained during the spring peak. Arrestment in development of Cooperia sp occurred during spring (14%) and fall (23%) peaks. Haemonchus placei larvae increased their propensity for arrestment in development from zero to 82% during the months following the peak level of infection in summer. Other nematodes encountered were Trichostrongylus axei and Nematodirus helvetianus.

Topical betamethasone 17-valerate is an anticorticosteroid in the rat. 2. Anti-inflammatory and anti-lymphocyte activities.

In the oxazolone-induced delayed hypersensitivity inflammation in the rat ear, betamethasone 17-valerate, in contrast to other topical corticosteroids, is incapable of suppressing oedema. When given in combination with triamcinolone acetonide, betamethasone 17-valerate competitively antagonizes the anti-inflammatory action of the active steroid. When tested in the mouse, betamethasone 17-valerate behaved as an anti-inflammatory agent 15 and 80 times as potent as betamethasone and hydrocortisone respectively. In an in vivo lymphocyte culture system in which preincubation with corticosteroids prevents subsequent phytohaemagglutinin induced DNA synthesis, betamethasone 17-valerate was less active than even hydrocortisone when rat lymph node cells were used, but with human cell preparations it was more potent than either hydrocortisone or betamethasone. Betamethasone 17-valerate behaves uniquely in the rat as an anticorticosteroid; in mouse and in man the compound behaves as a normal corticosteroid.