A dose-response investigation on the level of resistance to pyrantel citrate in nodular worms of pigs

This study was undertaken to determine the level of resistance against pyrantel citrate in strains of Oesophagostomum quadrispinulatum and Oesophagostomum dentatum which have previously been found resistant to this anthelmintic. Groups of pigs were artificially infected with batches of infective larvae which were previously found either susceptible or resistant to pyrantel citrate. After treatment with 1, 2 and 4 times the recommended dose (14 mg kg-1) of pyrantel citrate, the resistant O. quadrispinulatum population was reduced by 51.0, 76.2 and 86.1%, and O. dentatum by 41.2, 47.9 and 78.5%. The results indicated that O. dentatum was slightly more resistant (P less than 0.05) than O. quadrispinulatum to pyrantel citrate. Treatment of the susceptible worms with 1 and 2 times the recommended dose caused a reduction in worm numbers by 61.0 and 99.4%, respectively.     

Preventive anthelmintic treatment of grazing young cattle via supplementary feed and drinking water

Twenty-six first season calves were allocated into four groups which were turned out on May 21 to graze separate permanent pastures. One group (group A) remained untreated. The others were treated each month with albendazole either as an oral drench (group B) through supplementary feed (group C) or through the drinking water (group D). Neither clinical disease nor weight gain depressions were observed in any group. Although the infection levels were low, the faecal excretion of trichostrongylus eggs, the serum pepsinogen activities and the pasture larval contamination all indicated a marked reduction in the levels of infection of groups B, C and D. The serum pepsinogen activities of groups B and C were similar and remained below 1 unit of tyrosine/litre of serum whereas that of group D was intermediate between these two groups and group A. The labour saving principle which was applied to group C is recommended under conditions similar to those of the present experiment.     

Attempts to immunize cattle against Ostertagia ostertagi infections employing 'normal' and 'chilled' (hypobiosis-prone) third stage larvae.

Immunity to Ostertagia ostertagi infections in calves develops slowly and only becomes manifest towards the end of a grazing season in which they have been exposed to the parasite. In an attempt to hasten the onset of immune reactions, three immunization protocols were set up. Twenty four heifers were allocated into four groups. Beginning in January, animals in two of the groups were inoculated with four 1-monthly increasing dosages of either 'normal' or 'chilled' (hypobiosis-prone) larvae, those in the third group received a single large infection with 'chilled' larvae and those in the fourth group served as non-infected controls. All animals were turned out on a common pasture in late April. Development of immunity was evaluated through determinations of faecal egg counts, live weight gains, serum pepsinogen levels and specific serum antibody responses of three isotypes (IgG1, IgG2 and IgA). Significantly reduced egg excretions in the immunized groups were apparent early in the season, indicating that the immunizations had, in this respect, been efficacious. The 'chilled' and 'normal' larvae seemed equally efficient given as multiple and single infections. A single large dosage of 'chilled' larvae seemed to have adverse effects. Only moderate antibody responses were elicited probably because of low challenge infection level on pasture. Considerable variation in responses existed between and within the four groups, for which reason conclusions regarding correlations between antibody isotype responses and immune effects on parasites could not be made.     

Biological control of trichostrongyles in calves by the fungus Duddingtonia flagrans fed to animals under natural grazing conditions

The present study was conducted in the 1993 grazing season with yearling calves exposed to a pasture with a natural mixed trichostrongyle larval infection. It was shown that daily feeding with the microfungus Duddingtonia flagrans during the first 2 months of the season led to a lowered herbage infectivity and a reduced acquisition of Ostertagia sp. and Cooperia sp. later in the season. In addition, the procedure delayed the onset of clinical disease. This was due to the nematode-destroying effects of the fungi in the dung excreted by the fungus-treated calves, as evidenced by results from a parallel in vitro assay on faecal larval cultures. The paper discusses future research needs before practical biological control can be implemented.     

Efficacy of piperazine dihydrochloride against Ascaris suum and Oesophagostomum species in naturally infected pigs

A controlled trial was performed to evaluate the efficacy of piperazine dihydrochloride in a new granular formulation (Ascarex D) against naturally occurring infections with Ascaris suum, Oesophagostomum dentatum and O quadrispinulatum. Treatment effects were estimated on the basis of parasites recoverable from the intestinal contents. Given orally at 200 mg per kg body weight the compound showed an efficacy of 99 to 100 per cent against A suum and the nodular worms. Egg excretion of the respective species was reduced by 98 per cent and 100 per cent six days after treatment. No adverse reactions were observed after the treatment.     

Interactions between the predacious fungus Arthrobotrys oligospora and third-stage larvae of a series of animal-parasitic nematodes

Interactions between the predacious hyphomycete Arthrobotrys oligospora and third-stage larvae of nine animal-parasitic nematodes were tested in vitro. The trap-inducing capabilities of the ruminant trichostrongylus Cooperia oncophora, C. curticei, Haemonchus contortus and Ostertagia ostertagi and of equine cyathostomes were almost comparable to those of free-living soil nematodes, and significantly higher than those of the porcine Oesophagostomum dentatum and Oe. quadrispinulatum and of the murine Nematospiroides dubius. The trap-forming potential of Dictyocaulus viviparus was poor. All animal-parasitic nematodes were rapidly captured when fungal traps had been pre-induced in high numbers. The possible influence of predacious fungi on animal-parasitic nematode populations under natural conditions in the field is discussed.     

Outbreaks of early-season trichostrongylosis in calves in Denmark

This paper describes clinically manifest infections occurring as early as June and early July in first-season grazing calves in Denmark during the period 1972-1987. Two severe outbreaks in 1976, included in our experiments, were studied in detail. Herbage infectivity was particularly high in grass tufts surrounding cow pats that were present in high numbers around the time of turnout. It is hypothesized that the preceding extremely dry summer followed by a hard winter had indirectly retarded degradation of dung pats and thereby favoured the overwintering of the larval populations in the dung reservoirs. In a third experiment, conducted in the same year, the epidemiological pattern was more normal; presumably due to artificial irrigation of the pasture during the drought. Early-season cases that were recorded in 1980 and 1987 could possibly be related to cold winters and/or very early turnout. The findings are discussed in the light of ecological factors responsible for the breakdown of cow pats. The clinical implications are seen in relation to current control methods.     

Immunofluorescent immunoglobulin differentiation of vibrio fetus antibodies from bovine cervico-vaginal secretions

Reports on discrepancies between local and systemic immunity started to appear about 50 years ago (cf. Tomasi & Bienenstock 1968). Protection against infections has been shown in many cases to be closely related to the antibody content of external secretions and more or less independent from the serum antibody level.