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K Bairden

Publications and source records attributed to K Bairden.

At least 19 recordsLinked to original sources
PubMed1999

The relationship between the number and size of nematodes in the abomasum and the concentration of pepsinogen in ovine plasma.

Six-month-old lambs that had been naturally infected with predominantly Teladorsagia (Ostertagia) circumcincta were tested for plasma pepsinogen concentrations because pepsinogen concentrations may reflect the extent of damage to the abomasum. The distribution of pepsinogen concentrations among these lambs was positively skewed with most individuals having relatively low concentrations. Pepsinogen concentrations were more strongly associated with variation in the mean length of the adult female worms than with variation in the number of nematodes present. Previous trials have suggested that genetic variation in the growth of lambs is strongly influenced by genetic variation in worm length. Together these results imply that variation among lambs in the pathogenic effects of T. circumcincta depends upon the mean size of the worms as well as the number of worms present.

Abomasum↗
PubMed1998

Elimination of mucosal cyathostome larvae by five daily treatments with fenbendazole.

The efficacy of five daily treatments with 7.5 mg fenbendazole/kg bodyweight against mucosal cyathostome larvae was evaluated in 20 12- and 24-month-old ponies with naturally acquired cyathostome infections. After three weeks communal grazing on infected pasture and six weeks indoors, one group of 10 ponies were treated. Six weeks later, both groups of ponies were humanely destroyed and their burdens of large intestinal cyathostome worms, including luminal parasites and mucosal larvae, were assessed. In the control animals approximately 7 per cent of the total worm burden was present in the gut lumen and 93 per cent was present as larvae in the large intestinal mucosa. The efficacy of fenbendazole against the luminal cyathostomes was 90.7 per cent (P < 0.01). The total numbers of mucosal larvae, recovered after digestion, were reduced by 95.3 per cent (P < 0.0005); mucosal late third and fourth stage larvae were reduced by 99.4 per cent (P < 0.0001), and early inhibited third stage larvae by 91.5 per cent (P < 0.005).

Animals↗
PubMed1998

The influence of dietary supplementation with urea on resilience and resistance to infection with Haemonchus contortus.

Previous research has indicated that supplementing an apparently adequate diet with additional protein improves both host resistance and resilience in lambs infected with Haemonchus contortus. The present study tested the influence of supplementation with non-protein nitrogen (urea). Helminth-naive Hampshire Down lambs were given an apparently adequate basal diet or a diet supplemented with urea. The lambs were then infected with Haemonchus contortus for 10 weeks. Supplementation with urea had no discernible effect on resistance to infection; faecal egg counts, worm burdens, worm lengths and mean number of eggs per adult female worm did not differ between the 2 groups. However, lambs on the supplemented diet showed better resilience; they had greater packed red cell volumes, higher plasma albumin concentrations and increased liveweight gain compared to lambs on the basal diet. The loss of appetite following infection was less in lambs fed the urea-supplemented diet. The observed effect of urea supplementation was seemingly due to greater food consumption as well as the better diet.

Animal Nutritional Physiological Phenomena↗
PubMed1998

The processes influencing the distribution of parasitic nematodes among naturally infected lambs.

The impact of mixed, nematode infection upon a group of animals will depend upon the number of nematodes present, how they are distributed among hosts and whether individuals that are heavily parasitized with one species are more likely to be heavily parasitized with other species. A survey of over 500 six-month-old, Scottish Blackface lambs from a single farm in Southwest Strathclyde identified 7 different categories of nematodes in the abomasum and small intestine. There were considerable differences among years and among nematodes in the prevalence and mean intensity of infection. Ostertagia circumcincta was present in nearly all lambs and judged by prevalence and intensity is one of the most successful of all parasitic nematodes. Each category of nematodes had a skewed distribution; most animals had relatively few worms but a small proportion had many worms. The variance of the number of nematodes in each category were approximately equal to the square of the mean. The counts of adult O. circumcincta followed a negative binomial distribution, but the negative binomial distribution did not provide a good description of the observed values for the other species. These other species had a lower prevalence and possibly some sheep were not exposed to infection. There was no significant genetic variation among lambs in the number of nematodes present and therefore the differences among these lambs were unlikely to be a consequence of genetic differences in host susceptibility. Lambs with increased numbers of one species were more likely to be have increased numbers of the other species, but the correlations were weak and may reflect covariation in exposure to different parasites.

Abomasum↗
PubMed1997

The genetic basis of resistance to Ostertagia circumcincta in lambs.

The relationship between Ostertagia (Teladorsagia) circumcincta and sheep is one of the best understood host-parasite relationships in any species. The key components of resistance have been quantified, the extent of genetic control has been established for lambs, and methods now exist to breed lambs which will be both more resistant to worms and more productive than unselected lambs. A major gene for resistance has been identified within or around the major histocompatibility complex, and this gene appears to be the strongest yet identified for resistance to any parasite species. The most important mechanisms of resistance are local IgA responses which regulate worm fecundity and immediate hypersensitivity responses which regulate worm burdens. IgA responses develop before effective immediate hypersensitivity responses. Good simulation models now exist to predict, for example, outbreaks of disease and the response of sheep to selection. The challenge now is to use our improved understanding of the population biology to develop even better simulation models and to produce expert systems based on these models which can be used by veterinarians and others to determine optimal procedures for individual farms to control disease and reduce sub-clinical economic losses.

Animals↗
PubMed1997

Heterogeneity in the recognition of Ostertagia circumcincta antigens by serum antibody from mature, infected sheep.

The recognition of parasite molecules from third-stage and adult Ostertagia circumcincta by serum antibody was studied in a group of matched, mature Scottish Blackface sheep that had been naturally and then deliberately infected. A total of 20 molecules was recognized in somatic extracts from third-stage larvae and 31 molecules in somatic extracts from adult parasites. However, no sheep recognized all immunogenic molecules and no molecule was recognized by all sheep. There was no obvious relationship between recognition of any parasite antigen and polymorphism at class I loci or at the DRBI class II locus of the major histocompatibility complex in these outbred animals. Only 15 molecules from third-stage larvae were present at a frequency suitable for statistical analysis and recognition of three of these 15 molecules was associated with differences in worm burdens. Recognition of two of five molecules from adult parasites was associated with differences in worm length. These results indicate that variation in the recognition of specific, identifiable parasite molecules may be partly responsible for variation among sheep in resistance to O. circumcincta.

Animals↗
PubMed1997

Efficacy of a pour-on formulation of eprinomectin (MK-397) against nematode parasites of cattle, with emphasis on inhibited early fourth-stage larvae of Ostertagia spp.

OBJECTIVE: To evaluate efficacy of topically applied eprinomectin against inhibited early fourth-stage larvae (IL4) of Ostertagia spp in calves. ANIMALS: 4 groups (n = 6 [replicates]) for dose titration; 2 groups (n = 8 calves [replicates]) for dose confirmation. PROCEDURE: 2 dose titration studies-0, 125, 250, and 500 micrograms of eprinomectin/kg of body weight-Louisiana and Georgia- and 2 dose confirmation studies of selected therapeutic dosage (500 micrograms/kg) in Scotland and France. Monitor calves were used to determine inhibition percentage of Ostertagia IL4. Test calves were ranked by weight in replicates of 4 (titration trials) or 2 (confirmation trials) animals each, and within replicates, were randomly allocated to treatment groups. Drug treatments were done on day 0, and animals were euthanatized by replicate, with holding time between treatment and euthanasia varying among trials from 14 to 27 days. RESULTS: Observations indicated high efficacy (> 99%) of 500 micrograms of eprinomectin/kg in removal of Ostertagia IL4. Ostertagia and Cooperia were only genera common across sites, with efficacy of aforementioned dosage against adult and larval stages of both genera consistently high (> 99%). Results of 1 or both titration studies (500 micrograms/kg) indicated > 99 to 100% efficacy against adult Haemonchus placei, Trichostrongylus axei, T colubriformis, Bunostomum phlebotomum, Dictyocaulus viviparus, and Oesophagostomum radiatum. Lower efficacy values were observed at minimal (125 micrograms/kg) dosage. In France, 500 micrograms/kg was 85% effective against Trichostrongylus spp adults; however, numbers of control calves infected with Trichostrongylus spp and degree of infection were low. Adverse reactions were not evident. CONCLUSION: Eprinomectin given topically (500 micrograms) was highly effective against Ostertagia IL4 and other common nematodes of cattle.

Administration, Topical↗
PubMed1996

An ovine lymphocyte antigen is associated with reduced faecal egg counts in four-month-old lambs following natural, predominantly Ostertagia circumcincta infection.

Ovine lymphocyte antigen is associated with reduced faecal egg counts in 4-month-old lambs following natural, predominantly Ostertagia circumcincta infection. International Journal for Parasitology 26: 423-428. Ten lymphocyte antigens were defined in a flock of Scottish Blackface sheep known to be naturally exposed to infection with Ostertagia circumcincta. Population and family studies suggested that the 10 antigens were products of class I loci. Antigen G13br was in linkage disequilibrium with allele g2 at the DRB1 locus. The g2 allele has previously been associated with reduced faecal egg counts in a different crop of lambs from the same farm. In this study antigen G13br was also associated with a reduction in faecal egg counts. The results provide partial confirmation of the role of the major histocompatibility complex in resistance to natural, predominantly O. circumcincta infection.

Alleles↗
PubMed1996

Influence of soyabean meal supplementation on the resistance of Scottish blackface lambs to haemonchosis.

Protein supplementation improves the resistance of sheep to haemonchosis. This experiment investigated the Scottish blackface breed to establish whether dietary protein supplementation is still beneficial in a genetically resistant breed. Lambs were given either a basal diet or a diet supplemented with soyabean meal to give an additional 80 g crude protein kg dry matter-1. The lambs were given an initial loading dose of Haemonchus contortus, followed by a trickle infection for 10 weeks. The weight gains of the lambs given the supplemented diet were greater and their carcases were leaner, irrespective of infection status. Infected animals on the basal diet were more anaemic and hypoalbuminaemic than animals receiving the supplemented diet, although there were no statistically significant differences in mean worm burdens or faecal egg counts.

Analysis of Variance↗
PubMed1995

Immune response of lambs to vaccination with Ostertagia circumcincta surface antigens eliciting bile antibody responses.

Immune responses to surface antigens of infective larvae of Ostertagia circumcincta recognized by bile antibodies of sheep immune to challenge were studied in 5-month-old Finn-Dorset male lambs. The sheep were vaccinated subcutaneously with 2 doses of 25 micrograms/kg body weight of surface proteins immunoprecipitated by bile antibodies derived from protected lambs. These antigens were purified from immune complexes by affinity chromatography and then injected with beryllium hydroxide as an adjuvant. The immunized lambs were challenged with 5 x 10(4) L3 and the worm burdens evaluated on day 21 post challenge. These were significantly (P < 0.01) lower in the vaccinated group than in the challenged controls (72% protection). The mucosal and bile IgM, recognizing the L3 surface, showed significantly higher levels in the vaccinated lambs compared to the challenge controls. Mucosal and bile IgA antibody levels against the same antigens were low and no significant differences were observed between vaccinated and control lambs.

Animals↗
PubMed1995

Influence of supplementation with dietary soyabean meal on resistance to haemonchosis in Hampshire down lambs.

The influence of dietary protein supplementation on resistance to haemonchosis was examined in Hampshire down lambs fed either a basal diet or a diet supplemented with soyabean. At seven months of age the lambs were challenged with an initial loading dose of Haemonchus contortus, followed by a trickle infection three times a week. Blood and faecal samples were collected three times a week and bodyweights were recorded weekly. After 10 weeks the lambs were slaughtered and their worm burdens and carcase composition determined. Although their mean worm burdens were similar, the lambs given the basal diet had higher faecal egg counts, lower packed red cell volumes and lower concentrations of total plasma protein and plasma albumin than the lambs given the supplemented diet. The dietary supplementation also improved the carcase composition of the lambs.

Animal Feed↗
PubMed1995

Different patterns of faecal egg output following infection of Scottish blackface lambs with Ostertagia circumcincta.

Faecal nematode egg counts were monitored in 184 Scottish Blackface lambs during natural exposure to a mixed, predominantly Ostertagia circumcincta infection and 12 lambs were selected which showed consistently zero (low count group; nine lambs) or consistently positive faecal egg counts (high count group; three lambs). These lambs were then treated with anthelmintic and challenged with 50,000 infective larvae of O. circumcincta and monitored thrice-weekly for 38 weeks; they were then re-challenged with another 50,000 infective larvae of O. circumcincta and monitored for a further 8 weeks. All sheep gave positive egg counts following deliberate infection. However, there was considerable variation among sheep in the size and timing of the peak in egg production. In particular, the pattern of mean values for faecal egg counts was different in the two groups. Egg counts were lower in the later periods of the extended infection in both groups of sheep. During the first half of the extended infection, egg counts were lower in sheep from the low count group, but during the second half of the infection the pattern was reversed and egg counts were lower in sheep from the high count group. There was a weak positive correlation between egg counts following anthelmintic treatment and 28 days exposure to natural infection and egg counts 28 days after a deliberate infection. Egg counts in the later stages of the deliberate infection were strongly but negatively correlated with egg counts following natural infection. The results of these studies show that differences in egg count following natural infection can be reproduced in experimental infections and that there is substantial variation in the pattern of egg production over time in different sheep. They also suggest that naturally resistant lambs are better able to delay worm development than naturally susceptible lambs.

Abomasum↗
PubMed1995

A 4-year study on the effectiveness of alternate grazing of cattle and sheep in the control of bovine parasitic gastro-enteritis.

In many farming enterprises, animal management systems which could provide a practical and effective alternative to chemotherapy for the control of bovine helminthosis would be readily accepted. One system which has been proposed and shown to be effective in the short or medium term involves grazing different host species on a rotational basis. The study described here examined the effect of alternating cattle and sheep annually over an extended period of 4 years. Up to the second grazing season the system appeared to be successful, with a marked reduction in the cattle worm burdens. However, by the end of the study period the parasite burdens in calves grazed on the alternated pasture were equal to, or greater than, those of set-stocked control animals. It was thus clear that the alternate grazing strategy had failed. Data obtained from other parameters measured, i.e. faecal egg counts, pasture larval numbers and plasma pepsinogen levels, confirmed this observation.

Animal Feed↗
PubMed1995

Local and plasma antibody responses to the parasitic larval stages of the abomasal nematode Ostertagia circumcincta.

Ovine isotype-specific antibody responses to the parasitic larval stages of the abomasal nematode Ostertagia circumcincta were measured in a simple, indirect enzyme-linked immunosorbent assay. Analysis of variance of replicate tests showed that the assay was very reliable. There was substantial variation among individual sheep in their IgA and IgG1 responses even though the sheep had been matched for breed, age and sex, were born on the same farm, were reared identically and had the same history of exposure and challenge with O. circumcincta. The local IgA responses to a somatic extract of fourth-stage larvae were very similar to responses to excretory-secretory products of fourth-stage larvae. The responses to third stage larvae were correlated with the responses to fourth stage larvae. There was a negative correlation between parasite-specific plasma IgG1 and parasite-specific plasma IgA responses. There was only a moderate association between IgA responses in the mucus and the plasma. Therefore, antibody responses measured in plasma cannot be easily extrapolated to antibody responses in the abomasal mucus.

Abomasum↗
PubMed1995

A comparison of the responses to repeated experimental infections with Haemonchus contortus among Scottish Blackface lambs.

Twenty helminth-naive Scottish Blackface lambs were given three infections with 10,000 infective larvae of Haemonchus contortus at 8 week intervals. An additional six lambs served as uninfected controls and eight lambs were infectivity controls. The lambs were 7 months old at the start of the infection. Four of the 20 lambs developed severe haemonchosis and were put down during the experiment. The remaining 16 lambs plus uninfected controls were necropsied 8 weeks after the third infection. The mean faecal egg count peaked 6-8 weeks after the first infection, gave a second smaller peak 6-8 weeks after the second infection but produced no peak after the third infection. Mean red blood cell counts fell rapidly during the first infection, then rose gradually during the second and third infections. The mean values suggested that two infections were sufficient to produce effective immunity in the sheep population but they masked considerable individual variation. Eleven animals appeared relatively resistant following the first infection, while two animals were relatively susceptible to even the third infection. The repeatability of mean faecal egg counts or mean red blood cell counts for each animal during the replicate infections were very high, because the rankings of the individual sheep remained remarkably stable. Faecal egg counts were very strongly correlated with red blood cell counts. Multiple regression analysis showed that four factors--faecal egg counts, red blood cell counts, weight and sex--accounted for essentially all of the observed variation in worm burdens among the lambs. Therefore, under these controlled experimental conditions, additional markers appear unnecessary for the detection of resistance status.

Analysis of Variance↗
PubMed1995

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) second edition of guidelines for evaluating the efficacy of anthelmintics in ruminants (bovine, ovine, caprine)

The first edition of the W.A.A.V.P. anthelmintic guidelines for ruminants was published in 1982. Since then improved parasitological procedures have been developed, new therapeutic and prophylactic products have appeared requiring different test methods, and registration authorities are requesting more detailed record keeping and data validation. This second edition addresses these developments and fulfills the original goal of publishing guidelines for high quality, scientifically valid testing standards for trials that would be accepted as proof of efficacy by registration authorities regardless of country of origin. This second edition includes updated guidance on standard parasitological procedures, dose titration, dose confirmation and clinical trials, and provides guidelines for evaluating products for efficacy against anthelmintic resistant parasites, persistence of activity and prophylactic activity. Tests for efficacy against nematodes, trematodes and cestodes are included.

Animals↗
PubMed1995

The distribution of faecal nematode egg counts in Scottish Blackface lambs following natural, predominantly Ostertagia circumcincta infection.

Faecal samples were taken in 2 consecutive years from Scottish Blackface lambs on a commercial farm in central Scotland to examine variation among lambs in the number of nematode eggs in their faeces. Samples were taken at intervals of 4 weeks from 1 to 5 months of age. Lambs were treated with a broad-spectrum anthelmintic at each sample date. Ewes and lambs were naturally infected by grazing pasture contaminated with mixed, predominantly Ostertagia circumcincta, nematode species. The ewes were removed from the lambs when the lambs were three months old. Only 3 of the 6 sets of samples taken prior to removal of the ewes fitted a negative binomial distribution but all sets of samples taken after this did so. The mean and the variance differed with the month and year of sampling. The amount of variation among lambs increased as the lambs grew from 3 to 5 months of age, possibly because of heterogeneity in the rate of development of protective responses. Counts taken in August and September, when the lambs were 4 and 5 months of age, were positively correlated with each other. In contrast, counts taken at 1 or 2 months of age were negatively correlated with counts taken when the lambs were 3-5 months old. Sex, date of birth, sire and dam were all associated with variation in faecal egg counts but the size and significance of their influence was dependent upon the date when faecal samples were taken. Four factors: sire, dam, sex and year accounted for over two-thirds of the variation among older lambs in faecal egg counts.

Animal Husbandry↗