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Biomedical subjects

K Bairden

Publications and source records attributed to K Bairden.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1994

Surface and excretory/secretory antigens of fourth-stage larvae and adult Ostertagia circumcincta.

With the use of an enzyme-linked immunosorbent assay (ELISA), it was revealed that surface antigens of both adult and fourth-stage larvae (L4) of Ostertagia circumcincta induced high levels of serum IgG antibodies, while serum IgA antibody levels were low but increased significantly (P < 0.01) after infection. Immunofluorescence studies on the surface of viable L4 and adult nematodes showed that the IgG response was stage-specific only in animals vaccinated with adult surface extracts. The results of Western blot analysis using these antibodies suggested that at least eight polypeptides were shed from the L4 surface to the environment and that infection induced (or boosted) IgG antibody against a further four polypeptides. A comparison of reactivity of pre- and post-infection sera of sheep vaccinated with adult nematode surface antigens suggested that only one of the antigens stripped from the nematode surface was immunogenic and/or present in a concentration sufficient to induce an IgG response following parenteral vaccination. Infection boosted the IgG antibodies to a further four polypeptides. Only one polypeptide of 63 kDa seems to be shed in vivo from the adult nematode surface. Ten to eleven antigens were recognised in adult excretory/secretory products by serum IgG of multiple-infected sheep.

Animals↗
PubMed1993

Efficacy of abamectin against nematodes in cattle.

Eight controlled trials were conducted, using 96 cattle of European breeds, to evaluate the efficacy of abamectin against natural and artificially acquired infections of adult and fourth-stage larvae of all the economically important gastrointestinal nematodes and lungworms in Germany and the United Kingdom. Half the animals were treated on one occasion with abamectin at a dose of 200 micrograms/kg bodyweight given subcutaneously while the other half remained untreated. Worms were counted 14 or 21 days after treatment or 28 days after the last infection. The treatment was highly effective (> 99 to 100 per cent) (P < 0.05) at removing immature (L4) stages and adult worms of the following species: Ostertagia ostertagi (inhibited larvae included), Trichostrongylus axei, Haemonchus contortus, Bunostomum phlebotomum, Cooperia species Oesophagostomum radiatum and Dictyocaulus viviparus. Naturally acquired adult C surnabada and Trichuris discolor infections were also significantly (P < 0.05) reduced. For Nematodirus helvetianus the efficacy varied from 89.8 to > 99 per cent (P > 0.1 to < 0.01). Abamectin gave full protection against the gastrointestinal nematodes O ostertagi, H contortus, Cooperia species and O radiatum for at least seven days and against the lungworm D viviparus for at least 14 days after treatment.

Animals↗
PubMed1993

Laboratory selection for ivermectin resistance in Haemonchus contortus.

A strain of Haemonchus contortus, susceptible to ivermectin (IVM), was submitted to a selection procedure using IVM at 0.02 mg kg-1 during nine successive passages in lambs. Treatment reduced worm egg counts (epg) by more than 99% up to the seventh passage, but thereafter there was no significant reduction in epg. The efficacy of ivermectin against the ninth selected generation compared with the original susceptible strain was assessed. The results showed that animals infected with the selected strain and treated with IVM did not show any significant reduction (P > 0.05) in epg compared with a 99.9% reduction in the susceptible group. At necropsy, post-treatment worm burdens confirmed that the selection pressure applied to the original strain had been successful in stimulating resistance to IVM.

Animals↗
PubMed1993

Pharmacodynamics, pharmacokinetics and faecal persistence of morantel in cattle and goats.

Morantel could not be detected (< 0.05 microgram/ml) in the plasma of cattle or goats following the oral administration of morantel tartrate at a dose rate of 10 mg/kg bodyweight. No morantel was detected in the milk of lactating goats except in one animal where a concentration of 0.092 microgram/ml was detected at 8 h after drug administration. Morantel was highly effective against Cooperia oncophora infections in calves treated 6, 9 or 18 days after infection; however, was highly effective against Ostertagia ostertagi only when treated 18 days after infection. Morantel did not affect the fecundity of adult O. ostertagi surviving treatment 18 days after infection which had similar average numbers of eggs in their uteri (range 13.4 +/- 0.73-16.8 +/- 0.98) as did parasites from control animals (range 12.0 +/- 0.70-13.6 +/- 0.66). Morantel could be detected at a concentration of 96 +/- 4.5 micrograms/g (dry weight) in the faeces of a calf 24 h after treatment with 10 mg/kg bodyweight of morantel tartrate. The concentration of morantel in replicate samples of this faeces exposed to natural atmosphere, but not to soil or soil organisms, declined slowly over the following 322 days. At day 322 after the start of the experiment 8.8 micrograms/g of morantel could be measured in the remaining faecal material. Throughout the faecal degradation study the concentration of morantel in the crusts of the replicate sample pats was lower than the concentration in the core samples.

Animals↗
PubMed1993

The pattern of faecal egg output in lambs infected with a multiple resistant strain of Haemonchus contortus after treatment with albendazole.

Worm-free lambs (n = 6) were infected with 5,000 L3 of an ivermectin/benzimidazole/closantel resistant strain of Haemonchus contortus. On Day 21 post infection animals were allocated, according to worm egg counts, to 2 groups of 3 animals each and on Day 29 one group was treated with albendazole at 3.8 mg kg-1, while animals in the other group remained untreated as controls. All animals were slaughtered on Day 44 when the treated group was found to have 2,083 +/- 1,718 worms and the controls 2,783 +/- 633, a reduction of 25.2% in worm burdens. The pattern of egg output was monitored and it was found that 2 d after dosing, worm egg counts had been suppressed by 89% in the treated group; thereafter the egg counts increased, but never returned to the pretreatment levels and by Day 15 post treatment, they were still 41.1% lower in the treated group than in the controls.

Albendazole↗
PubMed1992

Establishment and pathogenicity of two strains of Ostertagia ostertagi and Cooperia oncophora in calves in different locations.

An experiment was carried out simultaneously in Glasgow and in Wageningen to investigate possible differences between the local strains of Ostertagia ostertagi and Cooperia oncophora. In each location calves of the local Friesian breed were infected with 100,000 larvae of either the Glasgow or Wageningen strain of O ostertagi or C oncophora. At both locations the calves received the same diet. The Glasgow strain of O ostertagi was more pathogenic than the Wageningen strain and a larger proportion of the worm burden was found in the abomasal mucosa. The number of ova per female was greater in the Wageningen strain. For C oncophora the Wageningen strain gave rise to higher worm burdens and longer worms. Differences were also present between locations. The British Friesians had higher worm burdens of C oncophora and the worms of this species were longer in this host. Compared with the Dutch Friesians the British calves had a higher proportion of O ostertagi in the mucosa. This experiment showed how difficult it is to compare data from the literature because of differences in parasite and host strains and laboratory techniques.

Abomasum↗
PubMed1992

Sequential in vivo measurements of body composition of calves exposed to natural infection with gastrointestinal nematodes.

Sequential in vivo measurements of total body water, exchangeable sodium and exchangeable potassium, made by radioisotopic dilution techniques, were used to determine changes in body composition in calves exposed to natural infections with gastrointestinal nematodes during their first grazing season. Two groups of calves were studied, one of which received a sustained release anthelmintic bolus at turn out. Over the grazing season the bolus-treated calves showed a significantly improved pattern of bodyweight gain, compared with the untreated control calves. There were also significant increases in both total body water and exchangeable potassium, as a percentage of the bodyweight, in the bolus calves compared with the controls. These findings indicated that body protein as a percentage of bodyweight was increased in the bolus animals. The bolus-treated calves also had significantly lower serum pepsinogen concentrations, faecal egg counts and worm burdens.

Animals↗
PubMed1992

Immune responses of sheep to surface antigens of infective larvae of Ostertagia circumcincta.

Immune responses to surface antigens of infective larvae of Ostertagia circumcincta 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 infective larvae surface or somatic extracts and Freund's or beryllium hydroxide adjuvants. It was found that only in lambs vaccinated with L3 surface extracts and beryllium hydroxide as an adjuvant did worm burdens differ significantly (P less than 0.01) from those of challenge controls (71.7% protection). Sheep vaccinated with the same antigenic preparation but administered with Freund's adjuvant or with beryllium adjuvant and somatic extracts demonstrated rather poor protection (32.4 and 30.5% respectively). All the vaccinated sheep showed a high IgG response to L3 surface antigens while significant levels of serum and bile IgA reacting with the surface extracts were only detected in those lambs vaccinated with L3 surface extracts and beryllium hydroxide. In immunofluorescence tests serum IgA of this group reacted with the whole surface of exsheathed larvae or with the site of opening of excretory pore while IgG antibodies reacted strongly with the anterior and posterior parts of the infective larvae. Both IgA and IgG responses to surface antigens were stage specific.

Animals↗
PubMed1991

Effect of sustained release and pulse release anthelmintic intraruminal devices on development of pathophysiological changes and parasite populations in calves infected with Ostertagia ostertagi and Cooperia oncophora.

An experiment was conducted in calves to investigate the effect of sustained release and pulse release anthelmintic intraruminal boli on the development of pathophysiological changes following daily infection with Ostertagia ostertagi and Cooperia oncophora for six weeks. After infection various pathophysiological changes were detected including increases in serum pepsinogen concentration, enteric plasma protein losses and in the catabolic rate of albumin. Such changes developed rapidly in the unprotected calves following patency after 17 days and persisted until the termination of the study. There were indications that the sustained anthelmintic release device was more efficacious than the pulse anthelmintic release device in reducing the worm burdens and early pathophysiological changes associated with infection. It was found at necropsy that the release of anthelmintic by the oxfendazole pulse release bolus had been delayed in several calves.

Animals↗
PubMed1990

Stage-specific cuticular proteins of Ostertagia circumcincta and Ostertagia ostertagi.

In this study we have shown that NHS-biotin and I125-streptavidin can detect cuticular polypeptides of Ostertagia spp. The labelled polypeptide profile of intact nematodes is simple compared to the profile obtained by labelling homogenates. None of the major internal polypeptides are labelled and the subset of proteins labelled in intact nematodes appears to be mainly surface associated. The results presented here demonstrate that NHS-biotin may be used as a reagent for the analysis of surface polypeptides. The surface polypeptide profiles of the five major developmental stages (L1, L2, L3, L4 and adult) of Ostertagia circumcincta show a series of stage-specific molecules with no polypeptides common to all stages, indicating that the cuticle is a dynamic structure which changes throughout the life cycle. Similarily comparison of Ostertagia ostertagi L3 and L4 stage surface profiles showed that each stage is clearly distinct; comparison of these stages between the two species shows an overall similarity.

Animals↗
PubMed1990

Pathophysiological and parasitological studies on a concurrent infection of Ostertagia ostertagi and Cooperia oncophora in calves.

Calves which had received daily concurrent infections of 2000 Ostertagia ostertagi and 10,000 Cooperia oncophora infective larvae over a 42-day period displayed a range of clinical signs typical of acute parasitic gastroenteritis including inappetence, weight loss, hypoalbuminaemia and diarrhoea. There were consistent and significant depressions in both digestive efficiency and nitrogen retention. Radioisotopic studies revealed marked disturbances in protein metabolism which were associated with high losses of plasma proteins into the gastrointestinal tract. On post mortem examination larval establishment of O ostertagi was seen to be high. The adverse changes were prevented by the prior administration of a morantel bolus.

Animals↗