Search PubMed⌕ Search

Biomedical subjects

K Bairden

Publications and source records attributed to K Bairden.

At least 55 records · Page 3Linked to original sources
PubMed1990

Pathophysiology of the periparturient egg rise in sheep: the role of prolactin.

The involvement of prolactin in the periparturient rise in the faecal nematode egg count in sheep was investigated. Ostertagia circumcincta larvae (5000 third stage larvae three times weekly) were administered to adult immune ewes from three weeks before parturition to three weeks afterwards. Ten ewes were injected twice daily with 2-bromo-alpha-ergocryptine (bromocriptine), an antagonist of prolactin secretion, for two weeks starting two days after lambing while 10 ewes remained untreated. Bromocriptine treatment was initiated approximately two weeks pre partum in three other ewes. Plasma pepsinogen concentrations rose significantly by one week after the start of O circumcincta larval challenge in all the ewes but faecal egg counts remained negative until approximately one week post partum. Plasma prolactin concentration was reduced to a very low level in all bromocriptine treated ewes but this did not alter the dynamics of the periparturient rise in faecal egg counts. Neither cell-mediated nor humoral immunity of the ewes, as assessed by their sensitivity to BCG inoculation and by antibody titre raised against horse red blood cells, respectively, were impaired during the rise in faecal egg count, nor were these parameters altered by manipulation of plasma prolactin concentration. Lamb growth rate was not retarded by low plasma prolactin concentration in the bromocriptine treated ewes. These results are not consistent with the generally held hypothesis that elevated plasma prolactin concentration is directly associated with the periparturient rise.

Animals↗
PubMed1989

Level of benzimidazole resistance in a strain of Ostertagia circumcincta studied over several infections in lambs.

A benzimidazole-resistant strain of Ostertagia circumcincta (HFRO) was used experimentally to infect lambs. The level of resistance, measured by an egg hatch assay, was studied throughout each infection and also after treatment of the lambs with fenbendazole. The HFRO strain was highly resistant to benzimidazoles. There was day-to-day variation in the level of resistance throughout a single infection with a high level of resistance in the early part of the infection, around Day 27 post-inoculation of infective larvae, falling to a lower level later in the infection. Egg hatch assays on the 3 days immediately post-treatment with fenbendazole showed the resistance level was high then resistance fell to the pre-treatment level after 7 days. Selection for benzimidazole resistance using fenbendazole treatment at the normal dose rate of 5 mg kg-1 over five passages of the HFRO strain in lambs failed to increase the resistance level. Storage of larvae over a 5-month period at 4 degrees C, prior to infection of lambs, did not produce any alteration in the resistance level. The possible reasons for the variations in resistance found with the HFRO strain are discussed along with the implications for sheep parasite control and further development of benzimidazole resistance.

Albendazole↗
PubMed1989

Pathophysiological and parasitological studies on Ostertagia ostertagi infections in calves.

Friesian calves given a low level infection of the abomasal parasite Ostertagia ostertagi over a six week period displayed a mild diarrhoea with high faecal egg counts and elevated plasma pepsinogen values. At necropsy on day 23 abomasal lesions characteristic of ostertagiasis were widespread. At 42 and 84 days oedema and congestion were also prominent. Total worm burdens on days 23 and 42 were similar but a marked decrease had occurred by day 84. Feed digestibility and nitrogen economy were not markedly affected but radioisotopic measurements demonstrated an increase in albumin disappearance and catabolic rates, and plasma faecal clearance during the course of the infection. Prior administration of a morantel sustained release bolus to a group of similarly infected calves reduced the total worm burdens to less than 50 per cent of those recorded in the infected calves on days 23 and 42 and this fell to 3 per cent on day 84. Abomasal damage and the adverse pathophysiological changes associated with infection were prevented in this group.

Abomasum↗
PubMed1988

Control of naturally acquired bovine parasitic bronchitis and gastroenteritis with an oxfendazole pulse release device.

Four groups, each of six male Friesian calves, were set-stocked on separate 0.66 ha paddocks from May 7 until October 23 1986. Each of the animals in groups 1 and 4 was dosed with an oxfendazole pulse release bolus at turn out whereas the animals in groups 2 and 3 were left untreated. Parasite-free naive tracer calves were introduced into each paddock for a limited period 12 days after turn out and again at the end of the trial. No adverse reactions or clinical signs were observed in either of the groups of calves which received boluses. The development of clinical parasitic gastroenteritis in both the untreated groups necessitated the humane slaughter of two animals and emergency anthelmintic treatment of the remainder. The lower plasma pepsinogen concentrations, and lower faecal egg and larval counts and worm burdens post mortem, together with the absence of clinical signs of parasitic gastroenteritis and bronchitis in the treated calves, confirmed the high efficacy of the bolus treatment.

Animals↗
PubMed1988

Immunity of ivermectin treated cattle to challenge from helminth parasites in the following season.

Two groups of yearling cattle which had been treated with ivermectin either three and eight, or three, eight and 13 weeks after turn out to trichostrongyle contaminated pasture in their first grazing season were exposed in the following season to natural challenge with helminth parasites. To assess their immunity to this challenge each group shared a pasture with parasite naive first season calves. No anthelmintic treatments were administered at any time during the year. Throughout the grazing period the yearlings showed normal respiratory rates, negative faecal lungworm larval counts, and, relative to the calves, low faecal trichostrongyle egg counts. All the first season calves developed patent lungworm infections and on one occasion the mean respiratory rates of each group of calves were significantly greater than those of the yearling cattle. At the end of the grazing period, from early May until late September or October 1986, the cattle were removed from pasture and together with parasite naive controls challenged with either 10 or 22 third stage larvae of Dictyocaulus viviparus/kg bodyweight and necropsied between 18 and 23 days later. Although the experimental challenge resulted in relatively heavy lungworm infection of the naive controls, none of the yearlings and only three of the 11 calves which had been at pasture were found to be infected. However, large numbers of arrested fourth stage larvae of Ostertagia ostertagi were present in all the naturally infected yearlings and calves.

Animals↗
PubMed1988

Effects of trichostrongyle larval challenge on the reproductive performance of immune ewes.

Ostertagia circumcincta larvae were administered to adult immune ewes either during the breeding period or around parturition to investigate whether reproductive performance was affected. Two groups of 25 ewes were given water or 12,000 ostertagia larvae three times weekly for five weeks before and five weeks after breeding to synchronised oestrus. Plasma pepsinogen levels were raised in the larval-challenged ewes during the treatment period but no significant effect of treatment was observed on ovulation rate or plasma progesterone concentration. Neither ewe live-weight nor body condition score differed between groups throughout gestation or for four weeks post partum and there was no effect from larval challenge during the breeding period on lambing rate, lamb birthweight or liveweight at four weeks old. A second experiment involved 20 twin-bearing immune ewes which were administered 17,000 ostertagia larvae three times weekly for three weeks before and three weeks after parturition. Plasma pepsinogen concentration was elevated during the larval challenge period and nematode eggs were detected in the faeces after parturition but there was no effect from treatment either on ewe liveweight and body condition score or on lamb birthweight and lamb liveweight at four weeks old. These results indicate that larval challenge with ostertagia larvae at dose rates comparable to larval intake from heavily contaminated pasture did not affect the general well being and reproductive performance of immune Greyface ewes.

Animals↗
PubMed1987

A survey by questionnaire of parasitic worm control in cattle and sheep at the Glasgow University Lanark practice.

The results of a questionnaire circulated in 1984 concerning parasitic worm control on cattle and sheep farms in a veterinary practice in the west of Scotland are reported. Control by grazing management or anthelmintic treatment was used in 92 per cent of the cattle herds and in all the sheep flocks. The use of anthelmintic drugs was greatest on farms where grazing control was also practised. Benzimidazoles were the most frequently used anthelmintic drugs.

Animals↗
PubMed1987

Nematodirus battus infection in calves.

In studies on the control of parasitic gastroenteritis in calves and sheep, involving an annual rotation of pastures grazed by these host species, it was shown that young cattle could play an important role in the epidemiology of Nematodirus battus, a species usually regarded as a parasite of lambs. Thus, young cattle readily acquired heavy burdens of N battus in spring and the contamination of pastures with eggs from these infections resulted in significant populations of larvae on the herbage, which were infective to both calves and lambs grazed on these pastures in the following year. Although the majority of the N battus eggs hatched in the spring, some hatched in the autumn. The calves developed a strong immunity to N battus during the grazing season as demonstrated by the absence of worms at necropsy in the autumn, despite the presence of infective larvae on the pasture.

Animals↗
PubMed1987

Control of parasitic bronchitis and gastroenteritis in grazing cattle by strategic prophylaxis with ivermectin.

In May 1985 four groups of 10 calves, aged between four and five months, were turned out on to separate, permanent pastures of equal area which had been seeded during the previous few days with larvae of Dictyocaulus viviparus. One group acted as a control, the second was vaccinated with lungworm vaccine before turnout and treated with thiabendazole three, eight and 13 weeks after turnout, while the third and fourth groups were given ivermectin three times (three, eight and 13 weeks after turnout) and twice (three and eight weeks after turnout), respectively. A severe outbreak of parasitic bronchitis resulted in the death of three control calves within five weeks of turnout and parasitic bronchitis and gastroenteritis affected the second group of calves after approximately four months at pasture. The calves given ivermectin excreted no lungworm larvae and remained free of clinical parasitism throughout the trial.

Animals↗
PubMed1987

Pathophysiological and parasitological studies on Cooperia oncophora infections in calves.

Calves which had received daily infections of Cooperia oncophora over a six week period showed inappetence, weight loss, impaired nitrogen retention and a loss of plasma proteins into the gut. During this period the infections occurred in the duodenum, jejunum and ileum and many larval stages were present in the mucosa of the small intestine. At necropsy, on weeks 3, 6 and 10 after the first infection, stunting and thickening of the villi were noted with excessive mucus production. Prior administration of a morantel slow release bolus prevented these changes. By week 12 most of the worms had been expelled yet a loss of plasma proteins to the gut was still occurring.

Animals↗
PubMed1986

The sequential development of type I and type II ostertagiasis in young cattle with special reference to biochemical and serological changes.

The sequential development of Type I and Type II ostertagiasis over a 2-year period in the same naturally infected cattle is described for the first time. Particular reference is made to biochemical and serological changes. Positive relationships were demonstrated between the clinical signs of both Type I and Type II disease, and marked increases in the levels of plasma pepsinogen, plasma gastrin and antibody titres to adult Ostertagia antigen. At necropsy, there were significant relationships between the combined total of adult and developing 5th stage larvae of Ostertagia spp. and the levels of both plasma pepsinogen and gastrin. By the end of the second grazing season the cattle had acquired an immunity to infection with Ostertagia spp. and had very low burdens of this parasite at necropsy. However some of these cattle maintained elevated plasma pepsinogen levels when under natural challenge by Ostertagia spp. larvae and the aetiology of these changes and the problems of diagnosis using this parameter are discussed. Similar trends of infection were observed for Cooperia oncophora, although resistance to the parasite developed more rapidly.

Abomasum↗
PubMed1986

Metabolism and growth in housed calves given a morantel sustained release bolus and exposed to natural trichostrongyle infection.

Three groups of calves, previously grazed on permanent pastures contaminated with bovine trichostrongyle (Ostertagia and Cooperia species) infective larvae, were housed from October to May. During the grazing season one group had received fenbendazole at fortnightly intervals to suppress trichostrongyle infections, one received a morantel sustained release bolus before grazing to limit trichostrongyle contamination of the pasture, and the control group was only medicated when heavy infections caused clinical type 1 ostertagiasis. Digestibility of the whole diet was poorer in the control cattle, particularly for dry matter, crude protein and energy fractions. Balance studies conducted throughout the winter housed period showed that both increased faecal and urinary nitrogen outputs in the control animals contributed to a significantly reduced overall nitrogen retention. The effects were most apparent during clinical type 2 ostertagiasis, which occurred in March in the control group.

Aging↗