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Biomedical subjects

N D Sargison

Publications and source records attributed to N D Sargison.

At least 19 recordsLinked to original sources
PubMed2006

Observations on the emergence of multiple anthelmintic resistance in sheep flocks in the south-east of Scotland.

Multiple resistance to benzimidazole, imidazothiazole and macrocyclic lactone anthelmintics is an emerging problem in the south-east of Scotland. The general management and nematode control strategies employed in four affected flocks (flocks 1-4) were investigated in an attempt to identify the risk factors which might have led to the appearance of production limiting disease associated with anthelmintic resistance. The important risk factors for multiple anthelmintic resistance could not be confirmed and it proved easier to criticise nematode control practices on theoretical grounds, than to propose practical solutions. It seems likely that different risk factors were involved in the four flocks. Lambs in flocks 1 and 2 had been treated with an anthelmintic at 3-4 weekly intervals with the aim of achieving suppressive nematode control, while sheep in flock 1 had been treated with an anthelmintic after they were moved onto clean grazing. Recently lambed ewes had been treated with moxidectin in three of the four flocks, with the aim of controlling their periparturient rise in faecal nematode egg output. All of these factors might have contributed to the emergence of multiple anthelmintic resistance, because they could have led to anthelmintic treatments at times when the nematode population in refugia was small, compared to that in the sheep. Annual rotation of the anthelmintic group was compromised by the emergence of benzimidazole resistance and did not prevent the emergence of multiple resistance in any of the flocks described, although the practice may have slowed the development of resistance. Underdosing may have selected for benzimidazole and imidazothiazole resistance in flock 2, associated with inaccurate estimation of the weights of terminal sire lambs. These investigations also highlighted problems associated with the diagnosis of anthelmintic resistance, in particular the confounding effects of the onset of host immunity to nematode parasites, the possible influence of the age of the adult nematode population, and the insensitivity of the undifferentiated faecal egg count reduction test in situations where resistance is emerging.

Animals↗
PubMed2006

The potential for improving welfare standards and productivity in United Kingdom sheep flocks using veterinary flock health plans.

Data from industry sources detailing variable costs in 2003 revealed that the average farmer keeping 1000 lowland ewes in the United Kingdom spent 3500 UK pounds annually on veterinary fees and medicines. Despite such expenditure, psoroptic mange and cutaneous myiasis are common in the UK, resistance to one or more anthelmintic group is not only common but increasing in frequency and distribution, and abortion outbreaks caused by Toxoplasma gondii and Chlamydophila abortus are frequently reported by veterinary laboratories. Welfare concerns also arise from farmers' intransigence towards tail docking and castration in lambs (mutilations), reported market forces necessitating long distance road transportation to slaughter plants, and an unwillingness to employ veterinary surgeons for obstetrical problems. The spread of sheep scab in the UK over the past decade illustrates the failure of flock owners to effect rudimentary biosecurity and disease control measures. A first step towards improving the health and welfare of sheep would be the immediate implementation of basic good husbandry practices, including ectoparasiticide treatment for sheep scab eradication, prophylaxis for cutaneous myiasis in selected lambs, and appropriate vaccination strategies for clostridial diseases and certain abortion agents. There would also be money from within current farm expenditure to provide veterinary attention for obstetrical problems affecting up to 2% of ewes per annum. Planned use of ecto- and endoparasiticides is urgently needed to maintain the efficacy of these unique drugs.

Animal Husbandry↗
PubMed2005

An outbreak of subacute fasciolosis in Soay sheep: ultrasonographic biochemical and histological studies.

A naturally occurring outbreak of subacute fasciolosis in a group of 17 seven-month-old Soay ram lambs was studied following the sudden death of two sheep. In addition to standard biochemical investigations, ultrasound examination of the liver and cranial abdominal cavity was undertaken. There was a significant positive linear correlation between liver weight and ultrasonographic determination of liver size (R=0.72, P<0.05). Ultrasonographic examination of the liver revealed multiple hyperechoic dots in the parenchyma giving a granular appearance to the hepatic texture in three sheep corresponding to the most advanced histopathological changes as determined by the size of the abscesses and their relatively mature fibrous capsules, and areas of hepatic necrosis. No distension of the bile duct system was noted nor was the gall bladder imaged. While serum concentrations of albumin, globulin and certain liver enzymes assisted in the diagnosis of subacute fasciolosis in sheep, only glutamate dehydrogenase, and gammaglutamyl transferase remained elevated four weeks after triclabendazole treatment.

Animals↗
PubMed2005

Failure of moxidectin to control benzimidazole-, levamisole- and ivermectin-resistant Teladorsagia circumcinda in a sheep flock.

Control of a benzimidazole-, levamisole- and ivermectin-resistant population of Teladorsagia circumcincta was attempted using moxidectin administered orally at the manufacturer's recommended dose rate of 200 microg/kg bodyweight. Ewes were dosed after lambing with the aim of controlling their periparturient rise in faecal egg output and lambs were dosed at six-week intervals throughout the summer. This regimen failed to suppress the establishment of significant numbers of infective helminth larvae on the pasture, resulting in unsatisfactory lamb production. Oral dosing with moxidectin was effective in removing adult female burdens of ivermectin-resistant T. circumcincta, but the effect of the drug did not persist against the resistant helminth population.

Administration, Oral↗
PubMed2003

Diagnosis and treatment of retropharyngeal injuries in lambs associated with the administration of intraruminal boluses.

The administration of intraruminal identification boluses to a group of 76 lambs resulted in 24 (32 per cent) showing signs of pharyngeal damage. In 16 of them the bolus was found to be in the retropharyngeal region by means of a hand-held microchip scanner, radiography and endoscopy. Purulent tracts were identified in the dorsal pharynx. In 13 of the 16 lambs the surgical removal of the bolus under general anaesthesia was followed by a normal clinical recovery, although the lambs did not grow as well as similar unaffected animals; three of the 24 lambs died. The administration of a larger bolus to 10 yearling rams did not result in any clinical signs of pharyngeal damage. The most important factors influencing the occurrence of this type of injury among this group of lambs were the size and age of the lambs, the positioning of the lambs during bolus administration, the relative size of the dosing gun and bolus, and the large number of animals in the group.

Administration, Oral↗