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Biomedical subjects

R L Coop

Publications and source records attributed to R L Coop.

At least 73 records · Page 4Linked to original sources
PubMed1984

Effect of anthelmintic treatment on the productivity of lambs infected with the intestinal nematode, Trichostrongylus colubriformis.

Liveweight gain, food intake, wool growth and concentration of serum constituents were measured in four groups of three-month-old lambs. Groups 1 and 2 were infected on five days each week with 2500 Trichostrongylus colubriformis larvae for 18 weeks. Group 2 lambs were treated with fenbendazole (5 mg kg-1) at week 10 and week 15. Group 3 lambs were similarly infected for 10 weeks, treated with fenbendazole, but given no further larvae. A fourth control group remained uninfected throughout the trial. All lambs were killed at week 20. Mean worm populations were 16,130, 430 and zero for groups 1, 2 and 3 respectively. Over the first 10 weeks of infection, liveweight gain was reduced by 52, 43 and 51 per cent and wool growth by 33, 28 and 27 per cent respectively, in groups 1, 2 and 3. Serum hypophosphataemia and hypoalbuminaemia occurred in all three infected groups. Between weeks 10 and 20 overall weight gain and wool growth in group 1 lambs were 44 and 46 per cent lower than the controls, whereas weight gains of group 2 and group 3 lambs were similar to or slightly higher than in the controls. However, wool growth in these two groups after treatment was only 73 to 74 per cent of control values. Serum phosphorus concentrations increased to control levels within one week of anthelmintic treatment and serum albumin concentrations by two to four weeks. The ability of group 2 lambs to improve their performance after anthelmintic treatment, in the face of continued challenge, was attributed to development of resistance to reinfection.

Animals↗
PubMed1983

Effect of phosphorus intake on growth rate, food intake and quality of the skeleton of growing lambs infected with the intestinal nematode Trichostrongylus vitrinus.

The performance of growing lambs dosed daily for 12 weeks with 2500 Trichostrongylus vitrinus larvae (I) or given no larvae (control, C) was compared at two levels of phosphorus intake; 2.75 gP/kg dry matter (normal, NP) and 1.88 pgP/kg dry matter (low, LP). Both low phosphorus and T vitrinus infection reduced dry matter intake and growth rate and the combined effect of low phosphorus and infection were additive. Plasma hypophosphataemia (less than 60 mg per litre) occurred in groups CLP, ILP and INP from week 3, the values gradually returning to normal levels in INP lambs by the end of the trial. T vitrinus infection did not depress plasma phosphorus concentration below that seen in the low phosphorus controls. Both low phosphorus intake and T vitrinus infection reduced the density and mineralisation of bone, the most severely affected bones occurring in groups ILP lambs. T vitrinus infection reduced the content and concentration of phosphorus in the rumen and the effect was greater at the lower intake of phosphorus. Infection also reduced the proportion of phosphorus in the rumen liquid phase. The number of T vitrinus recovered from the intestine was higher and villous atrophy more extensive in lambs from group ILP. It is suggested that development of 'resistance' may be delayed on a low phosphorus intake.

Animals↗
PubMed1983

Development of morphological changes in the small intestine of lambs continuously infected with Trichostrongylus vitrinus.

Groups of three-month-old worm-free Suffolk cross lambs were given 2500 Trichostrongylus vitrinus larvae on five days each week for four, six, eight and 13 weeks and killed one week later. Severe villous atrophy, epithelial erosion and cellular infiltration were common features in the duodenum and the following 2 to 3 m of intestine of lambs killed at weeks 5 and 7. There was evidence of intestinal recovery in the lambs killed at weeks 9 and 14; five of the seven lambs had large areas of intestine which appeared relatively normal and worm activity appeared to be confined largely within focal areas ("fingerprint lesions'). There was no change in the linear distribution of the worms in the intestine over the course of the experiment. The highest percentage of the larval challenge was recovered from lambs killed at week 5 and worm burdens were not cumulative. Lambs killed at week 14 were resistant to larval reinfection.

Animals↗
PubMed1980

Chronic subclinical ovine fascioliasis: plasma glutamate dehydrogenase, gamma-glutamyl transpeptidase and aspartate aminotransferase activities and their significance as diagnostic aids.

The effect of low grade chronic Fasciola hepatica infection on the concentration of plasma glutamate dehydrogenase (GD), gamma-glutamyl transpeptidase (gamma-GT) and aspartate aminotransferase (AST) was investigated in sheep dosed daily with three (AL3), eight (AL8) or 14 (AL14) metacercariae over 22 weeks or given a single dose of 200 metacercariae. Significant increases in plasma GD activity first occurred after nine, 12 and 23 weeks and in gamma-GT activity after 12, 24 and 32 weeks for groups AL14, AL8 and AL3 respectively. Changes in AST activity were not as clearly related to dose level. In sheep with single infection, both GD and gamma-GT were capable of detecting liver damage resulting from the migration of 10 or more flukes. Plasma GD and gamma-GT activities are more sensitive indicators of liver cell damage in chronic subclinical fascioliasis than AST activity and gamma-GT may be more suitable as a diagnostic aid on account of its greater stability.

Animals↗
PubMed1979

Chronic infection with Trichostrongylus vitrinus in sheep. Pathological changes in the small intestine.

Eight four-month-old sheep were infected daily for 90 days with 2500 Trichostrongylus vitrinus larvae. Infections were patent by week 3; mean faecal egg counts reached a peak of 645 epg at week 5, then subsequently declined. Mean worm burden at slaughter was 6100 (range 60--25,080). Two sheep had visible lesions in the small intestine at slaughter. In both sheep, numerous shallow red depressed areas extended for 5 to 7 metres distal to the pylorus while, in one, more extensive irregular depressed areas occupied the first 1.5 metres. Microtopographical examination and scanning electron microscopy showed that these affected areas were devoid of villi and contained numerous worms embedded in the mucosa. Histological examination revealed many similarities with the lesions caused by T colubriformis. Subtotal villous atrophy and crypt elongation were present in the intestines from five of the remaining six sheep, and in these the mucosa contained numerous mononuclear cells and intraepithelial globule leucocytes.

Animals↗
PubMed1979

Chronic infection with Trichostrongylus vitrinus in sheep. Some effects on food utilisation, skeletal growth and certain serum constituents.

The effect on food utilisation and skeletal growth of daily infection for 90 days with 2500 Trichostrongylus vitrinus larvae was investigated. Controls were killed initially or fed ad libitum. Food intake, digestibility of dry matter and nitrogen and content of body fat, protein, water and minerals were determined, and selected bones examined chemically and histologically. Serum constituents were determined weekly. Digestibility of food dry matter and nitrogen were reduced during weeks 3 and 5 after initial infection but subsequently recovered. Deposition of fat, protein, calcium and phosphorus in the body was reduced by 36, 58, 67 and 78 per cent respectively. Gross efficiency of utilisation of metabolisable energy was reduced by 36 per cent. Bone changes were associated with a reduction in osteoblastic activity. Hypoalbuminaemia, hyperglobulinaemia and hypophosphataemia were present in infected sheep. There were no significant changes in serum calcium or urea concentrations. It is concluded that the effects of continuous intakes of T vitrinus and T colubriformis larvae on host metabolism are essentially the same.

Animals↗
PubMed1976

Subclinical trichostrongylosis in growing lambs produced by continuous larval dosing. The effect on performance and certain plasma constituents.

Three groups of eight-four-month-old worm-free lambs were used to investigate the effect of Trichostrongylus colubriformis infection on growth rate, food intake, and concentration of plasma constituents. Groups ALC and ALI were fed ad libitum, the latter being dosed daily with 2500 infective larvae for 14 weeks. Lambs in group PF were paired to individuals in group ALI and offered the same quantity of food as the infected pair consumed. Hypophosphataemia and hypoalbuminaemia developed in ALI at week 3 and hyperglobulinaemia was present from week 6. There was no significant difference in plasma calcium, protein, urea or glucose concentration between the three groups at any stage. No clinical signs of parasitism were seen in seven of eight ALI lambs and egg counts were generally less than 2000 epg. Worm burdens of 1500-82,900 were found at slaughter. Group weight gain was only 50 per cent of PF lambs which received the same digestible energy intake. Group ALI consumed 15-5 kg dry matter per kg gain in bodyweight compared with 8-6 kg/kg and 9-8 kg/kg for ALC and PF respectively. The infections resulted in extensive villous atrophy and flattening of the intestinal mucosa. Bone growth was arrested and osteoporosis present in five group ALI lambs. The possible use of plasma constituents, particularly phosphorus, as aids for the diagnosis of the early stages of trichostrongylosis in the field is assessed.

Animals↗
PubMed1975

Amprolium poisoning of preruminant lambs: an investigation of the encephalopathy and the haemorrhagic and diarrhoeic syndromes.

An experiment was conducted to investigate the mechanisms responsible for the brain lesions, diarrhoea and haemorrhages produced by amprolium poisoning of preruminant lambs. The encephalopathy was preceded by a reduction of cerebrocortical transketolase activity. Diarrhoea was not associated with histological evidence of pathological change in the small intestine, and in lambs with severe diarrhoea the small intestinal levels of alkaline phosphatase and lactase were unaffected. Haemorrhages were associated with a thrombocytopenia which was attributed to degeneration of bone marrow megakaryocytes. The bone marrow of the majority of the lambs which had received amprolium for 3 wk or more was severely depopulated, erythrocyte precursors being the most severely affected. The marrow depopulation was atrributed to decreased cell production, as the majority of the remaining cells showed little evidence of degeneration and the number of mitotic figures in the marrow of amprolium-treated lambs was considerably reduced as compared with the controls.

Alkaline Phosphatase↗
PubMed1975

The effect of continuous doses of Trichostrongylus colubriformis larvae on the intestinal mucosa of sheep and on liver vitamin A concentration.

Eight 7-month-old sheep were dosed continuously with Trichostrongylus colubriformis larvae and 4 sheep were killed at 5 and 10 weeks from the commencement of infection. Flattening of the mucosa and villous atrophy were commonly present at slaughter, and parasites were often found in superficial channels parallel with the luminal surface. At 10 weeks the mucosa was thickened and highly cellular. Leucine aminopeptidase, alkaline phosphatase and maltase activity were reduced in the proximal third of the small intestine. Liver vitamin A was reduced in 3 of 4 infected sheep at 10 weeks, but serum vitamin A levels were comparable with those of worm-free control sheep throughout the experiment.

Alkaline Phosphatase↗