Gastrointestinal nematode parasites of sheep: a dynamic model for their effect on liveweight gain.

This paper presents an individual-based model for gastrointestinal nematode parasites of sheep and includes the effect of these parasites on the liveweight performance of young sheep. Parasitism is known to affect the host animal in at least two ways. The first induces a loss of appetite in the host, which reduces pasture consumption compared with the parasite-free animal. This effect is examined in the first part of the study. The second major effect of parasitism is a reduction in the metabolic efficiency of the host which decreases nutrients available for maintenance and growth. The latter part of the paper examines the consequences of incorporating this effect on the liveweight changes in individuals in a group of sheep. Previous models addressing this issue have only given mean liveweight and worm burden changes.

Prevalence of polycystic kidney disease in Persian cats in the United Kingdom.

The prevalence of polycystic kidney disease was assessed in 132 Persian cats, 46 of them referred for the investigation and treatment of medical or surgical conditions, and 86 apparently healthy cats referred specifically to be screened for the disease. Cats referred for the investigation of renomegaly or renal failure were excluded, and cats under 10 months old were only included if they had been examined postmortem. One hundred and twenty-six of the cats were examined ultrasonographically with a 7.5 MHz sector scanner, and the other six cats were examined postmortem. Forty-nine of the 86 cats referred specifically for screening (57.0 per cent) and 16 of the 46 cats referred for other clinical reasons (34.8 per cent) were affected by the disease, giving an overall prevalence of 49.2 per cent.

Tree water use and rainfall partitioning in a mature poplar-pasture system.

Traditionally, poplars (Populus) have been planted to control erosion on New Zealand's hill-slopes, because of their capacity to dry out and bind together the soil, by reducing effective rainfall and increasing evapotranspiration and soil strength. However, the effect of widely spaced poplars on the partitioning of soil water and rainfall has not been reported. This study determined rainfall partitioning for 18 mid-spring days in a mature P. deltoides (Bart. ex Marsh, Clone I78)-pasture association (37 stems per hectare, unevenly spaced at 16.4 +/- 0.4 m) and compared it with a traditional open pasture system in grazed areas of a hill environment. Tree transpiration was measured by the heat pulse technique. A time-driven mathematical model was used to set a zero offset, adjust anomalous values and describe simultaneous sap velocity time courses of trees. The model showed that daylight sap flow velocities can be represented with a nonlinear Beta function (R(2) > 0.98), and differences in the parameters representing the initiation, duration and conformation of the sap velocity can be tested statistically to discern tree transpiration differences during the day. Evapotranspiration was greater for the poplar-pasture association than for the open pasture (2.7-3.0 versus 2.2 mm day(-1)). The tree canopy alone contributed 0.92 mm day(-1) as transpiration and 1.37 mm day(-1) as interception, whereas evapotranspiration of the pasture understory was only 0.4-0.6 mm day(-1). Despite the higher water use of the poplar-pasture association, soil water in the 0-300 mm soil stratum was higher than, or similar to, that of the open pasture. Tree shading decreased evapotranspiration and pasture accumulation under the trees.

A study of the efficacy of topical and systemic therapy for the treatment of feline Microsporum canis infection.

Microsporum canis infection was induced in 21 healthy SPF-derived cats. Once infection was established (4 weeks after inoculation) the cats were divided into three equal groups housed in separate rooms and monitored for 16 weeks. During this time, group A cats received oral griseofulvin at approximately 50 mg/kg daily and were shampooed twice weekly with a product containing chlorhexidine and miconazole. Group B cats were treated with griseofulvin alone, and group C cats served as untreated controls. The cats were examined on a weekly basis and the severity of lesions was scored semi-quantitatively. In addition, hair samples were collected from each cat on a weekly basis by the MacKenzie brush technique and by the sticky-tape method. A semi-quantitative scoring system was also used for the assessment of fungal (M canis) growth. Generally, significant differences in clinical scores were not seen between the groups although at weeks 3, 4 and 11 there was a significant difference (P< or =0.015) with cats in group A having significantly lower median scores than those in group C. Median times to clinical resolution (return of clinical scores to zero) in groups A, B and C were at treatment weeks 2, 9 and 12, respectively (P>0.05). Median times for mycological resolution (persistently negative culture results) for groups A, B and C were at treatment weeks 2, 9 and 12, respectively, for the MacKenzie brush technique and at weeks 4, 8 and 12 for the sticky-tape technique. For both these results, the groups differed significantly (P< or =0.001) and in both instances group A had significantly more rapid resolution than groups B or C. Median culture scores were significantly different between the three groups using one or both of the sampling techniques at week 2 through to week 12 of treatment with median scores for either group A alone, or groups A and B being significantly lower than group C (P< or =0.026). These results showed a benefit from the addition of twice-weekly chlorhexidine-miconazole shampooing to systemic griseofulvin therapy alone in the treatment of M canis infected cats.

A case of feline primary hypoadrenocorticism.

A 2-year-old entire female British Shorthair cat was referred to the University of Bristol for investigation of lethargy, weakness, constipation and hypothermia. Clinical examination revealed a profoundly weak, hypovolaemic and hypothermic cat. Serum biochemistry revealed hyponatraemia, hyperkalaemia and hyperphosphataemia and the urine was isosthenuric. Lack of response to exogenous adrenocorticotrophic hormone confirmed a diagnosis of hypoadrenocorticism. Treatment consisted initially of intravenous fluid therapy and subsequently a combination of fludrocortisone and prednisolone per os. At follow-up, 20 months after the initial diagnosis the cat remained stable and free of clinical signs.

Effect of topographical aspect and farm system on the population dynamics of Trichostrongylus larvae on a hill pasture.

The population dynamics of Trichostrongylus colubriformis larvae were compared over two years on contrasting topographical aspects north (warm and dry) and south-facing (cool and moist) hill slopes) on paddocks which form part of the 'non-chemical' and conventional' farm systems at the AgResearch Ballantrae Hill Country Station located in a summer-moist region of New Zealand. Sheep faeces containing 50,000 Trichostrongylus eggs were incubated for 4 days at 25 degrees C and then deposited on each of 36 sub-plots in each of 8 plots in a 2 x 2 factorial design in the summer (summer trial) and again in autumn (autumn trial). Pasture was removed to ground level and larvae extracted from six sub-plots from each plot 2, 4, 6, 8, 11 and 14 weeks after contamination in all trials. Larvae were recovered from two strata, 0-5 cm above the soil surface and > 5 cm above the soil surface. Fewer (p < 0.001) larvae were recovered from herbage (47 vs. 118) and residual faeces (28 vs. 246) from the autumn than from the summer trials. This coincided with more rapid (p < 0.001) faecal disappearance in the autumn trials. In the summer trials, fewer (p < 0.003) larvae were recovered from the herbage (101 vs. 182) and residual faeces (140 vs. 352) from plots on the south than the north facing aspect. In the autumn trials there was a rapid (p < 0.0001) faecal disappearance from the south-facing aspect. In the autumn trials there was a non-significant (p < 0.10) trend for fewer larvae to be recovered from the south-facing aspect (2 vs. 54). This also coincided with more rapid faecal disappearance from the south-facing aspect. There was no effect of farm system on the number of larvae recovered. Despite greater (p < 0.0001) numbers of larvae recovered from the bottom stratum of herbage, the density of larvae (L3/kg DM) tended (p < 0.12) to be higher in the top stratum of herbage. It was concluded that season and aspect have a marked effect on the number of larvae recovered from herbage and that this was inversely related to the rate of faecal disappearance.

Controlling internal parasites in grazing ruminants without recourse to anthelmintics: approaches, experiences and prospects.

Interest in ways of raising stock without using anthelmintics has been stimulated by the desire for intensive grazing systems to adopt more sustainable methods of internal parasite control and by potential premiums for "organic" produce. This requires grazing management systems which are practicable and achieve levels of parasite control sufficient to meet realistic production objectives. This paper will summarise 3 years experience of lamb and cattle production without a recourse to anthelmintics on 2 production systems: a mixed cropping, lamb finishing, and cattle rearing unit and an all grass, mixed-stock, hill country unit in which all non-replacement lambs are sold at weaning. On both units parasite control was almost entirely dependent on integrated grazing management of sheep and cattle and strict systems of grazing management had to be rigidly applied. Acceptable productivity could be more readily achieved in sheep than cattle. Rams selected for resistance to nematodes were also used in both sheep flocks. Their influence on lamb production was equivocal. There is a need for more information on factors influencing parasite epidemiology and for consideration of strategies other than alternate grazing. The impact of pasture species on parasite epidemiology needs to be clarified. Current research indicates substantial differences between grasses in terms of parasite burdens acquired and production losses suffered by lambs grazing them. Grazing management may need to vary with pasture species. Also, specialty forage crops, particularly those containing condensed tannins (i.e. Hedysarum coronarium, Lotus pedunculatus and Lotus corniculatus) hold special promise as a means of countering parasite-induced production losses and dagginess. Using biological control of free-living larval stages and vaccination, may in the long term, also prove useful. Developing effective and acceptable systems for raising stock without using anthelmintics presents a considerable challenge, to parasitologists, as well as to plant breeders, agronomists, and farming systems researchers.

Regional Royal College of Physicians conference. 6 July 1994.

On Wednesday 6 July 1994 the College held a successful conference on the principal issues currently before physicians. Despite industrial action on the railways, attendance was excellent. Indeed it might have been difficult to accommodate all delegates if the trains had been running! The conference formed part of a College Day which included the first annual Comitia for Fellows, a discussion led by members of the Standing Committee of Members and a major lecture of general interest.

Regional conference in Birmingham.

This report is based on the regional conference held at the Queen Elizabeth Postgraduate Medical Centre in September 1993. The conference attracted about 140 participants and was a great success. The programme had been specifically designed to update physicians in areas of medicine where there had been significant management changes. Topics discussed ranged across a broad spectrum of specialties and were presented by a mixture of experts both local and national.

Disposition of warfarin enantiomers and metabolites in patients during multiple dosing with rac-warfarin.

1. The disposition of warfarin enantiomers and metabolites has been studied in 36 patients receiving chronic rac-warfarin therapy, titrated to approximately the same anticoagulant response. 2. A stereoselective h.p.l.c. assay was employed to determine the concentrations of (R)- and (S)-warfarin, (R,S)-warfarin alcohol and (S)-7-hydroxywarfarin in plasma and 24 h urine samples. The concentrations of (R)-7-hydroxywarfarin, (S,S)-warfarin alcohol and (R)-6- and (S)-6-hydroxywarfarin were also determined in urine samples. The fractions unbound of warfarin enantiomers were determined using equilibrium dialysis. 3. Wide variability was observed in daily dose requirements (mean 6.1 mg; range: 2.5-12 mg), in plasma concentrations of (S)-warfarin (0.48 mg l(-1); 0.11-1.02 mg l(-1)), (R)-warfarin (0.87 mg l(-1); 0.29-1.82 mg l(-1)), (R,S)-warfarin alcohol (0.31 mg l(-1); 0.02-0.72 mg l(-1)) and (S)-7-hydroxywarfarin (0.25 mg l(-1); 0.07-0.37 mg l(-1)) and the percentage unbound of (S)-warfarin (0.53%; 0.29%-0.82%) and (R)-warfarin (0.54%; 0.26%-0.96%). 4. The mean plasma clearances of warfarin enantiomers were 7.5 1 day-1 per 70 kg (2.5-22.1) for (S)-warfarin and 3.6 1 day-1 per 70 kg (1.6-8.8) for (R)-warfarin. There was a significant correlation between the estimated formation clearance of (S)-7-hydroxywarfarin and the clearance of (S)-warfarin, which accounted for much of the variability in the latter.(ABSTRACT TRUNCATED AT 250 WORDS)

Theophylline analysis at the chest clinic--comparison of a portable versus conventional system.

The running cost and clinical application of a new, portable, direct-injection, high-performance, liquid chromatograph for the measurement of theophylline was compared with conventional laboratory-based analysis by studying the two methods in two parallel chest clinics. Thirty-six patients were managed with the portable method and 33 by the conventional system. They were already receiving theophylline preparations for treatment of their asthma or chronic airflow limitation. Over the 12-week period of study, the percentage of patients with levels in the therapeutic range rose from 33% to approximately 87% in both clinics, but this change was achieved in only 6 weeks using the portable system. Patients whose theophylline levels were increased into the therapeutic range had improved symptom scores as measured by visual analogue scales but we were unable to demonstrate any significant change in spirometry. The cost of the portable system compared favourably with laboratory analysis, and had the additional benefit of quicker detection of non-compliance and facility for discussion with the patients at the time of consultation.

Do normal plasma neurotensin concentrations increase ileal output?

Infusions of neurotensin increase ileal secretion in experimental animals, and the volume of ileal effluent in patients with ileostomies. The aim of the present study was to determine whether normal postprandial plasma concentrations of neurotensin increase the volume of fluid leaving the ileum. Basal and peak postprandial plasma neurotensin concentrations were 23 (17-36) and 39 (25-43) pmol/l (median and range) respectively in five subjects with ileostomies and 15 (3-27) and 32 (15-82) pmol/l respectively in nine normal subjects. Infusion of neurotensin for 30 min at a rate of 6.3 pmol/kg/min into six patients with ileostomies increased ileostomy output about 10-fold, and produced a significant decrease in the concentration of solid material, but plasma neurotensin concentrations rose to 237 (82-422) pmol/l during infusion at this rate. Infusion of neurotensin at 2.3 pmol/kg/min, producing plasma levels of 60 (16-108), had no significant effect the amount or nature of ileostomy effluent. We conclude that normal postprandial plasma concentrations of neurotensin are unlikely to influence the volume of fluid leaving the ileum.

Changes in hospital management of acute severe asthma by thoracic and general physicians in Birmingham and Manchester during 1978 and 1985.

Hospital management of acute severe asthma in 14 large hospitals in Birmingham and Manchester was audited in a random 20% of 1196 patients aged 15-45 years admitted in 1985. Of the 239 admissions randomised, 192 were suitable for study. Results were compared with those from a study in the same hospitals using the same methods in 1978. The age and sex of the patients and their smoking history, duration of asthma, and hospital attendance were similar in 1978 and 1985. A much smaller proportion of patients presented with symptoms of over seven days' duration in 1985 (8.5%) than in 1978 (26%). The inpatient management of asthma appears to have improved in both thoracic and general units, with more thorough functional assessments, more frequent performance of relevant investigations (arterial blood gases and peak expiratory flow rates) and more frequent use of recommended treatment (nebulised bronchodilators, oral and intravenous corticosteroids). Less difference was found in 1985 between units with a specialist thoracic interest and those without, though some differences remained in 1985 in monitoring of peak expiratory flow rate and arterial blood gases, outpatient prescribing, and follow up arrangements. Inhaled preventive medication was prescribed more frequently than in 1978. In 1985 there was a 56% increase in admissions for asthma. The proportion of severely ill patients was similar to that in 1978, but in the most severe functional grade mean arterial carbon dioxide tension was higher in 1985 and more patients were ventilated. Our results suggest that hospital management by thoracic and general physicians has improved over the period 1978-85. Patients presented earlier in 1985, though there seems to have been an increase in asthma of all grades of severity.