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R B Williams

Publications and source records attributed to R B Williams.

At least 37 records · Page 2Linked to original sources
PubMed2002

Sustainable coccidiosis control in poultry production: the role of live vaccines.

The development of new methods of administering coccidiosis vaccines has facilitated their use in the hatchery and thereby improved prospects for the economic vaccination of broilers. The acquisition of protective immunity to Eimeria species is boosted by further exposure to infection after vaccination. Factors that affect the reproductive efficiency of non-attenuated and attenuated vaccines are considered and the key role that oocyst production plays in establishing and maintaining uniform immunity in a flock of chickens is discussed. In addition to immunisation, a possible advantage to the application of certain vaccines is that their use could repopulate poultry houses with drug-sensitive organisms. Theoretical rotation programmes in which the use of drugs is alternated with that of vaccines are described. Variability of the cross-protective immune response between strains of the same species should be considered during vaccine development and subsequent use. The significance of less common species of Eimeria, not included in all vaccines, also needs to be assessed. An important consideration is the occurrence of pathogens other than Eimeria (such as the bacterium Clostridium) in flocks given coccidiosis vaccines and the methods by which they might be controlled. More research is required into the relationship between bacterial and viral infections of poultry and coccidiosis vaccination. Vaccines need to be developed that are simple to apply and cost effective for use in areas of the world where small-scale poultry production is commonplace. In the near future it is likely that more live vaccines based upon oocysts derived from attenuated strains of Eimeria will be developed but in the longer term vaccines will be based on the selective presentation to the host of specific molecules that can induce protective immunity. This achievement will require significant investment from the private and public sectors, and, if successful, will facilitate the sustainable control of coccidiosis in poultry production.

Animals↗
PubMed2002

Comparison of an attenuated anticoccidial vaccine and an anticoccidial drug programme in commercial broiler chickens in Italy.

A live attenuated anticoccidial vaccine (Paracox) was compared with a nicarbazin-monensin anticoccidial drug shuttle programme in three crops of Italian broilers, comprising a total of 290,405 chickens. All birds received the antibiotic growth promoter avilamycin. No coccidiosis was evident during the trials, but the occurrence of oocysts in the litter demonstrated that a natural challenge was present. Vaccinated birds consistently performed at least as well as those treated with the anticoccidial drug shuttle. The final mean weights of vaccinated birds were significantly greater (P < 0.001) than those of birds treated with anticoccidial drugs, both for females at 36/37 days and males at 56 days. Feed conversion ratios, total mortality including culls, the proportion of rejects at the processing plant, and the moisture content of the litter were not significantly different between the two control methods. Growth curves showed that there was no post-vaccinal growth check in the vaccinated birds and no intolerance of the anticoccidial drug treatment. There was no overall seasonal effect, regardless of treatment, on the performance of the three crops reared from November 1997 to July 1998. These findings suggest that the use of this vaccine is likely to enable the replacement of anticoccidial drug shuttle programmes in broilers reared under conditions similar to those used in these Italian flocks.

Animal Feed↗
PubMed2002

Anticoccidial vaccines for broiler chickens: pathways to success.

The use of live vaccines, either attenuated or non-attenuated, for the control of coccidiosis due to Eimeria infections in broiler breeder or layer chickens is well established. Use in broilers, however, has been slow to gain acceptance. This has been partly for economic reasons, but also because of perceived adverse effects on early chick growth, particularly with non-attenuated vaccines, and concerns about timely onset of protective immunity in such short-lived birds. This review describes advances in understanding of epidemiological factors and recent improvements of administration methods that have helped to allay these fears and to make the use of anticoccidial vaccines in broilers technically achievable. Topics discussed include: (1) types of commercially available vaccine, (2) vaccines in development, (3) vaccination methods and equipment, (4) basis of vaccine efficacy and immunogenic variation of parasites, (5) key factors in the survival, sporulation and dissemination of vaccinal oocysts, (6) descriptions and significance of patterns of litter oocyst accumulation and occurrence of intestinal lesions in vaccinated flocks, (7) rotation of anticoccidial vaccination and chemotherapy to restore drug sensitivity to resistant wild-type coccidia, (8) combinations of anticoccidial vaccination and chemotherapy, (9) interactions between coccidiosis and clostridiosis in broilers and compatibilities of potential control methods, (10) published performance data for live anticoccidial vaccines in broilers, (11) possible further developments of live vaccines.

Animals↗
PubMed2001

Quantification of the crowding effect during infections with the seven Eimeria species of the domesticated fowl: its importance for experimental designs and the production of oocyst stocks.

The 'crowding effect' in avian coccidia, following administration of graded numbers of sporulated oocysts to naïve hosts, is recognisable by two characteristics. First, increasing doses of oocysts give rise to progressively higher oocyst yields, until a level of infection is reached (the 'maximally producing dose') above which further dose increases result in progressive decreases in oocyst yields. Second, the number of oocysts produced per oocyst administered (the 'reproductive potential') tends to decrease as the oocyst dose is increased. The dose that gives the maximal reproductive potential is the 'crowding threshold' and doses exceeding this are 'crowded doses'. Graded doses of Eimeria acervulina, Eimeria brunetti, Eimeria maxima, Eimeria mitis, Eimeria necatrix, Eimeria praecox or Eimeria tenella were given to chickens of the same breed, sex and age, reared on the same diet, under identical management. The two characteristics of the crowding effect were demonstrated graphically and, by interpolation, the estimated crowding thresholds were 903, < or =16, 39, < or =14, < or =16, < or =16 or 72 sporulated oocysts, respectively, for the seven Eimeria species enumerated above. This is apparently the first report of definitive experiments to quantify a crowding effect in E. brunetti, E. maxima, E. mitis, E. necatrix and E. praecox. Maximum experimental reproductive potentials were considerably lower than the theoretical reproductive potentials for all seven species. The interaction between availability of host intestinal cells and immunity contributing to the crowding effect is discussed. Standard curves obtained under specified conditions should be used to estimate appropriate infective doses for experimental designs or in vivo production of oocyst stocks. For experiments on effects of chemotherapy or immunisation on oocyst production, an infective dose lower than the crowding threshold should be used. For efficient production of laboratory or factory oocyst stocks, the maximally producing dose (which is greater than the crowding threshold), should be used.

Animals↗
PubMed2001

A novel method for counting eimerian oocysts at very low concentrations in aqueous suspensions.

A novel method for counting eimerian oocysts in samples of drinking water has been developed to fulfil the need for monitoring the delivery of very low concentrations of live anticoccidial vaccines to poultry via pipeline nipple-drinker systems. Advantages of the method are the ease of sample collection and processing, high degrees of accuracy and precision, and a sensitivity of one oocyst ml(-1). Results of a validation test are presented, with a protocol for the method and notes on its use. The coefficient of variation (CoV) of 10 sets of oocyst counts with nominal means of 10 to 160 oocysts ml(-1)ranged from about 16 per cent down to 6 per cent. The recovery efficiency for all 100 validation counts averaged 100.2 per cent with a range of 70-130 per cent. A practical example of field use of the method is given, including a modification to decrease the time taken for counting. In this case, when oocysts were pumped around a pipeline circuit of 129 m for 2.5 hours, the CoV of a mean of 112 oocysts ml(-1)(n = 10) was 12.4 per cent.

Animals↗
PubMed2001

Space-time pressure structure of pharyngo-esophageal segment during swallowing.

We applied high-resolution manometry with spatiotemporal data interpolation and simultaneous videofluoroscopy to normal pharyngeal swallows to correlate specific features in the space-time intraluminal pressure structure with physiological events and normal deglutitive transsphincteric bolus flow to define normal biomechanical properties of the pharyngo-esophageal (PE) segment. Pressures were recorded by microperfused catheter, and the two-dimensional space-time data sets were plotted as isocontours. On these were superimposed bolus trajectories, anatomic segment movements, and hyo-laryngeal trajectories from concurrent videofluoroscopy. Correlation of the highly reproducible space-time-pressure structure with radiographic images confirmed that primary deglutitive PE segment functions (pressure profile, laryngeal elevation, axial sphincter motion, timing of relaxation, contraction) are accurately discernible from single isocontour pressure visualization. Pressure during bolus flow was highly dependent on axial location within PE segment and time instant. The intrabolus pressure domain, corresponding to the space-time region between bolus head and tail trajectories, demonstrated significant bolus volume dependence. High-resolution manometry accurately, comprehensively, and highly reproducibly depicts the PE segment space-time-pressure structure and specific physiological events related to upper esophageal sphincter opening and transsphincteric flow during normal swallowing. Intrabolus pressure variations are highly dependent on position within the PE segment and time.

Adult↗
PubMed2001

Racehorse injuries, clinical problems and fatalities recorded on British racecourses from flat racing and National Hunt racing during 1996, 1997 and 1998.

For improvements to the safety and welfare of racehorses to be possible, it is essential to have access to basic descriptive information about the veterinary incidents encountered during horseracing. A 3 year surveillance study (1996-1998) was conducted by The Jockey Club into racing injuries, other postrace clinical problems and fatalities from all 59 British racecourses (mainland Britain only) to identify risk factors. During the survey there were 222,993 racing starts: 106,897 starts in flat races on turf (47.9%), 26,519 starts in flat races on all-weather surfaces (11.9%), 30,932 starts in chases on turf (13.9%), 51,786 starts in hurdle races on turf (23.2%) and 6,859 starts in National Hunt flat races (3.1%). Information was recorded about age of horses, racing surfaces and clinical events observed or attended by a veterinary team of 2 clinicians and one veterinary surgeon employed by the racing authority. Of the 2358 clinical events reported (1.05% of all starts), 1937 involved the musculoskeletal system and 421 involved other body systems. Six hundred and fifty-seven incidents (0.29% of starts) resulted in death or euthanasia. Eighty-one percent of limb injury reports involved forelimbs and 46% involved flexor tendons/suspensory ligaments. Nonlimb problems included epistaxis (0.83/1000 starts), 'exhausted horse syndrome' (0.47/1000 starts) and paroxysmal atrial fibrillation (0.20/1000 starts). Incidents including fatalities per 1000 starts were 24.7 from chases, 19.45 from hurdle races, 8.46 from National Hunt flat races and 3.97 from flat races. The overall tendon injury was higher in chases than in hurdle races, even though age-specific rates of tendon injury were higher in hurdle races than in chases. The risk of injuries per start increased significantly with age, while softer racing surfaces were associated with fewer fatalities and injuries than firmer surfaces. The survey described in this paper has provided an up-to-date description of the fatal and non-fatal horseracing incidents under conditions on mainland Britain, enabling progress to be made towards improving the safety and welfare of racehorses.

Age Factors↗
PubMed2001

Improved functional ability in patients with rheumatoid arthritis--longterm treatment with leflunomide versus sulfasalazine. European Leflunomide Study Group.

OBJECTIVE: We previously reported that the new disease modifying antirheumatic drug leflunomide resulted in significant improvement in functional ability compared with placebo and sulfasalazine in a 6 month double blind, randomized, Phase III trial in rheumatoid arthritis (RA). The current study compared functional disability in cohorts of patients with RA from the initial study who volunteered to continue treatment with leflunomide or sulfasalazine. METHODS: The Health Assessment Questionnaire (HAQ) was used to assess functional ability in patients completing 6 months of therapy who chose to continue in double blinded 12 and 24 month extensions. Patients on active regimens continued taking leflunomide 20 mg/day or sulfasalazine 2 g/day; those taking placebo were switched at Month 6 to sulfasalazine. RESULTS: Leflunomide significantly improved patients' functional ability compared to placebo (p < or = 0.0001) and sulfasalazine (p < or = 0.01) at 6 months. These changes were seen as early as Month 1, and continued improvements were seen in 12 and 24 month cohorts. Mean HAQ scores were significantly improved with leflunomide compared with sulfasalazine at 24 months (-0.65 vs -0.36; p = 0.0149); corresponding changes in HAQ Disability Index (DI) were -0.73 vs -0.56 and were not statistically different. Leflunomide is safe and well tolerated and no unexpected adverse events were noted during the 2 year period; diarrhea, nausea, and alopecia were less frequent with continued treatment. CONCLUSION: These longterm data confirm leflunomide improves functional ability as shown by reductions in HAQ scores. The benefit of leflunomide is reflected in other efficacy criteria, such as global assessments and the American College of Rheumatology response rates, all of which showed significantly more improvement with leflunomide than sulfasalazine at 24 months.

Adolescent↗
PubMed2000

Moderators of the effect of social support on depressive symptoms in cardiac patients.

Social support and depression have been shown to affect the prognosis of coronary patients, and social support has been found to influence depression in community and patient samples. We investigated the characteristics of coronary patients whose depressive symptomatology was most likely to improve with social support. We predicted that social support would be most beneficial for the most severely depressed, the old, the poor, the most severely ill, and those with poor functional status. Patients (n = 590) with documented coronary artery disease were assessed for depressive symptoms, social support, and functional status while in hospital. They were reassessed for depression 1 month later during a home visit. Depression scores were lower at follow-up (p = 0.001), and improvement was more marked among those reporting more support (p <0.001). The social support effect was strongest among those with high levels of depression at baseline (p <0.001) and those with lower income (p = 0.01). Unexpectedly, social support was more strongly associated with improvement in younger patients (p = 0.01). Social support did not interact with gender, disease severity, or functional status. These findings are partially consistent with the notion that social support is most effective for those who are most vulnerable and/or have few coping resources. These findings also have implications for the design and interpretation of psychosocial interventions.

Aged↗
PubMed2000

A new protocol for a challenge test to assess the efficacy of live anticoccidial vaccines for chickens.

The search for vaccines to control coccidioses caused by Eimeria species in chickens (Gallus gallus) is intensifying because of the increasing threat of drug resistance to anticoccidial agents. It is important, therefore, to develop a reliable standard method for the assessment of multivalent vaccine efficacy, because many criteria generally used to judge drug efficacy are not appropriate for vaccines. The lack of correlations between oocyst production, severity of lesions and bird weight gains is discussed. Furthermore, not all Eimeria species cause pathognomonic lesions. A new protocol for a vaccine efficacy test is described which uses growth rate of chickens after virulent challenge as the primary criterion and feed conversion ratio as the secondary criterion for protection against each of the separate coccidioses caused by the seven species of Eimeria that parasitize the chicken. The benefits to this protocol over previous ad hoc experimental designs are: (1) immunization is carried out with multivalent vaccines of Eimeria species up to the maximum of seven that may infect chickens; (2) assessments of immunity are carried out for each species separately so results can not be confounded; (3) the criteria of efficacy are those that are crucial to demonstrate commercial usefulness; (4) the possibility of drawing erroneous conclusions based upon inappropriate criteria such as oocyst production or lesion scores is avoided; (5) because the same criteria are used for each species, direct comparisons may be made amongst immunities to all of the species in the vaccine being tested. Results are presented from tests of three commercial batches of Paracox attenuated anticoccidial vaccine, showing that separate virulent challenges with all seven Eimeria species were controlled in vaccinated chicks.

Animals↗
PubMed2000

Hostility in marital dyads: associations with depressive symptoms.

We examined the relations of hostility (of self and spouse) with self-ratings of depressive symptoms in 898 spouse pairs. Self-ratings of hostility were initially examined as predictors of depression. Next, spouse self-ratings of hostility were added to the model. Finally, the interaction of self x spouse hostility was investigated. These relations were explored for three components of hostility (Cynicism, Aggressive Responding, and Hostile Affect). Age and education were controlled in all models and effects were examined separately for women and men. Self-ratings of Hostile Affect were positively related to depressive symptoms for both women and men. Self-ratings of Cynicism were also significantly related to depression, but only for men. All three components of spouse's hostility were positively related to one's own symptoms of depression for women. For men, however, spouse's hostility was not related to symptoms of depression. These findings highlight the need to study psychosocial risk factors in social units and have potential implications for intervention.

Adult↗
PubMed2000

Anticoccidial vaccination of broiler chickens in various management programmes: relationship between oocyst accumulation in litter and the development of protective immunity.

Paracox anticoccidial vaccine was administered to a 7-day-old flock of commercial broiler breeder stock subsequently reared to point-of-lay in the same house. For comparison, three subgroups of another flock of broiler breeders were also vaccinated with Paracox at 7 days of age, reared to 42 days and then transferred to new litter on another farm until point-of-lay. The first subgroup received no further treatment, but the second and third each received a second vaccination with Paracox, either immediately after transfer to the new litter or 42 days after transfer. Using an Eiomeria necatrix model, protective immunity was demonstrated by virulent challenge of samples of birds from all groups by the age of 37-40 days (30-33 days after the first vaccination), and was maintained to at least 122-125 days of age, whether the birds remained on the same litter or were transferred to another farm, and whether they received one or two anticoccidial vaccinations. Therefore, there is no disadvantage in transferring birds onto new litter 35 days after a single Paracox vaccination, nor is there any advantage in giving a second vaccination after such a transfer. Vaccinated birds seeded the new litter with oocysts, despite being clinically immune to coccidiosis. A supplementary laboratory experiment showed that birds vaccinated at 8 days of age passed almost no oocysts after a second vaccination at 43 days of age. This indicated that they were not only protected against clinical coccidiosis, but were almost solidly immune to a homologous infection 5 weeks after a single vaccination. Nevertheless, oocysts appeared in the litter of all four groups of commercial breeders throughout the trial, showing that wild-type heterologous infections occurred whether the birds were transferred to new litter or not, but these did not overwhelm the acquired protective immunity and cause clinical coccidiosis.

Animal Husbandry↗
PubMed2000

Social support and quality of life in patients with coronary artery disease.

The relationship between perceived social support and domain-specific health-related quality of life (HRQOL) was examined in a sample of cardiac catheterization patients after considering age, gender, race, education, and coronary artery disease (CAD) severity. Data was collected on 4,278 cardiac catheterization patients (63% males) and included 1,215 patients with non-significant CAD and 3,063 patients who had significant CAD ( > or = 75% stenosis of at least one major coronary artery). Among the patients with significant CAD, 2,721 were classified as low disease severity and 342 were considered high disease severity. Regression models indicated that a lack of social support was associated with significantly lower levels of HRQOL across all eight SF-36 HRQOL domains after considering disease severity and other demographic factors. The models also indicated that social support and other relevant variables interacted across various HRQOL domains. Physical function and physical role function were lower with age, whereas mental health, emotional role function, and vitality were higher with age. Females reported lower HRQOL than males across all domains. Minority patients reported lower levels of HRQOL than white patients across four domains. Increased disease severity was related to lower levels among four of the eight HRQOL domains. The observed interactions of social support with minority status, disease severity, and education suggest that a subset of individuals may suffer lower levels of HRQOL. These individuals may subsequently require the greatest degree of care and potentially benefit most from intervention.

Adult↗
PubMed2000

Coronary catherization patient and wife's perceptions of social support: effects due to characteristics of recipient, provider, and their interaction.

This investigation explored relationships between coronary catherization patient and wife's characteristics and their perceptions of social support. Participants were 124 male patients undergoing diagnostic catherization to detect coronary artery disease (CAD) and their wives. Patients and wives' mean ages were fifty-nine and fifty-six years, respectively. While visiting the hospital both patient and wife independently completed a brief questionnaire that assessed psychological and physical health characteristics and perceptions of social support. Congruent with the interdependent and overlapping contexts, and reciprocal relationships assumptions of Revenson's (1994) ecological/contextual framework, results suggested characteristics of patients and wives (e.g., age, mental health, social functioning, hostility, depression, general perceived health) to interactively moderate their perceptions of social support. Overall, perceptions of social support were found to be influenced by characteristics of the perceiver, the support provider, and their interaction. Concerns for supportive and helpful caregiving are discussed.

Adult↗