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G Beauchamp

Publications and source records attributed to G Beauchamp.

At least 19 recordsLinked to original sources
PubMed2006

Investigation of ground level and remote-sensed data for habitat classification and prediction of survival of Ixodes scapularis in habitats of southeastern Canada.

In southeastern Canada, most populations of Ixodes scapularis Say, the Lyme disease vector, occur in Carolinian forests. Climate change projections suggest a northward range expansion of I. scapularis this century, but it is unclear whether more northerly habitats are suitable for I. scapularis survival. In this study, we assessed the suitability of woodlands of the Lower Great Lakes/St. Lawrence Plain region for I. scapularis by comparing tick egg survival in four different woodlands. Woodlands where I. scapularis are established, and sand dune where I. scapularis do not survive, served as positive and negative control sites, respectively. At two woodland sites, egg survival was the same as at the positive control site, but at two of the sites survival was significantly less than either the positive control site, or one of the other test sites. Egg survival in all woodland sites was significantly higher than in the sand dune site. Ground level habitat classification discriminated among woodlands in which tick survival differed. The likelihood that I. scapularis populations could persist in the different habitats, as deduced using a population model of I. scapularis, was significantly associated with variations in Landsat 7 ETM+ data (normalized difference vegetation index [NDVI] and Tasselled Cap indices). The NDVI index predicted habitat suitability at Long Point, Ontario, with high sensitivity but moderate specificity. Our study suggests that I. scapularis populations could establish in more northerly woodland types than those in which they currently exist. Suitable habitats may be detected by ground-level habitat classification, and remote-sensed data may assist this process.

Animals↗
PubMed2006

Ixodes scapularis ticks collected by passive surveillance in Canada: analysis of geographic distribution and infection with Lyme borreliosis agent Borrelia burgdorferi.

Passive surveillance for the occurrence of the tick Ixodes scapularis Say (1821) and their infection with the Lyme borreliosis spirochaetes Borrelia burgdorferi s.l. has taken place in Canada since early 1990. Ticks have been submitted from members of the public, veterinarians, and medical practitioners to provincial, federal, and university laboratories for identification, and the data have been collated and B. burgdorferi detected at the National Microbiology Laboratory. The locations of collection of 2,319 submitted I. scapularis were mapped, and we investigated potential risk factors for I. scapularis occurrence (in Quebec as a case study) by using regression analysis and spatial statistics. Ticks were submitted from all provinces east of Alberta, most from areas where resident I. scapularis populations are unknown. Most were adult ticks and were collected in spring and autumn. In southern Québec, risk factors for tick occurrence were lower latitude and remote-sensed indices for land cover with woodland. B. burgdorferi infection, identified by conventional and molecular methods, was detected in 12.5% of 1,816 ticks, including 10.1% of the 256 ticks that were collected from humans and tested. Our study suggests that B. burgdorferi-infected I. scapularis can be found over a wide geographic range in Canada, although most may be adventitious ticks carried from endemic areas in the United States and Canada by migrating birds. The risk of Lyme borreliosis in Canada may therefore be mostly low but more geographically widespread than previously suspected.

Animals↗
PubMed2005

A longitudinal study of sero-conversion to tick-borne pathogens in smallholder dairy youngstock in Tanzania.

A longitudinal study of sero-conversion of youngstock to the tick-borne pathogens Theileria parva, T. mutans, Anaplasma marginale, Babesia bigemina and B. bovis was conducted over two years on smallholder dairy farms in Tanga region, Tanzania. There was evidence of maternal antibodies to all tick-borne pathogens in animals less than 18 weeks of age. Seroprevalence increased as expected with age in animals older than this but seroprevalence profiles underestimated the force of infection due to waning antibody levels between samplings. By the end of the 2-year study, less than 50% of study animals had seroconverted to each of the tick-borne pathogens investigated, consistent with the low levels of tick attachment observed on the study animals. Some associations between seroconversion to tick-borne pathogens, and counts of their known tick vectors on the animals, were identified as expected. However, some were not, suggesting that counts of some tick species may act as an index of rates of attachment of other vector species. Variation in acaricide treatment frequencies was not associated with variations in tick-borne pathogen seroprevalence suggesting that acaricides may be used more frequently than necessary on many farms. Most animals were zero-grazed, a management system associated with a significantly lower likelihood that animals seroconverted to any tick-borne pathogen except A. marginale. Seroprevalence varied locally with farm location (particularly for Babesia spp.) but was not well predicted by indices of ecological conditions. Our findings suggest that attempts to achieve a state of 'endemic stability' for tick-borne pathogens may be unreasonable on the smallholder dairy farms studied but reductions in the frequency of use of acaricides may be possible following prospective studies of effects on mortality and morbidity due to tick-borne pathogens.

Age Factors↗
PubMed2004

Risk factors for tick attachment to smallholder dairy cattle in Tanzania.

A cross-sectional study was conducted in Tanga and Iringa regions of Tanzania, and a longitudinal study in Tanga, to investigate tick-control methods and other factors influencing tick attachment to the cattle of smallholder dairy farms. Most farmers reported applying acaricides at intervals of 1-2 weeks, most used acaricides that require on-farm dilution and most farmers incorrectly diluted the acaricides. Rhipicephalus appendiculatus and Boophilus spp. ticks were those most-frequently encountered on the cattle, but few cattle carried ticks of any species (only 13 and 4.6% of tick counts of the cattle yielded adult R. appendiculatus and Boophilus spp., respectively). Animals were more likely to carry one or more adult Boophilus spp. ticks if they also carried one or more R. appendiculatus adults (OR=14.4, CI=9.2, 22.5). The use of pour-on acaricides was associated with lower odds that animals carried a R. appendiculatus tick (OR=0.29, CI=0.18, 0.49) but higher odds that they carried a Boophilus spp. tick (OR=2.48, CI=1.55, 3.97). Animals >4 months old and those with a recent history of grazing had higher odds of carrying either a R. appendiculatus (ORs=3.41 and 2.58, CIs=2.34, 4.98 and 1.80, 3.71), or a Boophilus spp. tick (ORs=5.70 and 2.18, CIs=2.34, 4.98 and 1.49. 3.25), but zero-grazing management did not prevent ticks attaching to cattle even when combined with high-frequency acaricide treatments. The odds that animals carried ticks varied amongst the agro-ecological zones (AEZs) and administrative districts where the farms were situated-but there was still considerable residual variation in tick infestation at the farm level.

Animal Husbandry↗
PubMed2004

Investigation of relationships between temperature and developmental rates of tick Ixodes scapularis (Acari: Ixodidae) in the laboratory and field.

Relationships between temperature and preoviposition, preeclosion, and premolt developmental periods for the tick Ixodes scapularis Say were investigated by holding field-collected ticks in the laboratory at temperatures of 0 to 32 degrees C at constant daylength. The duration of these developmental periods decreased significantly with increasing temperature. Host of origin, prior storage at 4 degrees C, and season of collection of the ticks were also significantly associated with variations in the duration of the preoviposition period. For each developmental stage, the effect of temperature on development rate was best described as a power relationship. Laboratory-derived relationships were used to predict dates for molting, oviposition, and eclosion of engorged larvae and nymphs, engorged adult females and egg masses, respectively, placed in the field during 1989-1992. Predicted dates for oviposition by adult females, eclosion of eggs, and molting of engorged larvae were within 2 wk of the observed dates, and field-observed seasonal activity of questing larvae and nymphs also was predicted well by laboratory data. Molting of engorged nymphs and seasonal activity of questing adult ticks were, however, poorly predicted. Our findings suggest that duration of development in the field, of larvae from engorged adult females, and of nymphs from engorged larvae, may be explained largely by temperature effects alone, whereas emergence of adult I. scapularis from engorged nymphs may depend on temperature-independent diapause phenomena. The significance of these findings for understanding current and future distributions of I. scapularis, and of the pathogens it transmits, is discussed.

Animals↗
PubMed2004

The challenge of teaching professionalism.

The medical profession has been conscious of all the changes happening in society in the last quarter of the 20th century and has tried to cope with it. Numerous criticisms about the profession and its professionals have stimulated a revision of the professional's behaviour and professionalism. The Royal College of Physicians and Surgeons of Canada has launched its own proposal under the name of CanMEDS 2000. Among the revised roles and competences one find professionalism. This theme is at the heart of our profession since the early days of the 20th century when medicine became a modern profession. Responsibility for the patient remains fundamental for any doctor but, today, society expects more accountability from the medical profession. We have the obligation to educate our residents not only for healing and caring of patients but also for active participation in managing the healthcare system. In this paper, we examine this renewed post-modern professionalism. My intention is to propose a visual approach for the teaching of professionalism.

Clinical Medicine↗
PubMed2003

Abdominal skin temperature variation in healthy broiler chickens as determined by thermography.

Abdominal skin temperature of healthy broiler chickens was determined by thermography to estimate the normal range of between- and within-bird temperature variation. Effects of potential confounding factors, such as bird's contention duration, abdominal side, age, and time of day, were also estimated. Mean skin temperature was estimated from thermogram pictures by computer image analysis of a predetermined abdominal area. Results demonstrated that skin temperature was not significantly affected by contention duration. However, skin temperature was higher on the right abdominal side in younger birds and at 1200 h. Between- and within-bird variation in healthy birds was small (< 0.5 degrees C) when age, abdominal side, and time of day were taken into account. This work suggests that skin temperature measurement using thermography can be adapted for the study of skin temperature in broiler chickens.

Abdomen↗
PubMed2001

Spatial variation in mercury concentrations in wild mink and river Otter carcasses from the James bay territory, Québec, Canada.

Mercury concentrations were analyzed in different organs/tissues of wild minks (Mustela vison) and river otters (Lutra canadensis) trapped during two seasons in the James Bay territory (49 degrees N to 55 degrees N, Québec, Canada). In 1993-94, mean total Hg concentration (microg/g, wet weight) in 39 wild mink and 12 river otter carcasses was greatest in fur/hair samples (30.1 and 20.7 microg/g, respectively) and least in brain samples (0.96 and 0.8 microg/g, respectively) with liver, kidney, and muscle samples showing intermediate values. Pooling data from the 1993-94 and 1994-95 trapping seasons revealed mean (SD) liver total Hg concentrations of 3.71 microg/g (3.91) in 316 wild mink carcasses and 4.05 microg/g (3.41) in 153 river otter carcasses. Log liver total Hg concentration increased with age in wild mink but not in river otter. Log liver total Hg concentration in each species was greatest in areas with moraine deposits and least in areas with rich clay deposits, but the effect of soil deposits could be confounded by uneven deposition of anthropogenic Hg. Controlling for type of soil deposits, log liver total Hg concentration decreased with increasing distance from local industrial centers in each species but varied little with changes in distance from hydroelectric reservoirs. In a subsample of carcasses from the moraine sector, log liver total Hg concentration was higher in wild mink than in river otter. Spatial variation in log liver total Hg concentration in relation to soil deposit type and proximity to industrial centers suggests that the two wild furbearer species could be useful indicators of environmental contamination.

Animals↗
PubMed2001

Characterization of the inflammatory infiltrate in canine chronic hepatitis.

Canine chronic hepatitis (CCH) is a progressive inflammatory disease of unknown etiology. To characterize the inflammatory infiltrate, 16 dogs with CCH were selected and classified into three groups based on the stage of fibrosis, as evaluated with Masson's trichrome stain. The inflammatory infiltrate in each liver section was immunohistochemically characterized and evaluated using CD3, lysozyme, lamba and kappa light chain, and alpha-smooth muscle actin antibodies. Numerous breeds were affected, and middle-aged females predominated in this select group. Necroinflammatory activity progressively increased and then waned as the hepatitis progressed to cirrhosis. CD3+ lymphocytes were the most numerous lymphoid cells in dogs with CCH. Degenerate hepatocytes were occasionally surrounded by CD3+ lymphocytes. Necrosis was positively correlated with the number of CD3+ lymphocytes. The lamba and kappa light chain-positive cell infiltrate was variable but generally mild. A positive correlation between the lambda and kappa light chain-positive cells and the portal alpha-smooth muscle actin was found. The number of alpha-smooth muscle actin-positive cells (myofibroblasts) in portal triads and fibrous septa was positively correlated with the stage of fibrosis. In contrast, no correlation was found between the number of lysozyme-positive cells (Kupffer cells) and the stage of fibrosis. These results further support the idea of an immune-mediated process in CCH and suggest that periductular myofibroblasts play an important role in canine liver fibrogenesis.

Actins↗
PubMed2001

Open antireflux repairs for simple reflux esophagitis: short- and long-term results.

This analysis of the results of open antireflux surgery clearly shows a benefit for antireflux surgery in most patients who have severe esophagitis with or without hiatal hernia. The authors of this article have found many variations in the methodology used to evaluate these results. Aside from these problems, however, the authors also have noticed the remarkably serious and honest work performed by most surgeons in trying to report the truth with the methodologies available to them. The principles of antireflux surgery can be found among the different studies that are reviewed in this article. These principles include: 1. The necessity of closing the crura; 2. The importance of repositioning the distal esophagus into the abdominal cavity; 3. The necessity of increasing the LES pressure by using the musculature of the fundus; 4. The preference for using a short and floppy fundoplication to avoid side effects; and 5. The need for long-term follow-up in evaluating results.

Esophagitis, Peptic↗
PubMed2001

The reproducibility of ophthalmic utility values.

PURPOSE: Utility values have been used in the ophthalmic literature to measure the quality of life associated with a health state. By convention, a utility value of 1.0 is associated with perfect health, and a value of 0.0 is associated with death. Construct validity of utility values has been demonstrated, particularly in regard to decreasing utility values as the vision decreases in the better seeing eye, but long-term test-retest reliability has not been demonstrated. The purpose of this study was to demonstrate the test-retest reliability of ophthalmic utility values. METHODS: One hundred fifteen patients with ophthalmic diseases and stable visual acuity underwent time trade-off utility analysis with retesting at various intervals ranging from 1 month to 2 years. The results were analyzed using the Wilcoxon signed rank test. The study was designed to have an 50% power, using a two-sided alpha of 5%, to be able to detect a 10% difference between the test and retest groups. RESULTS: The mean time from testing to retesting was 0.87 years, with a median time of 1.0 year and range of 1 month to 2 years. The mean utility value in the test group was 0.766 (SD = .21; 95% CI, 0.730-0.802), while the mean utility value in the retest group was 0.763 (SD = .22; 95% CI, 0.724-0.802). The difference between the means of the test-retest groups was not significant (P = .99). The intraclass correlation between the initial and follow-up utility scores was .5246 (P < .00005). CONCLUSIONS: Ophthalmic utility values appear to have good test-retest reliability over prolonged periods of time. This information is important because it gives researchers increased confidence in the validity of basic tools for ophthalmic cost-effective (cost-utility) analyses.

Adult↗
PubMed2000

The effect of prior residence and pair bond on scrounging choices in flocks of zebra finches, Taenopygia guttata.

In groups, animals can use the producer tactic to locate food patches and the scrounger tactic to join the food discoveries of other companions. At equilibrium, models predict a mixture of the two tactics with equal payoffs. Several factors may constrain the use of tactics and lead to biases in scrounging choices. I explored the effect of prior residence and pair bond as potential constraints on scrounging choices in flocks of zebra finches (Taenopygia guttata). Experimental flocks contained two birds already established in an aviary (prior residents) and two birds recently released in the aviary for the first time (new residents). All birds were previously trained to find food on a foraging grid. In the aviary, new residents followed prior residents from perches to the grid and relied heavily on prior residents to locate food patches. Low initial success by new residents probably favoured heavy reliance on the scrounger tactic. New residents that formed pair bonds with prior residents foraged closer to their mates and scrounged selectively from their mates in some cases. Prior residence, and pair bond to a lesser extent, influenced scrounging choices in zebra finches and could lead to deviation from the expected use of foraging tactics.

Journal Article↗
PubMed2000

Learning rules for social foragers: implications for the producer-scrounger game and ideal free distribution theory.

In population games, the optimal behaviour of a forager depends partly on courses of action selected by other individuals in the population. How individuals learn to allocate effort in foraging games involving frequency-dependent payoffs has been little examined. The performance of three different learning rules was investigated in several types of habitats in each of two population games. Learning rules allow individuals to weigh information about the past and the present and to choose among alternative patterns of behaviour. In the producer-scrounger game, foragers use producer to locate food patches and scrounger to exploit the food discoveries of others. In the ideal free distribution game, foragers that experience feeding interference from companions distribute themselves among heterogeneous food patches. In simulations of each population game, the use of different learning rules induced large variation in foraging behaviour, thus providing a tool to assess the relevance of each learning rule in experimental systems. Rare mutants using alternative learning rules often successfully invaded populations of foragers using other rules indicating that some learning rules are not stable when pitted against each other. Learning rules often closely approximated optimal behaviour in each population game suggesting that stimulus-response learning of contingencies created by foraging companions could be sufficient to perform at near-optimal level in two population games.

Animals↗
PubMed1999

Food exploitation: searching for the optimal joining policy.

Commonly invoked foraging advantages of group membership include increased mean food intake rates and/or reduced variance in foraging success. These foraging advantages rely on the occurrence of 'joining': feeding from food discovered or captured by others. Joining occurs in most social species but the assumptions underlying its analysis have been clarified only recently, giving rise to two classes of model: information-sharing and producer-scrounger models. Recent experimental evidence suggests that joining in ground-feeding birds might be best analysed as a producer-scrounger game, with some intriguing consequences for the spatial distribution of foragers and patch exploitation.

Journal Article↗