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Biomedical subjects

D J Shaw

Publications and source records attributed to D J Shaw.

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

The relationship between faecal egg counts, worm burden and tissue egg counts in early Schistosoma mattheei infections in cattle.

The relationships between schistosome faecal egg counts (EPG), total tissue egg counts (TEC) and adult female worm burdens (FW) recorded at post-mortem examination of 30 Friesian calves from three different field trials were analysed. The calves in study 1 (n=14) had been exposed to natural Schistosoma mattheei infections for 2 months, those of study 2 (n=9) for between 4 and 12 months, and those in study 3 (n=7) for 8 months. No clinical schistosomiasis was observed in any of the groups, and at perfusion, EPG's varied from 5 to 210, TEC's from 28,800 to 2,439,400 and FW's from 11 to 1218. There was as much variation in EPG, TEC and FW between calves with the same duration of exposure as between calves with different duration of exposure. There were very similar significant positive relationships between log transformed FW and log transformed EPG in all three groups (P<0.007, R2>0.46, slopes 0.957-1.015). There were also significant positive relationships between log transformed FW and log transformed TEC in all three groups (P<0.034, R2>0.45) and between log transformed TEC and log transformed EPG in all three groups (P<0.025, R2>0.48). All three studies had a linear relationship between log transformed FW and log transformed EPG with a slope value close to 1 (P>0.845 for different from one). This indicates that there was no evidence of density dependence in the three studies for the relationship between FW and EPG. In contrast, there was no consistent relationship (in terms of slope) between either log transformed TEC and log transformed FW in the three studies (after correcting for differential duration of exposure), or log transformed TEC and log transformed EPG. For all three sets of comparisons the predictability of one parameter based on another was poor for a single sample.

Animals↗
PubMed2002

Immunoassays to detect the serum antibody response of cattle to infection with Salmonella Typhimurium definitive type 104 and following vaccination with Bovivac S.

AIMS: To use ELISA and immunoblotting assays to examine the serum antibody response of cattle infected with Salmonella Typhimurium DT104 and following vaccination with Bovivac S. METHODS AND RESULTS: Three hundred and twenty-nine cattle, including 16 shedding multiresistant Salmonella Typhimurium DT104, were screened for serum antibodies binding to O=1, 4, 5, 12 lipopolysaccharide (LPS) antigens before and after vaccination with Bovivac S. Sera with an ELISA reading of 0.9A405 or above were shown to contain antibodies, of the IgG-class only, to the LPS of Salmonella Typhimurium using immunoblotting. Prior to vaccination, only 11 cattle had serum IgG-class antibodies to the O=4, 5 LPS antigens, and of these one also had antibodies to outer membrane proteins and H=i flagellar antigens. Following vaccination, 87 out of 315 cattle developed serum antibodies to the LPS of Salmonella Typhimurium. CONCLUSIONS: Evidence of infection of cattle with Salmonella Typhimurium was readily obtained with an LPS-based ELISA in association with an immunoblotting procedure, supplementing existing bacteriological procedures. This enabled the detection of an increase in the number of cattle with serum antibodies to Salmonella Typhimurium LPS following vaccination with Bovivac S. SIGNIFICANCE AND IMPACT OF THE STUDY: The immunoassays described provided evidence of infection with Salmonella Typhimurium and served as a valuable adjunct to established bacteriology.

Animals↗
PubMed2001

Dynamics of the 2001 UK foot and mouth epidemic: stochastic dispersal in a heterogeneous landscape.

Foot-and-mouth is one of the world's most economically important livestock diseases. We developed an individual farm-based stochastic model of the current UK epidemic. The fine grain of the epidemiological data reveals the infection dynamics at an unusually high spatiotemporal resolution. We show that the spatial distribution, size, and species composition of farms all influence the observed pattern and regional variability of outbreaks. The other key dynamical component is long-tailed stochastic dispersal of infection, combining frequent local movements with occasional long jumps. We assess the history and possible duration of the epidemic, the performance of control strategies, and general implications for disease dynamics in space and time.

Animal Husbandry↗
PubMed2001

Mapping and sequencing rat dishevelled-1: a candidate gene for cerebral ischaemic insult in a rat model of stroke.

A quantitative trait locus on chromosome 5 in the rat is linked to sensitivity to brain ischemia in the stroke-prone spontaneously hypertensive rat (SHRSP). The genes encoding atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) that map to this location have been excluded as candidate genes. We examined dishevelled-1 (DVL-1) as a further candidate gene. DVL-1 had not yet been identified in the rat, but Anp, Bnp, and DVL-1 map to the homologous regions of the rat chromosome 5 quantitative trait locus in both mice and man. Furthermore, DVL-1 is involved in the Notch signalling system, which plays a role in the disorder cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, the symptoms of, which include ischaemic stroke. We show with radiation hybrid mapping that rat DVL-1 indeed maps to chromosome 5, where it is positioned immediately next to microsatellite marker D5Rat49. We sequenced the complete coding sequence and a large part of the intronic genomic sequence for the SHRSP strain and its reference Wistar-Kyoto strain. The DVL-1 sequence in the two strains was identical. Our results essentially exclude the DVL-1 gene as the cause for sensitivity to cerebral ischaemic insult in this rat model of stroke.

Adaptor Proteins, Signal Transducing↗
PubMed2001

Index of potential contamination for schistosomiasis.

Schistosomiasis occurs under a wide variety of climatic, geographical and other conditions. The basic reason for the transmission of schistosomes is, however, the low level of sanitation in endemic areas with the result that faeces or urine, or both, containing schistosome eggs get into water that contains freshwater snails susceptible to infection. Unfortunately, the degree of contamination of natural habitats with schistosome ova is difficult to estimate; consequently, there are few data on how much contamination, relative to a defined snail population density, is necessary to initiate or maintain transmission of schistosomiasis. This article discusses a little-used method to estimate the degree of contamination or transmission - the index of potential contamination (IPC). The expected changes in IPC after praziquantel treatment will be considered, as well as the level of reduction in IPC that might be needed to affect transmission or reduce morbidity.

Adolescent↗
PubMed2000

Prevalence of small inversions in yeast gene order evolution.

Gene order evolution in two eukaryotes was studied by comparing the Saccharomyces cerevisiae genome sequence to extensive new data from whole-genome shotgun and cosmid sequencing of Candida albicans. Gene order is substantially different between these two yeasts, with only 9% of gene pairs that are adjacent in one species being conserved as adjacent in the other. Inversion of small segments of DNA, less than 10 genes long, has been a major cause of rearrangement, which means that even where a pair of genes has been conserved as adjacent, the transcriptional orientations of the two genes relative to one another are often different. We estimate that about 1,100 single-gene inversions have occurred since the divergence between these species. Other genes that are adjacent in one species are in the same neighborhood in the other, but their precise arrangement has been disrupted, probably by multiple successive multigene inversions. We estimate that gene adjacencies have been broken as frequently by local rearrangements as by chromosomal translocations or long-distance transpositions. A bias toward small inversions has been suggested by other studies on animals and plants and may be general among eukaryotes.

Candida albicans↗
PubMed1999

Diagnosis of larval cyathostominosis in horses in Belgium.

Between October 1996 and May 1997, 94 horses which were suspected of being infected with strongyles were examined clinically, and samples of faeces were examined for strongyle eggs and cyathostome larvae (L4) and adults. Blood samples were monitored for total protein, albumin and beta-globulins. In 28 of the horses (30 per cent) cyathostome L4 and adults were detected in the faeces, and were significantly associated with the horses' condition, the occurrence of diarrhoea, with lower concentrations of total protein and albumin, and with higher percentages of beta-globulin. Thirty-four of the horses (36 per cent) were excreting strongyle eggs, but in these animals the associations were with high concentrations of total protein and albumin, and lower percentages of beta-globulin. The results showed that during the winter, a horse in poor condition which has diarrhoea, an albumin concentration less than 20 g/litre, and a ratio of albumin:globulin less than 0.7 is very likely to be infected with L4 and adult stages of cyathostomes.

Animals↗
PubMed1999

The determination at housing of exposure to gastrointestinal nematode infections in first-grazing season calves.

Various parameter estimates were assessed at housing in calves that had been exposed to gastrointestinal nematodes during a first grazing season. The analysis involved 41 groups of first grazing season (FGS) calves on 15 different farms in Belgium and comprised groups that had received chemoprophylactic treatment and untreated controls. Serum pepsinogen levels gave the clearest division between chemoprophylactic-treated calf groups (all were <2.6 U tyr), and untreated calf groups in which sub-clinical (range: 2.0-4.1 U tyr) and clinical infections (range 3.7-6.3 U tyr) occurred. There was also a tight relationship between individual pepsinogen values and adult Ostertagia burdens obtained at slaughter. In chemoprophylactic-treated groups there was a significant negative relationship between mean serum pepsinogen levels at housing and the proportion of the grazing season covered by different chemoprophylactic systems. Although only limited data on crude adult Ostertagia antigen ELISA were available, a good relationship between optical densities and estimated exposure was also found. The parasitological parameters, faecal egg counts and pasture Ostertagia larval counts at housing, and weight gain per day, gave less clear divisions among the three categories (chemoprophylaxis, sub-clinical and clinical). Distinguishing how much exposure a calf group has experienced during a first grazing season could help in designing more appropriate control measures for the FGS calves in the next year, assuring good protection and at the same time allowing sufficient exposure for the development of acquired immunity to Ostertagia, and for this serum pepsinogen is recommended.

Abomasum↗
PubMed1999

The epidemiology of a recent focus of mixed Schistosoma haematobium and Schistosoma mansoni infections around the 'Lac de Guiers' in the Senegal River Basin, Senegal.

A village with mixed Schistosoma mansoni and S. haematobium infections (probably in a early endemic phase) was identified around the Lac de Guiers in the Senegal River Basin. In documenting the epidemiology of both schistosomes, we focused on prevalence and intensity of infection, transmission patterns and the impact of treatment. S. mansoni prevalences (near 100%) and egg counts (overall geometric mean eggs per gram of faeces (epg) of 589 were high in all age groups, with 35% of individuals excreting > 1000 epg, and showing a slow decline in egg output only after the age of 30 years. The overall prevalence (28%) and egg counts (2% > 50 eggs/10 ml) of S. haematobium were low, with mean counts of 6.3 eggs/10 ml. Maximal mean S. mansoni egg counts were found in 5-9 year-old boys and in 15-19 year-old girls; S. haematobium maximal counts in 1-4 year-old boys and in girls aged 5-9. Extremely high Biomphalaria pfeifferi infection ratios were recorded over the whole year. Following a single treatment, re-infection was rapid with prevalences and mean egg counts of both Schistosoma species reaching pretreatment levels within 7 months.

Adolescent↗
PubMed1999

Larval migration inhibition activity in abomasal mucus and serum from calves infected with Ostertagia ostertagi.

The present study investigated whether abomasal mucus from calves naturally infected with gastrointestinal nematodes possessed larval migration inhibition (LMI) activity in vitro, and whether LMI activity was greater in mucus from previously immunised animals, compared to primary infected and uninfected calves. LMI activity was also assessed in serum from calves during both natural and artificial Ostertagia ostertagi infections, in an attempt to monitor the development of acquired immunity. Both abomasal mucus and serum exhibited larval paralysing activity. Although the LMI capacity of the abomasal mucus was very variable, the highest paralysing activity was consistently observed in mucus from previously immunised calves. LMI activity in serum increased significantly during both artificial and natural Ostertagia infections. After a challenge infection, sera from immunised animals showed a significantly higher LMI capacity, compared to previously uninfected calves. Moreover, serum LMI activity was significantly negatively correlated with Ostertagia worm counts after the challenge infection. The present results suggest that LMI activity in serum and/or abomasal mucus reflects a protective immune response against O. ostertagi in the abomasal mucosa.

Abomasum↗
PubMed1999

No evidence of linkage disequilibrium between a CAG repeat in the SCA1 gene and schizophrenia in Caucasian and Chinese schizophrenic subjects.

Several recent studies have reported evidence for a schizophrenia locus on chromosome 6p, with a variety of linked markers spanning a approximately 40 cM region between D6S470 and D6S291. However because of the wide region implicated and the difficulty of inferring phenotype from genotype in complex disorders, it is difficult to define its location precisely using linkage data. An alternative approach is to search for linkage disequilibrium. On chromosome 6p, allelic association with a (CAG)29 allele of a triplet repeat marker in the SCA1 gene has been reported, and we have attempted to replicate this finding using a Caucasian case-control sample of 211 affected subjects and 204 controls, and a Han Chinese sample of 100 affected family trios. In the case-control sample, the frequency of the (CAG)29 allele was similar in cases and controls (35%), and no other alleles provided evidence for allelic association. Likewise, there was no evidence for preferential transmission of the (CAG)29 allele to affected offspring in the Chinese sample, although a different allele, (CAG)26, was more often transmitted to the affected offspring. However this data did not reach statistical significance (P = 0.1). We conclude that our data does not support the notion that there is a locus for schizophrenia close to the SCA1 gene. However, since linkage disequilibrium will vary between distinct populations, we cannot exclude this possibility.

Asian People↗
PubMed1998

Gastrointestinal nematode infections of first-grazing season calves in Western Europe: associations between parasitological, physiological and physical factors.

Analysis of 85 studies on gastrointestinal nematode infections in first-grazing season (FGS) calves is presented. The studies cover a 26-year period and were carried out in 13 countries in Western Europe. Both control and chemoprophylactic-treated (early in the season) FGS calf groups were included. In 53 of the 85 studies, clinical outbreaks of parasitic gastroenteritis (PGE) were observed during the FGS in the control groups. The mean initial age (and weight) of the control calf group was significantly associated with PGE outbreaks: 82% of control calf groups < or = 6 months of age had outbreaks of PGE, compared to only 33% of control calf groups > 6 months of age. In 92% of trials where the geometric mean faecal egg count (MFEC) was > or = 200 EPG on Day 56, PGE outbreaks were observed, but where it was < 200 EPG, only 29% had PGE. The use of these two factors in assessing the likelihood of PGE outbreaks in untreated calf groups in the future FGS is therefore, proposed. No chemoprophylactic-treated groups had PGE, but there was a highly significant negative relationship between maximum faecal egg counts in the chemoprophylactic-treated calves and the proportion of the trial covered by the different chemoprophylactic systems. Higher stocking densities were significantly associated with higher pasture contamination in both control and chemoprophylactic-treated calves. A highly significant positive relationship between the weight gained in the chemoprophylactic-treated groups and the estimated duration of the various chemoprophylactic systems was found, but there were large variations in weight gains (60-160 kg) between groups even with the same chemoprophylactic. Despite this and other highly significant associations, it was not possible to indicate what weight gains were obtained by the end of the FGS, from factors measured early in the FGS.

Age Factors↗
PubMed1998

Gastrointestinal nematode infections of first-grazing season calves in Western Europe: general patterns and the effect of chemoprophylaxis.

Research on the prevention of gastrointestinal nematode infections of cattle has mainly concentrated on comparing a specific chemoprophylactic treatment system to an untreated control group on a particular farm. Here, the results from analysis of 85 studies involving over 2000 first grazing season (FGS) calves put onto pasture for at least 4 months from late spring/early summer over a 26-year period in 13 countries in Western Europe are presented. Both control and chemoprophylactic treated FGS calf groups were considered. All chemoprophylactic systems (slow- and pulse-release boli, strategic treatments) were given early in the grazing season. Two general infection levels emerged--'sub-clinical' (32 studies) and 'clinical' (53 studies). The 'sub-clinical' infections were characterised by no clinical symptoms of parasitic gastroenteritis (PGE) being observed in the control groups. Mean faecal egg counts in the 'clinical' control groups were significantly higher than those for 'sub-clinical' control groups for almost the entire season with overall peaks of 275 and 100 EPG respectively. Maximum pasture larval counts were also significantly higher in the 'clinical' control groups with 44% of 'clinical' pastures > 10,000 L3 kg(-1) dry herbage by the end of the FGS, compared to only 15% of 'sub-clinical' pastures. There was a significant positive relationship between log transformed worm burdens from tracers put onto pastures for 2 weeks and the corresponding pasture larval count. No evidence of density dependence in tracer worm burden was observed. Weight gains in the 'clinical' control groups (375 g/day) were significantly lower than those of the 'sub-clinical' control groups (530 g/day). No symptoms of PGE were observed in any of the chemoprophylactic treated groups, but in those studies with an outbreak of PGE in the control group, the treated groups had significantly higher faecal egg and pasture larval counts than treated groups in 'sub-clinical' studies. The overall weight gain in chemoprophylactic treated calves in 'clinical' studies (600 g/day) was significantly lower than the chemoprophylactic treated calves in 'sub-clinical' studies (690 g/day), and was not significantly different from the weight gain of control calves in 'sub-clinical' studies. These results indicate that on heavily infected pastures, chemoprophylaxis will prevent PGE, but calves will still suffer production losses.

Analysis of Variance↗
PubMed1998

Epidemiology of Mecistocirrus digitatus and other gastrointestinal nematode infections in cattle in Mindanao, Philippines.

Over a period of 14 months, faecal and serum samples were collected monthly from cattle of 1 to 30 months old on three ranches (20-25 animals ranch-1 sample-1) in Mindanao, Philippines. Individual faecal egg counts, serum pepsinogen levels and Mecistocirrus digitatus specific antibodies were determined, and infective larvae from pooled faecal samples were examined. Post mortem worm counts were carried out on tracer calves (n = 16) that had been kept for 30 days with the herds on two of the ranches. A number of gastrointestinal nematode species were present: M. digitatus, Haemonchus placei, H. similis, Trichostrongylus axei, Cooperia punctata, C. pectinata, Bunostomum phlebotomum and Oesophagostomum radiatum. Strongyle eggs first appeared in the faeces of calves of two months old, egg counts peaked when animals were 3-6 months old, after which they steadily and significantly declined. Faecal egg output of M. digitatus increased up to the age of 10 months, after which there was a steady but not significant decline until the age of 24 months. In faecal cultures the relative proportion of Cooperia larvae decreased from over 70% in 0-6 month old animals to 30% in 19-24 month old animals, and a corresponding 30% increase in the proportion of Mecistocirrus was observed. Both serum pepsinogen and M. digitatus specific antibodies levels increased during the first year of life, and then remained at the same level in older animals. Whereas the total faecal egg output did not significantly vary throughout the year, worm counts from tracer calves indicated a marked seasonality in transmission.

Aging↗
PubMed1998

Patterns of macroparasite aggregation in wildlife host populations.

Frequency distributions from 49 published wildlife host-macroparasite systems were analysed by maximum likelihood for goodness of fit to the negative binomial distribution. In 45 of the 49 (90%) data-sets, the negative binomial distribution provided a statistically satisfactory fit. In the other 4 data-sets the negative binomial distribution still provided a better fit than the Poisson distribution, and only 1 of the data-sets fitted the Poisson distribution. The degree of aggregation was large, with 43 of the 49 data-sets having an estimated k of less than 1. From these 49 data-sets, 22 subsets of host data were available (i.e. host data could be divided by either host sex, age, where or when hosts were sampled). In 11 of these 22 subsets there was significant variation in the degree of aggregation between host subsets of the same host-parasite system. A common k estimate was always larger than that obtained with all the host data considered together. These results indicate that lumping host data can hide important variations in aggregation between hosts and can exaggerate the true degree of aggregation. Wherever possible common k estimates should be used to estimate the degree of aggregation. In addition, significant differences in the degree of aggregation between subgroups of host data, were generally associated with significant differences in both mean parasite burdens and the prevalence of infection.

Animals↗
PubMed1998

Morbidity induced by Schistosoma haematobium infections, as assessed by ultrasound before and after treatment with praziquantel, in a recently expanded focus (Senegal River basin).

Seven years after the completion of two dams in the Senegal River basin, 203 individuals from four villages around Podor in the middle valley, where Schistosoma haematobium infections were present, were examined in June 1995. In December 1995 a single dose of praziquantel (40 mg/kg) was given to each of these subjects, who were re-examined in April 1996. Clinical and parasitological signs of infection were investigated at both examinations, and ultrasonography was performed to check for lesions of the urinary tract induced by S. haematobium. As uninfected controls, 200 people from four villages where S. haematobium was absent were similarly examined, in November 1995. Prior to treatment, bladder irregularities were observed in 43% of the subjects from Podor but only 6% of the uninfected controls. The severity of the bladder lesions visible by ultrasonography was significantly associated with intensity of infection, despite the generally low levels of infection in the subjects mean = 13.1 eggs/10 ml urine). Four months after treatment, however, the frequency of bladder irregularities among the subjects (11%) was similar to that in the uninfected controls and intensities of infection and other clinical signs of disease had also significantly declined. The prevalence of haematuria, for example, fell from 35% pre-treatment to 10% post-treatment. The results indicate that the onset of S. haematobium morbidity can be relatively rapid even in areas with seasonal and low levels of transmission, and demonstrate that treatment to reduce morbidity in such areas is important and could be relatively simple and very effective.

Adolescent↗
PubMed1998

Polypoid lesions of airways: early experience with computer-assisted detection by using virtual bronchoscopy and surface curvature.

PURPOSE: To test the application of a technique developed by the authors for the computer-assisted diagnosis of polypoid airway lesions from surface rendered virtual bronchoscopic reconstructions. MATERIALS AND METHODS: A computer algorithm was developed to detect polypoid airway lesions by means of segmentation of the bronchial surface with curvature classification. This method was tested with a bronchial phantom, five cadaveric lung specimens, and virtual bronchoscopic studies in 16 patients. RESULTS: For the patient studies, the sensitivity and specificity of the method were 47%-88% and 58%-89%, respectively, depending on the value of an adjustable parameter (the mean curvature threshold). The sensitivity increased (by 20% to 34%) when only lesions larger than 5 mm in diameter were considered. CONCLUSION: With this method, polypoid airway lesions can be detected automatically, although false-positive diagnoses present an important limitation.

Adult↗