Surrey, United Kingdom
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Chambers M.A.,University of Surrey | Carter S.P.,AHVLA | Wilson G.J.,AHVLA | Jones G.,AHVLA | And 3 more authors.
Veterinary Record | Year: 2014

Bovine tuberculosis (TB) is a significant threat to the cattle industry in England and Wales. It is widely acknowledged that a combination of measures targeting both cattle and wildlife will be required to eradicate bovine TB or reduce its prevalence until European official freedom status is achieved. Vaccination of cattle and/or badgers could contribute to bovine TB control in Great Britain, although there are significant gaps in our knowledge regarding the impact that vaccination would actually have on bovine TB incidence. Laboratory studies have demonstrated that vaccination with BCG can reduce the progression and severity of TB in both badgers and cattle. This is encouraging in terms of the prospect of a sustained vaccination programme achieving reductions in disease prevalence; however, developing vaccines for tackling the problem of bovine TB is challenging, time-consuming and resource-intensive, as this review article sets out to explain.


Arnold M.E.,Animal Health and Veterinary Laboratories Agency AHVLA | Irvine R.M.,Avian Virology and Mammalian Influenza Group | Tearne O.,Animal Health and Veterinary Laboratories Agency AHVLA | Rae D.,Animal Health and Veterinary Laboratories Agency AHVLA | And 2 more authors.
Epidemiology and Infection | Year: 2013

SUMMARY The aim of this study was to evaluate potential sampling strategies for detection of infected flocks that could be applied during an outbreak of low pathogenicity notifiable avian influenza (LPNAI) initiated in duck holdings, following initial detection. A simulation model of avian influenza virus transmission and spread within and between holdings, respectively, was used to predict the impact on the size and duration of an outbreak of (i) changing the tracing window within which premises that might be the source of infection or that may have been infected by the index premises were sampled and (ii) changing the number of birds sampled in the flock being tested. It has shown that there is potential benefit in increasing the tracing window in terms of reducing the likelihood of a large outbreak. It has also shown that there is comparatively little benefit from increasing the number of birds sampled per flock. Copyright © Cambridge University Press 2012.


Arnold M.E.,Animal Health and Veterinary Laboratories Agency AHVLA | Martelli F.,AHVLA | Mclaren I.,AHVLA | Davies R.H.,AHVLA
Zoonoses and Public Health | Year: 2014

Salmonella enterica serovar Enteritidis (S. Enteritidis) is one of the most prevalent causes for human gastroenteritis and is by far the predominant Salmonella serovar among human cases, followed by Salmonella Typhimurium. Contaminated eggs produced by infected laying hens are thought to be the main source of human infection with S. Enteritidis throughout the world. Although previous studies have looked at the proportion of infected eggs from infected flocks, there is still uncertainty over the rate at which infected birds produce contaminated eggs. The aim of this study was to estimate the rate at which infected birds produce contaminated egg shells and egg contents. Data were collected from two studies, consisting of 15 and 20 flocks, respectively. Faecal and environmental sampling and testing of ovaries/caeca from laying hens were carried out in parallel with (i) for the first study, testing 300 individual eggs, contents and shells together and (ii) for the second study, testing 4000 eggs in pools of six, with shells and contents tested separately. Bayesian methods were used to estimate the within-flock prevalence of infection from the faecal and hen post-mortem data, and this was related to the proportion of positive eggs. Results indicated a linear relationship between the rate of contamination of egg contents and the prevalence of infected chickens, but a nonlinear (quadratic) relationship between infection prevalence and the rate of egg shell contamination, with egg shell contamination occurring at a much higher rate than that of egg contents. There was also a significant difference in the rate of egg contamination between serovars, with S. Enteritidis causing a higher rate of contamination of egg contents and a lower rate of contamination of egg shells compared to non-S. Enteritidis serovars. These results will be useful for risk assessments of human exposure to Salmonella-contaminated eggs. © 2013 Crown.


Arnold M.E.,Animal Health and Veterinary Laboratories Agency AHVLA | Martelli F.,AHVLA | Mclaren I.,AHVLA | Davies R.H.,AHVLA
Epidemiology and Infection | Year: 2014

SUMMARY A key element of national control programmes (NCPs) for Salmonella in commercial laying flocks, introduced across the European Union, is the identification of infected flocks and holdings through statutory sampling. It is therefore important to know the sensitivity of the sampling methods, in order to design effective and efficient surveillance for Salmonella. However, improved Salmonella control in response to the NCP may have influenced key factors that determine the sensitivity of the sampling methods used to detect Salmonella in NCPs. Therefore the aim of this study was to compare estimates of the sensitivity of the sampling methods using data collected before and after the introduction of the NCP, using Bayesian methods. There was a large reduction in the sensitivity of dust in non-cage flocks between the pre-NCP studies (81% of samples positive in positive flocks) and post-NCP studies (10% of samples positive in positive flocks), leading to the conclusion that sampling dust is not recommended for detection of Salmonella in non-cage flocks. However, cage dust (43% of samples positive in positive flocks) was found to be more sensitive than cage faeces (29% of samples positive in positive flocks). To have a high probability of detection, several NCP-style samples need to be used. For confirmation of Salmonella, five NCP faecal samples for cage flocks, and three NCP faecal boot swab samples for non-cage flocks would be required to have the equivalent sensitivity of the EU baseline survey method, which was estimated to have an 87% and 75% sensitivity to detect Salmonella at a 5% within-flock prevalence in cage and non-cage flocks, respectively. © Cambridge University Press 2013.


Hateley G.,AHVLA
Cattle Practice | Year: 2014

The appearance in 2011 of a previously undescribed arbovirus, Schmallenberg, marked the second occurrence in Northern Europe of a major vector-borne disease epizootic within ten years. Knowledge of this novel virus has grown as rapidly as it has spread, from being an unquantifiable threat to an endemic disease. This paper reviews our understanding of the virus and diseases it causes; looks at the current disease situation; considers recent research findings including the results of European Union collaborative research; examines the current risk to our livestock industry and methods available to mitigate that risk; finally, a horizon scanning section looks at the potential for further animal and human disease incursion, and how these threats can be managed.


Rhodes S.,Animal Health and Veterinary Laboratories Agency AHVLA | Holder T.,Animal Health and Veterinary Laboratories Agency AHVLA | Clifford D.,Animal Health and Veterinary Laboratories Agency AHVLA | Dexter I.,Animal Health and Veterinary Laboratories Agency AHVLA | And 10 more authors.
Clinical and Vaccine Immunology | Year: 2012

We describe the performance of cell-based and antibody blood tests for the antemortem diagnosis of tuberculosis (TB) in South American camelids (SAC). The sensitivity and specificity of the gamma interferon (IFN-γ) release assay, two lateral flow rapid antibody tests (Stat-Pak and Dual Path Platform [DPP]), and two enzyme-linked immunosorbent assay (ELISA)-based antibody tests (Idexx and Enferplex) were determined using diseased alpacas from Mycobacterium bovis culture-confirmed breakdown herds and TB-free alpacas from geographical areas with no history of bovine TB, respectively. Our results show that while the sensitivities of the IFN-γ and antibody tests were similar (range of 57.7% to 66.7%), the specificity of the IFN-γ test (89.1%) was lower than those of any of the antibody tests (range of 96.4% to 97.4%). This lower specificity of the IFN-γ test was at least in part due to undisclosed Mycobacterium microti infection in the TB-free cohort, which stimulates a positive purified protein derivative (PPD) response. The sensitivity of infection detection could be increased by combining two antibody tests, but even the use of all four antibody tests failed to detect all diseased alpacas. These antibody-negative alpacas were IFN-γ positive. We found that the maximum sensitivity could be achieved only by the combination of the IFN-γ test with two antibody tests in a "test package," although this resulted in decreased specificity. The data from this evaluation of tests with defined sensitivity and specificity provide potential options for antemortem screening of SAC for TB in herd breakdown situations and could also find application in movement testing and tracing investigations. Copyright © 2012, American Society for Microbiology. All Rights Reserved.


Arnold M.E.,Animal Health and Veterinary Laboratories Agency AHVLA | Gosling R.J.,AHVLA | Martelli F.,AHVLA | Mueller-Doblies D.,AHVLA | Davies R.H.,AHVLA
Epidemiology and Infection | Year: 2015

There has been a rapid rise in the prevalence of cases of monophasic Salmonella Typhimurium (mST) in both humans and farm animals, and it has been found in pigs, cattle and poultry. It is therefore vital to have a good understanding of how to efficiently detect infected farms. The objective of this project was to determine sample type sensitivity in the detection of Salmonella to detect infected groups of animals on both pig (breeder, grower and finisher sites) and cattle (beef and dairy) farms, using data collected from a study investigating farms that were positive for mST, and to explore any variation between different age groups and management practices. A Bayesian approach in the absence of a gold standard was adopted to analyse the individual and pooled faecal sample data collected from each epidemiological group on each of the farms. The sensitivity of pooled sampling depended on the prevalence of infection in the group being sampled, with a higher prevalence leading to higher sensitivity. Pooled sampling was found to be more efficient at detecting positive groups of animals than individual sampling, with the probability of a random sample from a group of animals with 5% prevalence testing positive being equal to 15·5% for immature pigs (3·6% for an individual faecal sample, taking into account the sensitivity and infection prevalence), 7·1% for adult pigs (1·2% for individual sampling), 30% for outdoor cattle (2% for individual sampling) and 34% for indoor cattle (1% for individual sampling). The mean prevalence of each epidemiological group was higher in outdoor farms than indoor for both pigs and cattle (mean within-farm prevalence of 29·4% and 38·7% for outdoor pigs and cattle, respectively, compared to 19·8% and 22·1% for indoor pigs and cattle) Copyright © Cambridge University Press 2014.


Smith R.P.,Animal Health and Veterinary Laboratories Agency AHVLA | Giles M.,Animal Health and Veterinary Laboratories Agency AHVLA | Cheney T.,Animal Health and Veterinary Laboratories Agency AHVLA | Mitchell E.S.E.,AHVLA Carmarthen | Ellis-Iversen J.,AHVLA
Cattle Practice | Year: 2013

In 2008,493 cattle diagnostic submissions to the Animal Health and Veterinary Laboratories Agency (AHVLA) in England and Wales were given a diagnosis of coccidiosis. These were mainly from faecal samples, and the main clinical presenting sign was diarrhoea (81%). The majority of affected animals were in either the preor post-weaned age groups, with post-weaned animals less likely to present with diarrhoea. A significantly greater proportion of dairy cattle than beef were present compared with the background cattle population. The spread of submissions amongst geographical regions was generally representational of the cattle population. However, a significantly larger number of coccidiosis cases than expected were identified from the Taunton and Carmarthen regions, and significantly less from Caernarfon and Cardiff. These regional differences are discussed in light of regional cattle demographics and other factors that might influence submission of samples to a Regional Laboratory. The temporal patterns of coccidiosis submissions from 1999-2008 were described and a statistically significant decline in coccidiosis diagnoses per month was detected, as well as a trend towards higher diagnoses rates in the summer and autumn months. Although the results are based on opportunistic sampling, they do represent the best data available on cattle coccidiosis and the findings concur with results from previous studies and anecdotal summaries.


PubMed | Animal Health and Veterinary Laboratories Agency AHVLA and AHVLA
Type: Journal Article | Journal: Epidemiology and infection | Year: 2015

There has been a rapid rise in the prevalence of cases of monophasic Salmonella Typhimurium (mST) in both humans and farm animals, and it has been found in pigs, cattle and poultry. It is therefore vital to have a good understanding of how to efficiently detect infected farms. The objective of this project was to determine sample type sensitivity in the detection of Salmonella to detect infected groups of animals on both pig (breeder, grower and finisher sites) and cattle (beef and dairy) farms, using data collected from a study investigating farms that were positive for mST, and to explore any variation between different age groups and management practices. A Bayesian approach in the absence of a gold standard was adopted to analyse the individual and pooled faecal sample data collected from each epidemiological group on each of the farms. The sensitivity of pooled sampling depended on the prevalence of infection in the group being sampled, with a higher prevalence leading to higher sensitivity. Pooled sampling was found to be more efficient at detecting positive groups of animals than individual sampling, with the probability of a random sample from a group of animals with 5% prevalence testing positive being equal to 155% for immature pigs (36% for an individual faecal sample, taking into account the sensitivity and infection prevalence), 71% for adult pigs (12% for individual sampling), 30% for outdoor cattle (2% for individual sampling) and 34% for indoor cattle (1% for individual sampling). The mean prevalence of each epidemiological group was higher in outdoor farms than indoor for both pigs and cattle (mean within-farm prevalence of 294% and 387% for outdoor pigs and cattle, respectively, compared to 198% and 221% for indoor pigs and cattle).


PubMed | Animal Health and Veterinary Laboratories Agency AHVLA and AHVLA
Type: Journal Article | Journal: Epidemiology and infection | Year: 2014

A key element of national control programmes (NCPs) for Salmonella in commercial laying flocks, introduced across the European Union, is the identification of infected flocks and holdings through statutory sampling. It is therefore important to know the sensitivity of the sampling methods, in order to design effective and efficient surveillance for Salmonella. However, improved Salmonella control in response to the NCP may have influenced key factors that determine the sensitivity of the sampling methods used to detect Salmonella in NCPs. Therefore the aim of this study was to compare estimates of the sensitivity of the sampling methods using data collected before and after the introduction of the NCP, using Bayesian methods. There was a large reduction in the sensitivity of dust in non-cage flocks between the pre-NCP studies (81% of samples positive in positive flocks) and post-NCP studies (10% of samples positive in positive flocks), leading to the conclusion that sampling dust is not recommended for detection of Salmonella in non-cage flocks. However, cage dust (43% of samples positive in positive flocks) was found to be more sensitive than cage faeces (29% of samples positive in positive flocks). To have a high probability of detection, several NCP-style samples need to be used. For confirmation of Salmonella, five NCP faecal samples for cage flocks, and three NCP faecal boot swab samples for non-cage flocks would be required to have the equivalent sensitivity of the EU baseline survey method, which was estimated to have an 87% and 75% sensitivity to detect Salmonella at a 5% within-flock prevalence in cage and non-cage flocks, respectively.

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