[Show abstract][Hide abstract] ABSTRACT: What are all the species of pathogen that affect our livestock? As 6 out of every 10 human pathogens came from animals, with a good number from livestock and pets, it seems likely that the majority that emerge in the future, and which could threaten or devastate human health, will come from animals. Only 10 years ago, the first comprehensive pathogen list was compiled for humans; we still have no equivalent for animals. Here we describe the creation of a novel pathogen database, and present outputs from the database that demonstrate its value. The ENHanCEd Infectious Diseases database (EID2) is open-access and evidence-based, and it describes the pathogens of humans and animals, their host and vector species, and also their global occurrence. The EID2 systematically collates information on pathogens into a single resource using evidence from the NCBI Taxonomy database, the NCBI Nucleotide database, the NCBI MeSH (Medical Subject Headings) library and PubMed. Information about pathogens is assigned using data-mining of meta-data and semi-automated literature searches. Here we focus on 47 mammalian and avian hosts, including humans and animals commonly used in Europe as food or kept as pets. Currently, the EID2 evidence suggests that:
[Show abstract][Hide abstract] ABSTRACT: Eradicating disease from livestock populations involves the balancing act of removing sufficient numbers of diseased animals without removing too many healthy individuals in the process. As ever more tests for bovine tuberculosis (BTB) are carried out on the UK cattle herd, and each positive herd test triggers more testing, the question arises whether 'false positive' results contribute significantly to the measured BTB prevalence. Here, this question is explored using simple probabilistic models of test behaviour. When the screening test is applied to the average UK herd, the estimated proportion of test-associated false positive new outbreaks is highly sensitive to small fluctuations in screening test specificity. Estimations of this parameter should be updated as a priority. Once outbreaks have been confirmed in screening-test positive herds, the following rounds of intensive testing with more sensitive, albeit less specific, tests are highly likely to remove large numbers of false positive animals from herds. Despite this, it is unlikely that significantly more truly infected animals are removed. BTB test protocols should become based on quantified risk in order to prevent the needless slaughter of large numbers of healthy animals.
[Show abstract][Hide abstract] ABSTRACT: A scientific literature review and consensus of expert opinion used the welfare definitions provided by the Farm Animal Welfare Council (FAWC) Five Freedoms as the framework for selecting a set of animal-based indicators that were sensitive to the current on-farm welfare issues of young lambs (aged ⩽6 weeks). Ten animal-based indicators assessed by observation - demeanour, response to stimulation, shivering, standing ability, posture, abdominal fill, body condition, lameness, eye condition and salivation were tested as part of the objective of developing valid, reliable and feasible animal-based measures of lamb welfare The indicators were independently tested on 966 young lambs from 17 sheep flocks across Northwest England and Wales during December 2008 to April 2009 by four trained observers. Inter-observer reliability was assessed using Fleiss's kappa (κ), and the pair-wise agreement with an experienced, observer designated as the 'test standard observer' (TSO) was examined using Cohen's κ. Latent class analysis (LCA) estimated the sensitivity (Se) and specificity (Sp) of each observer without assuming a gold standard and predicted the Se and Sp of randomly selected observers who may apply the indicators in the future. Overall, good levels of inter-observer reliability, and high levels of Sp were identified for demeanour (κ = 0.54, Se ⩾ 0.70, Sp ⩾ 0.98), stimulation (κ = 0.57, Se = 0.30 to 0.77, Sp ⩾ 0.98), shivering (κ = 0.55, Se = 0.37 to 0.85, Sp ⩾ 0.99), standing ability (0.54, Se ⩾ 0.80, Sp ⩾ 0.99), posture (κ = 0.45, Se ⩾ 0.56, Sp = 0.99), abdominal fill (κ = 0.44, Se = 0.39 to 0.98, Sp = 0.99), body condition (κ = 0.72, Se ⩾ 0.38 to 0.90, Sp = 0.99), lameness (κ = 0.68, Se > 0.73, Sp = 1.00), and eye condition (κ = 0.72, Se ⩾ 0.86, Sp = 0.99). LCA predicted that randomly selected observers had Se > 0.77 (acceptable), and Sp ⩾ 0.98 (high) for assessments of demeanour, lameness, abdominal fill posture, body condition and eye condition. The diagnostic performance of some indicators was influenced by the composition of the study population, and it would be useful to test the indicators on lambs with a greater level of outcomes associated with poor welfare. The findings presented in this paper could be applied in the selection of valid, reliable and feasible indicators used for the purposes of on-farm assessments of lamb welfare.
[Show abstract][Hide abstract] ABSTRACT: Salmonella spp are a major foodborne zoonotic cause of human illness. Consumption of pork products is believed to be a major source of human salmonellosis and Salmonella control throughout the food-chain is recommended. A number of on-farm interventions have been proposed, and some have been implemented in order to try to achieve Salmonella control. In this study we utilize previously developed models describing Salmonella dynamics to investigate the potential effects of a range of these on-farm interventions. As the models indicated that the number of bacteria shed in the faeces of an infectious animal was a key factor, interventions applied within a high-shedding scenario were also analysed. From simulation of the model, the probability of infection after Salmonella exposure was found to be a key driver of Salmonella transmission. The model also highlighted that minimising physiological stress can have a large effect but only when shedding levels are not excessive. When shedding was high, weekly cleaning and disinfection was not effective in Salmonella control. However it is possible that cleaning may have an effect if conducted more often. Furthermore, separating infectious animals, shedding bacteria at a high rate, from the rest of the population was found to be able to minimise the spread of Salmonella.
[Show abstract][Hide abstract] ABSTRACT: Mathematical formulations for the basic reproduction ratio (R(0)) exist for several vector-borne diseases. Generally, these are based on models of one-host, one-vector systems or two-host, one-vector systems. For many vector borne diseases, however, two or more vector species often co-occur and, therefore, there is a need for more complex formulations. Here we derive a two-host, two-vector formulation for the R(0) of bluetongue, a vector-borne infection of ruminants that can have serious economic consequences; since 1998 for example, it has led to the deaths of well over 1 million sheep in Europe alone. We illustrate our results by considering the situation in South Africa, where there are two major hosts (sheep, cattle) and two vector species with differing ecologies and competencies as vectors, for which good data exist. We investigate the effects on R(0) of differences in vector abundance, vector competence and vector host preference between vector species. Our results indicate that R(0) can be underestimated if we assume that there is only one vector transmitting the infection (when there are in fact two or more) and/or vector host preferences are overlooked (unless the preferred host is less beneficial or more abundant). The two-host, one-vector formula provides a good approximation when the level of cross-infection between vector species is very small. As this approaches the level of intraspecies infection, a combination of the two-host, one-vector R(0) for each vector species becomes a better estimate. Otherwise, particularly when the level of cross-infection is high, the two-host, two-vector formula is required for accurate estimation of R(0). Our results are equally relevant to Europe, where at least two vector species, which co-occur in parts of the south, have been implicated in the recent epizootic of bluetongue.
[Show abstract][Hide abstract] ABSTRACT: A participatory study was carried out in the Oromia region of Ethiopia to ascertain the principal epidemiological features of rabies and its impact on livestock owners. Due to the variation in topography (and therefore livestock and human populations within the study area) villages from both high (>1500m) and lowland areas were included. Local development agents who had no knowledge of the study's purpose recruited a total of one hundred and ninety six participants from eleven lowland and ten highland villages. A facilitator trained in animal health and participatory techniques conducted the interviews with groups of up to eleven participants. Methods used included ranking, scoring, proportion piling, seasonality calendars and open discussions to investigate a set of questions pre determined from a pilot study. The relative importance of rabies to other zoonoses, temporal distributions of the disease, the species affected, current methods of control within affected species and consequences of their loss were all explored. Data was compared between high and lowland areas and previously published studies. The study found that rabies was considered the zoonosis of greatest risk to public health in both areas. It reportedly occurred with higher frequency in highland areas and subsequently affected more livestock in these parts. Two distinct temporal patterns within the areas were described and participants provided reasons of biological plausibility for the occurrence. Livestock were found to contribute as a higher proportion of all species affected than previously shown in published material. This is likely to be due to the low level of reporting of affected animals to the available veterinary services, from where comparative data originated. The death of infected livestock species was found to have numerous social and economic implications and the ramifications of this are made greater by the perception that the highest incidence of clinical disease being in areas of greatest livestock density. The underestimation of the burden of disease by central bodies is likely to influence the economic rationale behind effective rabies control in the future.
[Show abstract][Hide abstract] ABSTRACT: Japanese encephalitis (JE) is one of the most well studied arthropod zoonotic diseases with human and animal research and their integration spanning 6-7 decades. JE research and policy in some Asian countries has epitomized the 'One Health' strategy of attainment of optimal health for people, animals, and the environment. However, despite significant mitigation of JE in some Asian countries primarily due to vaccination programs and infrastructural development, JE continues to be a major disease burden in the Asian region. Arthropod-borne zoonotic infections such as JE present some of the greatest challenges to animal and human health globally. Their emergence involves a complex interplay of vectors, hosts, environment, climate, and anthropogenic factors. Therefore, the integrated management of infectious agents that affect both humans and animals is perhaps the most highly coveted strategy that public health policy makers aspire to attain in the twenty-first century. This is in response to the seemingly growing challenges of controling the burden of emerging infectious diseases such as shrinking financial budgets and resources, increasing demand for public health deliverables, demographic shifts and mobility, global trade economies, and climate and landscape changes. Thus, while JE research and policy is an excellent example of the One Health strategy in action, further work is required to address the obstinate burden of transmission.
Current topics in microbiology and immunology 08/2012;
[Show abstract][Hide abstract] ABSTRACT: SUMMARYA central tenet of close-contact or respiratory infection epidemiology is that infection patterns within human populations are related to underlying patterns of social interaction. Until recently, few researchers had attempted to quantify potentially infectious encounters made between people. Now, however, several studies have quantified social mixing behaviour, using a variety of methods. Here, we review the methodologies employed, suggest other appropriate methods and technologies, and outline future research challenges for this rapidly advancing field of research.
[Show abstract][Hide abstract] ABSTRACT: In order to use body condition scoring as a cross-farm assessment tool, it is important that different assessors can consistently grade sheep along the same scale. This paper examined the intra- and inter-assessor reliability of three trained and experienced assessors who independently assessed the body condition of 141 Lleyn, Cambridge-cross and Welsh Mule-crossbred ewes using full- or half-point scoring precision of a six-point ordinal scale. Assessor reliability was evaluated using percentage (%) agreement, weighted kappa (κw), and Kendall's coefficient of concordance (W). Kruskal–Wallis one-way analysis of variance and graphical representation of the data were also used to examine for assessor bias. The on-farm studies found that the intra-assessor reliability of an assessor, who provided training in the scoring method, was higher when half- (96%, κw 0.7, W 0.7) rather than full-unit scoring precision (79%, κw 0.6, W 0.6) was used. Similarly, a higher level of inter-observer agreement was found when two additional assessors applied half- (94%, κw 0.6, W 0.7) rather than full-unit scores (93%, κw 0.4, W 0.4). Consequently, the effect of a brief re-calibration exercise on the between-observer agreement for the assessment of full-unit body condition scores (BCS) was examined. Prior to the exercise, the paired agreement between two assessors and the trainer ranged from 68 to 78%, κw 0.3–0.5, and W 0.4–0.5. Following the re-calibration exercise, the level of inter-observer agreement increased to 75–93%, κw 0.4–0.7, and W 0.4–0.6. No significant effect of assessor bias was found (p>0.05). However, most sample sheep were identified within the mid-range of body condition (BCS 2–3), which affected the analysis and interpretation of reliability data. Overall, the results suggested that trained and experienced assessors reliably scored the body condition of sheep using both half- and full-unit scores, and that a period of re-calibration may offer a feasible means of maintaining the consistency of cross-farm assessments performed by different assessors.
Small Ruminant Research - SMALL RUMINANT RES. 05/2012;
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