Disease Systems

Edinburgh, United Kingdom

Disease Systems

Edinburgh, United Kingdom
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Prentice J.C.,Institute of Biodiversity | Prentice J.C.,University of Glasgow | Marion G.,Biomathematics and Statistics Scotland | Hutchings M.R.,Disease Systems | And 3 more authors.
Journal of the Royal Society Interface | Year: 2017

Livestock disease controls are often linked to movements between farms, for example, via quarantine and pre- or post-movement testing. Designing effective controls, therefore, benefits from accurate assessment of herd-to-herd transmission. Household models of human infections make use of R∗, the number of groups infected by an initial infected group, which is a metapopulation level analogue of the basic reproduction number R0 that provides a better characterization of disease spread in a metapopulation. However, existing approaches to calculate R∗ do not account for individual movements between locations which means we lack suitable tools for livestock systems.We address this gap using next-generation matrix approaches to capture movements explicitly and introduce novel tools to calculate R∗ in any populations coupled by individual movements. We show that depletion of infectives in the source group, which hastens its recovery, is a phenomenon with important implications for design and efficacy of movement-based controls. Underpinning our results is the observation that R∗ peaks at intermediate livestock movement rates. Consequently, under movement-based controls, infection could be controlled at high movement rates but persist at intermediate rates. Thus, once control schemes are present in a livestock system, a reduction in movements can counterintuitively lead to increased disease prevalence. We illustrate our results using four important livestock diseases (bovine viral diarrhoea, bovine herpes virus, Johne's disease and Escherichia coli O157) that each persist across different movement rate ranges with the consequence that a change in livestock movements could help control one disease, but exacerbate another. © 2017 The Authors.

PubMed | Centers for Disease Control and Prevention, Disease Systems, VetAgro Sup, University of Nottingham and National Veterinary Institute
Type: Journal Article | Journal: Epidemiology and infection | Year: 2015

The bacterium Francisella tularensis causes the vector-borne zoonotic disease tularemia, and may infect a wide range of hosts including invertebrates, mammals and birds. Transmission to humans occurs through contact with infected animals or contaminated environments, or through arthropod vectors. Tularemia has a broad geographical distribution, and there is evidence which suggests local emergence or re-emergence of this disease in Europe. This review was developed to provide an update on the geographical distribution of F. tularensis in humans, wildlife, domestic animals and vector species, to identify potential public health hazards, and to characterize the epidemiology of tularemia in Europe. Information was collated on cases in humans, domestic animals and wildlife, and on reports of detection of the bacterium in arthropod vectors, from 38 European countries for the period 1992-2012. Multiple international databases on human and animal health were consulted, as well as published reports in the literature. Tularemia is a disease of complex epidemiology that is challenging to understand and therefore to control. Many aspects of this disease remain poorly understood. Better understanding is needed of the epidemiological role of animal hosts, potential vectors, mechanisms of maintenance in the different ecosystems, and routes of transmission of the disease.

Marsh M.K.,University of York | McLeod S.R.,Australian Department of Primary Industries and Fisheries | Hutchings M.R.,Disease Systems | White P.C.L.,University of York
Wildlife Research | Year: 2011

Context Social structure of group-living animals has important implications for processes such as gene flow, information transfer, resource utilisation, and disease spread. However, due to the difficulties associated with measuring relationships among wild animals and deriving meaningful estimates of social structure from these interactions, quantifying sociality of evasive species can be challenging. Aims Our aim was to quantify the pattern of social interactions among free-ranging European wild rabbits (Oryctolagus cuniculus) in a temperate region of Australia. Methods We used proximity logging devices to collect data on the dyadic interactions among two populations of rabbits. We then applied recently developed social structure and network analytical techniques to infer estimates of sociality and contact networks from recorded interactions. Key results We found large heterogeneities in the strength of association indices and network centrality measures within but not between populations. Network analytical techniques revealed clustering of rabbits into distinct social groups. Conclusions Most associations within social groups were strong and highly stable over time whereas interactions between groups were rare and transient, indicating low levels of inter-group mixing. Despite the apparent differences in habitat quality between sites, the network characteristics were extremely similar between the two populations. Implications Our results highlight the importance of heterogeneities in individual behaviour in determining the dynamics of directly transmitted diseases at the population level. © 2011 CSIRO.

PubMed | Future Farming Systems, SAC Consulting, Animal and Veterinary Science and Disease Systems
Type: Evaluation Studies | Journal: Journal of animal science | Year: 2014

The laser methane detector (LMD) has been proposed as a method to characterize enteric methane (CH4) emissions from animals in a natural environment. To validate LMD use, its CH4 outputs (LMD-CH4), were compared against CH4 measured with respiration chambers (chamber-CH4). The LMD was used to measure CH4 concentration (L/L) in the exhaled air of 24 lactating ewes and 72 finishing steers. In ewes, LMD was used on 1 d for each ewe, for 2-min periods at 5 hourly observation periods (P1 to P5, respectively) after feeding. In steers fed either low- or high-concentrate diets, LMD was used once daily for a 4-min period for 3 d. The week after LMD-CH4 measurement, ewes or steers entered respiration chambers to quantify daily CH4 output (g/d). The LMD outputs consisted of periodic events of high CH4 concentrations superimposed on a background of oscillating lower CH4 concentrations. The high CH4 events were attributed to eructation and the lower background CH4 to respiration. After fitting a double normal distribution to the data set, a threshold of 99% of probability of the lower distribution was used to separate respiration from eructation events. The correlation between mean LMD-CH4 and chamber-CH4 was not high, and only improved correlations were observed after data were separated in 2 levels. In ewes, a model with LMD and DMI (adjusted R(2) = 0.92) improved the relationship between DMI and chamber-CH4 alone (adjusted R(2) = 0.79) and between LMD and chamber-CH4 alone (adjusted R(2) = 0.86). In both experiments, chamber-CH4 was best explained by models with length of eructation events (time) and maximum values of CH4 concentration during respiration events (L/L; P < 0.01). Correlation between methods differed between observation periods, indicating the best results of the LMD were observed from 3 to 5 h after feeding. Given the short time and ease of use of LMD, there is potential for its commercial application and field-based studies. Although good indicators of quantity of CH4 were obtained with respiration and eructation CH4, the method needed to separate the data into high and low levels of CH4 was not simple to apply in practice. Further assessment of the LMD should be performed in relation to animal feeding behavior and physiology to validate assumptions of eructation and respiration levels, and other sources of variation should be tested (i.e., micrometeorology) to better investigate its potential application for CH4 testing in outdoor conditions.

PubMed | Moredun Research Institute, Biomathematics and Statistics Scotland, A-Life Medical and Disease Systems
Type: Journal Article | Journal: Journal of the Royal Society, Interface | Year: 2017

Livestock disease controls are often linked to movements between farms, for example, via quarantine and pre- or post-movement testing. Designing effective controls, therefore, benefits from accurate assessment of herd-to-herd transmission. Household models of human infections make use of R

Houdijk J.G.M.,Disease Systems | Kyriazakis I.,Northumbria University | Kidane A.,Disease Systems | Kidane A.,Hawassa University | Athanasiadou S.,Disease Systems
Veterinary Parasitology | Year: 2012

It is increasingly being recognized that non-chemical parasite control strategies may need to be combined to control more effectively gastrointestinal parasitism, result in resilient production systems and reduce reliance on anthelmintics. Here, we consider if and how metabolizable protein (MP) supplementation and anti-parasitic plant secondary metabolites (PSM) may modulate parasite epidemiology through intervention in pasture contamination, development of infection on pasture and larval challenge as target processes. We then propose that combining two or more non-chemical parasite control strategies may have additive effects on host resistance, especially if the individual strategies target different drivers of parasite epidemiology, different processes in the parasite life cycle or different phases of acquired immunity to parasites. This epidemiological framework is used to review recent findings on combining maternal MP supplementation and grazing the PSM-rich bioactive forage chicory as an example of combining nutritional treatments to manipulate parasite epidemiology in a temperate production system. In the absence of available data for combined nutritional strategies in tropical production systems, we make predictions on the consequences of combining such strategies in these systems. We conclude that currently published studies on combining nutritional strategies under temperate conditions show potential to improve additively host resilience and reduce reliance on anthelmintics; however, effects on epidemiology have to date not shown the additive results hypothesized. The framework developed may assist further in evaluating combined (nutritional) strategies to manipulate parasite epidemiology. © 2011 Elsevier B.V..

Tolossa K.,Hawassa University | Debela E.,Hawassa University | Athanasiadou S.,Disease Systems | Tolera A.,Hawassa University | And 2 more authors.
Journal of Ethnobiology and Ethnomedicine | Year: 2013

Background: Plants have traditionally been used for treatment of human and livestock ailments in Ethiopia by different ethnic and social groups. However, this valuable source of knowledge is not adequately documented, which impedes their widespread use, evaluation and validation. Here, we recorded indigenous knowledge and standard practices for human and livestock disease control, of three ethnic groups (Aari, Maale and Bena-Tsemay) in South Omo Zone of Southern Nations, Nationalities and Peoples Regional State, Ethiopia. Methods: A cross-sectional study was carried out using a semi-structured questionnaire to document knowledge of 50 traditional healers (40 male and 10 female) in medicinal plant use for treatment of human and livestock ailments. Descriptive statistics were used to analyze and summarize the ethno-botanical data. Results: Ninety-one plants, with claimed medicinal properties against a total of 34 human and livestock ailments, were reported and botanically identified as belonging to 57 genera and 33 plant families. Most of the plant species reported belonged to one of seven major families: Lamiaceae, Solanaceae, Menispermiaceae, Fabaceae, Asteraceae, Plumbaginaceae and Geraniaceae. Woody plants (shrubs 21% and trees 29%) were the major growth form used, whilst roots (40%) and leaves (35%) were the major plant parts used in the study areas. Healers mostly practice oral administration of plant preparations (65%). Multiple medicinal plants were cited against particular ailments, and mixing of two or more different medicinal plants (14.3%) against a single ailment was also commonly reported. Conclusion: This study showed that traditional medicine, mainly involving the use of medicinal plants, is playing a significant role in meeting the primary healthcare needs of the three ethnic groups. Acceptance of traditional medicine and limited access to modern healthcare facilities could be considered as the main factors for the continuation of the practice. Documented knowledge of the traditional healers can be used to support the country's human and livestock health care system and improve lives and livelihoods. Information generated will be used in future studies to validate bioactivity of selected medicinal plants used by traditional healers, so to increase their acceptability in health care systems both nationally and internationally. © 2013 Tolossa et al.; licensee BioMed Central Ltd.

Houdijk J.G.M.,Disease Systems
Small Ruminant Research | Year: 2012

This review addresses the question whether host resistance to gastrointestinal nematodes is sensitive to metabolizable protein (MP) or metabolizable energy (ME) scarcity. Several ruminant studies have addressed this question, and with additional data from monogastric models and post-rumen infusion methodologies, there is convincing evidence that host resistance to gastrointestinal nematodes is sensitive to MP scarcity and not (moderate) ME scarcity. A possible evolutionary reason for this variation has been evoked. Attempts to dissect the role of MP and ME scarcity on resistance to parasites in ruminants is hampered by the modifying role of the rumen, as ME supplementation usually results in confounding MP supply, arising from increased microbial protein synthesis. The latter contributes less to intestinal MP than by-pass protein, and has an amino acid composition that is less compatible with that of immune proteins, compared to MP arising from animal protein sources. Thus, the largest benefits from supplementation on host resistance to gastrointestinal nematodes are expected to arise from protein-rich foods rather than from energy-rich foods. In addition, dietary protein quality in terms of level of by-pass protein and amino acid composition of resulting intestinal MP are important factors to consider in non-chemical parasite control strategies in small ruminant production systems. © 2011 Elsevier B.V.

Hardstaff J.L.,University of York | Marion G.,Biomathematics and Statistics Scotland | Hutchings M.R.,Disease Systems | White P.C.L.,University of York
Research in Veterinary Science | Year: 2014

Tuberculosis (TB) caused by infection with Mycobacterium bovis (. M. bovis) and other closely related members of the M. tuberculosis complex (MTC) infects many domestic and wildlife species across Europe. Transmission from wildlife species to cattle complicates the control of disease in cattle. By determining the level of TB hazard for which a given wildlife species is responsible, the potential for transmission to the cattle population can be evaluated. We undertook a quantitative review of TB hazard across Europe on a country-by-country basis for cattle and five widely-distributed wildlife species. Cattle posed the greatest current and potential TB hazard other cattle for the majority of countries in Europe. Wild boar posed the greatest hazard of all the wildlife species, indicating that wild boar have the greatest ability to transmit the disease to cattle. The most common host systems for TB hazards in Europe are the cattle-deer-wild boar ones. The cattle-roe deer-wild boar system is found in 10 countries, and the cattle-red deer-wild boar system is found in five countries. The dominance of cattle with respect to the hazards in many regions confirms that intensive surveillance of cattle for TB should play an important role in any TB control programme. The significant contribution that wildlife can make to the TB hazard to cattle is also of concern, given current population and distribution increases of some susceptible wildlife species, especially wild boar and deer, and the paucity of wildlife TB surveillance programmes. © 2013 Elsevier Ltd.

PubMed | Disease Systems
Type: | Journal: BMC veterinary research | Year: 2013

A common approach to the application of epidemiological models is to determine a single (point estimate) parameterisation using the information available in the literature. However, in many cases there is considerable uncertainty about parameter values, reflecting both the incomplete nature of current knowledge and natural variation, for example between farms. Furthermore model outcomes may be highly sensitive to different parameter values. Paratuberculosis is an infection for which many of the key parameter values are poorly understood and highly variable, and for such infections there is a need to develop and apply statistical techniques which make maximal use of available data.A technique based on Latin hypercube sampling combined with a novel reweighting method was developed which enables parameter uncertainty and variability to be incorporated into a model-based framework for estimation of prevalence. The method was evaluated by applying it to a simulation of paratuberculosis in dairy herds which combines a continuous time stochastic algorithm with model features such as within herd variability in disease development and shedding, which have not been previously explored in paratuberculosis models. Generated sample parameter combinations were assigned a weight, determined by quantifying the models resultant ability to reproduce prevalence data. Once these weights are generated the model can be used to evaluate other scenarios such as control options. To illustrate the utility of this approach these reweighted model outputs were used to compare standard test and cull control strategies both individually and in combination with simple husbandry practices that aim to reduce infection rates.The technique developed has been shown to be applicable to a complex model incorporating realistic control options. For models where parameters are not well known or subject to significant variability, the reweighting scheme allowed estimated distributions of parameter values to be combined with additional sources of information, such as that available from prevalence distributions, resulting in outputs which implicitly handle variation and uncertainty. This methodology allows for more robust predictions from modelling approaches by allowing for parameter uncertainty and combining different sources of information, and is thus expected to be useful in application to a large number of disease systems.

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