The impact of local heterogeneity on alternative control strategies for foot-and-mouth disease

The 2001 epidemic of foot-and-mouth disease (FMD) in the UK resulted in the death of nearly 10 million livestock at a cost that was estimated to be up to 8 billion pounds. Owing to the controversy surrounding the epidemic, the question of whether or not alternative policies would have resulted in significantly better control of the epidemic remains of great interest. A hexagonal lattice simulation of FMD in Cumbria is used to address the central question of whether or not better use could have been made of expert knowledge of FMD transmission to target pre-emptive culling, by assuming that the premises at greatest risk of becoming infected can be targeted for culling. The 2000 UK census and the epidemiological database collected during the epidemic are used to describe key characteristics of disease transmission, and the model is fit to the epidemic time-series. Under the assumptions of the model, the parameters that best fit the epidemic in Cumbria indicate that a policy based on expert knowledge would have exacerbated the epidemic compared with the policy as implemented. However, targeting more distant, high-risk farms could be more valuable under different epidemic conditions, notably, if risk factors of sufficient magnitude could be identified to aid in prioritizing vaccination or culling of farms at high risk of becoming infected.     

Estimating the per-contact probability of infection by highly pathogenic avian influenza (H7N7) virus during the 2003 epidemic in The Netherlands

Estimates of the per-contact probability of transmission between farms of Highly Pathogenic Avian Influenza virus of H7N7 subtype during the 2003 epidemic in the Netherlands are important for the design of better control and biosecurity strategies. We used standardized data collected during the epidemic and a model to extract data for untraced contacts based on the daily number of infectious farms within a given distance of a susceptible farm. With these data, we used a maximum likelihood estimation approach to estimate the transmission probabilities by the individual contact types, both traced and untraced. The estimated conditional probabilities, conditional on the contact originating from an infectious farm, of virus transmission were: 0.000057 per infectious farm within 1 km per day, 0.000413 per infectious farm between 1 and 3 km per day, 0.0000895 per infectious farm between 3 and 10 km per day, 0.0011 per crisis organisation contact, 0.0414 per feed delivery contact, 0.308 per egg transport contact, 0.133 per other-professional contact and, 0.246 per rendering contact. We validate these outcomes against literature data on virus genetic sequences for outbreak farms. These estimates can be used to inform further studies on the role that improved biosecurity between contacts and/or contact frequency reduction can play in eliminating between-farm spread of the virus during future epidemics. The findings also highlight the need to; 1) understand the routes underlying the infections without traced contacts and, 2) to review whether the contact-tracing protocol is exhaustive in relation to all the farm's day-to-day activities and practices.     

Modelling studies to estimate the prevalence of foot-and-mouth disease carriers after reactive vaccination

Foot-and-mouth disease (FMD) is a highly contagious and economically significant viral disease of cloven-hoofed animals. Vaccination can be used to help restrict the spread of the infection, but evidence must be provided to show that the infection has been eradicated in order to regain the FMD-free status. While serological tests have been developed, which can identify animals that have been infected regardless of vaccination status, it is vital to know the probable prevalence of herds with FMD carriers and the within-herd prevalence of those carriers in order to design efficient post-epidemic surveillance strategies that establish freedom from disease. Here, we present the results of a study to model the expected prevalence of carriers after application of emergency vaccination and the impact of this on the sensitivity of test systems for their detection. Results showed that the expected prevalence of carrier-containing herds after reactive vaccination is likely to be very low, approximately 0.2%, and there will only be a small number of carriers, most likely one, in the positive herds. Therefore, sensitivity for carrier detection can be optimized by adopting an individual-based testing regime in which all animals in all vaccinated herds are tested and positive animals rather than herds are culled.     

The Effect of the Post 2001 Reforms on FMD Risks of the International Live Animal Trade

The 2001 UK foot and mouth disease (FMD) epidemic marked a change in global FMD management, focusing less on trade isolation than on biosecurity within countries where FMD is endemic. Post 2001 policy calls for the isolation of disease-free zones in FMD-endemic countries, while increasing the opportunities for trade. The impact of the change on disease risk has yet to be tested. In this paper, we estimate an empirical model of disease risk that tests for the impact of trade volumes before and after 2001, controlling for biosecurity measures. In the pre 2001 regime, we find that poor biosecurity was associated with the probability of reporting an outbreak. In the post 2001 regime, the risks changed, with trade being a much greater source of risk. We discuss the trade-off between trade restrictions and biosecurity measures in the management of FMD disease risks.     

Assessment of coastal protection as an ecosystem service in Europe

Mapping and assessment of ecosystem services is essential to provide scientific support to global and EU biodiversity policy. Coastal protection has been mostly analysed in the frame of coastal vulnerability studies or in local, habitat-specific assessments. This paper provides a conceptual and methodological approach to assess coastal protection as an ecosystem service at different spatial–temporal scales, and applies it to the entire EU coastal zone. The assessment of coastal protection incorporates 14 biophysical and socio-economic variables from both terrestrial and marine datasets. Those variables define three indicators: coastal protection capacity, coastal exposure and human demand for protection. A questionnaire filled by coastal researchers helped assign ranks to categorical parameters and weights to the individual variables. The three indicators are then framed into the ecosystem services cascade model to estimate how coastal ecosystems provide protection, in particular describing the service function, flow and benefit. The results are comparative and aim to support integrated land and marine spatial planning. The main drivers of change for the provision of coastal protection come from the widespread anthropogenic pressures in the European coastal zone, for which a short quantitative analysis is provided.     

Demographic structure and pathogen dynamics on the network of livestock movements in Great Britain

Using a novel interpretation of dynamic networks, we analyse the network of livestock movements in Great Britain in order to determine the risk of a large epidemic of foot-and-mouth disease (FMD). This network is exceptionally well characterized, as there are legal requirements that the date, source, destination and number of animals be recorded and held on central databases. We identify a percolation threshold in the structure of the livestock network, indicating that, while there is little possibility of a national epidemic of FMD in winter when the catastrophic 2001 epidemic began, there remains a risk in late summer or early autumn. These predictions are corroborated by a non-parametric simulation in which the movements of livestock in 2003 and 2004 are replayed as they occurred. Despite the risk, we show that the network displays small-world properties which can be exploited to target surveillance and control and drastically reduce this risk.     

Risk of Foot-and-Mouth Disease spread due to sole occupancy authorities and linked cattle holdings

Livestock movements in Great Britain are well recorded, have been extensively analysed with respect to their role in disease spread, and have been used in real time to advise governments on the control of infectious diseases. Typically, livestock holdings are treated as distinct entities that must observe movement standstills upon receipt of livestock, and must report livestock movements. However, there are currently two dispensations that can exempt holdings from either observing standstills or reporting movements, namely the Sole Occupancy Authority (SOA) and Cattle Tracing System (CTS) Links, respectively. In this report we have used a combination of data analyses and computational modelling to investigate the usage and potential impact of such linked holdings on the size of a Foot-and-Mouth Disease (FMD) epidemic. Our analyses show that although SOAs are abundant, their dynamics appear relatively stagnant. The number of CTS Links is also abundant, and increasing rapidly. Although most linked holdings are only involved in a single CTS Link, some holdings are involved in numerous links that can be amalgamated to form "CTS Chains" which can be both large and geographically dispersed. Our model predicts that under a worst case scenario of "one infected - all infected", SOAs do pose a risk of increasing the size (in terms of number of infected holdings) of a FMD epidemic, but this increase is mainly due to intra-SOA infection spread events. Furthermore, although SOAs do increase the geographic spread of an epidemic, this increase is predominantly local. Whereas, CTS Chains pose a risk of increasing both the size and the geographical spread of the disease substantially, under a worse case scenario. Our results highlight the need for further investigations into whether CTS Chains are transmission chains, and also investigations into intra-SOA movements and livestock distributions due to the lack of current data.     

Antimicrobial use in organic and conventional dairy herds

Use of antimicrobials for food-producing animals is a major public concern due to the risk of antimicrobial resistance. Although dairy production has a relatively low usage of antimicrobials, the potential for further reduction should be explored. The objective of the study was to estimate the current differences in antimicrobial use in Danish organic and conventional dairy herds and to describe the differences between them. Based on data from three different sources, 2604 herds (306 organic and 2298 conventional) were identified for the study. These herds had been either organic or conventional for the entire period from 2015 to 2018. Antimicrobial use was calculated as the treatment incidence in Animal Daily Doses (ADDs)/100 animals/day for three age groups: adult cattle, young stock and calves. For adult cattle, the ratio of median treatment incidence between conventional and organic production ranged from 2.8 : 1 to 3.4 : 1, depending on the specific year. For cows, 25% of the organic herds had a higher treatment incidence than the 25% of conventional herds with the lowest treatment incidence. Antimicrobial use for young stock was low and at a similar level in both the organic and conventional production systems. For calves, the median treatment incidence was 1.2 times higher in conventional herds and 1.6 times higher for the 75th percentile. Analyses of treatment incidence in adult cattle showed an overall decrease from 2015 to 2018 in both organic and conventional herds. The decrease was greater for the conventional herds (0.12 ADD/100 animals/day) compared to the organic herds (0.04 ADD/100 animals/day) over the 4-year period. In addition, herd size was an important risk factor for treatment incidence in conventional herds, increasing by 0.07 ADD/100 animals/day per 100 cows, whereas herd size had a minor influence on the treatment incidence in organic herds. The results of this study demonstrate the large variation in antimicrobial use within both organic and conventional herds, suggesting that further reduction is possible. Furthermore, herd size appears to be a risk factor in conventional herds but not in organic herds – an aspect that should be studied in more detail.     

Effects of potential mining activities on migration corridors of Chiru (Pantholops hodgsonii) in the Altun National Nature Reserve,China

The Altun National Nature Reserve (ANNR) on the Qinghai–Tibetan Plateau (QTP) of China plays a key role in protecting the endemic, endangered Chiru (Pantholops hodgsonii). However, increasing mining activities in the ANNR pose a threat its habitats and migration corridors. This study aims to clearly understand potential effects of mining activities on habitats and migration corridors of Chiru. Using a linkage mapper corridor simulation tool in combination with the planned mining zones and roads distribution, we estimated the potential effects of these activities on migration corridors in eight scenarios (I: no mining activities; II: eastern mining zones exploited; III: central zones exploited; IV: western zones exploited; V: western and central zones exploited; VI: eastern and central zones exploited; VII: western and eastern zones exploited; VIII: all zones exploited). The results indicated that locations and length of potential Chiru migration corridors were different in 8 scenarios, thereby influencing the distribution and migration of Chiru in the ANNR; the protection importance value index (NIVI) of each core habitat changed in 8 scenarios. The western and central mining activities (in scenario V) would affect the Chiru migration most strongly, as the total length of all corridors was the longest with a length of 991.1 km and the total number of corridors was 25 which was the highest among the 8 scenarios. In scenario V, all migration corridors were greatly altered and the corridor length sharply increased. Also, the total length (942.8 km) of migration corridor was the second longest in scenario VI, and the third in scenario III. The central mining activities will significantly affect the seasonal migration routes for Chiru. Our results suggested that exploration of the central mining zones should be forbidden and central zones need to be strictly protected. Also, the northwestern region of the ANNR where most of migration corridors are located should also be strictly protected.     

Short- and long-range dispersal of medfly, Ceratitis capitata (Dipt., Tephritidae), and its invasive potential

Abstract:  Data were obtained from mark recapture trials pertaining to the dispersal of medfly, Ceratitis capitata (Dipt., Tephritidae), over both short (10–160 m) and very long distances (0.5–9.5 km) within the surveillance trapping array in Adelaide, Australia. They could be related to previously reported data sets by expressing the capture rates of each set in common terms that corrected for differences in recapture rate resulting from type of trap, season or climate. The mean capture rate at each distance from the point of release in each data set was expressed as a percentage of the real or inferred rate of that set at a distance of 100 m. The resulting distribution of dispersal distances conformed to both an inverse power model and a modified Cauchy model regardless of whether the present and previous data were combined or not. The modified Cauchy model inferred that the median distance flown was extremely short and 90% of flies displaced only 400–700 m despite the fact that a consistent trend in declining catch rates was obtained up to 9.5 km. The spread of invading propagules in quarantined zones in the first generation is likely to be limited by a decline to non-viable density within 1 km or less of the incursion point and the spread of larger infestations could be limited by the longevity of the dispersers. The results also have significance to the ability of surveillance trapping arrays to detect infestations and also to methods of distributing insects for the 'sterile insect technique'.     

Dispersal kernels of the invasive alien western corn rootworm and the effectiveness of buffer zones in eradication programmes in Europe

Europe is attempting to contain or, in some regions, to eradicate the invading and maize destroying western corn rootworm (WCR). Eradication and containment measures include crop rotation and insecticide treatments within different types of buffer zones surrounding new introduction points. However, quantitative estimates of the relationship between the probability of adult dispersal and distance from an introduction point have not been used to determine the width of buffer zones. We address this by fitting dispersal models of the negative exponential and negative power law families in logarithmic and non-logarithmic form to recapture data from nine mark-release-recapture experiments of marked WCR adults from habitats as typically found in the vicinity of airports in southern Hungary in 2003 and 2004. After each release of 4000–6300 marked WCR, recaptures were recorded three times using non-baited yellow sticky traps at 30–305 m from the release point and sex pheromone-baited transparent sticky traps placed at 500–3500 m. Both the negative exponential and negative power law models in non-log form presented the best overall fit to the numbers of recaptured adults (1% recapture rate). The negative exponential model in log form presented the best fit to the data in the tail. The models suggested that half of the dispersing WCR adults travelling along a given bearing will have travelled between 117 and 425 m and 1% of the adults between 775 and 8250 m after 1 day. An individual-based model of dispersal and mortality over a generation of WCR adults indicated that 9.7–45.3% of the adults would escape a focus zone (where maize is only grown once in 3 consecutive years) of 1 km radius and 0.6–21% a safety zone (where maize is only grown once in 2 consecutive years) of 5 km radius and consequently current European Commission (EC) measures are inadequate for the eradication of WCR in Europe. Although buffer zones large enough to allow eradication would be economically unpalatable, an increase of the minimum width of the focus zone from 1 to 5 km and the safety zone from 5 to 50 km would improve the management of local dispersal.     

Evaluation of a contract breeding management program in Ohio dairy herds: test day summary and economic measures

A field study was conducted to assess the impact of a contract breeding program that was offered by a breeding co-operative and featured tail chalking and daily evaluation of cows for insemination by co-operative technicians; dairy employees no longer handled estrous detection and insemination activities. From early 2002 until mid-2004, herd-level test day summary records related to production and reproduction were obtained for 32 herds identified as well-managed client herds of the breeding co-operative. Using analyses that controlled for other predictors and random herd-level effects, average days to first service were less by 13 days (P=0.0037) and estrous detection rate was greater by 12% (P=0.0011) for program than for non-program herds. Although first service conception rate was slightly less and the program herds used 0.34 more services per conception (P=0.1488) than non-program herds, the program herds averaged 16 fewer days before pregnancy (P=0.028). Test day summary information and representative estimates of feed, milk, and semen prices were used in a spreadsheet-based model to estimate a partial budget annuity value for an average cow in each herd on each test day. Value of an average cow from a contract herd did not significantly differ from a non-contract herd, even though the analyses suggested an economic benefit for the program herds; the modeling did not, however, account for costs of the program implementation. Additional analyses did not find any significant associations between technician and on days to first service, first service conception rate, estrous detection rate, services per conception, or days open.     

Estimates for local and movement-based transmission of bovine tuberculosis in British cattle

Both badgers and livestock movements have been implicated in contributing to the ongoing epidemic of bovine tuberculosis (BTB) in British cattle. However, the relative contributions of these and other causes are not well quantified. We used cattle movement data to construct an individual (premises)-based model of BTB spread within Great Britain, accounting for spread due to recorded cattle movements and other causes. Outbreak data for 2004 were best explained by a model attributing 16% of herd infections directly to cattle movements, and a further 9% unexplained, potentially including spread from unrecorded movements. The best-fit model assumed low levels of cattle-to-cattle transmission. The remaining 75% of infection was attributed to local effects within specific high-risk areas. Annual and biennial testing is mandatory for herds deemed at high risk of infection, as is pre-movement testing from such herds. The herds identified as high risk in 2004 by our model are in broad agreement with those officially designated as such at that time. However, border areas at the edges of high-risk regions are different, suggesting possible areas that should be targeted to prevent further geographical spread of disease. With these areas expanding rapidly over the last decade, their close surveillance is important to both identify infected herds qucikly, and limit their further growth.     

Cross‐decades stability of an avian hybrid zone

Hybrid zones are particularly valuable for understanding the evolution of partial reproductive isolation between differentiated populations. An increasing number of hybrid zones have been inferred to move over time, but in most such cases zone movement has not been tested with long‐term genomic data. The hybrid zone between Townsend's Warblers (Setophaga townsendi) and Hermit Warblers (S. occidentalis) in the Washington Cascades was previously inferred to be moving from northern S. townsendi southwards towards S. occidentalis, based on plumage and behavioural patterns as well as a 2000‐km genetic wake of hermit mitochondrial DNA (mtDNA) in coastal Townsend's Warblers. We directly tested whether hybrid zone position has changed over 2–3 decades by tracking plumage, mtDNA and nuclear genomic variation across the hybrid zone over two sampling periods (1987–94 and 2015–16). Surprisingly, there was no significant movement in genomic or plumage cline centres between the two time periods. Plumage cline widths were narrower than expected by neutral diffusion, consistent with a ‘tension zone’ model, in which selection against hybrids is balanced by movement of parental forms into the zone. Our results indicate that this hybrid zone is either stable in its location or moving at a rate that is not detectable over 2–3 decades. Despite considerable gene flow, the stable clines in multiple phenotypic and genotypic characters over decades suggest evolutionary stability of this young pair of sister species, allowing divergence to continue. We propose a novel biogeographic scenario to explain these patterns: rather than the hybrid zone having moved thousands of kilometres to its current position, inland Townsend's met coastal Hermit Warbler populations along a broad front of the British Columbia and Alaska coast and hybridization led to replacement of the Hermit Warbler plumage with Townsend's Warbler plumage patterns along this coastline. Hence, hybrid zones along British Columbia and Alaska moved only a short distance from the inland to the coast, whereas the Hermit Warbler phenotype appears stable in Washington and further south. This case provides an example of the complex biogeographic processes that have led to the distribution of current phenotypes within and among closely related species.     

Integrating phylogeography and paleoecology to investigate the origin and dynamics of hybrid zones: insights from two widespread North American firs

Secondary contact between closely related taxa routinely occurs during postglacial migrations. After initial contact, the location of hybrid zones may shift geographically or remain spatially stable over time in response to various selective pressures or neutral processes. Studying the extent and direction of introgression using markers having contrasted levels of gene flow can help unravel the historical dynamics of hybrid zones. Thanks to their contrasted maternal and paternal inheritance, resulting in different levels of gene flow for mitochondrial and chloroplast DNA (mtDNA and cpDNA), the Pinaceae stand out as a relevant biological model for this purpose. The objective of the study was to assess whether the hybrid zone between Abies balsamea and Abies lasiocarpa (two largely distributed Pinaceae) has moved or remained stable over time by analysing the distribution of cytoplasmic DNA variation as well as published palaeobotanical data. Interspecific gene flow was higher for cpDNA than mtDNA markers; hence, the geographic distribution of mitotypes was more congruent with species distributions than chlorotypes. This genetic signature was contrary to expectations under a moving hybrid zone scenario, as well as empirical observations in other conifers. Genetic evidence for this rare instance of stable hybrid zone was corroborated by the colonization chronology derived from published fossil data, indicating that the two fir species initially came into contact in the area corresponding to the current sympatric zone 11 kyr ago. While an explanatory analysis suggested the putative influence of various environmental factors on the relative abundance of cytoplasmic genome combinations, further research appears necessary to assess the role of both demographic history and selective factors in driving the dynamics of hybrid zones.     

Marine no-take zone rapidly benefits endangered penguin

No-take zones may protect populations of targeted marine species and restore the integrity of marine ecosystems, but it is unclear whether they benefit top predators that rely on mobile pelagic fishes. In South Africa, foraging effort of breeding African penguins decreased by 30 per cent within three months of closing a 20 km zone to the competing purse-seine fisheries around their largest colony. After the fishing ban, most of the penguins from this island had shifted their feeding effort inside the closed area. Birds breeding at another colony situated 50 km away, whose fishing grounds remained open to fishing, increased their foraging effort during the same period. This demonstrates the immediate benefit of a relatively small no-take zone for a marine top predator relying on pelagic prey. Selecting such small protected areas may be an important first conservation step, minimizing stakeholder conflicts and easing compliance, while ensuring benefit for the ecosystems within these habitats.     

Management of disease control and epidemics in AI in Denmark

The author's presentation constituted a survey of the control of contagious diseases at Danish AI stations. The control is performed in accordance with EU regulations and requires documented freedom from Aujeszky's disease, Classical Swine Fever and Brucellosis (based on blood testing) before transfer to quarantine sections and to AI stations. The Danish regulations regarding Porcine Reproductive and Respiratory Syndrome (PRRS) are described for both sero-positive and sero-negative stations. At some stations, all boars are vaccinated against both American PRRS (Ingelvac PRRS vet.) and European PRRS (Progressis vet.), and are subsequently sero-positive for PRRS. The period from vaccination until the time that semen can be used is described, and the reason for its length is explained. Furthermore, the process applied when distinguishing Yersinia from Brucellosis reactions is described. The purpose of this control is to prevent Yersinia-positive herds that supply boars from compromising supplies from Yersinia-negative herds through cross-reactions with Brucellosis. The vaccinations required before transfer to isolation and AI stations (Glasser's disease, pleuropneumonia caused by Actinobacillus pleuropneumoniae, erysipelas and PPV) as well as vaccinations done regularly at the AI stations (erysipelas and PPV) are described. Finally, a survey is presented of other diseases found at Danish AI stations (primarily pneumonia and leg problems) and their medical treatment.     

Disease contact tracing in random and clustered networks

The efficacy of contact tracing, be it between individuals (e.g. sexually transmitted diseases or severe acute respiratory syndrome) or between groups of individuals (e.g. foot-and-mouth disease; FMD), is difficult to evaluate without precise knowledge of the underlying contact structure; i.e. who is connected to whom? Motivated by the 2001 FMD epidemic in the UK, we determine, using stochastic simulations and deterministic 'moment closure' models of disease transmission on networks of premises (nodes), network and disease properties that are important for contact tracing efficiency. For random networks with a high average number of connections per node, little clustering of connections and short latency periods, contact tracing is typically ineffective. In this case, isolation of infected nodes is the dominant factor in determining disease epidemic size and duration. If the latency period is longer and the average number of connections per node small, or if the network is spatially clustered, then the contact tracing performs better and an overall reduction in the proportion of nodes that are removed during an epidemic is observed.     

Parallels,differences and lessons: a comparison of the management of foot-and-mouth disease and COVID-19 using UK 2001/2020 as points of reference

Foot-and-mouth disease (FMD) is an extremely infectious viral infection of cloven-hoofed animals which is highly challenging to control and can give rise to national animal health crises, especially if there is a lack of pre-existing immunity due to the emergence of new strains or following incursions into disease-free regions. The 2001 FMD epidemic in the UK was on a scale that initially overwhelmed the national veterinary services and was eventually controlled by livestock lockdown and slaughter on an unprecedented scale. In 2020, the rapid emergence of COVID-19 has led to a human pandemic unparalleled in living memory. The enormous logistics of multi-agency control efforts for COVID-19 are reminiscent of the 2001 FMD epidemic in the UK, as are the use of movement restrictions, not normally a feature of human disease control. The UK experience is internationally relevant as few countries have experienced national epidemic crises for both diseases. In this review, we reflect on the experiences and lessons learnt from UK and international responses to FMD and COVID-19 with respect to their management, including the challenge of preclinical viral transmission, threat awareness, early detection, different interpretations of scientific information, lockdown, biosecurity behaviour change, shortage of testing capacity and the choices for eradication versus living with infection. A major lesson is that the similarity of issues and critical resources needed to manage large-scale outbreaks demonstrates that there is benefit to a ‘One Health’ approach to preparedness, with potential for greater cooperation in planning and the consideration of shared critical resources.     

青藏高原土地利用变化对生态系统服务价值影响的多情景模拟

青藏高原具有突出的生态服务价值,但气候多变、环境脆弱的基底,使其易受人类活动的干扰.本文基于土地利用数据和改进当量因子法,定量分析1992-2015年青藏高原土地利用变化对生态系统服务价值时空分布影响,并结合CA-Markov模型模拟探讨自然发展和生态保护情景下土地利用与生态系统服务价值的相互关系.结果 表明:1992...