Risk Of Brucellosis Transmission Research Articles

Identification and mapping of objects targeted for surveillance and their role as risk factors for brucellosis in livestock farms in Kazakhstan.

Objects for Targeted Surveillance (OTS) are infrastructure entities that can be considered as focal points and conduits for transmitting infectious animal diseases, necessitating ongoing epidemiological surveillance. These entities encompass slaughterhouses, meat processing plants, animal markets, burial sites, veterinary laboratories, etc. Currently, in Kazakhstan, a funded research project is underway to establish a Geographic Information System (GIS) database of OTSs and investigate their role in the emergence and dissemination of infectious livestock diseases. This initial investigation examined the correlation between brucellosis outbreaks in cattle and small ruminant farms in the southeastern region of Kazakhstan and the presence of OTSs categorized as "slaughterhouses," "cattle markets," and "meat processing plants. The study area (namely Qyzylorda, Turkestan, Zhambyl, Almaty, Zhetysu, Abay and East Kazakhstan oblasts), characterized by the highest livestock density in the country, covers 335 slaughterhouses (with varying levels of biosecurity), 45 livestock markets and 15 meat processing plants. Between 2020 and 2023, 338 cases of brucellosis were reported from livestock farms in this region. The findings of the regression model reveal a statistically significant (p<0.05) positive association between the incidence of brucellosis cases and the number of OTSs in the region. Conversely, meat processing plants and livestock markets did not exhibit a significant influence on the prevalence of brucellosis cases. These results corroborate the hypothesis of an elevated risk of brucellosis transmission in regions with slaughterhouses, likely attributable to increased animal movements within and across regions, interactions with vehicles and contact with slaughterhouse staff. These outcomes mark a pivotal advancement in the national agricultural development agenda. The research will be extended to encompass the entire country, compiling a comprehensive OTS database.

Global dynamics of a reaction-diffusion brucellosis model with spatiotemporal heterogeneity and nonlocal delay

The increase of animal transportation and livestock lead to repeated outbreaks of brucellosis, and its transmission process is extremely complex. According to the clinical symptoms and infectious differences of the diseased sheep, it is further divided into acute infection and chronic infection, and a reaction-diffusion SLICB (susceptible-latent-acute infected-chronic infected-brucella) model with seasonality, spatial heterogeneity and nonlocal delay is proposed to understand the transmission law of brucellosis and analyze its transmission risk. Based on the basic reproduction number of the model, the final development trend of brucellosis transmission among sheep is analyzed by persistence theory. The of the model is numerically calculated by the generalized power method, and simulation analysis shows that: (i) extending the latent period and increasing the random walk rate of infected sheep can effectively prevent brucellosis from developing into an endemic disease; (ii) the greater the density of acute infections, the higher the risk of brucellosis transmission, and the density of infected sheep and the time to reach the stable state will have a large deviation if only consider acute or chronic sheep; (iii) reaching the peak time will be delayed if the peak time of sheep birth is delayed. These results can provide some suggestions for the control of brucellosis.

Seroprevalence of Bovine Brucellosis in Selected Sites of Central Highland of Ethiopia.

Brucellosis is a contagious, economically significant bacterial disease that affects animals worldwide and is one of the most neglected zoonotic diseases in the world. The disease poses a barrier to the trade of animals and animal products, represents a public health hazard, and is an impediment to free animal movement. A cross-sectional study was carried out from December 2019 to May 2020 in order to determine seroprevalence and identify potential risk factors for brucellosis in dairy cows in the Central Highlands of Ethiopia with recent cases of abortion. Purposive sampling was carried out on the farms and kebeles in question to screen for recent cases of abortion in dairy cows. For the purpose of performing serological testing, 352 blood samples from dairy cattle were obtained. The Rose Bengal Plate test was used to initially screen the serum samples, and the Complement Fixation test was utilized as a confirmatory test. Using combined RBPT and CFT tests, the overall seroprevalence of bovine brucellosis was 0.6% (95% CI: 0.16-2.09). Retained fetal membrane (OR = 32.74, p = 0.006), market-based stock replacement (OR = 16.55, p = 0.002), breeding method (OR = 7.58, p = 0.027), and late stage of abortion (OR = 14.74, p = 0.0002) are all significantly associated risk factors. The present seroprevalence study revealed that brucellosis is prevalent at a lower rate among dairy cattle in the study areas. However, there is a possible risk of brucellosis transmission in dairy cattle and the exposed human population in research locations because no control measures were put in place there. Implementing a test and slaughter method with compensation for farmers is advised due to the low prevalence of bovine brucellosis in government-owned and small-holder farms.

Scavengers reduce potential brucellosis transmission risk in the Greater Yellowstone Ecosystem

AbstractScavengers likely play an important role in ecosystem energy flow as well as disease transmission, but whether they facilitate or reduce disease transmission is often unknown. In the Greater Yellowstone Ecosystem, scavengers are likely to reduce the transmission and subsequent spread of brucellosis within and between livestock and elk by consuming infectious abortion materials, thereby removing the infectious agent from the landscape. We used remote cameras to monitor the time to removal of simulated abortion materials by scavengers at 264 sites from February to June in 2017 and 2018 and assessed the effects of habitat and land management on time to removal in southwest Montana. Time to removal of fetal materials decreased in grassland habitats ( = 2.9 d, credible interval = [1.8–5.0]) in comparison to sagebrush habitats ( = 5.4 d [3.4–9.3]) and forest habitats ( = 5.2 d [3.3–9.0]). In addition, there was an 88% probability that time to removal of fetal materials was slower at sites where mammalian scavengers were actively reduced ( = 6.5 d [3.4–12.8]) compared to sites with no scavenger reduction ( = 4.1 d [2.3–7.8]). Our research indicates that if elk and livestock are commingling during the brucellosis risk period, there is a 90% probability that abortion materials will be removed by scavengers within 16 d across all sites. Coyotes, red foxes, golden and bald eagles, Corvus spp., and turkey vultures were the dominant scavengers, removing 90% of the fetal materials. Actions to maintain the breadth and diversity of scavengers on the landscape are potential management options that could reduce disease transmission risk to livestock in a system where the wildlife reservoir is difficult to address.

Elk migration influences the risk of disease spillover in the Greater Yellowstone Ecosystem.

Wildlife migrations provide important ecosystem services, but they are declining. Within the Greater Yellowstone Ecosystem (GYE), some elk Cervus canadensis herds are losing migratory tendencies, which may increase spatiotemporal overlap between elk and livestock (domestic bison Bison bison and cattle Bos taurus), potentially exacerbating pathogen transmission risk.We combined disease, movement, demographic and environmental data from eight elk herds in the GYE to examine the differential risk of brucellosis transmission (through aborted foetuses) from migrant and resident elk to livestock.For both migrants and residents, we found that transmission risk from elk to livestock occurred almost exclusively on private ranchlands as opposed to state or federal grazing allotments. Weather variability affected the estimated distribution of spillover risk from migrant elk to livestock, with a 7%–12% increase in migrant abortions on private ranchlands during years with heavier snowfall. In contrast, weather variability did not affect spillover risk from resident elk.Migrant elk were responsible for the majority (68%) of disease spillover risk to livestock because they occurred in greater numbers than resident elk. On a per‐capita basis, however, our analyses suggested that resident elk disproportionately contributed to spillover risk. In five of seven herds, we estimated that the per‐capita spillover risk was greater from residents than from migrants. Averaged across herds, an individual resident elk was 23% more likely than an individual migrant elk to abort on private ranchlands.Our results demonstrate links between migration behaviour, spillover risk and environmental variability, and highlight the utility of integrating models of pathogen transmission and host movement to generate new insights about the role of migration in disease spillover risk. Furthermore, they add to the accumulating body of evidence across taxa that suggests that migrants and residents should be considered separately during investigations of wildlife disease ecology. Finally, our findings have applied implications for elk and brucellosis in the GYE. They suggest that managers should prioritize actions that maintain spatial separation of elk and livestock on private ranchlands during years when snowpack persists into the risk period.

A multifaceted risk model of brucellosis at the human-animal interface in Egypt.

Brucellosis is a highly contagious zoonosis affecting humans and a wide range of domesticated and wild animal species. An important element for effective disease containment is to improve knowledge, attitudes and practices (KAP) of afflicted communities. This study aimed to assess the KAP related to brucellosis at the human-animal interface in an endemic area of Egypt and to identify the risk factors for human infection. A matched case-control study was conducted at the central fever hospitals located in six governorates in northern Egypt. Face-to-face interviews with cases and controls were conducted using a structured questionnaire. In total, 40.7% of the participants owned farm animals in their households. The overall mean practice score regarding animal husbandry, processing and consumption of milk and dairy products were significantly lower among cases compared with controls (-12.7±18.1 vs. 0.68±14.2, respectively; p<.001). Perceived barriers for notification of animal infection/abortion were predominate among cases and positively correlated with participants' education. The predictors of having brucellosis infection were consumption of unpasteurized milk or raw dairy products and practicing animal husbandry. Applying protective measures against infection significantly reduced its risk. A model predicting risk factors for brucellosis among those who own animal showed that frequent abortions per animal increased the chance for brucellosis infection among human cases by 50-fold (95% CI: 8.8-276.9), whereas the use of protective measures in animal care reduced the odds (OR=0.11 [95% CI: 0.03-0.45]). In conclusion, consumption of unprocessed dairy products was equally important as contact with infected/aborted animals as major risk factors for Brucella spp. infection among humans in Egypt. There is poor knowledge, negative attitudes and risky behaviours among villagers which can perpetuate the risk of brucellosis transmission at the human-animal interface. This supports the need for integrating health education into the national brucellosis control programme.

Spatio-Temporal network analysis and modeling at the wildlife-livestock interface to evaluate the risk of Brucellosis transmission.

Spatio-Temporal network analysis and modeling at the wildlife-livestock interface to evaluate the risk of Brucellosis transmission.

Linking spring phenology with mechanistic models of host movement to predict disease transmission risk

Abstract Disease models typically focus on temporal dynamics of infection, while often neglecting environmental processes that determine host movement. In many systems, however, temporal disease dynamics may be slow compared to the scale at which environmental conditions alter host space‐use and accelerate disease transmission. Using a mechanistic movement modelling approach, we made space‐use predictions of a mobile host (elk [Cervus Canadensis] carrying the bacterial disease brucellosis) under environmental conditions that change daily and annually (e.g., plant phenology, snow depth), and we used these predictions to infer how spring phenology influences the risk of brucellosis transmission from elk (through aborted foetuses) to livestock in the Greater Yellowstone Ecosystem. Using data from 288 female elk monitored with GPS collars, we fit step selection functions (SSFs) during the spring abortion season and then implemented a master equation approach to translate SSFs into predictions of daily elk distribution for five plausible winter weather scenarios (from a heavy snow, to an extreme winter drought year). We predicted abortion events by combining elk distributions with empirical estimates of daily abortion rates, spatially varying elk seroprevelance and elk population counts. Our results reveal strong spatial variation in disease transmission risk at daily and annual scales that is strongly governed by variation in host movement in response to spring phenology. For example, in comparison with an average snow year, years with early snowmelt are predicted to have 64% of the abortions occurring on feedgrounds shift to occurring on mainly public lands, and to a lesser extent on private lands. Synthesis and applications. Linking mechanistic models of host movement with disease dynamics leads to a novel bridge between movement and disease ecology. Our analysis framework offers new avenues for predicting disease spread, while providing managers tools to proactively mitigate risks posed by mobile disease hosts. More broadly, we demonstrate how mechanistic movement models can provide predictions of ecological conditions that are consistent with climate change but may be more extreme than has been observed historically.

Unintended Consequences of Bovine Brucellosis Management on Demand for Elk Hunting in Northwestern Wyoming

Management strategies proposed to mitigate the risk of brucellosis transmission between elk and cattle (e.g., test-and-slaughter of all elk, elimination of feedgrounds, use of contraceptives) could result in a substantial decrease in elk (Cervus elaphus nelsoni) populations. These strategies could impact hunting and outfi tting industries through reduced regional elk populations. Loss of hunters, particularly nonresidents, could result in economic losses for the state and hinder elk management. We estimated 2 empirical models using panel data from multiple hunt areas to determine effects of elk population changes on demand for elk hunting licenses in northwest Wyoming. First, we used a fi xed-effects logit model to estimate elk hunter success by hunt area as a function of elk density and other characteristics. Second, we estimated demand for elk licenses as a function of license and hunt area characteristics, including hunter success rates and elk populations. With the resulting equation system, we predicted the effects of reduced elk populations on hunter success and elk license demand. Elk population positively affects hunter success and license demand. On average, model results predict that each 10% reduction in elk population would cause a 3.5% decrease in resident elk hunting applicants and a 0.4 to 1.4% decrease in nonresident applicants. In the 7 elk-herd units affected by feedground management, a 50% decrease in elk population could decrease annual license revenues by $83,000 and annual regional expenditures associated with elk hunting by $520,000. These costs should be weighed against potential benefi ts of brucellosis management, including reduced feedground management costs and reduced costs to cattle producers of brucellosis prevention activities.

Risk assessment and management of brucellosis in the southern greater Yellowstone area (I): A citizen-science based risk model for bovine brucellosis transmission from elk to cattle

Livestock producers and state wildlife agencies have used multiple management strategies to control bovine brucellosis in the Greater Yellowstone Area (GYA). However, spillover from elk to domestic bison and cattle herds continues to occur. Although knowledge is increasing about the location and behavior of elk in the SGYA, predicting spatiotemporal overlap between elk and cattle requires locations of livestock operations and observations of elk contact by producers. We queried all producers in a three-county area using a questionnaire designed to determine location of cattle and whether producers saw elk comingle with their animals. This information was used to parameterize a spatially-explicit risk model to estimate the number of elk expected to overlap with cattle during the brucellosis transmission risk period. Elk-cattle overlap was predicted in areas further from roads and forest boundaries in areas with wolf activity, with higher slopes, lower hunter densities, and where the cost-distance to feedgrounds was very low or very high. The model was used to estimate the expected number of years until a cattle reactor will be detected, under alternative management strategies. The model predicted cattle cases every 4.28 years in the highest risk herd unit, a higher prediction than the one case in 26 years we have observed. This difference likely indicates that ongoing management strategies are at least somewhat effective in preventing potential elk-cattle brucellosis transmission in these areas.Using this model, we can infer the expected effectiveness of various management strategies for reducing the risk of brucellosis spillover from elk to cattle.

Effects of elk density on elk aggregation patterns and exposure to brucellosis

Increasing elk (Cervus elaphus nelsoni) populations across the West in response to increased demand for recreational and hunting opportunities may have negative, unintended consequences for disease transmission risk. Historically, free-ranging elk populations were not thought to sustain brucellosis (Brucella abortus), but recent studies suggest increasing elk densities may result in free-ranging elk serving as maintenance hosts for the disease. We evaluated spatial variation in elk density, group sizes, and adult female brucellosis seroprevalence in 39 elk management districts in the Greater Yellowstone Ecosystem using a Bayesian approach. We used modeled relationships to estimate the effects of reducing elk density by 10–90% on grouping patterns and seroprevalence rates. Reducing the density of the 3 highest density elk herds by 10%, 50%, and 90% was predicted to result in a 9%, 39%, and 59% decrease in mean group size, whereas reducing the density of the 3 lowest density elk herds was predicted to result in only a 0%, 0.7%, and 1.3% decrease in mean group size. We estimated seroprevalence rates of 0.01–0.27 across management districts, and seroprevalence increased as elk density increased. For the 7 of 39 management districts with >10% estimated seroprevalence, 10%, 50%, and 90% reductions in elk density resulted in predicted mean seroprevalence reductions of 2%, 7%, and 9%, respectively. For the 14 management districts with ≤1% estimated seroprevalence, 10%, 50%, and 90% reductions in elk density resulted in no measurable change in predicted mean seroprevalence. Our results suggest that elk density has an important effect on elk group sizes, which may influence the risk of brucellosis transmission and resultant exposure rates. Manipulating elk density may in turn affect brucellosis seroprevalence rates. However, debate among the diverse stakeholders involved in elk management on the effectiveness of reducing density, group sizes, and brucellosis exposure rates in elk, relative to other interests and objectives, is necessary prior to manipulation of elk density for this purpose. © 2015 The Wildlife Society.

Seroprevalence and potential risk factors for Brucella spp. infection in traditional cattle, sheep and goats reared in urban, periurban and rural areas of Niger.

IntroductionIn Niamey, Niger, interactions within the interface between animals, humans and the environment induce a potential risk of brucellosis transmission between animals and from animals to humans. Currently, little is known about the transmission of Brucella in this context.Results5,192 animals from 681 herds were included in the study. Serum samples and hygroma fluids were collected. A household survey enabled to identify the risk factors for transmission of brucellosis. The true adjusted herd-level prevalence of brucellosis ranged between 11.2% and 17.2% and the true adjusted animal-population level prevalence was 1.3% (95% CI: 0.9–1.8%) based on indirect ELISA test for Brucella antibodies. Animals aged of 1–4 years were found to be more susceptible than animals less than 1 year old (Odds ratio [OR] of 2.7; 95% CI: 1.43–5.28). For cattle, the odds of brucellosis seropositivity were higher in rural compared to the periurban areas (OR of 2.8; 95% CI: 1.48–5.17) whereas for small ruminants the risk of seropositivity appeared to be higher in urban compared to periurban areas (OR of 5.5; 95% CI: 1.48–20.38). At herd level, the risk of transmission was increased by transhumance (OR of 5.4; 95% CI: 2.84–10.41), the occurrence of abortions (OR of 3.0; 95% CI: 1.40–6.41), and for herds having more than 50 animals (OR of 11.0; 95% CI: 3.75–32.46). Brucella abortus biovar 3 was isolated from the hygromas.Conclusionbrucellosis in Niger is a serious problem among cattle especially in the rural areas around Niamey and among sheep in the urban areas of Niamey. The seroprevalence varies across strata and animal species with important risk factors including herd size, abortion and transhumance at herd level and age at animal population level. For effective control of brucellosis, an integrated approach seems appropriate involving all stakeholders working in public and animal health.

Integrating ecology with management to control wildlife brucellosis

Bison (Bison bison) and elk (Cervus elaphus) in the greater Yellowstone ecosystem have long been infected with Brucella abortus. The continued culling of large numbers of Yellowstone bison to reduce the risk of brucellosis transmission to cattle could negatively affect long-term conservation. A desirable management objective is to reduce the level of B. abortus infection while conserving wildlife populations. Identifying the ecological factors that influence immune suppression and vulnerabilityto infection will help initiate effective control measures. Seasonal food restriction during pregnancy has the potential to limit resources available for immune defence and may be an important factor sustaining brucellosis in wild ungulate populations. Consequently, effective management practices will need to include a diverse range of integrated methods, which include maintaining separation of livestock and wildlife, managing habitat to reduce brucellosis transmission, and reducing disease prevalence in wildlife. The long-term success of these management practices will depend on sound science and support of the stakeholders involved.

Estimating probabilities of active brucellosis infection in Yellowstone bison through quantitative serology and tissue culture

Summary1. Disease management along the boundaries of wildlife reserves is a growing conservation problem worldwide, as infected wildlife can migrate outside protected areas and pose a threat to livestock and human health. The bison Bison bison population in Yellowstone National Park has long been infected with Brucella abortus, but culling of Yellowstone bison to prevent transmission to cattle has been ineffective at reducing brucellosis infection. This management strategy is negatively affecting long‐term bison conservation because of difficulties in diagnosing actively infected animals.2. We integrated age‐specific serology and B. abortus culture results from slaughtered Yellowstone bison to estimate probabilities of active brucellosis infection using a Bayesian framework. Infection probabilities were associated with age in young bison (0–5 years old) and with elevated antibody levels in older bison (&gt;5 years old). Our results indicate that Yellowstone bison acquire B. abortus infection early in life but typically recover as they grow older.3. A tool was developed to allow bison management to better reflect the probability that particular animals are infective, with the aim of conserving Yellowstone bison while reducing the risk of brucellosis transmission to cattle. Combining selective removal of infectious bison with additional management practices, such as vaccination, has the potential to advance an effective brucellosis reduction programme.4. Synthesis and applications. We conclude that active B. abortus infection in Yellowstone bison is age dependent, which allows true infection probabilities to be estimated based on age and quantitative diagnostic tests. These findings have important application to disease management worldwide where accurate diagnostic tests for wildlife are unavailable. Estimation of true infection probabilities can replace culling practices that conflict with wildlife conservation. The ability to identify infective individuals can improve management practices that support conservation, particularly when human health is at risk or endangered wildlife species are involved.

Elk distribution and spatial overlap with livestock during the brucellosis transmission risk period

Summary 1. The presence of Brucella abortus within free‐ranging wildlife populations is an important conservation and management issue because of the risk of brucellosis transmission between wildlife and livestock. Predicting wildlife distributions is necessary to forecast wildlife and livestock spatial overlap and the potential for brucellosis transmission. 2. We used Global Positioning System data collected from telemetry‐collared female elk Cervus elaphus to develop resource selection function (RSF) models during the brucellosis transmission risk period (the abortion and calving periods). We validated extrapolation of predictive models at two nearby elk ranges within the Greater Yellowstone Ecosystem. Additionally, we integrated extrapolated RSF maps and domestic livestock distributions to estimate the relative probability of elk and livestock commingling during the brucellosis transmission risk period. 3. The top‐ranked model predicted that areas selected by elk had a lower probability of wolf Canis lupus occupancy, were privately owned and south facing, and had steeper slopes, lower road densities and higher Normalized Difference Vegetation Index (NDVI). Elk selected forests and shrublands over grasslands; however, the strength of selection decreased as snowpack increased. Elk selection for privately owned lands may lead to spatial overlap with livestock and increase the risk of elk and livestock intermingling. Furthermore, if both elk and livestock concentrate in areas of higher NDVI, increased spatial overlap may occur in these areas. 4. Predictive accuracy was highest in the study area where the model was developed. When compared to the model development area, predictive accuracy of extrapolated RSF maps was similar or better in one of the elk ranges and lower in the other elk range. 5. Synthesis and applications. Extrapolated RSF and spatial overlap maps can provide a foundation for identifying the highest risk areas of elk and livestock spatial overlap during the brucellosis transmission risk period. However, the predictive accuracy of the models is limited when applied to different areas. Site‐specific models of spatial overlap would therefore be needed to provide the most accurate estimates of elk and livestock spatial overlap during the transmission risk period. The degree to which spatial overlap may lead to actual transmission risk needs to be investigated as this is not yet known and could have important implications for managing transmission risk.

Timing of parturition events in Yellowstone bison Bison bison: implications for bison conservation and brucellosis transmission risk to cattle

AbstractYellowstone bison Bison bison are chronically infected with brucellosis (caused by the bacterium Brucella abortus), which raises concerns about possible transmission to cattle when they migrate to winter ranges outside the Yellowstone National Park. We monitored bison from April to mid‐June during 2004‐2007 to estimate the timing and location of parturition events that may shed tissues infected by B. abortus. Observed abortions (N = 29) occurred from January through 19 May, while peak calving (80% of births) occurred from 25 April to 26 May, and calving was finished by 5 June. Observed parturition events (N = 115) occurred in the Park and on the Horse Butte peninsula in Montana, USA, where cattle were not present at any time of the year. Allowing bison to occupy public lands outside the Park where cattle are never present (e.g. Horse Butte peninsula) until most bison calving is completed (late May or early June) is not expected to significantly increase the risk of brucellosis transmission from bison to cattle because: 1) bison parturition is essentially completed weeks before cattle occupy nearby ranges, 2) female bison meticulously consume birthing tissues, 3) ultraviolet light and heat degrade B. abortus on tissues, vegetation and soil, 4) scavengers remove fetuses and remaining birth tissues and 5) management maintains separation between bison and cattle on nearby ranges. Allowing bison to occupy public lands outside the Park through their calving season will help conserve bison migratory behaviour and reduce stress on pregnant females and their newborn calves, while still minimizing the risk of brucellosis transmission to cattle.

Spatio-temporal overlap between Yellowstone bison and elk - implications of wolf restoration and other factors for brucellosis transmission risk

1. In the Greater Yellowstone Ecosystem, bison Bison bison and elk Cervus canadensis nelsoni act as hosts for Brucella abortus. The presence of B. abortus within wildlife populations is an important conservation issue because of the risk of brucellosis transmission from wildlife to cattle. 2. We investigated conditions facilitating contact between bison (40–60% seroprevalence) and elk on a shared winter range in the Madison headwaters area of Yellowstone National Park. We evaluated the effects of snow pack, season, elk and bison population sizes, and wolf Canis lupus predation risk on the degree of spatial overlap between bison and elk from 1991 to 2006. 3. Sixty-eight per cent of 10 093 independent elk observations occurred within the known bison wintering range, 29% occurred within the distribution of bison within the winter range at the time of sampling and 14% occurred within 100 m of bison. Spatial overlap between bison and elk measured across these three spatial scales increased with week of the season, snow pack, and on days when wolves were within the same drainage area as elk, but decreased with cumulative levels of wolf predation risk. 4. Wolves contributed to immediate, short-term responses by elk that increased spatial overlap with bison, but longer-term responses to wolves resulted in elk distributions that reduced spatial overlap with bison. Spatial overlap increased through the winter and peaked when late-term abortion events and parturition occurred for bison. 5. Synthesis and applications. Despite this high level of association, elk exposure to B. abortus in the Madison headwaters (2–4%) was similar to those in free-ranging elk populations that do not intermingle with bison (1–3%), suggesting that B. abortus transmission from bison-to-elk under natural conditions is rare. Our results suggest that risk-driven elk behavioural responses to wolves are unlikely to have important disease implications. Management of brucellosis in greater yellow stone ecosystem elk populations should focus on reducing elk-to-elk transmission risk and, wherever possible, curtailing practices that increase elk density and group sizes during the potential abortion period.

Editor's choice: Where the buffalo roam – bison and brucellosis in Yellowstone

Kilpatrick, A.M., Gillin, C.M. & Daszak, P. (2009) Wildlife–livestock conflict: the risk of pathogen transmission from bison to cattle outside Yellowstone National Park. Journal of Applied Ecology, 46, 476–485. An enduring symbol of the American West, great migratory herds of bison Bison bison once roamed the Great Plains in their millions (Berger & Cunningham 1994). Sadly, this wildlife spectacle is no more, as in parallel with population declines and extirpation in other migratory ungulates (Bolger et al. 2008; Harris et al. 2009), bison are now restricted to a number of small remnant populations. The causes of population decline in bison and other migrants are well known – hunting, habitat loss, fencing – and their need for space makes the conservation of these wide ranging species a major challenge (Berger 2004; Thirgood et al. 2004). The only free-ranging herd of bison remaining in the United States is found in the Greater Yellowstone Ecosystem of Montana, Wyoming and Idaho. At the start of the 20th century, this population had been reduced to 23 individuals, but with protection it has increased to nearly 5000. Bison spend most of the year at higher altitudes in the Yellowstone National Park but during severe winters they graze at lower elevations outside the park. Here they come into conflict with cattle ranching because of the risk of transmission of brucellosis from bison to cattle. Brucellosis is a bacterial disease that causes weight loss, abortion and reduced milk yields in cattle. The maintenance of brucellosis-free status in cattle is economically important to the livestock industry, and as a result, culling bison is part of the Government interagency disease control strategy (Clarke et al. 2005). The conservation success of Yellowstone's bison indirectly led to the culling of 1600 bison during the 2007/08 winter. For this issue's Editor's Choice selection, Kilpatrick et al. (2009) develop a quantitative risk assessment integrating both ecological and epidemiological data to assess the spatio-temporal risk of transmission of brucellosis from bison to cattle. The model demonstrates that the risk of transmission is highly variable in space, time and frequency and can be predicted by climatic conditions and the abundance of bison. Critically, the model suggests that the risk of brucellosis transmission is very low in most years and is periodically high only in certain localized areas around the park. The authors suggest alternative management strategies, such as financially compensating ranchers for grazing rights in localized areas, would be more cost-effective than the current policy of culling bison to control population size. Another management proposal is to the consider the section of the Greater Yellowstone Ecosystem which occurs in Montana as a separate zone from the rest of the state in terms of brucellosis infection status and provide yearly testing of cattle in that zone. This would cost a fraction of the $2.5 million that the current management strategies cost per year. Similarly, compensating ranchers for the financial value of all the cattle that graze in the affected areas around the park would cost about half the current yearly amount. The results of Kilpatrick et al.'s study have generated considerable interest from scientists, managers and the general public – particularly in the United States. In the month since the paper was published online it has been picked up in the mainstream media more than 100 times. Perhaps this is a reflection of the iconic status of the bison in American popular culture – but it does highlight the critical role of good ecological research in influencing natural resource management decisions. The primary role of the Editor's Choice initiative is to showcase papers that we believe best fulfil the journal's mission of publishing ecological studies with management relevance. Kilpatrick et al.'s study is a particularly good example of the connection between good science and real-world problem solving and we expect that the paper will be both widely cited and highly influential.