Probability Of Extinction Research Articles

Metrics for quantifying how much different threats contribute to red lists of species and ecosystems.

Red lists are a crucial tool for the management of threatened species and ecosystems. Among the information red lists provide, the threats affecting the listed species or ecosystem, such as pollution or hunting, are of special relevance. This information can be used to quantify the relative contribution of different threat factors to biodiversity loss by disaggregating the cumulative extinction risk across species into components that can be attributed to certain threats. We devised and compared 3 metrics that accomplish this and may be used as indicators. The first metric calculates the portion of the temporal change in red list index (RLI) values that is caused by each threat. The second metric attributes the deviation of an RLI value from its reference value to different threats. The third metric uses extinction probabilities that are inferred from red list categories to estimate the contribution of a threat to the expected loss of species or ecosystems within 50years. We used data from Norwegian Red Lists to test and evaluate these metrics. The first metric captured only a minor portion of the biodiversity loss caused by threats because it ignores species whose red list category does not change. Management authorities will often be interested in the contribution of a given threat to the total deviation from the optimal state. This was measured by the remaining metrics. The second metric was best suited for comparisons across countries or taxonomic groups. The third metric conveyed the same information but uses numbers of species or ecosystem as its unit, which is likely more intuitive to lay people and may be preferred when communicating with stakeholders or the general public.

Viability analysis of Kordofan giraffe (Giraffa camelopardalis antiquorum) in a protected area in Cameroon

AbstractRepresenting one of the last populations of an IUCN Critically Endangered subspecies, estimates suggest the Kordofan giraffe of Cameroon's Bénoué Complex number fewer than 300 individuals, threatened by poaching and habitat degradation. This study investigated the viability of Bénoué National Park's Kordofan giraffe and efficacy of available interventions through a population viability analysis using VORTEX. The relative impacts of anti‐poaching activity, population supplementation, habitat protection and vaccination were explored, alongside a sensitivity analysis investigating parameter uncertainty. The baseline model projects a 78.6% probability of extinction (PE) within 100 years. Poaching of just two individuals every 5 years results in a 98.1% PE, highlighting anti‐poaching activity as a vital intervention. Movement of a female‐biased group into the park proved effective, with supplementation of 24 females reducing the PE by over 35%, sustaining a raised population size above the baseline for over 60 years on average. Annual carrying capacity reduction of 2% year−1 for 20 years resulted in a 97.8% PE. Conversely, habitat restoration had little consequence unless combined with further interventions. These findings underscore the magnitude of the threat facing Bénoué National Park's Kordofan giraffe. Conservation management should prioritise strengthening existing anti‐poaching activity in conjunction with protecting wildlife corridors to aid dispersal.

Assessing the extinction risks of amphibians impacted by infectious diseases

Emerging infectious diseases (EIDs) are a major threat to amphibians worldwide. Determining the extinction risk of species susceptible to EIDs is challenging because of data limitations, especially in the initial stages of emergence and spread of disease. The fast rate of spread of many EIDs makes it necessary to assess the extinction risk of impacted host species before detailed mechanistic (epidemiological) or correlative (ecological niche) models can be developed. We present a simple method for identifying species that are at the highest risk of extinction due to an EID. Our method incorporates projections of the spatial spread of disease into IUCN Red List assessments under criteria A3 (based on future population reductions), D2 (plausible future threats), and E (probability of extinction). We apply this method to assess the extinction risk of salamander species in Europe susceptible to population declines caused by Batrachochytrium salamandrivorans (Bsal), the agent of the salamander plague. Our results indicate a high risk of extinction for European salamanders as a result of the spreading Bsal infection. Depending on the rate of spread from the current Bsal localities, and the emergence of new localities through human travel and transport, the number of species threatened by Bsal can range from a few to almost 30 of the 40 species that occur in Europe. Our method allows preliminary assessments of extinction risk based on limited information. For species at risk of extinction due to fast-spreading EIDs, it provides a pragmatic and precautionary solution until more realistic models can be developed.

Rapid and continuing regional decline of butterflies in eastern Denmark 1993-2019

Many butterfly populations respond negatively to land-use intensification in human-dominated landscapes. Networks of protected sites have been established with the aim to halt species loss. We undertook annual surveys of all occurrence sites of 22 uncommon butterfly species in eastern Denmark during the period 2014–2019 and compared to a systematic atlas survey done 1989–1993, in order to assess trends in regional occupancy of species. Three out of 22 species went regionally extinct between 1993 and 2015. One species sustained a single population through the study period. Logistic regression for the remaining 18 species showed 10 to be in strong decline from 1993 to 2015, two showed a declining trend and six had stable trends. For all species except one, the declining trend continued 2015–2019. For five species, a sustained strong decline was evident. In 1993, the total count of occurrence sites for all 22 butterfly species was 565, which by 2019 had declined to 158 sites (a 72 % loss over 26 years). From 2015 to 2019 alone, the total count of occurrence sites shrank from 200 to 158 (a 21 % decline over just four years). Legal protection of areas (Natura 2000 and Danish Nature Protection Act §3) was, unexpectedly, not associated with lower probability of local extinction for butterfly population. The observed sustained decline across species suggests an overall low efficiency of the network of protected sites, probably due to a combination of misguided management regimes and payment of extinction debts from the past.

Local colonisations and extinctions of European birds are poorly explained by changes in climate suitability

Climate change has been associated with both latitudinal and elevational shifts in species’ ranges. The extent, however, to which climate change has driven recent range shifts alongside other putative drivers remains uncertain. Here, we use the changing distributions of 378 European breeding bird species over 30 years to explore the putative drivers of recent range dynamics, considering the effects of climate, land cover, other environmental variables, and species’ traits on the probability of local colonisation and extinction. On average, species shifted their ranges by 2.4 km/year. These shifts, however, were significantly different from expectations due to changing climate and land cover. We found that local colonisation and extinction events were influenced primarily by initial climate conditions and by species’ range traits. By contrast, changes in climate suitability over the period were less important. This highlights the limitations of using only climate and land cover when projecting future changes in species’ ranges and emphasises the need for integrative, multi-predictor approaches for more robust forecasting.

The synzootic potential of common epidemics in chamois populations

Southern chamois (Rupicapra pyrenaica) is a medium-sized and gregarious mountain ungulate with populations affected by periodic outbreaks of border disease virus (BD), infectious keratoconjunctivitis (IKC), and sarcoptic mange (SM). Even though the impact of each disease on chamois populations has been described in detail, there is a lack of information about the potential impact of concomitant epidemics and the synzootic potential (co-occurring enzootic or epizootic processes producing worse health outcomes in wildlife) on chamois populations. Furthermore, whether a specific order of apparition of epidemics is more or less harmful for the host population is practically unknown not only for chamois but also for most mammal populations. Using a population viability analysis (PVA), we studied the consequences of multiple disease outbreaks with synzootic potential on growth rates and probabilities of extinction of virtual populations exposed to hard winters, density dependence, and co-occurring BD, IKC, and SM outbreaks. Such infections are not under cross-immunity nor density-dependent processes and thus are supposed to affect population demography independently. Heavy snowfalls are also likely to occur in our simulated populations. Our simulations showed that a second outbreak, even caused by a low virulent pathogen, causes an increase in the probability of extinction of the host population with regard to the first outbreak. IKC-BD- and SM-BD-affected populations had a higher risk of becoming extinct in 50 years confirming the extra risk of multiple outbreaks on the viability of the affected populations.

Względność zrównoważenia w przyrodzie na przykładzie działania Hipotezy Czerwonej Królowej

The worrying phenomenon of our times is a rapid decline in the biodiversity, that is directly related to the disorder in environmental sustainability. However, the question is whether before the appearance of the Homo sapiens there was a greater eco-sustainability? Or maybe even without the presence of the man such state would be rather correlated with some natural processes, that happen independently of our interference? The paper attempts to explain the relativity of environmental sustainability described by the Red Queen Hypothesis (RQH). That model presents competition in nature, which may be extrapolated to all interactions in the world of living organisms. The RQH shows that in the evolutionary terms not keeping pace on the run threatens not only progress but also poses an increasing risk of elimination of a given individual. So in that way environmental sustainability is relative and the model explains the probability of a constant extinction, so in fact a fall.

Identifying functionally distinctive and threatened species

Functional traits determine species' responses to environmental change and/or determine species' effects on ecosystem functions. When species with distinctive functional traits are threatened, there is a risk that ecosystem properties are also threatened. This is because functionally distinctive species may be those that have irreplaceable roles in an ecosystem and/or those that would be able to survive unusual environmental disturbances. To include functional distinctiveness as a criterion in conservation strategies, we need formal quantification of species' degree of distinctiveness while incorporating extinction risk. Based on previously developed quantitative methods, we develop a framework that links different metrics of functional distinctiveness and accounts for all species' extinction probabilities. Our framework is particularly relevant at the local scale, where species extinctions impact ecosystem functioning and where conservation policies are developed. As a case study, we thus applied our framework to the mammals of Indian dry forests known to be threatened with a drastic decrease in functional diversity and identified top-priority species as the threatened, most functionally distinctive species. We notably highlight that although some of the top-priority species we identified are charismatic and targeted by conservation actions, others are not. On the basis of this case study, we note that less charismatic, less known species that may be key for ecosystems could be revealed by applying our framework to a range of ecosystems and taxa.

Multipatch stochastic epidemic model for the dynamics of a tick-borne disease

Spatial heterogeneity and migration of hosts and ticks have an impact on the spread, extinction and persistence of tick-borne diseases. In this paper, we investigate the impact of between-patch migration of white-tailed deer and lone star ticks on the dynamics of a tick-borne disease with regard to disease extinction and persistence using a system of Itô stochastic differential equations model. It is shown that the disease-free equilibrium exists and is unique. The general formula for computing the basic reproduction number for all patches is derived. We show that for patches in isolation, the basic reproduction number is equal to the largest patch reproduction number and for connected patches it lies between the minimum and maximum of the patch reproduction numbers. Numerical simulations for a two-patch deterministic and stochastic differential equation models are performed to illustrate the dynamics of the disease for varying migration rates. Our results show that the probability of eliminating or minimizing the disease in both patches is high when there is no migration unlike when it is present. The results imply that the probability of disease extinction can be increased if deer and tick movement are controlled or even prohibited especially when there is an outbreak in one or both patches since movement can introduce a disease in an area that was initially disease-free. Thus, screening of infectives in protected areas such as deer farms, private game parks or reserves, etc. before they migrate to other areas can be one of the intervention strategies for controlling and preventing disease spread.

Fitness-based mobility enhances the maintenance of biodiversity in the spatial system of cyclic competition

In ecosystems, species are willing to stay longer when they are in good environments and, in this regard, explaining biodiversity and understanding the relative effect of species’ behavior is a fundamental issue in ecological sciences. Staying or moving stands for the movement of the population, and mobility has been accepted as one of the important mechanisms in systems of cyclic competition. In this paper, we investigate the biodiversity in the system of cyclic competition when an individual’s mobility is affected by environmental fitness. We found that fitness-based mobility, which is defined by the ratio of the difference between predator and prey among species, can lead to the slow behavior of species when local fitness is higher than the average fitness and enhance the biodiversity of species. The fitness-based mobility behavior is successful in reducing the extinction probability on the lattice network. However, when the average degree of the network increases, the extinction probability increases significantly. In addition, when we consider the same model on heterogeneous networks, the extinction probability is always 1 regardless of the sensitivity to the fitness. The finding indicates that the heterogeneous network destroys species coexistence. Through extensive numerical investigations, we provided solid evidence supporting the great importance of fitness-based mobility in maintaining biodiversity. We further highlighted the significant relationship among fitness, the fraction of empty sites, and the tunable parameter by investigating the correlation that the relationship is not influenced by mobility.

The implications of seasonal climatic effects for managing disturbance dependent populations under a changing climate

Abstract The frequency of ecological disturbances, such as fires, is changing due to changing land use and climatic conditions. Disturbance‐adapted species may thus require the manipulation of disturbance regimes to persist. However, the effects of changes in other abiotic factors, such as climatic conditions, are frequently disregarded in studies of such systems. Where climatic effects are included, relatively simple approaches that disregard seasonal variation in the effects are typically used. We compare predictions of population persistence using different fire return intervals (FRIs) under recent and predicted future climatic conditions for the rare fire‐dependent herb Eryngium cuneifolium. We used functional linear models (FLMs) to estimate the cumulative effect of climatic variables across the annual cycle, allowing the strength and direction of the climatic impacts to differ over the year. We then estimated extinction probabilities and minimum population sizes under past and forecasted future climatic conditions and a range of FRIs. Under forecasted climate change, E. cuneifolium is predicted to persist under a much broader range of FRIs, because increasing temperatures are associated with faster individual growth. Climatic impacts on fecundity do not result in a temporal trend in this vital rate due to antagonistic seasonal effects operating through winter and summer temperatures. These antagonistic seasonal climatic effects highlight the importance of capturing the seasonal dependence of climatic effects when forecasting their future fate. Synthesis. Awareness of the potential effects of climate change on disturbance‐adapted species is necessary for developing suitable management strategies for future environmental conditions. However, our results suggest that widely used simple methods for modelling climate impacts, that disregard seasonality in such effects, may produce misleading inferences.

Estimating population viability of the northern Great Plains piping plover population considering updated population structure, climate change, and intensive management

One challenge in wildlife conservation is understanding how various threats and management actions may influence long-term population viability. This is particularly evident when there is considerable uncertainty regarding population structure and vital rates. Reassessment of current knowledge and population trends is necessary for listed species to improve management actions that benefit conservation. We present an updated population viability analysis for northern Great Plains piping plovers (Charadrius melodus circumcinctus) based on the latest scientific data on survival, fecundity, and connectivity. Further, we explore the consequences of potential management actions and the stochastic effects of global climate change on population viability through changes in survival and fecundity. Our results predict elevated risks of extinction after 50 years (0.088 – 0.373) compared to previous predictions (0.033) based on assumed conditions of low connectivity among four major breeding groups structured as a metapopulation. We explored eight scenarios based on empirically-derived, higher connectivity rates and found that the northern Great Plains population never had a mean predicted population growth rate greater than one (0.946 – 0.996). Two scenarios that simulated a reduction in adult survival showed higher extinction probabilities (0.267 – 0.373), whereas two other scenarios that simulated an increase in fecundity exhibited lower extinction probabilities (0.088 – 0.103). These results indicate that viability of the northern Great Plains population of piping plovers could be improved with management actions that increase fecundity as long as adult survival is not simultaneously reduced. Lastly, breeding groups appeared to function less independently when connectivity rates were higher, as the breeding population was divided evenly among breeding groups. This indicates that the presumed metapopulation structure of our study system may need to be re-evaluated, and that empirically-based estimates of connectivity are essential to assessing population viability of mobile species that exhibit a spatially structured distribution.

A gene bank's collection of genetic diversity among minor chicken breeds

Genetic differences among heritage or fancier breeds of chickens have not been quantified in the United States. Gene banks collecting germplasm for conserving these breeds need this information as do breeders and companies raising them. Our goal was to evaluate genetic diversity of 10 heritage/fancier chicken breeds that are a component of the national collection and to use this information to establish a baseline of their genetic diversity and future conservation efforts. Breeds could be broadly classified as European, Asian, Mediterranean, and United States (US) in origin. The US breeds were composite breeds developed between the 1849 and 1935. Animals (n=24-31 per breed) were sampled for DNA analysis from 2 or 3 hatcheries per breed and a total of 8 hatcheries. The hatcheries were assumed to maintain and breed their own populations of the studied breeds. Effective population sizes ranged from 47 to 145 and used to estimate probabilities of extinction for a 50-generation timeline. It was determined that Crevecoeur and Aseel had a probability of extinction that exceeded 40%, the remaining 8 breeds had probabilities of <28%. ADMIXTURE analysis indicated the minimal CV corresponded to 9 populations. In that analysis New Hampshire and Rhode Island Red were classified as the same population, which was not unusual given that New Hampshire was developed as a subpopulation of Rhode Island Red. Crevecoeur and Buttercup were the 2 most genetically divergent breeds based on pairwise Fst among the breeds and principal component analysis, which was supported by the ADMIXTURE results. Inbreeding coefficients computed from genomic information was lowest for Crevecoeur, Rhode Island Red, Buttercup, and Andalusian (0.8-2.6%), while New Hampshire, Buckeye, and Aseel were highest (12.8-14.3%). Within breed Fst among hatcheries supplying animals for sampling generally indicated a genetic structure was present on a breed-by-breed basis. Genetic relationships within hatchery were also computed for each breed. Several of the hatcheries had sent samples that suggested genetic relationships as high as half-sibs while several others had genetic relationships closer to first cousins. We conclude that the chicken breeds evaluated have substantial genetic variability within the in situ populations and the gene bank has captured this diversity for future use.

Influence of Aboveground Pipeline and Associated Factors on Movement of Winter-Active Boreal Mammals in the Alberta In-Situ Oil Sands

Aboveground pipelines (AGP) associated with in-situ oil sands may restrict mammal movement, potentially increasing extinction probability and decreasing reproductive success. Our 12-year study used winter track count techniques to assess the response of winter-active mammals to AGP in northern Alberta, Canada. The primary questions were: which species were most prone to movement obstruction by AGP, facilities or natural factor(s)?; and which factor exerted the strongest influence on crossing likelihood? A total of 2,068 trails of 12 different species were observed. All species crossed more than half of the time. Focal species crossed on average 80% of the time. Crossing likelihood of white-tailed deer (Odocoileus virginianus), ermine (Mustela erminea), coyote (Canis latrans), lynx (Lynx canadensis), and fisher (Martes pennanti) were significantly influenced by predictors including pipeline height, pipeline corridor width, infrastructure age, vegetation type, and proximity to infrastructure. Deer and lynx crossing likelihood was positively affected by pipe height. Deer, coyote, and ermine crossing likelihood was positively affected by age of pipe. Fisher and deer crossing likelihood was negatively affected by pipeline corridor widths. Our investigations show that most species cross AGP with high crossing frequencies of pipe heights, ranging from 130 cm to 160 cm. These findings are important for impact mitigation because of the scarcity of published studies of wildlife movement responses to AGP, our inclusion of small and mid-sized carnivores, and our investigation of multiple factors. We highlight mitigation and design improvements, effects of pipeline corridor widths, and challenges posed by coupling infrastructure with pipelines, serving to reduce movement barriers and fragmentation.

Applying simple genomic workflows to optimise practical plant translocation outcomes

Translocation is an important conservation tool for reducing the probability of extinction of threatened plants. It is also becoming an increasingly common management practice, as habitats are destroyed and climate change pushes more plants beyond the limits of their tolerances. Here we outline the case for informing translocations with dedicated genomic data. We begin by describing principles for using genomic and genetic approaches to enhance the efficiency and success of translocation actions. This includes ensuring that translocated populations are adaptively representative, diverse, and composed (to the greatest possible extent) of unrelated individuals. We then use two Australian case studies to illustrate how these principles have been applied in practice and in a resource-efficient way. For Prostanthera densa, we describe how genomic data have quantitatively informed complex decisions, such as whether, and how extensively, to mix individuals from spatially isolated populations in translocated populations. For Fontainea oraria, genomic data have been used during post-translocation monitoring to confirm that newly established populations incorporate and recombine the little diversity that remained in wild individuals. Overall, we illustrate how a simple workflow can support the development and planning of genomic studies and translocation activities in tandem. In order to ensure greater adoption of translocation genomic workflows, funding bodies in charge of biodiversity management and conservation must direct the necessary resources towards them.

Breeding season management is unlikely to improve population viability of a data-deficient migratory species in decline

A major challenge in conservation is developing effective approaches to mitigate population declines in the face of ongoing environmental change. For migratory species, it is often more feasible to implement management during periods of stationarity, like the breeding season, when populations are less mobile. However, such management strategies are only successful if the demographic rates targeted (e.g., reproductive rates) contribute substantively to population growth. Thus, evaluation of population growth rate sensitivity to variation in demographic parameters is needed to determine the most effective conservation strategies. This is especially true for small and declining populations that require targeted and urgent action to mitigate declines under current and future environmental change. Here, we used a coupled integrated population model-Bayesian population viability analysis (IPM-BPVA) to estimate demographic rates and population viability within the context of climatic and management-related changes for a data-deficient, declining population of black terns in the Upper Midwestern United States. We found that current conservation efforts during the breeding season are unlikely to reverse the declines observed within the last decade (from an average of 307 breeding pairs in 2013 to 53 in 2022). Rather, interventions aimed at increasing adult survival are projected to reduce local extinction probability by 30–46 % compared to no additional management or management targeting other rates, depending on the climate scenario. Our results highlight the importance of enhancing management efforts for migratory species during migration and nonbreeding periods, which constitute a much larger, and generally riskier, proportion of the annual cycle compared to the breeding season.

Periodic environmental effect: stochastic resonance in evolutionary games of rock-paper-scissors

A balance in nature is maintained by the coexistence of multiple species through interspecific competition. The evolutionary dynamics of cyclic interactions contain interactions that represent different biological behaviors. Biological behavior is influenced by the external environment, which may affect the stability of ecosystems. We investigated the evolutionary dynamics of interspecific competition after a periodic change in the external environment affects species. We consider that when the periodic external environments affect mortality, interspecific cyclical competition may be more pronounced, and thus increase the probability of extinction of species. By performing Monte Carlo simulations, we observed that the evolutionary dynamics of interspecific cyclic competition have different responsivity when subjected to external periodic changes at different frequencies, and stochastic resonance phenomena occurred. We show that the influence of the periodic external environment and its frequency is one of the factors that determine whether ecosystems coexist stably.

Landscape context and spatial attributes matter for New England cottontail occupancy

AbstractIn response to the widespread threat of habitat loss, managers of imperiled species commonly focus on restoring habitat to encourage species establishment (i.e., the field of dreams hypothesis). Habitat management strategies for the rare New England cottontail (Sylvilagus transitionalis) have largely followed the field of dreams hypothesis, focusing on increasing the area of young and regenerating forest throughout the species' range to increase populations of the species. Recently researchers indicated that these practices may not be as effective when the introduced eastern cottontail (Sylvilagus floridanus) co‐occupies patches with the New England cottontail. Using data from the New England Cottontail Regional Monitoring Program collected in Connecticut, USA, from 2016–2020 and geospatial data to create dynamic occupancy models, we determined how both patch and landscape characteristics influence New England cottontail and eastern cottontail occupancy patterns. We ran 4 dynamic occupancy models: 1 at the patch scale and 1 at the landscape scale for each species. Large patches and short interpatch distances increased both species' occupancy patterns more than vegetation height &lt;2.5 m. New England cottontail occupancy and colonization positively responded to the amount of shrublands within the landscape and weakly responded to forest regeneration, the vegetation type most commonly created by management actions for the species. New England cottontail colonization probability was low at both the patch and landscape scale, and lower than extinction probabilities, suggesting the current landscape may not be sufficient to allow metapopulations to persist. Overall, our results indicate that solely focusing on habitat restoration, or applying the field of dreams hypothesis, to conserve New England cottontail, a species that is area dependent, dispersal limited, and threatened by an introduced competitor, does not promote species persistence on the landscape.

Connectivity and fragment size drive plant dispersal and persistence traits in forest steppe fragments

IntroductionLand use changes have seriously fragmented grasslands leading to extensive biodiversity loss worldwide. Habitat fragmentation affects grasslands at both local and landscape scales, adversely affecting the probability of species colonisation and extinction. In our study, we addressed the effects of fragment size and landscape-scale habitat connectivity on the vegetation composition in two grassland types, i.e., loess steppe fragments (situated on kurgans) and sand steppe fragments of the Pannonian forest steppe region.MethodsWe collected frequency data on vascular plant species in 12 1 m × 1 m quadrats in altogether 60 fragments along a connectivity gradient in sand steppes and loess steppe fragments. We analysed whether habitat specialists, generalists and exotic species were affected by the level of fragmentation based on species richness and traits related to local persistence (life span, clonality and soil seed bank type) and dispersal (dispersal strategy and seed mass) in the two grassland types using linear mixed-effects models.ResultsBased on our results, both fragment size and landscape-scale connectivity were important in shaping the trait composition of the vegetation. We observed more fragmentation effects in generalist than in specialist species. We found that isolation resulted in fewer specialist species with autochorous dispersal strategy in loess steppe fragments, but, at the same time, also fewer exotics. Isolated loess steppe fragments harboured fewer generalist species with persistent seed bank. Large loess steppe fragments supported more wind-dispersed species than smaller ones. In isolated sand steppe fragments, generalists were more frequent with endozoochorous dispersal strategy and without clonal propagation. Life span, clonal propagation and seed mass did not depend on the level of fragmentation in the two grassland types.DiscussionOur results imply that both sand and loess steppe fragments can rely to some extent on the persistence of clonal perennial specialist and generalist species in small and isolated patches to mitigate fragmentation effects. In conclusion, these processes should be supported by the preservation of large fragments, increase of habitat connectivity combined with targeted management of exotic species.

Evaluation of early single dose vaccination on swine influenza A virus transmission in piglets: From experimental data to mechanistic modelling.

Swine influenza A virus (swIAV) is a major pathogen affecting pigs with a huge economic impact and potentially zoonotic. Epidemiological studies in endemically infected farms permitted to identify critical factors favoring on-farm persistence, among which maternally-derived antibodies (MDAs). Vaccination is commonly practiced in breeding herds and might be used for immunization of growing pigs at weaning. Althoughinterference between MDAs and vaccination was reported in young piglets, its impact on swIAV transmission was not yet quantified. To this aim, this study reports on a transmission experiment in piglets with or without MDAs, vaccinated with a single dose injection at four weeks of age, and challenged 17days post-vaccination. To transpose small-scale experiments to real-life situation, estimated parameters were used in a simulation tool to assess their influence at the herd level. Based on a thorough follow-up of the infection chain during the experiment, the transmission of the swIAV challenge strain was highly dependent on the MDA status of the pigs when vaccinated. MDA-positive vaccinated animals showed a direct transmission rate 3.6-fold higher than the one obtained in vaccinated animals without MDAs, estimated to 1.2. Vaccination nevertheless reduced significantly the contribution of airborne transmission when compared with previous estimates obtained in unvaccinated animals. The integration of parameter estimates in a large-scale simulation model, representing a typical farrow-to-finish pig herd, evidenced an extended persistence of viral spread when vaccination of sows and single dose vaccination of piglets was hypothesized. When extinction was quasi-systematic at year 5 post-introduction in the absence of sow vaccination but with single dose early vaccination of piglets, the extinction probability fell down to 33% when batch-to-batch vaccination was implemented both in breeding herd and weaned piglets. These results shed light on a potential adverse effect of single dose vaccination in MDA-positive piglets, which might lead to longer persistence of the SwIAV at the herd level.