The Effect of Partial and Temporary Vaccination on African Swine Fever Eradication Rates

African swine fever (ASF) is one of the most severe diseases of pigs, with drastic impact on pig industry. Wild boar populations play the role of ASF virus epidemiological reservoir. No effective and safe ASF vaccine is available, yet, but a future vaccine will not be 100% effective and will provide protection for no more than a few months. We present an individual-based spatially explicit model of wild boar demography and ASF epidemiology, allowing to simulate a vaccination campaign. We tested how many animals should be vaccinated in relation to vaccine efficacy and to the duration of vaccine protection. We estimated how these parameters will affect ASF eradication probabilities. We also assessed how partial vaccination will interact with a series of ecological, epidemiological, and management-related factors linked to ASF persistence. In the case of a highly effective vaccine with short duration, eradication chances were generally low, and the virus disappeared only when simulating a high effort (2.5 vaccinated wild boars/km2). A vaccine with low efficacy and long duration was even less effective in eradicating the ASFV, as none of the simulated scenarios provided acceptable eradication rates. Our results indicate that, under realistic conditions, vaccination against the ASF genotype II virus cannot be seen as an effective stand-alone tool for eradication. Its use should be integrated into a more comprehensive strategy, making use of all the available management tools, such as density control through hunting and carcass removal. If the vaccine will exhibit 12 months or longer duration of its protection, splitting the vaccination effort into two or three bait distribution campaigns during the year will be a feasible option. If the vaccine will exhibit a duration of its immunization significantly shorter than 1 year, a single distribution at the end of winter will maximize the probability of eradication

Estimating the risk of environmental contamination by forest users in African Swine Fever endemic areas

Background: African Swine Fever (ASF) is a highly lethal viral disease caused by the African Swine Fever Virus (ASFV), the only virus of the Asfaviridae family, which affects different species of wild and domestic suids, and for which no vaccination or effective medical treatment is currently available. The virus can survive for long periods in the environment, and humans can unintentionally act as vectors through infected fomites, a risk that is linked to the ASF introduction into pig farms. We ran a simulation study, in which we reconstructed the probability process leading to the different forms of human-mediated ASF contamination in ASF endemic areas. We compared the infection risks related to different types of human forest activities and produced estimates of the minimum expected number of humaninduced contamination events occurring annually at the scale of some European countries. Results: When analysed on a short temporal scale and in a relatively small spatial context, ASF environmental contamination appeared as a rather unlikely event for most of the simulated forest uses, with contamination probabilities often lower than 0.1%. When scaling up the contamination process to a whole year and to large geographic areas, though, the accumulation of the same forest activities, repeated several times per month within the same patch of forest, produced the expectation that thousands of contamination events would occur each year, with potentially relevant epidemiological consequences. Wild boar supplemental feeding and forest logging emerged as the riskiest activities in terms of contamination probabilities, but risk was highly influenced by the frequency and intensity of the different types of forest use. Conclusions: The risk of human-mediated ASF environmental contamination should not be disregarded when planning management actions to reduce ASF circulation and prevent its breach into the pig farming system. Supplemental feeding should be strongly reduced or avoided in ASF affected areas. Wild boar hunting, which is often employed as an active management tool in ASF affected areas, should be seen as both a tool for controlling wild boar density and as a potential risk for further contamination. It is essential to implement and enforce strict biosecurity measures for all forest-based human activities in ASF endemic areas

Optimizing Vaccination Strategies against African Swine Fever Using Spatial Data fromWild Boars in Lithuania

Abstract: African swine fever (ASF) is one of the most severe suid diseases, impacting the pig industry and wild suid populations. Once an ASF vaccine is available, identifying a sufficient density of vaccination fields will be crucial to achieve eradication success. In 2020–2023, we live-trapped and monitored 27 wild boars in different areas of Lithuania, in which the wild boars were fed at artificial stations. We built a simulation study to estimate the probability of a successful ASF vaccination as a function of different eco-epidemiological factors. The average 32-day home range size across all individuals was 16.2 km2 (SD = 16.9). The wild boars made frequent visits of short durations to the feeding sites rather than long visits interposed by long periods of absence. A feeding site density of 0.5/km2 corresponded to an expected vaccination rate of only 20%. The vaccination probability increased to about 75% when the feeding site density was 1.0/km2. Our results suggest that at least one vaccination field/km2 should be used when planning an ASF vaccination campaign to ensure that everyone in the population has at least 5–10 vaccination sites available inside the home range. Similar studies should be conducted in the other ecological contexts in which ASF is present today or will be present in the future, with the objective being to estimate a context-specific relationship between wild boar movement patterns and an optimal vaccination strategy

The role of wild canids and felids in spreading parasites to dogs and cats in Europe. Part I: Protozoa and tick-borne agents.

Over the last few decades, the world has witnessed radical changes in climate, landscape, and ecosystems. These events, together with other factors such as increasing illegal wildlife trade and changing human behaviour towards wildlife, are resulting into thinning boundaries between wild canids and felids and their domestic counterparts. As a consequence, the epidemiology of diseases caused by a number of infectious agents is undergoing profound readjustements, as pathogens adapt to new hosts and environments. Therefore, there is a risk for diseases of wildlife to spread to domestic carnivores and vice versa, and for zoonotic agents to emerge or re-emerge in human populations. Hence, the identification of the hazards arising from the co-habitation of these species is critical in order to plan and develop adequate control strategies against these pathogens. In the first of this two-part article, we review the role that wild canids and felids may play in the transmission of protozoa and arthropod-borne agents to dogs and cats in Europe, and provide an account of how current and future progress in our understanding of the ecology and epidemiology of parasites, as well as of host-parasite interactions, can assist efforts aimed at controlling parasite transmission.This is the accepted manuscript. The final version is available at http://dx.doi.org/10.1016/j.vetpar.2015.04.02

The role of wild canids and felids in spreading parasites to dogs and cats in Europe. Part II: Helminths and arthropods.

Over the last few decades, ecological factors, combined with everchanging landscapes mainly linked to human activities (e.g. encroachment and tourism) have contributed to modifications in the transmission of parasitic diseases from domestic to wildlife carnivores and vice versa. In the first of this two-part review article, we have provided an account of diseases caused by protozoan parasites characterised by a two-way transmission route between domestic and wild carnivore species. In this second and final part, we focus our attention on parasitic diseases caused by helminth and arthropod parasites shared between domestic and wild canids and felids in Europe. While a complete understanding of the biology, ecology and epidemiology of these parasites is particularly challenging to achieve, especially given the complexity of the environments in which these diseases perpetuate, advancements in current knowledge of transmission routes is crucial to provide policy-makers with clear indications on strategies to reduce the impact of these diseases on changing ecosystems.This is the author accepted manuscript. The final version is available from Elsevier at http://dx.doi.org/10.1016/j.vetpar.2015.04.02

Evidence-based African swine fever policies : do we address virus and host adequately?

African swine fever (ASF) is one of the most threatening diseases for the pig farming sector worldwide. Prevention, control and eradication remain a challenge, especially in the absence of an effective vaccine or cure and despite the relatively low contagiousness of this pathogen in contrast to Classical Swine Fever or Foot and Mouth disease, for example. Usually lethal in pigs and wild boar, this viral transboundary animal disease has the potential to significantly disrupt global trade and threaten food security. This paper outlines the importance of a disease-specific legal framework, based on the latest scientific evidence in order to improve ASF control. It compares the legal basis for ASF control in a number of pig-producing regions globally, considering diverse production systems, taking into account current scientific evidence in relation to ASF spread and control. We argue that blanket policies that do not take into account disease-relevant characteristics of a biological agent, nor the specifics under which the host species are kept, can hamper disease control efforts and may prove disproportionate.https://www.frontiersin.org/journals/veterinary-science#am2022Veterinary Tropical Disease

Impact of emergency oral rabies vaccination of foxes in northeastern Italy, 28 December 2009-20 January 2010: preliminary evaluation.

Fox rabies re-emerged in northeastern Italy in 2008, in an area bordering Slovenia. In 2009, the infection spread westward to Veneto region and in 2010 to the provinces of Trento and Bolzano. Aerial emergency oral fox vaccination was implemented in the winter 2009-10. Since this vaccination was performed at altitudes below the freezing level, a statistical analysis was conducted to evaluate its impact. Of the foxes sampled following the vaccination campaign, 77% showed a rabies antibody titre of ≥0.5 IU/ml

ASF Exit Strategy: Providing cumulative evidence of the absence of African swine fever virus circulation in wild boar populations using standard surveillance measures

EFSA assessed the role of seropositive wild boar in African swine fever (ASF) persistence. Surveillance data from Estonia and Latvia investigated with a generalised equation method demonstrated a significantly slower decline in seroprevalence in adult animals compared with subadults. The seroprevalence in adults, taking more than 24 months to approach zero after the last detection of ASFV circulation, would be a poor indicator to demonstrate the absence of virus circulation. A narrative literature review updated the knowledge on the mortality rate, the duration of protective immunity and maternal antibodies and transmission parameters. In addition, parameters potentially leading to prolonged virus circulation (persistence) in wild boar populations were reviewed. A stochastic explicit model was used to evaluate the dynamics of virus prevalence, seroprevalence and the number of carcasses attributed to ASF. Secondly, the impact of four scenarios on the duration of ASF virus (ASFV) persistence was evaluated with the model, namely a: (1) prolonged, lifelong infectious period, (2) reduction in the case‐fatality rate and prolonged transient infectiousness; (3) change in duration of protective immunity and (4) change in the duration of protection from maternal antibodies. Only the lifelong infectious period scenario had an important prolonging effect on the persistence of ASF. Finally, the model tested the performance of different proposed surveillance strategies to provide evidence of the absence of virus circulation (Exit Strategy). A two‐phase approach (Screening Phase, Confirmation Phase) was suggested for the Exit Strategy. The accuracy of the Exit Strategy increases with increasing numbers of carcasses collected and tested. The inclusion of active surveillance based on hunting has limited impact on the performance of the Exit Strategy compared with lengthening of the monitoring period. This performance improvement should be reasonably balanced against an unnecessary prolonged ‘time free’ with only a marginal gain in performance. Recommendations are provided for minimum monitoring periods leading to minimal failure rates of the Exit Strategy. The proposed Exit Strategy would fail with the presence of lifelong infectious wild boar. That said, it should be emphasised that the existence of such animals is speculative, based on current knowledge.info:eu-repo/semantics/publishedVersio