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A rabbit-census method, based on systematic counts conducted at night or at dawn and dusk, was developed and validated in terms of estimating the total number of rabbits present in a given area. Initially, models were developed under semi-natural conditions to describe the relationships between the numbers of rabbits counted and population size. Confidence limits were also calculated. The models were developed by comparing rabbit counts with the actual number of rabbits present, from a known population of animals. Only spotlight counts at night were considered reliable enough to estimate rabbit population size. During the autumn and winter months these represented ~60% of the population present. The model was subsequently validated, in two different exercises, following a series of field trials conducted under a variety of conditions on commercial farms. Initially, population estimates derived from the model were compared with those calculated using an alternative census technique. Population estimates, using the two techniques, were very similar at nine of the ten study sites. A second validation exercise was also conducted whereby the number of rabbits removed at each of the sites was compared with the difference between the mean pre- and post-removal spotlight counts. The results further supported the proposition that spotlight counts represent ~60% of the population present, with the difference between the two mean spotlight counts representing 61.2% (± 11.0, s.d.) of the number of rabbits removed. The census method therefore shows considerable promise as a means to estimate rabbit numbers under a range of agricultural conditions and therefore has the potential to predict accurately the economic costs of rabbit damage and also to gauge the effectiveness of various methods of rabbit control.

African swine fever (ASF) is a highly contagious disease affecting all suids including wild boar. As the disease can damage commercial pig production and its circulation can threaten international trade, understanding the risks produced by free-living wild boar (as a wildlife reservoir) is important to ensure proportionate policies to exclude the disease, as well as an effective contingency response. The recent spread of the virus into Western Europe has produced concerns in many stakeholders including pig producers and national governments. Unlike in mainland Europe, where wild boar are widespread, in Britain, free-living populations have only recently re-established, and whilst these are still relatively small and isolated, they may provide a sufficient reservoir capable of sustaining disease and may thus present a continual source of infection risk to domestic pigs. This study focuses on one component of the risk produced by wild boar, specifically the distribution and persistence of virus in a landscape produced by the natural circulation of disease within wild boar. We used a spatial individual-based model run across a representation of a real landscape to explore the epidemiological consequences of an introduction of ASF into the Forest of Dean, currently hosting the largest population of wild boar in England. We explore various scenarios including variations in the prophylactic management of boar, as well as variations in reactive management (contingency response) following the detection of disease to evaluate their value in reducing this specific risk (presence of ASF virus of wild boar origin in the landscape). The abundance and distribution of wild boar is predicted to increase across our study extent over the next 20 years. Outbreaks of ASF are not predicted to be self-sustaining, with the median time to disease "burn-out" (no new infections) being 14 weeks. Carcass removal, as a tool in a package of reactive management, was of limited value in reducing the duration of outbreaks in this study. We ...

ContextRabies causes ~55 000 human deaths each year, primarily as a result of bites from dogs, which are the major rabies reservoir in the developing world. Current rabies control strategies include vaccination, culling and surgical sterilisation of dogs. However, recently developed immunocontraceptives could be used alongside vaccination to apply fertility control to more animals. AimsWe used a modelling approach to explore (1) whether adding single-dose contraceptives to rabies vaccination would improve effectiveness of rabies eradication, (2) how sensitive control methods are to variation in population parameters and (3) the effects of applying control continuously or in pulses on rabies eradication. MethodsA continuous time, compartmental model was created to describe canine rabies epidemiology. Parameters were derived from the literature. The following three control methods were applied at varying rates and durations: vaccination, vaccination plus fertility control (v + fc) and culling. Outcomes were classified into the following three categories: rabies persistence, rabies eradication and population extinction. Key resultsWhen control was applied continuously for up to 24 months, vaccination was least effective; the effort required to eradicate rabies was about twice that required with culling or v + fc. At realistic control rates, only v + fc consistently resulted in rabies eradication. Increasing population growth rate and city size made rabies eradication harder; for vaccination, considerably greater control rates and durations were required, whereas culling and v + fc showed only minor decreases in effectiveness. When control was applied for 1 or 2 months (for one month every 12 months or every 6 months) per year for up to 20 years, vaccination became less effective because of population turnover between control periods; v + fc lost little effectiveness, as decreased birth rates reduced the input of susceptible animals. ConclusionsUsing immunocontraception alongside vaccination could improve rabies control campaigns by reducing the proportion of the population that must be treated, or reducing the necessary duration of the campaign. It could also make control effective under larger population growths, in larger cities and when control is pulsed. ImplicationsImmunocontraceptives could become a useful tool in canine rabies control by allowing fertility control to be applied on a large scale. Further work is required to improve understanding of dog ecology and parameterise location-specific models, which could be used to inform management plans.