Risk assessments to inform policy decisions regarding importation of pets from North America

Emergency rabies control in a community of two high-density hosts

Background

Rabies is a fatal viral disease that potentially can affect all mammals. Terrestrial rabies is not present in the United Kingdom and has been eliminated from Western Europe. Nevertheless the possibility remains that rabies could be introduced to England, where it would find two potentially suitable hosts, red foxes and badgers. With the aim to analyse the spread and emergency control of rabies in this two species host community, a simulation model was constructed. Different control strategies involving anti-rabies vaccination and population culling were developed, considering control application rates, spatial extent and timing. These strategies were evaluated for efficacy and feasibility to control rabies in hypothetical rural areas in the South of England immediately after a disease outbreak.

Results

The model confirmed that both fox and badger populations, separately, were competent hosts for the spread of rabies. Realistic vaccination levels were not sufficient to control rabies in high-density badger populations. The combined species community was a very strong rabies host. However, disease spread within species appeared to be more important than cross-species infection. Thus, the drivers of epidemiology depend on the potential of separate host species to sustain the disease. To control a rabies outbreak in the two species, both species had to be targeted. Realistic and robust control strategies involved vaccination of foxes and badgers, but also required badger culling. Although fox and badger populations in the UK are exceptionally dense, an outbreak of rabies can be controlled with a higher than 90% chance, if control response is quick and follows a strict regime. This requires surveillance and forceful and repeated control campaigns. In contrast, an uncontrolled rabies outbreak in the South of England would quickly develop into a strong epizootic involving tens of thousands of rabid foxes and badgers.

Conclusions

If populations of both host species are sufficiently large, epizootics are driven by within-species transmission, while cross-species-infection appears to be of minor importance. Thus, the disease control strategy has to target both host populations.

European pet travel: misleading information from veterinarians and government agencies

Inter-country travel of companion animals provides an opportunity for introduction of zoonotic pathogens, such as rabies virus and Echinococcus spp. Regulations are in place to control this threat, but Schengen Agreements mean that border controls between some European countries are minimal, and animals may enter countries without any checks that they have been appropriately treated. Veterinarians provide an important source of information for people intending to travel with their pets. We conducted a telephone survey to investigate provision of correct advice to someone intending to travel with their dog to Norway. Mainland Norway is considered free of both rabies and E. multilocularis and is a signatory to the Schengen Agreement. Ten randomly selected veterinary clinics were surveyed in Austria, Belgium (Wallonia), Finland, France, Germany, Norway, Sweden, Switzerland and United Kingdom. The information provided was scored as correct, incorrect or incomplete. The information provided by secondary information sources (website or government agency), which the clinic had referred the caller to, was also assessed (correct, incorrect, incomplete). Whilst the majority of clinics provided appropriate information regarding rabies, many clinics did not provide correct information regarding treatment for E. multilocularis. Less than one in 10 clinics provided the correct information regarding both pathogens directly at the time of calling. The correct information was obtained, once taking into account secondary sources, just 62% of the time. Countrywise, most clinics in Finland provided correct advice, either directly or indirectly via referring the caller to another source, whilst the majority in Belgium, Germany and France did not. The apparent paucity of readily accessible, correct advice for owners intending to travel with their dogs is concerning. The compulsory treatment regulations are only as good as the checks that ensure compliance, and this is also lacking in some countries.

How to make predictions about future infectious disease risks

Formal, quantitative approaches are now widely used to make predictions about the likelihood of an infectious disease outbreak, how the disease will spread, and how to control it. Several well-established methodologies are available, including risk factor analysis, risk modelling and dynamic modelling. Even so, predictive modelling is very much the ‘art of the possible’, which tends to drive research effort towards some areas and away from others which may be at least as important. Building on the undoubted success of quantitative modelling of the epidemiology and control of human and animal diseases such as AIDS, influenza, foot-and-mouth disease and BSE, attention needs to be paid to developing a more holistic framework that captures the role of the underlying drivers of disease risks, from demography and behaviour to land use and climate change. At the same time, there is still considerable room for improvement in how quantitative analyses and their outputs are communicated to policy makers and other stakeholders. A starting point would be generally accepted guidelines for ‘good practice’ for the development and the use of predictive models.