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A most unwelcome parasite

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IN a paper on pp 366-368 of this week's Veterinary Record, Paul Torgerson and Philip Craig describe what they refer to as a simple risk assessment to estimate the likelihood of dogs infected with the tapeworm Echinococcus multilocularis being imported into the UK in the event of the Pet Travel Scheme (PETS) being changed. They also come to a simple conclusion — namely, that if the current requirement under the PETS for dogs to be treated with praziquantel before entering the country is abandoned, it is almost inevitable that E multilocularis will be introduced.

Their observations are relevant to efforts to safeguard public health, where, particularly in the case of a parasite like E multilocularis, prevention is better than cure. They are also relevant in the context of the ongoing debate about the future of the PETS, which remains uncertain as the European Commission seeks to harmonise pet travel rules across the EU. For the time being, a derogation from EU pet travel rules allows the UK and some other EU member states (Sweden, Finland, Malta and the Republic of Ireland) to impose stricter requirements on animals entering the country than most other member states, including the requirement that animals are treated with praziquantel to remove tapeworms. However, having already been extended on more than one occasion, with the most recent proposal for an extension having been made in June this year (see VR, June 27, 2009, vol 164, p 792), the derogation is expected to expire at the end of 2011, after which it may no longer be possible to insist on such treatment.

The consequences of possible changes to the PETS were discussed at a seminar organised by the BSAVA and the BVA at the BSAVA Congress in April (see VR, April 11, 2009, vol 164, p 443, pp 446-448). Concern was expressed about various aspects, including changes to the requirements for serological testing to ensure that animals have been successfully vaccinated against rabies, and removal of a requirement that animals should also be treated against ticks. However, there was particular concern about the prospect of losing the requirement for treatment against tapeworms, because the consequences of human infection with E multilocularis are so severe.

The UK is currently free of E multilocularis but it is endemic in parts of Europe (including Germany, France and Switzerland) and is believed to be extending its geographical range. Although foxes are the usual definitive host, dogs are also susceptible to infection and, if infected, present a hazard to their owners. If the parasite were to be introduced into the UK by an untreated travelling pet, there is a good chance that it could become established in wildlife, given the high density of the UK fox population and the fact that there are a number of potential intermediate hosts. Experience from other parts of the world suggests that, once established, it is very difficult to eradicate.

The EC's most recent proposal to extend the derogation was welcomed by the BVA, which, along with the BSAVA, believes that the existing pet travel rules provide an important tool for balancing the free movement of animals with the risk of spreading zoonotic diseases. It has also been welcomed by the Federation of Veterinarians of Europe (FVE), which has just published an opinion on the pet travel issue discussing rabies, echinococcosis and other diseases which, in the absence of adequate controls, can be spread by travelling pets. Among other things, the FVE urges the Commission to initiate, as soon as possible, an EU-wide echinococcosis risk assessment, to be followed by an appropriate prevention, reduction and control strategy throughout the EU. It also recommends further investigation into the spread of ticks and tickborne diseases in the EU and the development of an EU strategy to reduce the incidence of these diseases, based on the outcome of the investigations.*

Controls applied to the movement of pets need to be evidence-based and proportionate. The problem is that, in many instances, whether in relation to rabies, echinococcosis or other diseases that can be spread by travelling pets, data are lacking, which makes quantitative risk assessment difficult. This was illustrated by a necessarily qualitative risk assessment in relation to E multilocularis undertaken by the European Food Safety Authority in 2007, which nevertheless concluded that abandoning current controls would increase the risk of introducing the parasite into areas considered free of it. More data are needed and further analyses must be carried out, but the paper in this week's Veterinary Record is an example of just the kind of assessment that is needed.


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