The UK is currently free from a number of parasites with zoonotic potential that are endemic in mainland Europe. Echinococcus multilocularis, the cause of cystic echinococcosis, is one of these parasites and listed on the World Health Organisation’s (WHO) 17 most neglected diseases. The adult tapeworm is carried by both foxes and domestic canids, with foxes acting as a reservoir of infection, and microtine voles as intermediate hosts. Cats can act as definitive hosts for E.multilocularis but have a lower worm burden with lower fecundity than canids. Eggs that are produced have also been demonstrated to be more likely to be non-infective in experimental infections.
Echinococcus multilocularis is a severe zoonosis, with local and metastatic spread of cysts leading to hepatopathy and potential multiple organ involvement. If resection of cysts is possible then this remains the best option for treatment, in combination with albendazole for at least two years. If not resectable, life-long treatment with albendazole is required. Despite significant advances in treatment over the past two decades, infected individuals can still expect a significant reduction in life expectancy.
In the 1980s, human alveolar echinococcosis was vanishing from Europe due to improved food hygiene, decreased occupational risk of exposure, and a decimated fox population after a number of rabies epidemics. The control of rabies in Western and Central Europe, however, reversed this trend, as the fox population exploded and spilled over into urban areas.
In the year 2000, 559 cases were recorded in Europe. The last decade has seen a doubling of disease incidence in France, Germany, Austria and Switzerland, a dramatic increase in the Baltic States, and the disease becoming established in the Jutland peninsula of Denmark, Sweden, Norway, and the north-western coast of France. As well as the urbanisation of the red fox, it is also thought that increased immune suppression in the human population due to an increasing use of radiotherapy, corticosteroids, and an increased prevalence of HIV, may also be playing a role in increased human infection.
Now, only the UK, Ireland, Malta, Finland, and Iceland have endemic free status in Europe. The Pet travel scheme currently still requires dogs to be treated with praziquantel between 1 and 5 days before entry to the UK. This simple treatment has currently prevented endemic foci from developing, and as such it remains vital. It has been demonstrated that if this compulsory treatment is abandoned altogether, then it is almost inevitable that E.multilocularis will be introduced into the UK.
For every 10,000 dogs travelling on a short visit to an endemic country such as Germany, the probability of at least 1 returning with the parasite is approximately 98 per cent. This probability increases to over 99 per cent if dogs have been longer term residents. Although the one to five day rule has provided protection against this, it does allow a window of opportunity for infection.
If E.multilocularis is allowed entry into the UK, the large fox and microtine vole population will make the prevention of endemic E.multilocularis difficult, if not impossible to achieve.
It is therefore vital that the opportunity for the parasite to gain entry to the UK is kept to a minimum, and if this to be achieved, then OVs will continue to play a vital role.
Advice to OVs
- Stay up to date with the current distribution of E.multilocularis in Europe, particularly reports of autochthonous cases in countries that are currently thought to be free of the parasite.
- Stress to clients travelling to Europe the importance of the compulsory tapeworm treatment before return to the UK, and that infected dogs represent an immediate zoonotic risk to owners, as well as increasing the risk of the parasite establishing itself in the UK.
- Advise treatment with praziquantel for every 30 days that pet dogs are abroad.
- Advise a further treatment with praziquantel within 30 days after a return to the UK. This will prevent egg shedding if dogs have become infected with E.multilocularis in the potential five day window between compulsory treatment and return to the UK.
- Advise that if clients wish to obtain tapeworm treatment for E.multilocularis prevention while they are abroad, they should ask for products containing praziquantel rather than epsiprantel, if both are available. While epsiprantel is licensed for E.multilocularis treatment and prevention in some countries and is efficacious, current data suggests that praziquantel is superior regarding prevention of egg shedding.
- Advise that owners prevent their pet cats and dogs from predating or scavenging microtine voles while they are abroad, if it is practical to do so.