Recent changes to regulations on the transport of pets across Europe may have increased the threat of introducing rabies from rescue dogs into countries considered free of the disease, suggests research published in Veterinary Record.
In 2012 the European Union (EU) changed its requirements for the non-commercial movement of cats, dogs, and ferrets across the borders of EU and European Economic Area countries.
Up to that point, countries free of rabies virus - the UK, Ireland, Malta, Sweden and Norway - had required an additional blood test to be carried out a month after microchipping and rabies vaccination to prove that an animal was not at risk.
For the UK, animals then underwent a 6 month wait after the successful blood test, and were given tick and tapeworm treatment 24-48 hours before being granted entry.
But the new Pet Travel Scheme has dispensed with this additional test. Now microchip identification, a pet passport certifying that the animal has been vaccinated against rabies at least 21 days previously, and preventive treatment against tapeworm 24-120 hours before travel, are the only entry requirements.
The figures suggest that the new rules have made it easier to move pet dogs across the EU. The numbers entering Norway rose from about 5000 in 2011 to around 7500 in 2012.
To test the effectiveness of the rule changes, the researchers tested the antibody levels of 75 strays/rescue dogs certified as having been vaccinated against rabies at least 21 days earlier, and legally imported into Norway from Eastern Europe in 2012.
They focused in particular on dogs that had come from Romania, Hungary, the Balkans and Baltic countries - areas where rabies is still endemic.
An antibody level of more than or equal to 0.5 International Units/ml blood is regarded as an internationally acceptable threshold denoting that the animal is protected against rabies - providing that it has been vaccinated before any exposure to the virus.
The antibody levels of the stray/rescue dogs were compared with those from 1766 pet dogs whose Swedish owners had not acquired them from overseas. These pets were tested at the same laboratory as the re-homed dogs 4-6 months after their rabies vaccination.
In dogs vaccinated 4-6 months before testing, just 45.5% had antibody levels of at least 0.5 IU/ml. This compares with 85.7% of the conventionally owned dogs from Sweden.
Among all 75 stray/rescue dogs, 35 (47%) had antibody levels of at least 0.05 IU/ml. But 31 had levels of less than or equal to 0.2 IU/ml. And of these, 14 (19%) had levels equal to or below 0.1 IU/ml - too low to indicate any response to the vaccination. The vaccination date was only recorded for 56 of the dogs.
Most of the dogs came from Romania (63), where there were 318 reported cases of rabies cases among wild animals and 139 among pets in 2012. The country of origin was unknown in 4, and the remaining 8 came from Hungary.
The researchers speculate about the reasons for the low antibody levels. Many of the re-homed dogs were in poor condition, so their immune responses may have been compromised, but rabies vaccination of strays elsewhere has worked well, they say.
Various different vaccines had been used, but all had been approved for the European market, so there is no suggestion that these products were defective.
"Hence one might question if dogs with no detectable antibody responses have been properly vaccinated before rehoming and adoption in Norway," write the researchers, who describe the rise in the numbers arriving from rabies endemic areas as "worrying."
They go on to say that a 3 week delay after vaccination is usually long enough to provide protection. "However, this is no longer the case when dogs are moved from rabies-endemic areas into rabies-free areas, particularly for free-roaming dogs which may unknowingly have been exposed to rabies virus before vaccination," they warn. In a linked editorial, Paula Boyden, Veterinary Director at the charity The Dogs Trust, says that the concerns raised by the study apply to the UK too.
The proportion of dogs transported under the Pet Travel Scheme into the UK, including from rabies endemic countries, rose 78% between 2011 and 2013, she says.
Poor compliance with rabies vaccination probably also means poor compliance with worming treatment too, she suggests, adding that the checks associated with the movement of dogs "are simply not fit for purpose."
She continues: "Vaccinating a dog which is already incubating disease will have little or no effect," adding that a further complication is that different sizes of dogs respond differently to the rabies vaccine as do dogs of different ages.
She acknowledges that the numbers of new cases of rabies in Europe have fallen over the past 20 years. But she warns: "Whilst the risk of rabies may be low, it is not absent. Does it have to take a case of the disease in the UK before this process is critically reviewed?"