Vaccinations prevent a variety of diseases, but can be dangerous
Two years ago Dominque Frebourg moved from France to Hong Kong. She brought all her worldly possessions, including her three cats.
Adhering to Hong Kong's animal import regulations, she vaccinated them before leaving France for a variety of diseases, including rabies.
'We did a lot of paperwork before we came and all the vaccines were done,' explains Frebourg.
Until a month ago, she believed all her furry felines were in good health but then noticed seven-year old Nanaki had a lump on the back of her neck, which was soon diagnosed as an abscess.
Frebourg took Nanaki to see vet Gerry Pahl at Victoria Veterinary Clinics in Tuen Mun for a second opinion. A biopsy revealed the growth had initially been misdiagnosed and the lump was a vaccine-associated fibrosarcoma (VAS), a cancer caused by an administered vaccine.
'A few weeks ago I thought it was an abscess, but now Nanaki might die because it was vaccinated,' she says.
Pahl says: 'As Nanaki has had several vaccinations, we can't say for sure which one resulted in the vaccine-associated fibrosarcoma ... Nanaki's tumour is on the back between the shoulder blades, where vaccines are normally given. It's a very aggressive cancer and it's really big now.'
He adds the tumour has quickly grown deep down into the spine, making it extremely difficult to surgically remove.
VAS was first discovered by the University of Pennsylvania School of Veterinary Medicine in 1991, and associated with the increased use of rabies vaccines and adjuvanted feline leukaemia virus vaccines.
While VAS is a problem for cats, (the condition does not significantly affect dogs), it's rare: the estimated incidence is 0.5 to 2 in 10,000 cats.
'It's uncommon, but you still don't want it to happen to your pet. Nanaki is the first cat I've treated with VAS,' says Pahl.
While most animals receive injections and vaccines in the same location, at the back of the neck between the shoulder blades, the vet says it's difficult to pinpoint the trigger of a VAS.
'The issue is if you are relocating back to the UK or most countries, you are required to vaccinate against rabies. So any cat being prepared needs the vaccination, but this has a risk of cancer forming,' he says.
According to Pahl, research suggests that a component inside the vaccines that causes the cancer is adjuvant, an agent that helps slowly release the vaccine into the body over time. While the connection between sarcoma formation and vaccine adjuvant is still controversial, many states and vets in the United States have switched to adjuvant free-vaccines. In Hong Kong, the Agriculture, Fisheries and Conservation Department provides rabies vaccines directly to cat owners and private veterinarians, so Pahl suggests owners who need to export their feline check whether the vaccine is adjuvant-free.
'I think the government should provide adjuvant-free vaccines, there are rabies vaccines that are available in the US and have been made specifically for this purpose [of reducing the risk of VAS],' says Pahl.
For other routine vaccinations, such as feline distemper, the vet says these vaccinations 'are important and should be routinely done to protect them.'
One method of lessening the health risk of VAS is to administer the rabies vaccine on the back right hind leg, as recommended in some guidelines in the US. Leukaemia vaccine should be administered on the left hind leg.
This way, if a VAS develops, it's traceable and the tumour can be removed through amputation.
'If the animal is unlucky enough to get the cancer, an amputation may well save the animal's life, a lot of times we catch it when it's too late,' says Pahl. 'With this particular case [Nanaki], we are planning on doing surgery to remove as much as we can.'
In recounting recent developments, Frebourg says: 'I've tried to be good to our pets and give them the right vaccines - because we've been asked to do it. I thought they should be in good health and not sick.'
At time of publication, Nanaki's surgery to remove the tumour went well and she is recovering.