Are we overlooking adverse reactions in cats?
That’s the question Patricia Cornwell of White Mill Vet Centre in Sandwich is asking after attending a Merial feline infectious disease seminar, Cats Whiskers, at the Cats’ Protection headquarters in Haywards Heath. The event considered FeLV testing, reactions following vaccination and the benefits of updated calicivirus strains, with presentations from Professors Tim Gruffydd-Jones, Michael Day and Margaret Hosie
“The information from Professors Michael Day and Tim Gruffydd-Jones of Bristol is very enlightening. I think that we all accept that with all vaccinations there is a degree of risk but the level of tissue damage with some vaccines is quite alarming,” Patricia said.
“Of course vaccination is still safe but are we doing enough? Many pet owners are already a bit uneasy with vaccination so should we all not be doing all we can to minimise adverse vaccine reactions where possible? “According to Professor Day, official UK figures put adverse reactions rates at 0.61/10,000 doses but this might not reflect the true picture. I’m sure the majority of vets are fully compliant with the VMD scheme but with the pressure on vets today it is perhaps understandable if some reporting of adverse reactions gets missed. Of course we are also reliant too on owners to spot any potential adverse reactions, and more importantly report them to their vets.”
Prof. Day presented findings from a three-year study by the US-based Banfield Hospital Group, which also cast doubt on official UK incidence. During this time the Banfield Hospital Group monitored adverse reactions following vaccinations in 496,000 cats and 2,560 adverse reactions were recorded. This is somewhat higher then the UK figure and it will be interesting to see Rachael Dean’s report from the AHT that is due out next year.
Of these reactions, Prof. Day reported that the vast majority were relatively minor, occurring within three days of vaccination. Over 50% of reactions were linked to lethargy or pyrexia but vomiting, facial oedemas and generalised pruritus also occurred.
“Of course the big issue is vaccinerelated sarcomas,” said Mrs Cornwell. “At White Mill we have not recorded a single incident and generally our vaccine adverse reaction rate is low. We switched to the Purevax range some time ago and we have seen the number of adverse reactions fall away even further. However, I was surprised at how many in the audience reported cases of vaccine-related sarcomas when questioned by Prof. Day.”
According to Prof. Gruffydd-Jones, vaccine side effects have become more common and he suggested that the rise in adverse reaction rates was linked to the introduction of adjuvanted FeLV vaccines but that these were mainly minor reactions, normally lasting no more than 48 hours.
Prof. Gruffydd-Jones went on to explain that the problem of sarcomas was first highlighted in the USA and there have been marked differences in incidents reported. He suggested that more recent studies (Gobar & Kass, 2002; Kass et al, 2003) have estimated UK incidence at around 50-100 cases from around three million vaccinations annually.
He remarked that the pathogenesis of injection site-related sarcomas is not clear and that along with the belief of a link with rabies and FeLV vaccination, other vaccine components had been documented. However, he suggested that the period of development between sarcoma development following vaccination is normally within a year and so any lump still palpable after a month should be investigated.
When it came to routine vaccination and boosters, Prof. Gruffydd-Jones raised the issue of FeLV in routine vaccinations. In his opinion, developing feline leukaemia through lack of vaccination was a greater danger than the perceived potential danger of sarcoma development.
Tissue changes
Following the presentation of Prof. Gruffydd-Jones, Prof. Day presented his research on tissue changes following vaccination.
Professor Day’s study involved three groups of 15 kittens. Each group was given a different vaccine type. These were two adjuvanted vaccines – lipid or alum – and a third was a nonadjuvanted range.
Each kitten had two injections at two body sites, being the scruff of the neck or lumber region. From these kittens Prof. Day was able to obtain 900 histopathological sections which created 43,200 pieces of information. The injection sites were sampled at 7, 21 and 62 days post vaccination. A scoring system was devised to grade cellular inflammatory scores.
The findings of the research were quite alarming. Both adjuvanted vaccines produced quite extensive reactions compared to the nonadjuvanted product, and even at 62 days Prof. Day had slides showing that residual adjuvant was still present following just a single vaccination.
The question has to be asked if this is the sort of reaction following a single vaccination then what could we expect to see following a second or third administration into the same site? Prof. Day concluded by suggesting that this would make a useful study.
For us, Patricia Cornwell concluded, our adverse reactions have decreased since switching to a non-adjuvanted product but the question remains about consumer attitude to vaccination. In many ways we are being caught up in the human vaccine debate following issues such as MMR but perhaps there is more we should be doing to minimise the discomfort to cats, and ease the mind of the more savvy pet owner of today.
