VACCINATION: IS IT WORTHWHILE?

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1 Vet Times The website for the veterinary profession VACCINATION: IS IT WORTHWHILE? Author : JENNY MOFFETT Categories : Vets Date : March 2, 2009 JENNY MOFFETT assesses the pros and cons of vaccination and not, and suggests that finding a middle ground may be the most beneficial approach VACCINATION, whether of humans or animals, is one of the most controversial health topics around. There is a great deal of information and misinformation on the subject, which can leave both vets and pet owners confused. Much of the debate was sparked in the 1990s, following the publication of a paper that proposed links between the MMR vaccination and autism in children. Although the association was subsequently overturned, the no smoke without fire doubt has persisted in parents minds. Takeup rates for the MMR injection have plummeted and, according to the NHS, last year s vaccination figures dipped below protective population levels against measles. It is likely that such public debates have affected pet owners willingness to vaccinate their animals, and any client with an enquiring mind, and access to the internet, will be exposed to the to vaccinate or not question. Add this to the everincreasing choice of companion animal vaccine products and protocols available to veterinary practitioners, and it is no wonder there is confusion. In this article, I explore the issues surrounding vaccination, specifically against feline infectious disease, and identify whether prevention can represent a viable alternative. Many clients now hold negative beliefs surrounding pet vaccination: It doesn t work, It can do more harm than good, It is expensive and unnecessary and We are over-vaccinating our pets. Some of these statements hold an element of truth: vaccination does not work in all cases; 1 / 11

2 there are many infectious feline diseases for which there is no vaccine and, where there is, no guarantee can be provided as to whether it is 100 per cent effective. It is also well documented that vaccines can have side effects, and there has been much discussion of a link between booster shots and certain types of neoplasia. Pet owners also draw on their own experiences regarding pet vaccination. Think of the cat that developed signs of cat flu despite vaccination, or the cat that became lethargic and inappetent after an annual booster the owners of these individuals may have concluded that vaccination is neither good nor useful. So, leaving vaccination aside, what preventive measures can a client take to protect his or her cat from infectious disease? Two main points of action are: decreasing the chances of the cat coming into contact with the pathogen; and building its resistance to disease. The main way of reducing exposure to a pathogen is to keep a cat inside and housed alone. Outdoor cats will have more exposure to disease, although neutering and taking them in at night will decrease disease risk factors, such as straying and fighting. In multi-cat households or catteries, other excellent measures include: attention to hygiene and disinfection; protocols for cleaning (such as kitten beds and food bowls cleaned first); isolation kennels; protocols for disease testing; foot baths; sneeze barriers; segregation or low mixing of cats; and quarantine of new animals. Building a cat s disease resistance involves supporting its immune system with excellent pet care, good nutrition, regular parasite control and timely, appropriate veterinary intervention. The problem with relying on preventive measures alone, however, is that they do not ensure that a cat will not come into contact with an infectious disease. Feline panleucopenia virus (FPV), for example, is an extremely resistant pathogen that can be carried into a house on the clothes and shoes of a visitor. Unless your client and his or her cat live in a sealed environment, it is possible that the virus can enter. And, if the cat is naïve to this virus, the results will be devastating. On top of this, closed-house systems do not allow for feline bids for freedom or necessary, and often unanticipated, visits to the vet. If we work on the premise that some vaccinations are necessary, how can we work out which ones are? The choice comes down to risk assessment: is the risk of failing to vaccinate a cat greater than the risk associated with vaccinating? Both risks involve two factors: the chance of occurrence, and impact should it happen. For example, a single, indoor-only cat has a low, but possible, risk of developing feline panleucopenia (low chance of occurrence). But, if the cat did develop the disease, it could die (high impact). We then look at the risks associated with vaccination, which can largely be grouped under adverse reactions. According to the VMD, which runs the suspected adverse reaction (SAR) surveillance scheme, there were 2,158 SARs reported for the period of 1995 to This equates to about 0.61 SARs per 10,000 doses of vaccine sold. Although many SARs are not reported to the VMD, it is also likely that some incidents included in the figures are not true vaccination reactions either. Thus, with FPV vaccination, it is a comparison of low occurrence and low impact (the majority of reactions to the FPV vaccine involve either a transient fever and listlessness, or a temporary swelling at the 2 / 11

3 injection site) to the risk of an animal contracting a potentially fatal disease. Although it is hard to quantify the likelihood of FPV infection, the high impact, should it occur, warrants a decision in favour of vaccination. The European Advisory Board on Cat Diseases (ABCD) has, since its launch in 2006, established a series of guidelines for several major feline infectious diseases. These guidelines also incorporate the idea of risk assessment and, currently, the ABCD recommends a range of core and non-core vaccines. Core vaccines Vaccination against FPV is recommended as a core vaccine. The ABCD refers to the ubiquity of this virus in the environment, its resilience to some common hygiene and disinfection measures and the devastating effects of the disease. ABCD recommendations include an initial vaccination at eight to nine weeks of age, followed by a second vaccination three to four weeks later (at a minimum of 12 weeks of age). When it comes to booster vaccinations, research suggests cats that respond to FPV vaccination maintain a solid immunity for several years (seven or more) in the absence of any repeat vaccination or natural challenge, according to the ABCD. A first booster, 12 months after completion of the primary vaccination course, is recommended with subsequent revaccinations at a minimum three-yearly interval. Vaccination against feline herpes virus (FHV) is the second core vaccine. Although the main source of this virus is other cats (those that are acutely infected, or latently infected and experiencing reactivation), it can survive in the environment and indirect transmission is possible. Because of this, and the severe disease the virus causes, the ABCD recommends a primary course and regular booster injec tions for all cats (two injections at around nine to 12 weeks). The ABCD recommends annual boosters in cats that are exposed to high-risk situations, such as boarding catteries, multicat households and cat shows. In situations evaluated as low risk (such as strictly indoor cats with no possible contact with other cats), threeyearly intervals, says the ABCD, may be an alternative option. The third vaccine that the ABCD classifies as core is the feline calicivirus (FCV) vaccine, and it is recommended that all kittens should be vaccinated against FCV (again, two injections at around nine and 12 weeks). A regular booster, says the ABCD, should be administered every three years in lowrisk situations (mainly indoor-only cats with little or no contact to others). Cats in crowded, highrisk situations (such as boarding catteries) should, however, be revaccinated at yearly intervals. 3 / 11

4 Vaccination against rabies has also been classified by the ABCD as a core vaccine, but only in countries where the disease is endemic. In the UK, it is considered optional, but becomes core should the owner of the cat travel to a country where the disease is present. The Cat Group of the Feline Advisory Bureau also supports the discriminatory use of feline vaccines in the UK. Like the ABCD, The Cat Group supports routine vaccination against FCV, FHV and FPV. However, it has a less wellde fined opinion on booster intervals, stating: The Cat Group recognises that there is a genuine difference of opinion among clinicians and scientists at present on the necessary frequency of booster vaccination for adult cats. Furthermore, at present there is insufficient data available to determine optimum booster intervals in adult cats. Non-core vaccines Vaccines against feline leukaemia virus (FeLV), on the other hand, are classified as non-core by the ABCD. Transmission of this virus is based on direct contact and a single, indoor cat has little or no risk of exposure. So, if a cat will not go outside or meet other cats, FeLV vaccination is not necessary. However, if it is possible that future exposure to the virus cannot be discounted, such as if the circumstances of the cat or its owner change, vaccination is recommended. Out of all the commonly used boosters in the UK, FeLV vaccines have, perhaps, received the worst press. Reports of a condition known as vaccineassociated fibrosarcoma have been widely discussed. However, the incidence of this condition is thought to be 0.04 cases per 10,000 in the UK, which is a small risk, especially when compared to incidence of FeLV (FAB figures put this at one to two cases per 100 cats). The ABCD comments: In most circumstances, FeLV should be included in the routine vaccination programme for pet cats. It provides good protection against a potentially life-threatening infection, and the benefits for most cats considerably outweigh any small risk of serious adverse effects. With regards to boosters, most vaccine manufacturers recommend annual injections, as there is little data to support an immunity duration of longer than one year after primo-vaccination. Older cats have significantly lower susceptibility to FeLV infection than younger cats, but they can still be infected in the face of a sufficiently severe challenge the ABCD suggests that in cats older than three to four years, a booster every two to three years would be sufficient. Other non-core vaccines available in the UK include those against Bordetella bronchiseptica and Chlamydophila felis. There are no current ABCD guidelines on these vaccines, but more information is expected later in In addition, a feline immunodeficiency virus (FIV) vaccine is commercially available in the US and Australia, but it is not licensed in Europe. This has relevance, 4 / 11

5 in that cats imported from these countries may test positive for FIV in standard diagnostic tests here. Also, cats that have been vaccinated with the FIV vaccine abroad may not be protected against FIV isolates found in the UK. In conclusion, it seems that there is middle ground to be reached between the two opinions ( not vaccinating is best and vaccinating against every pathogen, every year, is best ). The key is to tailor disease control measures on a case-by-case basis an indoor cat will have different requirements to one in a multi-cat household with outdoor access. It is the modern practitioner s role to guide clients through the decision-making process. Many of the ABCD s guidelines, especially those that recommend booster intervals exceeding one year, work outside of current vaccine manufacturers recommendations. Therefore, the pros and cons of vaccinating on an annual or a three-yearly basis, as well as the value of a yearly health check regardless of vaccine protocol, must be clearly communicated to the client. In this way, he or she can give informed consent to the vaccination process. In return, your reward will be the knowledge that you are reinforcing the trust of your client in your work, and exercising best practice in one of the most common clinical encounters in companion animal practice. Further reading ABCD guidelines on rabies in cats (2008). Available at accessed on January 27, ABCD guidelines on feline immunodeficiency virus (2008). Available at accessed on January 27, ABCD guidelines on feline leukaemia virus (2007). Available at accessed on January 27, ABCD guidelines on feline calicivirus (2007). Available at accessed on January 27, ABCD guidelines on feline herpesvirus (2006). Available at accessed on January 27, ABCD guidelines on feline panleukopenia (2006). Available at accessed on January 27, Carvel J (2008). Warning of measles epidemic risk as cases rise sharply, The Guardian, November 28, Feline Advisory Bureau (2008). Policy Statement 4: Vaccination of cats, available at on January 28, Schultz R D (2006). Duration of immunity for canine and feline vaccines: a review, Veterinary Microbiology 117: / 11

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7 A computer-generated image illustrating the viral capsid structure of feline parvovirus. Image credit: MAVIS AGBANDJEMCKENNA AND LAKSHMANAN GOVINDASAMY, UNIVERSITY OF FLORIDA. A kitten showing signs of severe feline herpes infection. 7 / 11

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9 Haemorrhagic diarrhoea in a cat with feline panleucopenia infection. Images on this page courtesy of: ALBERT LLORET, UNIVERSITAT AUTÒNOMA DE BARCELONA VETERINARY TEACHING HOSPITAL. 9 / 11

10 Severe gingivitis in a cat with feline immunodeficiency virus. Images on this page courtesy of: ALBERT LLORET, UNIVERSITAT AUTÒNOMA DE BARCELONA VETERINARY TEACHING HOSPITAL. 10 / 11

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