Michael J. Day, BSc, BVMS(Hons), PhD, DSc, DECVP, FASM, FRCPath, FRCVS
Global Feline Vaccination Guidelines
Guidelines for feline vaccination are produced by the American Association of Feline Practitioners,1 the European Advisory Board on Cat Diseases2 and the WSAVA Vaccination Guidelines Group (VGG)3,4. The fundamental principle of these guidelines, as encapsulated by the VGG, is that ‘We should aim to vaccinate every animal with core vaccines. Non-core vaccines should be given no more frequently than is deemed necessary.’
The WSAVA guidelines suggest that we should aim to vaccinate more animals. This relates to the phenomenon of ‘herd immunity.’ Herd immunity suggests that, for some diseases, where a minimum percentage (for example 75%) of a herd of animals is vaccinated, it is difficult for an infectious disease outbreak to occur. The ‘herd’ for a small animal practitioner is the population of cats living within his or her practice area – and our aim should be to have as many of these animals vaccinated as possible, in order to reduce the chances of disease outbreak in the herd. In order to apply the principles of vaccination guidelines, it is firstly necessary to understand the definitions of ‘core’ and ‘non-core’ vaccines. Core vaccines are those that all animals should receive to protect them against diseases of global significance or where legislation may dictate [i.e., canine rabies]. The use of non-core vaccines is dictated by geographical location, lifestyle and exposure risk. Some vaccines are not recommended because there is little scientific justification for their use. Core vaccines for the cat are those that protect against feline parvovirus (FPV), feline calicivirus (FCV) and feline herpesvirus-1 (FHV). In rabies-endemic countries, rabies vaccination is also considered core for cats, even if not dictated by legislation. Non-core vaccines are those for which use is dictated by geographical location, lifestyle and exposure risk. Non-core vaccines for the cat are those that protect against feline leukaemia virus (FeLV), feline immunodeficiency virus (FIV), Chlamydia felis and Bordetella bronchiseptica. Vaccines against feline infectious peritonitis (FIP) are currently not recommended for use.
WSAVA guidelines provide generic advice to practitioners, but it is impossible to ensure that the guidelines are tailored to best fit the local situation in each of the 86 WSAVA member countries. The VGG encourages national associations to adapt and modify the guidelines for local use where appropriate. This process might involve altering the classification of a vaccine. For example, in the UK, FeLV vaccine is often considered core for the cat and administered routinely to kittens.
Core Vaccination of Kittens
Core vaccination of kittens (FPV, FCV, FHV) begins at 8–9 weeks of age, with a second vaccine given 3–4 weeks later and a third vaccine given at 16 weeks of age or older. The 26- or 52-month fourth vaccine is also an integral part of the kitten programme. Increasing evidence suggests that maternally derived antibody (MDA) may persist for up to 20 weeks in some kittens,5 which underpins the current advice that the third kitten vaccine be given at 16 weeks of age or older. Where rabies is endemic, kittens should receive 1 dose of vaccine at 12 weeks of age, but the VGG suggests that in a high-risk situation (i.e., in an endemic area with recognized clinical cases), a second dose of vaccine may be given 2–4 weeks later.
Core Vaccination of Adult Cats
Most FPV vaccines now carry a licensed duration of immunity (DOI) of 3 years; however, most vaccines against FCV, FHV and non-core products all have a 1-year DOI. A product with licensed 3-year DOI also against FCV and FHV has recently become available. Rabies vaccines (including one non-adjuvanted product) also have a 3-year DOI in many countries. Selecting products with extended DOI allows reduced frequency of administration of that component in a fashion consistent with the legal ‘summary of product characteristics’ (SPC). Guidelines may still advise triennial revaccination with products carrying a 1-year licensed DOI. For the cat, there are field serological data that show persistent seropositivity for 4 or more years post-core MLV vaccination6 and one experimental challenge study that shows immunity for a minimum period of 7.5 years following vaccination of kittens with killed adjuvanted trivalent vaccine7. WSAVA guidelines, therefore, recommend that adult cats receive MLV core FPV vaccine no more frequently than every 3 years. The frequency of administration of MLV core FHV and FCV vaccines depends on individual risk assessment of the lifestyle of the cat. A low-risk cat (e.g., a solitary, indoor-only cat that does not visit boarding catteries) should only require triennial booster vaccination. In contrast, a high-risk cat (e.g., a cat in an indoor-outdoor or multicat household or one that regularly visits boarding catteries) may benefit from annual FHV/FCV revaccination. Using product ranges that split out FPV from the respiratory components, such a protocol is entirely feasible. The study supporting the licence of the 3-year FHV/FCV vaccine clearly shows protection from clinical disease (but not virus shedding) in vaccinated cats challenged after 3 years.8 Rabies vaccination of adult cats may now be performed triennially using products with an appropriate licensed duration of immunity (DOI) of 3 years.
In most situations, MLV (‘infectious’) core vaccines are preferred over killed (‘non-infectious’) vaccines. The exceptions to this rule would be: (1) the rare requirement to vaccinate a pregnant queen, (2) vaccination of cats with known retrovirus infection, (3) vaccination of cats in multicat households where there is no circulating respiratory virus, and (4) for rabies vaccination where 3-year DOI is required.
Non-core vaccines should be selected for the individual cat based on assessment of that particular animal’s risk of exposure to the disease and assessment of the benefits of vaccination to that pet versus the risk of adverse reaction. Decision making for non-core vaccines would be facilitated by having available good-quality data and disease distribution maps related to small animal infectious diseases. Unfortunately, with the exception of rabies in the USA and Europe, such distribution maps are not widely available. Some national schemes have been developed by industry or academic groups which allow practitioners to input cases of particular infectious diseases into a database that presents the information as disease distribution maps. Additionally, consideration must be given to the vaccine requirements of the individual animal, based on assessment of their lifestyle (e.g., indoor versus outdoor, travel and boarding frequency and location, solitary or multicat household). Vaccination is now an example of ‘individualised medicine’ and is no longer as simple as having a practice ‘vaccination protocol.’
For example, where non-core FeLV vaccination is selected for kittens, an initial dose is given at 8 weeks of age, with a second 3–4 weeks later, followed by a 12-month booster. It is more important to vaccinate kittens against FeLV than it is adult cats, as there is development of some naturally acquired immunity in adult animals. The VGG recommends that adult cats are revaccinated against FeLV no more frequently than every 2 or 3 years, depending on risk.
Minimize Adjuvanted Vaccines
Although it is now recognized that the feline injection-site sarcoma (FISS) may be associated with a wide range of injectable or topical products, it is clear that vaccines, and particularly adjuvanted FeLV, FIV and rabies vaccines, are one such risk factor in the transformation of local chronic inflammation to neoplasia. A number of strategies have been proposed to minimise the surgical consequences of any FISS that might develop in a cat. The WSAVA has suggested vaccination into the skin of the lateral abdomen, while the AAFP continues to advise vaccination into the distal hindlimb for rabies and FeLV and the distal forelimb for other vaccines. A recent study has shown the efficacy of vaccination for FPV and rabies when vaccine is administered into the distal tail, although there remain some concerns about this procedure.9 Whichever anatomical site is chosen, basic principles should be to avoid the scruff of the neck, to rotate sites of injection and to record these sites in the medical record of the animal.
The Annual Health Check
All aspects of vaccination should fall under an annual health check programme that reduces the emphasis on vaccination as a reason for visiting the practice and considers holistically the overall health and wellbeing of the pet. A discussion about which vaccines (or serological tests) might be offered in any one year is just one part of the annual health check. The importance of vaccination can be reinforced by using the VGG fact sheets. Vaccination (or serology) should be appropriately invoiced so emphasis is placed on the professional consultation. The use of in-house serological testing can reliably inform the need for FPV revaccination as there is a strong correlation between seropositivity and protection.10 Any seropositive adult cat does not require revaccination against FPV. This correlation is not as strong for FCV and FHV, as seronegative cats might still be protected by cellular or mucosal immunity.
1. Scherk MA, Ford RB, Gaskell RM, et al. 2013 AAFP Feline Vaccination Advisory Panel report. J Feline Med Surg. 2013;15:785–808.
2. Hosie MJ, Addie D, Belak S, et al. Matrix vaccination guidelines: ABCD recommendations for indoor/outdoor cats, rescue shelter cats and breeding catteries. J Feline Med Surg. 2013;15:540–44.
3. Day MJ, Horzinek M, Schultz RD, Squires RA. WSAVA Guidelines for the vaccination of dogs and cats. J Small Anim Pract. 2016;57:E1–E45.
4. Day MJ. Small animal vaccination: a practical guide for vets in the UK. In Practice. 2017;39:110–118.
5. Jakel V, Cussler K, Hanschmann KM, et al. Vaccination against feline panleukopenia: implications from a field study in kittens. BMC Vet Res. 2012;8:62.
6. Mouzin DE, Lorenzen MJ, Haworth JD, et al. Duration of serologic response to three viral antigens in cats. J Am Vet Med Assoc. 2004;224:61–6.
7. Scott FW, Geissinger CM. Long-term immunity in cats vaccinated with an inactivated trivalent vaccine. Am J Vet Res. 1999;60:652–58.
8. Jas D, Frances-Duvert V, Vernes D, et al. Three-year duration of immunity for feline herpesvirus and calicivirus evaluated in a controlled vaccination-challenge laboratory trial. Vet Microbiol. 2015;177:123–31.
9. Hendricks CG, Levy JK, Tucker SJ, et al. Tail vaccination in cats: a pilot study. J Feline Med Surg. 2014;16:275–80.
10. Mende K, Stuetzer B, Truyen U, et al. Evaluation of an in-house dot enzyme-linked immunosorbent assay to detect antibodies against feline panleukopenia virus. J Feline Med Surg. 2014;16:805–11.