Questions and Answers from Feline Infectious Disease Webinar by Martha Cannon

Feline Vaccines Webinar: Answers to questions that weren’t answered on the night

Q: does it matter if the vaccines used for the primary course are not of the same type/brand?

A: Good question Claire! The vaccine manufacturers would undoubtedly say “yes”, but in practical terms I think the only area in which there might potentially be an issue would be with Calicivirus (FCV) vaccine. As we discussed in the webinar FCV is a very variable virus so no vaccine can include vaccine virus strains that will cover ALL field strains of the virus, and different vaccine companies do use different strains  and combinations of virus in their vaccines – so while all vaccines give pretty good general cover there will be some strains of FCV which are covered by one vaccine and not with another. Therefore if a kitten gets two different vaccines for 1st and 2nd vacc it will only be guaranteed to have maximal protection against those viruses covered by both vaccines. In my opinion this is still going to give pretty good protection against FCV (especially in view of the fact that we will never get 100% protection) and so for most purposes this may be another area in which we can apply the mantra of “Vaccinate more individual cats, but vaccinate each individual cat less often”.

Q: I will be naughty — I know this is off topic — to the both of you Feline Plasmacytic Pododematitis — any new ideas — have had 2 cases recently.

A: OK Shona, I’ll indulge you just this once! Here are recent brief (v brief!) notes that I put together on Plasma Cell Pododermatitis  a couple of years ago — hope they help:

  • Clinical Presentation: Single or multiple swollen pads, soft/spongy texture, may ulcerate as secondary complication. Variably painful.
  • Pathology: Plasma cells and small number of lymphocytes.
  • Aetiology: Unknown, possible association with FIV  (Simon et 1993)  not confirmed in other studies. Currently immune-mediated component suspected. No consistent infectious agent identified.
  • Signalment: No age, breed, sex predilection.
  • Treatment: Traditionally immunosuppressive doses of corticosteroids, recent interest in Vitamin E and doxycycline. Some may self resolve.
  • Prognosis: Variable and currently unpredictable

Q: if a cat has been diagnosed with nocardiosis it obviously needs a lot of vet visits due to that so is a high risk environment, would you annually booster this cat with inactivated virus ?or never again if the practice does not stock inactivated flu-vaccines.

A: I guess your concern is that the presence of  Nocardiosis may indicate that the cat is immunosuppressed? Depending on the details of the case, if the cat appears negative on in-house FeLV and FIV tests it might be worth running an FIV pcr test in case of antibody negative FIV. Beyond that, if the prognosis from the Nocardiosis is good enough to suggest long term survival i.e. the Nocarida is cleared or in full “control” then I would vaccinate as usual once the cat was in the best health – with live vaccine if no killed vaccine available.

Q: would you vaccinate a cat in kidney failure?

A: If we are thinking about chronic renal failure and the cat is relatively well, living at home and hopefully with good life-time ahead of it, then I would certainly vaccinate. If the cat is in end stage CRF with likely  a short future lifespan I would discuss with the owner whether they want to vaccinate  or not. For a cat in acute renal failure, or acutely decompensated CRF – i.e. hospitalised on iv fluids etc, then I would wait until it had recovered (as far as recovery is possible) before resuming vaccinations, bearing mind that even if that means delaying the booster for some months, we will still only need a single vaccine to bring things back on track.

Q: Don’t you think the Lappin study should be given more weight, I ve had  a cat that similar with similar histological diagni

A: Sorry the whole question didn’t come through so I don’t know the exact question — but I think that further work is needed before we can really know the clinical significance of his laboratory findings, which so far are on a very small number of cats and using vaccine regimes which are rather different to that which we use in practise. We need to be very careful before extrapolating from these initial findings and  I would guess that Mike Lappin might be doing further work on it. I do think it would be helpful if vaccine companies had the information available to let us know which, if any, of their vaccine viruses are raised on CRF-K lines though.

Q: is the every second year for felv vaccination acceptable for any vaccine brand used? or does it depend on the vaccine companies data sheet guidelines?

A: The ABCD group are an independent group of experts. Even though they are funded by Merial their recommendations are not specific to any on vaccine brand. You can read the recommendations in much more detail on their web-site www.abcd-vets.org it’s well worth visitng as there is so muvh good information there.

Q: Hello, How treatment  cat flu.

A: Sorry Aurelius — that’s a huge topic — and I can’t cover it here. Maybe we can have a second webinar on that?!

Q: Any advice on FPLV protection in very young kittens in a rescue environment?

A: Hi David, this isn’t something I have personal experience of, so I am “cheating” and copying the relevant section from the ABCD web-site (www.abcd-vets.org) — I’m sure they won’t mind me sharing it with you — but do go the web-site too — it’s excellent!

“Feline Panleukopenia control in specific situations — Shelters

Random source populations with largely unknown vaccination histories, continuous resident turnover, and high risk for infectious disease characterize most shelters. Vaccine costs become a significant management aspect when multiplied by thousands of doses. Therefore, only those antigens that demonstrate a clear benefit against common and significant shelter diseases should be utilized.
FPV has re-emerged as a significant cause of mortality in cats in shelters and rescue homes throughout Europe and the United States. With rare exceptions, all kittens and cats over 4 to 6 weeks of age should be vaccinated regardless of physical condition, pregnancy, or housing status. Kittens should be vaccinated beginning at 4 weeks of age in the face of an outbreak, and at 6 weeks of age otherwise. MLV vaccines are advantageous for their faster onset of action, greater efficacy at overcoming maternal antibody, and greater likelihood of conferring sufficient immunity. (Greene and Addie, 2005; Greene and Schulz, 2005). Although concerns have been raised regarding their reversion to virulence, this has never been documented (Greene and Schulz, 2005). Cats of unknown status should not be housed together.

Vaccination should be repeated every 3 to 4 weeks in kittens, until 16 weeks of age. If adult cats are ill or otherwise compromised at the time of initial vaccination, another injection when the cat is in good health (at least two weeks after the initial vaccine) should be considered.

When vaccination is being used to control disease in the face of an outbreak, the more rapid induction of immunity induced by a MLV preparations is of clinical advantage over killed vaccines.

Passive immunisation can be used in shelters when available. It is useful at admission if other diseases are present or in an environment with high infection pressure, as it provides immediate protection. Efficacy of immunoglobulins to prevent infection, including FPV, has been proven in experimental studies and in the field some 50 years ago. Efficacy of immunoglobulins depends on many factors, including the antibody titre against the specific agent and volume administered, the relative importance of serum antibodies in controlling the particular infection involved, and the timing of administration of the antibodies compared to exposure.

Commercial products containing highly concentrated immunoglobulins (multivalent hyperimmune immunoglobulin preparations) are available in some European countries for cats (heterologous preparation produced in horses, containing a combination of antibodies against FPV, FHV-1, and FCV). They are marketed for prophylactic (usually 1 injection of 1 vial/animal subcutaneously) and therapeutic (usually 3 injections of 1 vial/animal subcutaneously every 24 hours) use. Protection lasts for about 3 weeks. During this period, active immunization (vaccination) is not recommended because the immunoglobulins will bind to the vaccinal antigens, tying them up in immune complexes. Although large amounts of foreign protein are administered, allergic reaction are rare if a cat is treated for the first time, and treatment is usually not associated with side effects. Repeated treatment (with an interval of more than 1 week), however, is not recommended because cats can display anaphylactic reactions to the product produced in horses (Hartmann and Hein, 2002).

Besides commercial products, customised (hyper)immune serum may be administered. Immune serum is derived from healthy individuals or from groups of animals that have recovered from a specific disease, whereas hyperimmune serum comes from animals that had been repeatedly vaccinated against specified infectious agents. If such sera are used, their antibody content and consequently the duration of protection are unknown. Like all exogenous proteins, administered antibodies are quickly eliminated from the body.
Feline immune sera can be prepared in veterinary practice, but blood donors must be carefully screened for insidious infections (e.g. FIV, FeLV, Bartonella infection). Ideally, the blood type of donor and recipient should match; if cross-matching cannot be performed, only type A cats should be used as donors. The minimum amount required for protection is unknown, but the dose recommended for cats is 2 to 4 ml serum per kilogram body weight. Careful attention must be paid to sterility during collection, storage and administration. Jugular vein puncture is preferred, and the area over the jugular vein should be shaved and prepared for aseptic venipuncture. Blood should be collected (at least twice the amount of required serum) into sterile tubes without additives. Serum can be stored at -20° C in single dose aliquots as IgG is a very stable molecule and can be kept for up to a year if frozen promptly after collection (Levy and Crawford, 2000). Usually, sera are given subcutaneously; intraperitoneal injection is more feasible in kittens. If for an instant effect intravenous administration is required, plasma (instead of serum) should be used (Greene and Schultz, 2005). “

Q: Hi Martha, great talk. I’m in Sydney and vets don’t seem to vaccinate against FeLV as commonly here. Do you have any information on prevalence in Australia? And how often do you perform an Felv test in an unwell cat? Finally, is there an average incidence of FeLV infection for the UK and is there an incidence of vaccine suspected sarcoma reactions?

A: I have no experience of FeLV prevalence in Australia, but I would guess that, as in the UK, the incidence will vary with location and lifestyle, so no “average incidence” I’m afraid, it depends where you are in the country. With regards to Australia, a brief literature search (PubMed gives free access, http://www.ncbi.nlm.nih.gov/pubmed) throws up the following:

Muirden A (2002) Prevalence of feline leukaemia virus and antibodies to feline immunodeficiency virus and feline coronavirus in stray cats sent to an RSPCA hospital.”

Vet Rec. 18;150(20):621-5.

Abstract

A total of 517 stray cats at an RSPCA veterinary hospital were tested for feline leukaemia virus (FeLV), feline coronavirus (FCoV) and feline immunodeficiency virus (FIV). The prevalence of FeLV was 3.5 per cent in all the cats, 1.4 per cent in healthy cats and 6.9 per cent in sick cats. FeLV positivity was associated only with disease of non-traumatic origin. Antibodies to FCoV were present in 22.4 per cent of the cats, and their prevalence was significantly higher in cats over two years old and in feral/semiferal cats. The prevalence of antibodies to FIV was 10.4 per cent in all the cats, 4.9 per cent in healthy cats and 16.7 per cent in sick cats. The prevalence of FIV antibodies was significantly higher in entire males and neutered males than in females, in cats over two years old compared with younger cats, and in cats suffering disease of non-traumatic origin rather than in healthy cats or cats suffering only from trauma. Sex, age and health status were each independently highly associated with FIV antibodies.

Malik R et al (1997) Prevalences of feline leukaemia virus and feline immunodeficiency virus infections in cats in Sydney. Aust Vet J. 1997 May;75(5):323-7.

Objective:

To determine prevalences of feline leukaemia virus (FeLV) and feline immunodeficiency virus (FIV) infections in ‘healthy’ cats that, through acute misadventure or other circumstance, were presented to veterinary practitioners. Prevalences of FeLV and FIV in this population were compared to those in a population of predominantly sick cats. DESIGN AND PROCEDURES: Serum specimens were obtained over a 2-year period from 200 cats older than 1 year of age presented to veterinary clinics for routine procedures, including cat fight injuries or abscesses, vehicular trauma, neutering, dental scaling, vaccination, grooming or boarding. An additional 894 sera were obtained over approximately the same period from specimens submitted by veterinarians to a private clinical pathology laboratory, mainly from sick cars suspected of having immune dysfunction, but including some sera from healthy cats being screened prior to FeLV vaccination. FIV antibody and FeLV antigen were detected in samples using commercial enzyme immunoassays. RESULTS: Amongst 200 ‘healthy’ cats, the prevalence of FeLV infection was 0 to 2%, and the prevalence of FIV was 6.5 to 7.5%, depending on the stringency of the criteria used to define positivity. FIV infection was significantly more prevalent in cats which resided in an inner city environment (P = 0.013). Of the 894 serum specimens submitted to the laboratory by practitioners, 11/761 (1.4%) were FeLV positive, while 148/711 (20.8%) were FIV positive. The prevalence of FIV was significantly higher in these predominantly ‘sick’ cats than in cats seen for routine veterinary procedures (P < 0.00001), while there was no difference in the prevalence of FeLV (P = 0.75) CONCLUSIONS: The prevalence of FeLV and FIV in healthy cats may have been substantially overestimated in some previous Australian surveys. FeLV infection would appear to be a rare cause of disease in Australian cats. The higher prevalence of FIV positivity in sick as opposed to healthy cats infers that FIV infection contributes to the development of disease.”

So that would suggest it is similar to our experience in Oxford at least. How often do we run an FeLV test in a sick cat? Again, not easy to answer, other than that we do it when the cat’s background and clinical signs place it on the differential list – so sick kitten’s of unknown origin, sick rescue cats, cats with non-regenerative anaemia, bone marrow disorders, some types of lymphoma e.g. mediastinal (but most lymphomas are FeLV negative these days), pyrexia of unknown origin… etc.

Fortunately incidence of Injection Site Sarcomas per injection given is very low, it isn’t possible to have completely accurate data but most estimates suggest around 1–10 per 10,000 cats. However, a straw poll (show of hands) of delegates at any small animal meeting in the UK tends to show that half to two thirds of small animal vets here have first hand experience of them within their practise – so a low incidence per injection, but significant numbers of cats nonetheless.

Q: Do you test for FeLV before vaccinating?

A: In most cases no, I don’t test before vaccinating because FeLV is so rare in the general healthy cat population in my region. I would test if I had a high index of suspicion though – maybe if a young kitten came from a rescue centre that I knew had a high incidence.

Q: Do you think the temperature of the vaccine is important at the moment of the vaccination to prevent sarcoma

A: Interesting question Gustavo. To date studies have not been able to find any reliably consistent link with any factors associated with vaccine administration, but Kass et al (2003) did find a “possible” association with colder vaccines (i.e. given straight from the fridge rather than at room temperature) – nothing of statistical significance though.

Kass PH et al (2003) Multicenter case-control study of risk factors associated with development of vaccine-associated sarcomas in cats. J Am Vet Med Assoc. 2003 Nov 1;223(9):1283-92.

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