Feline Panleukopenia Virus is a widespread infectious disease of cats found in most regions of the world. This disease most commonly infects kittens but may occur in cats of any age. Cats may be carriers of the virus, but infection can also be spread by dogs, racoons, and other wildlife. Panleukopenia causes suppression of the immune system associated with diarrhea, vomiting, loss of appetite, severe dehydration, and secondary infections. Cats may develop sepsis and the disease is often fatal. As the virus is very hardy in the environment and is carried by many animals, a large proportion of cats will be exposed to this disease.
Thankfully, a very effective vaccine for panleukopenia virus is widely available and is given as a part of most core vaccine series in cats and kittens. This is often administered in combination with Feline Viral Rhinotracheitis (FHV-1) and Calicivirus as the “FVRCP” combination vaccine. Traditionally this is given as part of a kitten series and then every 3 years as an adult. It has been recently suggested that vaccination for panleukopenia may often be more durable than this. Animals who have strong positive titres for panleukpenia will generally not be further boosted by re-vaccination.
The purpose of this study was to evaluate the response of healthy adult cats to panleukopenia vaccination. 112 cats were included in a prospective trial between April 2012 and September 2014. Cats were clinically healthy and had received panleukopenia vaccination no less than 12 months ago. Retrovirus positive cats were excluded from the study.
Cats received a modified live “FVRCP” vaccine containing panleukopenia virus. Serum samples were collected at 0, 7, and 28 days. Data were collected on signalment, environment, lifestyle, cohabitation, contact with other cats, and vaccine history. Antibody titres were determined by hemagglutination inhibition and an adequate response to vaccination considered a four-fold increase in titre.
Positive antibody titres (>1:40) were present in 64.3% of cats on day 0. An adequate response to vaccination was observed in 48.3% of cats, with 40.7% showing an adequate response by 7 days post vaccination.
In multivariate analysis of the collected information, only previous vaccination, pre-vaccination titre, and breed were associated with response to vaccination. Cats with no previous vaccines or a low titre were more likely to show a response to vaccination. Domestic shorthaired cats were more likely to respond to vaccination than purebred cats.
While 64% of cats were protected against panleukopenia pre-vaccination, more than 1/3 of cats were not, showing the need for continued education and vaccination programs. While most of the cats who did not respond to vaccination were those with high pre-vaccine titres, 5 cats with no or low antibodies were also non-responders. This may be due to genetic or immunologic effects that prevented antibody production.
More than half of the cats did not benefit from vaccination. The authors recommend that antibody titres be measured in cats with previous FPV vaccination prior to re-vaccination, and that for those with a high titre (>1:160) re-vaccination not be performed.
Several limitations to this study exist. One of these is the limited geographic region data was collected from, which may not represent international trends. The study also looked only at boosters with a single type of modified live vaccine. Killed vaccines may have a different antibody response, as may different brands or formulations of modified live vaccines. As there was a large historical component of the study, it is possible that inaccurate data may have been collected. It is also possible that cell-mediated immunity is present in some cats with inadequate titres, however this is difficult to measure without challenge studies. (MRK)
Hosie MJ, Addie DD, Boucraut-Baralon C, et al. Matrix vaccination guidelines: 2015 ABCD recommendations for indoor/outdoor cats, rescue shelter cats and breeding catteries. J Feline Med Surg 2015; 17: 583–587.