Feline panleukopenia: A diagnostic laboratory's perspective - Veterinary Medicine
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Feline panleukopenia: A diagnostic laboratory's perspective
Despite the development of highly effective vaccines, this ancient feline disease continues to be the bane of cats housed in close contact. Find out what you need to watch for in at-risk populations and how to approach diagnosis and disease prevention.


Finally, virus isolation for FPL virus has been successful in feline cell lines that are young and rapidly dividing. A commonly used cell line is Crandall feline kidney cells. FPL virus is disseminated throughout the body within seven days and can be recovered from feces and urine for several weeks after infection,7 but many laboratories will not accept fecal or urine samples for virus isolation because these samples can be toxic to cells used for culture. Although not commonly done, virus can also be cultured from oropharyngeal swabs and buffy coat samples. It is critical that these samples be obtained during the early viremic phase, submitted in viral transport media, and chilled en route. Some suppliers of specialized viral culture media include Becton, Dickinson and Company (Franklin Lakes, N.J.) and Remel (Lenexa, Kan.). Appropriate postmortem samples include spleen, mesenteric lymph nodes, and ileum. These samples should be submitted chilled by overnight delivery. In most laboratories, virus cultures are incubated for seven days with one blind passage, resulting in an average turnaround of two weeks. If cytopathic effect is observed, the cells will be stained with FPL-specific conjugate to confirm the presence of the virus. Virus isolation is useful to obtain an isolate for further characterization, particularly in epidemiology studies. One of the principal drawbacks of virus isolation is the length of time between submission and receipt of results.


Parvoviruses are remarkably stable in the environment, and because these viruses are also resistant to lipid solvents and disinfectants, they are among the toughest viral particles to eradicate from a contaminated facility. A gram of infected stool from a clinical case of FPL can contain as much as 109 viral particles.17 Reports on the exact longevity of the virus are variable, and many environmental factors affect the duration of virus viability. However, it is generally accepted that parvovirus particles can infect new hosts for six months to a year after they are shed,1,7 and there are many anecdotal reports of cases of FPL occurring on premises years after infected cats have recovered or been removed.

Cats with FPL can require intense supportive care, but hospitalization of highly contagious animals puts other patients at risk. When treating patients suspected of having FPL, a quarantine facility and diligent staff able to follow strict decontamination procedures are necessary to maintain an environment free of infectious particles. Parvovirus particles spread easily on hands and on shoes, clothing, and other fomites. So changing clothes, regular hand washing, and the use of foot baths are basic quarantine procedures that should be instituted. FPL virus can be inactivated by using a 1:20 to 1:32 dilution of sodium hypochlorite (4 oz household bleach in 1 gal water); 4% formalin solutions and 1% glutaraldehyde solutions also inactivate the virus.6,18,19 However, because of the robust nature of the virus, sanitation measures alone cannot be relied on to prevent the spread of this disease.

Vaccination is inexpensive, confers long immunity, and is the most effective measure for preventing FPL. Modified live and killed vaccines are available, which are often combined with feline calicivirus and feline herpesvirus; both confer excellent immunity. A 1999 study showed that cats vaccinated with a single dose of an inactivated vaccine for FPL had solid protection for 7.5 years (the length of the study).20 The modified live vaccines will produce more rapid immunity than the killed vaccines, but they need to be used with caution because they can cause cerebellar hypoplasia in fetuses if given to pregnant queens or in kittens less than 4 weeks of age.10 The age during which maternal immunity blocks vaccine-induced immunity varies, but it can be as long as 14 to 16 weeks of age. Further, there is an unavoidable period of waning maternal immunity that is no longer protective but is still able to block vaccine-induced immunity. This small window of incomplete protection is the Achilles' heel of any vaccination regimen. Being able to convey these key concepts to owners can be critical in ensuring that kittens receive the appropriate number of booster vaccinations. Vaccination regimens for kittens vary with the product being used, but they typically start at 8 to 10 weeks of age, are repeated every two to four weeks, and conclude with a booster at 12 to 16 weeks of age.


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