Feline: Panleukopenia


Background Information

Panleukopenia virus causes vomiting, diarrhea, and can cause sudden death in cats. The virus is transmitted primarily by the fecal-oral route (including through exposure to objects/clothing/hands contaminated with virus from feces). Panleukopenia is very durable unless inactivated by an effective disinfectant, and can persist in the environment for months or even years. The incubation period is generally less than 14 days, and cats may shed infectious virus for 2-3 days before signs are observed. Kittens are at highest risk for this disease, and adult cats with current vaccinations are at very low risk.

Control is dependent on effective vaccination, keeping cats separate during the time they may be incubating the disease, and careful cleaning and disinfection of all areas in which cats are housed.


Vaccination for panleukopenia is highly effective if performed correctly. A good vaccine program can substantially reduce spread of infection in a shelter. Modified live subcutaneous vaccination will provide more rapid protection than killed vaccine, and is more effective than intranasal vaccine. All cats 4-5 weeks of age and older should receive a modified live panleukopenia vaccine immediately upon shelter entry (Brun, Chappuis et al. 1979) . A delay of even a day makes it almost certain that the cat will be exposed before the vaccine can offer protection. Even injured and mildly ill cats should be vaccinated, unless they are certain to be euthanized within a few days.

Vaccination recommendations:

  • All cats > 4 weeks old (including injured and mildly ill) vaccinated immediately upon intake with a modified live subcutaneous FPLV vaccine.
  • Cats under 16 weeks boostered every two weeks while in shelter.
  • Cats in foster care vaccinated at least one week prior to shelter return.
  • Possible exceptions: Cats already diagnosed with FPLV, cats who will definitely be euthanized within a few days. For pregnant cats expected to carry kittens to term, balance the risk of inducing abortion or birth defects (reportedly very uncommon with currently used vaccines) against the risk of death of mom and kittens from virulent disease. During high risk periods, it may be indicated to vaccinate pregnant cats, especially if they must remain in the shelter for several days or more.

Vaccine warnings:

  • Vaccination with MLV FVRCP in pregnant cats may cause birth defects or abortion. However, this has rarely been documented. This risk must be balanced against the risk of panleukopenia in the shelter in deciding whether or not to vaccinate pregnant cats.
  • The subcutaneous MLV FVRCP vaccine can cause full blown URI if the cat gets vaccine in the nose or mouth. Do not draw vaccine up in front of the cats nose, and clean vaccine spilled on the fur immediately with alcohol.
  • MLV vaccination may cause a weak false positive parvo test within about 5-12 days after vaccination.


Signs include:

  • Vomiting
  • Diarrhea
  • Dehydration
  • Sudden death/found dead in cage (especially suspicious in adolescent to adult cats with or without concurrent URI)

Diagnosis may include:

  • Symptoms and exposure history
  • Positive results on an Idexx brand Parvo snap test
    • False negatives may occur more commonly than when using these tests for canine parvo (one small study found 20-50% false negatives on various brands - Neuerer et al, Journal of Feline Medicine and Surgery, 2008)
    • False positives were rare in the Neuerer study, occurring 0-6% of tested samples depending on brand of test
    • Vaccine induced positives were rare on the Idexx brand test (only 1/64 recently vaccinated kittens tested positive on an Idexx brand test; other brands had a higher rate of positive results following vaccination ( Patterson, E. V., M. J. Reese, et al. (2007). "Effect of vaccination on parvovirus antigen testing in kittens." J Am Vet Med Assoc 230(3): 359-63.)
  • Low white blood cell count on CBC or blood smear
  • Segmental enteritis observed on necropsy  
  • See panleukopenia diagnosis cheat sheet for further information  
  • Log all test results in a central location, including age, date of shelter entry, date of test, and location of cat. (See attached outbreak log)  

Population monitoring

  • Noticing, testing and removing sick cats ASAP will help stop spread.
  • During an outbreak, have trained, designated staff check all cats at least twice daily.
  • Provide written instructions detailing what to do when a possible case is recognized:
  • Who to contact
  • What diagnostics to perform (parvo test, blood smear, etc.)
  • What to do with the cat
  • How to clean the cage and other areas the cat contaminated
  • What to do with exposed cats
  • In addition to the daily walk-throughs, ALL staff should be trained to recognize possible signs of panleukopenia (detailed above).
  • It is particularly important that staff look over all cats for possible signs prior to cage cleaning, to prevent spread during cleaning.

Quarantine/Removal of Exposed Cats

Risk assessment:

Exposure can occur due to shedding of virus up to three days before development of clinical signs. Overall risk depends on daily level of sanitation and cleaning procedures in place during the days preceding diagnosis of the first case.

Risk due to environmental spread is reduced if :

  • Bleach or potassium peroxymonosulfate used daily to disinfect all cat areas
  • Cats remain in the same kennel throughout their shelter stay
  • Transport carriers, if used, are metal and are cleaned thoroughly between each use (plastic airline carriers are harder to clean effectively)
  • Cats are handled with hand washing or change of gloves between cats
  • Cat areas are steel, sealed concrete, or other non-porous, non-scratched surface and can be effectively disinfected
  • Common rooms, exam surfaces and carriers are cleaned and bleached between each use.
  • The shelter is not overcrowded.

Risk due to cat immune status is reduced if:

  • All cats are vaccinated immediately upon intake as described above
  • Risk is very low in cats 4 months old that are either:
  • vaccinated with an MLV SC vaccine at least one week prior to exposure
  • documented history of complete series (killed or live) at least two weeks and within three years prior to exposure.
  • Risk is greater in kittens under 4 months old even if vaccinated (due to maternal antibody interference)
  • Risk is greater in cats vaccinated less than a week before exposure, or vaccinated with a killed or intranasal vaccine
  • Risk is greatest in closely exposed, unvaccinated cats
  • All ages should be considered at risk if unprotected by vaccines. Panleukopenia is regularly documented in adult cats in shelters, both strays and those surrendered by their owners.

Serology may be a useful tool to identify cats at low risk and limit the number of cats requiring quarantine. Serological tests for panleukopenia are available from several laboratories. Not all laboratories have been validated; consult with your local veterinary school. Unfortunately, no in-house test kits are currently validated and available. Cats with a protective IgG titer at the time of exposure can be considered immune, and need not be quarantined.

If a single case occurs in a cat area where all cats have been vaccinated and careful sanitation is practiced daily, quarantine may not be necessary. If spread is observed or few of the above precautions are in place, the whole room or even the whole shelter may need to be considered at risk/exposed.


At risk/exposed cats must be strictly isolated to prevent continued spread of disease. Depending on resources, this can be done either by a 14 day quarantine or euthanasia of exposed cats. At minimum, every effort should be made to hold stray cats through the legally required holding period. Quarantined cats should be removed to a separate isolation ward, separate building, or foster care. Any area where cats are quarantined must be able to be thoroughly cleaned and disinfected - no carpet, furniture, wood, grass, etc. Large dog crates can be used to quarantine animals in foster homes. Foster parents should be counseled carefully about the need to prevent contamination of their homes, as well as the grave prognosis should the cats become ill.

Precautions for quarantine:

  • Minimize handling of cats during quarantine.
  • Wear protective clothing (lab coats or smocks, boots or shoe covers, and gloves)
  • Shoe covers or dedicated boots for quarantine are preferable to foot baths.
  • If foot baths are used, they must be of sufficient depth to completely submerge tread of shoes, and a scrub brush used to mechanically remove contaminants. Bleach foot baths must be changed daily or more often if heavily soiled. Trifectant or Virkon-S are better choices for foot baths, as they have more activity in the face of organic matter.
  • Use supplies (brooms, feeding carts, scrub brushes, etc.) dedicated to quarantine and used only in that room.
  • Changes gloves or thoroughly wash hands between handling quarantine cats.
  • Handle cats in quarantine after caring for healthy cats.
  • Quarantine precautions should be maintained for 14 days. Although most cases will become evident within the first 7-10 days, it is very sad to go through all the effort of a ten day quarantine, only to have a cat break with signs on day ll and have to start all over again!

Serum for exposed/unvaccinated cats

For kittens and cats that were not vaccinated at the time of exposure , vaccination after exposure will likely have little benefit.

In exposed, unvaccinated kittens, 2 mls of serum from an immune cat given SC or intraperitoneal soon after exposure may provide some protection (Greene's Infectious Diseases of the Dog and Cat, 2 nd Edition, page 56). If this is done, vaccination should be delayed by 2-4 weeks, and continued 2-4 weeks longer than usual.

Cleaning and disinfection

  • Panleukopenia is very durable in the environment, and is reliably inactivated only by bleach* or potassium peroxymonosulfate**
  • Most quaternary ammonium disinfectants (e.g. Triple Two, Parvosol, Roccal) do not reliably kill panleukopenia virus
  • Alcohol hand sanitizers do not kill panleukopenia virus
  • Use and change gloves or wash hands well with soap and water after handling suspect cases
  • Thoroughly scrub with soap or detergent prior to disinfection
  • Routinely use a disinfectant proven effective against FPLV daily at least during known high risk periods, preferably use at all times (you never know)
  • Eliminate swapping of cages and carriers without thorough cleaning between cats
  • Make sure surfaces are either non-porous and cleanable, or disposable. Eliminate plastic litter pans, carriers and other supplies if at all possible
  • For wood, plastic and other porous material that can't be eliminated, disinfect with potassium peroxymonosulfate
  • Clean and disinfect ALL areas of the shelters. Remember door knobs, telephones, vehicles, carriers and other equipment
  • Known heavily contaminated areas should be cleaned, then disinfected, and left to dry without rinsing. Repeat after 24 hours before reopening to incoming cats.

* Notes on bleach: Bleach must be applied to a clean surface to be effective. 5% household bleach should be freshly diluted at 1:32 (1/2 cup per gallon). Correct dilution is very important: too weak is ineffective, too strong is overly corrosive and irritating to cats and humans. Spray bottles should be non-see-through plastic, as bleach is inactivated by light. Bleach solution should be made up fresh using newly purchased bleach, as solution becomes inactivated with storage.

** Potassium peroxymonosulfate is marketed as Trifectant or Virkon-S and can be obtained from many animal supply outlets.

*** Other notes on cleaning: see UC Davis Shelter Medicine Cleaning Protocol.

Cat Intake

Cat intake should be minimized until the shelter can be thoroughly cleaned and all exposed/at risk cats transferred to quarantine. If kittens are out in foster care, return to the shelter should be discouraged if possible. Ideally, they should be adopted through off-site events or directly out of the foster home. If returned to the shelter, kittens should be vaccinated at least a week prior to return. If cat intake must be continued, designate one clean area of the shelter for this purpose.

Documentation and notification

  • Local veterinary hospitals, other shelters and rescue groups should be notified of the occurrence of panleukopenia in the community.
  • Adopters who have taken home a high risk cat since three days before the first case was recognized should be notified of signs to watch for and advised of what action to take should signs be observed. A sample form for adopters is attached.
  • All new cases should be documented on the attached outbreak tracking form to allow for easier recognition.

Facts about Panleukopenia for the Public

  • Panleukopenia is a highly infectious viral disease. Signs include diarrhea (sometimes bloody), vomiting, lethargy and fever, and death. It can range from mild diarrhea to fatal disease.
  • Diarrhea in an otherwise bright, alert, eating, drinking kitten is more likely due to diet change, stress, parasites, or dietary indiscretion.
  • Because it is so contagious, cats that were potentially exposed to Panleukopenia should be isolated in an easily cleaned area for 14 days to make sure they are not going to come down with it.
  • Panleukopenia is part of the vaccine series recommended for all cats and provides excellent protection. Adult cats that are current on their vaccinations are at minimal risk for this illness.
  • And...whatever your shelter's policy will be regarding what to do if the kitten develops symptoms or comes down with panleuk. Who to call, who will pay, etc.


Brun, A., G. Chappuis, et al. (1979). "Immunisation against panleukopenia: early development of immunity." Comp Immunol Microbiol Infect Dis 1 (4): 335-9.

The time necessary to obtain the immunity of cats against Panleukopenia has been studied by means of a modified live vaccine. This vaccine makes it possible to obtain a very early post-vaccinal immunity: the full immunity is reached 72 hr after the inoculation of the vaccine by the subcutaneous route. Furthermore, we have demonstrated that a sensitive kitten can be admitted in a contaminated environment immediately after vaccination without showing any clinical evidence of the disease.

Summary recommendations

  • Designate and train at least two staff members who can be responsible for twice daily walk-throughs to check for suspicious/symptomatic animals.
  • Use MLV SC FVRCP and make sure every cat is vaccinated immediately upon arrival, including mildly sick or injured cats. Possible exception for pregnant cats and kittens less than 4 weeks of age.
  • Add bleach, Virkon-S or Trifectant to daily cat cleaning. Clean entire shelter followed by bleach disinfection during the outbreak and on a routine basis.
  • Use Virkon-S or Trifectant for unbleachable areas such as wooden and gravel kennels and runs, areas of cracked or unfinished concrete, etc.
  • Quarantine and isolate all at-risk cats for 14 days.
  • Minimize foster kitten return and place new intakes into non-contaminated rooms
  • Develop a written protocol and train all staff on recognition and response to panleukopenia.
  • Please let me know how it goes!

Other Resources

Lay-staff friendly (but don't believe the part about quaternary ammonium maybe being adequate for disinfection!):

Animal Sheltering Magazine Article: May-June 2001 Keeping Your Cats Healthy: Guarding Against Panleukopenia

Please note: the on-line location of this magazine issue changes from time to time, Therefore the link I have provided takes you to the general listing of the back issues available from Animal Sheltering Magazine. From this link you should look for their link to the location of the May-June 2001 issue. While you are there you should check out many of the other interesting issues they have made available for free.