Feline Panleukopenia

Feline panleukopenia (FPV) is a highly contagious viral disease of cats found worldwide. FPV, commonly referred to as feline distemper, is caused by the feline parvovirus, an un-enveloped DNA virus. Common clinical signs include lethargy, vomiting, diarrhea, and sudden death. Many kittens and unvaccinated cats do not survive FPV, and management in shelters requires strict isolation of affected cats and aggressive supportive care.

The virus can persist in the environment for more than a year. Fortunately, certain disinfectants (e.g., accelerated hydrogen peroxide, dilute bleach) are effective against this pathogen. 

Clinical Signs

The feline parvovirus infects and kills rapidly dividing cells, such as those in the bone marrow and intestines. Infected cats often develop diarrhea because of damage to cells lining the intestines. They also develop shortages of all white blood cell types which are necessary to fight infection.

The most common clinical signs of FPV include:

• Depression
• Anorexia
• Fever
• Vomiting
• Dehydration
• Diarrhea
• Lethargy
• Sudden death

More subtle signs can resemble other illnesses. Sick cats may sit for long periods of time in front of their water bowls but not drink much water. Infected kittens and cats may be found deceased in their kennel even without showing notable signs of illness. By the time a cat displays signs of illness, they may be severely ill.

Infected cats can shed the virus, while not showing any clinical signs. These subclinical cases contribute to disease transmission in a population.

Infection during early to mid-pregnancy commonly results in abortion or stillbirth. Kittens may survive when infection occurs late in pregnancy, but the virus may affect brain development, resulting in a condition called "cerebellar hypoplasia" which affects coordination and movement. Cerebellar hypoplasia is not contagious to other cats, and kittens can live full lives as long as incoordination does not negatively impact their functional status and quality of life.

Incubation and Transmission

Animals may appear healthy during the incubation period which is the time from exposure to the onset of symptoms. FPV incubation is typically 2-7 days but can be as long as 2 weeks. Therefore, kittens with panleukopenia may appear healthy and be moved through normal shelter pathways (e.g., surgery, adoption, foster) before becoming ill a few days later. It is essential to monitor kittens for early signs of illness for early recognition, treatment, and management of this infectious disease.

FPV is shed in feces and all bodily secretions (e.g., urine, vomit). Infected cats may begin to shed the virus before showing clinical signs. Clinical studies demonstrate that most cats shed the virus for 14 days or less, but in a research setting, they have been documented to shed for up to 6 weeks. The virus can remain on a cat's coat long after recovery, increasing the risk of transmission. 

FPV transmission occurs through:

• Direct contact with an infected cat
• Contact with fomites (contaminated objects) such as hands, instruments, clothing, food and water dishes, toys, and bedding
• Droplet transmission especially with concurrent respiratory disease
• Mechanical vectors such as insects and rodents

Diagnosis

Relevant clinical signs and a history of being unvaccinated and/or exposure to the virus are highly suggestive of an FPV diagnosis. Sudden death in an unvaccinated cat should also raise concerns for FPV in the shelter.

ELISA Point-of-Care testing

The most common diagnostic test for FPV is the Enzyme-Linked Immunofluorescent Antibody (ELISA) point-of-care test performed in the shelter. The canine parvovirus (CPV) antigen test can be used because of structural similarity to CPV. Results are most accurate if the test is administered in the first few days of infection.

Interpretation can be complicated:

• Always interpret results in light of clinical signs.
• A positive result and concurrent clinical signs in a patient should be interpreted as infection, and shelters should take preventive measures against transmission. 
• Though uncommon, vaccination within 5-7 days with an MLV FVRCP vaccine can result in a false positive ELISA test. 
• False negative results may occur due to test accuracy (lower sensitivity) and timing of sampling and shedding. 
• An animal with negative results on an ELISA test, but a highly suggestive clinical history and signs, should be handled as though infectious. 
• PCR, a more sensitive test, can be performed on whole blood or feces to more accurately diagnose FPV in suspect cases with negative ELISA results.

Polymerase Chain Reaction (PCR) Testing

PCR is available through diagnostic laboratories to confirm the antigen’s presence in whole blood or feces of an ill animal, or on tissues obtained at necropsy. Diagnostic labs using quantitative PCR can also help distinguish positive results due to vaccines rather than infection. This test is only available through diagnostic laboratories, so there is a delay in results.

Hematology

A complete blood count or blood smear can be done in many shelters or sent out for a nominal fee to test for a low white cell count (a hallmark of FPV).

Necropsy and Histopathology

Sudden death of unknown cause or euthanasia due to severe illness in kittens or unvaccinated cats should prompt testing of the deceased for FPV. 

Necropsy and histopathology are often the quickest and least expensive route to a definitive diagnosis, and allow for risk assessment, and interventions on a population basis.

Treatment & Management of the Individual Cat

FPV has a high mortality rate despite early or aggressive therapy. However, some cats survive, particularly adults. 

Panleukopenia is treated with supportive care, as a specific cure is not available for the viral infection. Supportive care can include:

• Fluid therapy to correct dehydration and electrolyte abnormalities
• Antibiotics to fight off secondary bacterial infections
• Control of vomiting and diarrhea
• Pain management

The disease can be severe, and the virus is highly contagious. Shelters should consider the following when making treatment decisions:

• Treatment entails several days of intensive care therapy often requiring overnight monitoring. 
• Shelters may not have the clinical resources, facilities, and trained staff to provide appropriate isolation and treatment.
• Cats under treatment should remain in isolation for at least 14 days. With severe disease, recovery to reach adoptability may take longer.
• The virus can persist in the environment long-term, endangering the lives of current and future residents.

This  Resource Assessment tool can help inform whether cats with FPV can be treated in the shelter context.

Cats with FPV must be moved to an isolation area separate from unaffected and unexposed populations of cats. Skilled staff with clinical treatment experience and knowledge of biosecurity should be assigned to the isolation ward. If isolation is not available, animals with panleukopenia virus should be removed from the facility for treatment (e.g., offsite to a veterinarian’s office) or euthanized to curtail their suffering and minimize disease spread.

Treatment & Management of the Population

A diagnosis or suspicion of FPV in a shelter should prompt a population-level risk assessment and diagnostic testing of sick cats. Shelters should have distinct housing areas to effectively manage infectious disease: healthy housing (holding, adoption), quarantine (exposed cats) and isolation (sick cats).

An outbreak strategy that only removes obviously ill cats from the general population is insufficient due to sub-clinical shedders. A comprehensive risk assessment based on age, history and vaccination status along with establishing and maintaining a clean break between exposed animals and unexposed animals will be essential to stopping transmission. Additionally, increased monitoring of animals will help identify early or subtle signs of illness.

Recovered cats and kittens may continue to shed the virus for at least 14 days from diagnosis. Repeated testing for the presence of panleukopenia virus helps document when a cat or kitten is no longer shedding a virus, shortening their post-recovery isolation period. Affected cats should be bathed prior to release from isolation because the virus can survive for extended periods on haircoats and be transmitted to new environments.

Prevention

Vaccination

Vaccination is a critical lifesaving tool for preventing feline panleukopenia, and modified-live, injectable FPV vaccines are considered core in shelters. All cats four weeks of age and older entering a shelter environment should be vaccinated at intake as reflected in vaccination guidelines for shelter-housed cats. The vaccine starts working quickly and can provide immunity within hours. There is a very small risk that vaccinating pregnant queens may induce abortion or abnormalities in kittens. This must be balanced against the life-threatening risk of contracting FPV.

Sanitation

FPV is a non-enveloped virus and resists some common shelter disinfectants. A shelter's standard sanitation protocol should include products and processes that kill non-enveloped viruses. Such products include accelerated hydrogen peroxide, potassium peroxymonosulfate, and bleach at appropriate dilutions and contact times. Proper sanitation requires thorough cleaning of all organic matter before disinfection.

Housing

Housing that separates animals into smaller groups based on species, health, age, and other factors helps maintain optimum animal health during a shelter stay. Design must allow separation between exposed and ill cats from unexposed, healthy cats. Primary enclosures that allow sanitation and care without handling can reduce stress and minimize opportunities for FPV fomite transmission. 

Population Management

Crowding of susceptible animals in a shelter challenges all preventive strategies and is more likely to result in FPV. Crowding can concentrate the pathogen and increase viral load in the shelter, leading to increased transmission through contact and fomites. Population management strategies that promote pathway planning and minimize length of stay help control FPV transmission and enable other preventive strategies (e.g., vaccination and sanitation) to be most effective.

Fun fact: Feline parvovirus existed before the strain that affects dogs. The first vaccination efforts to control canine parvovirus were made using feline panleukopenia vaccines!

Experiencing an outbreak? 

Request a Shelter Consultation with the ASPCA Shelter Medicine Services team.

Resources

• Infectious Disease Management in Animal Shelters, 2nd edition. Chapter 15, “Feline Panleukopenia”
• Outbreak Management Webinar 

Last reviewed November 2023