Panleukopenia in Cats (Feline Distemper) – With NEW Facts

The Definition of Panleukopenia in Cats 

Panleukopenia in cats is a highly contagious, frequently fatal, viral disease. It is most often called feline distemper, but it is more closely related to the parvovirus. The definition of panleukopenia is a decrease of all white blood cell lines in the body. 

panleukopenia in cats

Feline panleukopenia infects, replicates, and ruptures rapidly dividing cells. Characteristic sites of infection include the bone marrow, heart, intestines, and developing fetus. Due to this, kittens are the most affected. 

What Are The Symptoms of Feline Panleukopenia?

The feline panleukopenia virus is endemic in the environment. Infection occurs in most cats at some point in their life yet; they show no symptoms! Cats with active clinical conditions show typical symptoms. This includes pyrexia (fever), lethargy, anorexia (loss of appetite), vomiting, and diarrhea. 

Pyrexia (104°–107°F [40°–41.7°C])

Pyrexia usually occurs after an incubation period of two to seven days. This is the body’s response to the onset of clinical infection. 

Lethargy and anorexia

Lethargy and anorexia occur concurrently with the onset of pyrexia. Lethargy can be difficult to detect in cats due to their sedentary nature. Disinterest in food, toys, or avoiding contact with owners can all be signs of an underlying issue. 

Vomiting and diarrhea 

This develops one to two days after the onset of fever. Feline panleukopenia destroys the gastrointestinal lining by targeting high turnover intestinal cells. Vomits are generally bilous (bile-tinged) and unrelated to eating. Diarrhea is not always present and is only hemorrhagic (bloody) in 3-15% of cases. 

Extreme dehydration 

It develops once vomiting and diarrhea begin. Affected cats may sit at their water bowls for hours, have dull coats, and lose elasticity in their skin.

Purulent discharge

Feline panleukopenia damages the cat’s bone marrow and weakens its immune system. As a result, secondary infections can cause purulent discharge (pus) from the cat’s eyes and/or nose. 

Fetal abnormalities

Pregnant cats infected with feline panleukopenia may have transplacental transmission to kittens in-utero. Infection of the fetus during gestation can cause resorption, mummification, abortion, or stillbirth. The outcome of the disease is dependent on the stage of gestation.

Cerebellar hypoplasia

Kittens in-utero can also develop cerebellar hypoplasia (under-development). The cerebellum is an area of the brain required for coordination. Hypoplasia of the cerebellum results in kittens born lacking motor control. These kittens also have ataxia (wobbly legs) or tremors. Affected kittens will have normal mentation. 

In neonatal kittens (less than four weeks old), the cerebellum is still developing. As such, young kittens infected with feline panleukopenia are at risk of cerebellar hypoplasia.

Sudden death

Terminal cases are hypothermic and may result in septic shock or disseminated intravascular coagulation. In young kittens, sometimes the only symptom is sudden death (called fading kittens). 

When Are Cats Most Susceptible to FP?

Feline panleukopenia virus, like the canine parvovirus, is likely to be prevalent in any environment. Young kittens, sick cats, and unvaccinated cats are the most susceptible. Kittens between three to five months show clinical infection with the highest mortality rate. 

Outbreaks of feline panleukopenia often occur during warmer months of the year. This is due to an increase of cats wandering outside and coming in contact with unknown cats.

How is Infection of Panleukopenia in Cats Transmitted?

Regions with high cat populations serve as reservoirs of feline panleukopenia. This includes catteries, animal shelters, and unvaccinated feral cat colonies. Viral transmission occurs when susceptible cats come into contact with infected cats. This can occur directly or indirectly. 

Shedding of the virus occurs in all secretions and excretions (feces, urine, blood, and saliva). Oronasal exposure to infected cats, their secretions, or contaminated fomites results in infection.

The acute phase of illness lasts one to two days. During this time, biting insects are also able to transmit disease. Survivors of the disease can continue to shed the virus for up to six weeks after recovery. 

Viral particles are very resistant to inactivation. Transportation of the virus over long distances can occur via fomites. Fomites include contaminated bedding, bowls, shoes, clothes, and unwashed hands. 

The virus can survive for up to a year in the environment. Many cats become infected without direct contact with a diseased cat. 

Diagnosing Feline Panleukopenia

Key features of the history and clinical signs can create a presumptive diagnosis. This includes exposure to an infected cat, lack of vaccination, and signs of illness. The presence of leukopenia on a complete blood count is also a diagnostic indicator. 

Confirmation of the diagnosis requires an immunochromatographic test kit. This detects fecal canine parvovirus antigens. The test has a sensitivity of 50-80% and a specificity of 94-100%. False negatives are expected as the fecal antigen is only detectable for a short period—vaccination of a cat five-12 days before testing can result in a false positive. 

Differential diagnoses should include other causes of pyrexia, lethargy, leukopenia, and gastrointestinal signs. This includes bacterial diseases such as salmonellosis or campylobacteriosis. The Feline Leukemia Virus (FeLV) and Feline Immunodeficiency Virus (FIV) can also have similar presentations.

Concurrent infections of feline leukemia virus and feline parvovirus can manifest with panleukopenia. Investigation of non-infectious differentials such as toxins or foreign bodies is also essential. 

Available Treatment Options Against FP

There is no cure for feline panleukopenia. Treatment focuses on supportive care to allow the cat’s immune system to combat the virus. Aggressive fluid therapy and supportive nursing care are the mainstays of treatment. This must be in an isolation unit to prevent transmission of the virus. Implementation of appropriate barrier nursing is vital. 

Severe dehydration has severe consequences and needs close monitoring and intervention. This includes electrolyte disturbances, hypoglycemia (low glucose), hypoproteinaemia (low protein), and anemia (low red blood cells). 

Intravenous fluid therapy with a balanced isotonic crystalloid solution is critical. The addition of vitamins B and 5% glucose will also provide supportive care. Fresh-frozen plasma transfusions support plasma oncotic pressure and provide clotting factors. Whole blood transfusions are the preference in anemic cats. 

cat on intravenous fluid therapy

Secondary opportunistic bacterial infections occur due to a weak immune system. The disrupted gastrointestinal mucosal barrier also allows bacterial translocation. This permits bacteria from the gastrointestinal system to enter the bloodstream. 

Parenteral, broad-spectrum antibiotics are a mainstay of treatment. It is crucial to avoid nephrotoxic (kidney damaging drugs) until the correction of dehydration. 

Consideration of other complicating factors such as internal parasitism is important. This is of note in shelter environments. Once there is control of vomiting, anthelmintics (intestinal wormers) can aid in treatment. 

Antiemetic (anti-vomiting) therapy can provide symptomatic relief to allow enteral (oral) feeding. Maropitant is the first-line choice for cats. Combination with ondansetron can be effective for critical cases. 

The introduction of enteral feeding should occur as early as possible. This promotes gastrointestinal mucosal healing, which replenishes the protective mucosal barrier. Parenteral nutrition is reserved for critical cases. Attempts at enteral nutrition should be made as soon as possible. 

The production of interferons in the body exerts an antiviral effect. Recombinant feline interferon omega has been an effective treatment in canine parvovirus. The FDA does not approve its use to treat feline panleukopenia!

The widespread practice of passive immunotherapy is present in some countries. This involves the use of immune serum from solidly immune cats or a commercial product raised in horses. Limited evidence is available about the efficacy of treatment. 

The prognosis for infected kittens less than eight weeks old is poor. Provision of intensive treatment in older cats shows a better forecast. Without supportive care, up to 90% of symptomatic cats may die. 

Common Side Effects of the Panleukopenia Vaccine

Feline panleukopenia vaccines are available in an attenuated and modified-live virus form. Both are safe and side effects are rare. 

It is essential to avoid the modified-live virus vaccine in susceptible cats. This includes pregnant, immunosuppressed, sick, or kittens less than four weeks old. Side effects can mimic true viral panleukopenia. As with all vaccines, some cats may be lethargic for a day or two after vaccination. 

Cats rarely display a severe allergic reaction and go into anaphylactic shock. However, this can occur as a result of a response to an adjuvant of the vaccine. A reaction can occur within a few minutes to a few hours after vaccination. Any signs of respiratory distress or facial swelling should be immediately attended to!

How to Prevent Feline Panleukopenia in Cats

Vaccination is an effective way to prevent feline panleukopenia. The virus is very immunogenic, and vaccines are effective at preventing disease. Cats that recover from feline panleukopenia usually have lifelong immunity. 

Vaccination of kittens should be from six to nine weeks of age. They should receive two or three modified-live vaccine doses three to four weeks apart. 

kitten receiving vaccination

Administration of the final dose should not be before 16 weeks of age. This is to deter maternal antibodies from inactivating the vaccine virus. It is ideal to complete a follow-up vaccination at 26-52 weeks of age to insure adequate immunization. 

Vaccination of adult cats for feline panleukopenia should occur at least triennially. Annual vaccination is recommended in regions with high populations of unvaccinated cats. 

Commercial titer testing kits are available to assess an individual cat’s immunity to feline panleukopenia. The use of these kits can mitigate revaccination for owners that prefer that option. Limit exposure to the virus at all times. This includes keeping cats indoors and away from unvaccinated cats. Avoid areas that have come in contact with an infected cat. 

Feline panleukopenia is resistant to many household disinfectants. A 1:32 diluted bleach solution (of 2% household bleach) can be used to clean surfaces and potential fomites. Peroxygen disinfectants are also very effective!

Clean contaminated surfaces of organic material before application of disinfectants. The solution should be left for 10 minutes or more at room temperature to inactivate the virus. 

Any soiled bedding or toys used by an infected cat should be discarded.