Feline Upper Respiratory Viruses
Part Three: Panleukopenia
Wilma Lagerwerf, RVT, RLAT
This is the third in a series of articles to explain the nature of the disease viruses that are contained within the routine vaccines typically administered at nine and 12 weeks of age. The purpose is to help the reader understand each virus that is included, what it does, how cats get infected, what is done to treat it and how to avoid or manage it.
This article deals with the virus called Panleukopenia, a parvovirus which causes severe infections virulent enough to warrant inclusion of the vaccine in a regular vaccination schedule. In addition, upper respiratory viruses can occur at the same time as a panleukopenia infection.
Panleukopenia is known and referred to by a multitude of names and symbols in literature. Authors assume the reader knows that they mean the same thing. There are so many that the following is a list in order of those most frequently used (the first three listed) followed by those less frequently used:
Panleukopenia (often shortened to "Panleuk" in verbal discussion)
FPV (Feline Panleukopenia Virus OR Feline Parvo Virus)
FP (Feline Panleukopenia)
Feline Infectious Enteritis
Feline Infectious Gastroenteritis
Maladie du jeune chat
In this article the virus will be referred to as Panleukopenia.
What is Panleukopenia?
Panleukopenia is an infection so severe that it was referred to as "Cat Plague" in earlier times when infections would nearly wipe out cat populations in certain geographical areas. It is a highly contagious, severe parvovirus that causes enteric (bowel), immune system and nervous system disease. This parvovirus is very small and hardy, with several strains that affect not only domestic cats and kittens, but any felid - such as lions, bobcats and tigers. It is important to be aware of this disease as the fatality rate in susceptible cats/kittens is 50-90%.
What does Panleukopenia Virus Do?
A) Active Disease
Panleukopenia virus affects three major body systems in the cat. The system it chooses is dependent on the age of the cat at time of infection.
Blood/Lymphatic System:specifically depression of the white blood cells (called WBCs) and thus the immune system. This happens in all cases and is unique to this virus.
Gastrointestinal System:specifically attacks the rapidly reproducing cells lining the intestines of the gut.
Nervous system: specifically affects the rapidly reproducing cells of the portion of the brain called the cerebellum and the retina of the eye when they are in their developing stage.
Panleukopenia virus will attack and destroy white blood cells in cats. This is a VERY TYPICAL finding with this virus, and the degree of WBC depression is used as an indication as to the severity of the infection. This destruction of WBCs is called "leukopenia" - "Leuk" meaning WBCs and "penia" meaning a reduced number. The more severe the leukopenia the poorer the prognosis for that individual. The steady decline of white blood cells begins about three days after infection, and by the fourth to the sixth day it may be hard for the veterinarian to find them at all in a blood sample. Through the suppression of WBCs the immune system is also severely depressed. 100% of cats/kittens that are infected with Panleukopenia.
The gastrointestinal form of Panleukopenia occurs when the virus attacks the rapidly growing cells that line most of the intestines. (This virus attacks rapidly reproducing cells.) Once a cat is infected, infection will show in the gut and WBCs from the second to the sixth day afterwards. If the infection is severe or the infected cat is very young, death can occur so quickly (eight to 12 hours) that a seemingly healthy individual is dead for no apparent reason! Death in kittens can be so rapid that postmortem exam would show little because many of the disease characteristics would not have developed yet.
The first syptom is a fever, with depression and lack of appetite, which lasts about 24 hours. The temperature will return to normal for a short period before rising very high again, with severe depression, vomiting, no appetite and rapid dehydration, followed later by diarrhea. These symptoms can vary from none at all in healthy adults to full high fever and sudden death in kittens. If death does not occur rapidly (with the first temperature increase), then the second time the fever rises depression will be severe and the cat/kitten will lay with its head dropped between its legs and belly to the floor (VERY TYPICAL). Often these cats/kittens will also hang their heads above the water bowl. Diarrhea usually follows the second fever's rise, but in many fatal cases, the cat/kitten does not make it to this stage.
If a cat/kitten is older than 16 weeks and survives the first 48 hours, the chances of recovery are much improved. If death still has not occurred in five to seven days, then recovery is rapid with proper care. Mortality is up to 90% in kittens less than six months old. Older cats are more resistant, but death rates can approach 50% in susceptible adults as well.
If a female is infected with panleukopenia virus while she is pregnant, she can abort, or give birth to stillborn kittens or mummified fetuses, and it can result in permanent infertility afterwards. What happens to the kittens in utero is explained under "Nervous System" effects of panleukopenia.
When a female is infected with Panleukopenia virus for the first time while pregnant, it affects not only her (as discussed above) but the kittens she is carrying as well. If the infection occurs in the first stages of pregnancy, then the effect on the kittens will likely be abortion, resorption and stillbirth. If the infection occurs during the last trimester of the prenatal period and up to two weeks after birth, the rapidly reproducing cells of the cerebellum of the kittens will be infected (remember that this virus likes rapidly reproducing cells). The area of rapid cell growth at this time is a certain germinal layer of the brain (cerebellum) AND the retinal cells of the eye.
Kittens affected this way show no signs of their affliction until they begin to walk and become mobile, at which time they experience difficulty walking, turning and keeping their balance, swaying while standing with legs wide apart and tail high to help keep balance. Kittens show exaggerated movements and head twitching and may fall to either side easily. This ataxia (lack of proper balance) and abnormal movement is generally non-progressive, but may seem so, as it takes until three to four weeks of age to become evident. As mobility increases in these affected kittens, they will show more completely the extent of the ataxia they will have for the rest of their lives.
Severity of Symptoms
As with other feline viruses, how many of the above signs a cat gets, and to what degree, is dependent on many things, all of which are important.
Age is the most important factor in this disease. Infection can occur any time post conception, with the severity as well as the range of symptoms age-dependent. Generally adults are less severely affected.
The amount of virus with which the cat came in contact is significant. The more virus it contacted, the sicker it may be. This can vary from a few mild signs, all of the above or anywhere in between.
The presence of other disease is another factor. The healthier a cat is, the better its natural immune system can work to fight infection. Cats that have parasitic infections (worms and fleas) will be more severely affected with the intestinal form, and the presence of other bacterial or viral infections will mean a more severe infection with Panleukopenia.
Previous infection or vaccination can affect the severity of the infection. If an individual cat or kitten has survived a previous infection, it is likely immune for life. If an individual cat or kitten has been vaccinated (and not exposed to the virus during the response time to that vaccination) then it is likely that individual will react anywhere from not at all to much less severely than an unvaccinated individual.
B) Latent and "Carrier" Disease
A "carrier" or "latent" stage for Panleukopenia generally does not occur, with most cats not shedding the virus in body secretions beyond three weeks of active disease. Only an occasional cat who survives previous infection (and has gone through the active phase of the disease) will carry the virus up to one year, thus truly representing a carrier cat.
Virus shedding cats for Panleukopenia are usually in the active phase of the disease and can spread virus to the environment and other cats.
How are Cats Infected with panleukopenia?
Cats must come in contact with the Panleukopenia virus to become infected. This virus must be taken in internally through the eyes, nose or mouth.
Direct Contact: Direct contact is from a sick or active carrier cat directly to another cat, usually once they come in contact with each other. In catteries, multiple cat households and shelters, the chances of this happening are high, and the virus is passed around rapidly. This may happen many times over during the course of infection, so that each time the "other" cat takes in more virus.
Indirect Contact: A cat deposits virus all over other cats, litter pans, furnishings, food and water bowls, the environment in which it lives, through its body secretions (urine, saliva, feces and nasal secretions). This is, by far, the most common way for a cat to become infected with Panleukopenia - a cat comes in contact with virus-contaminated objects and takes in a dose of virus from them, rather than directly from the cat who put it there. People also spread this virus from cat to cat through their hands and clothing. Ectoparasites, such as fleas, can spread the virus when they feed from multiple hosts.
Panleukopenia virus is an extremely hardy virus and survives most temperatures and disinfectants. It is possible for a cat to get infected both directly and indirectly at the same time, but the hardiness of the virus makes both ways equally infective. The cat who is shedding virus could have done so a long time before the next cat comes across it and becomes infected as well.
In-utero: Unborn kittens will be infected from the mother during pregnancy as explained previously.
The worst shedders of viruses are cats/ kittens currently ill with the virus. Due to the ability of the virus to survive so well in extreme temperatures in the environment, the infective secretions from these cats can be present for up to 13 months at ideal (room) temperature. Also, common environmental contamination both indoors and out can be assured due to the resistance of the virus to all disinfectants BUT bleach.
How is Panleukopenia Diagnosed?
Most veterinarians will diagnose Panleukopenia based on the clinical symptoms they see, the history prior to illness (including vaccination) and a total WBC count from a blood sample.
How is Panleukopenia Treated?
A cat/kitten sick with Panleukopenia virus requires mostly supportive care for the symptoms it produces, as it is a virus infection. Strict isolation is essential to reduce the environmental contamination. Veterinarians will often prescribe antibiotics as well, but only because they wish to avoid the resulting bacterial infections that happen in conjunction with the damage from the virus infection.
Supportive care is dependent upon which symptoms and which form of the disease was produced.
Blood/ Lymphatic System: WBCs will be markedly reduced in all cases, and this makes the individuals susceptible to all infections as well as Panleukopenia. Whole blood transfusions can be used to help replace WBCs.
Gastrointestinal System: Treatment is usually aimed at symptoms such as severe dehydration through nutrient support and warmth and supportive care to return "the will to live." Vitamin supplementation with vitamins B, C and A is used frequently (in specified amounts) and antibiotics are given to reduce the risk of secondary infection.
Nervous System: There is no treatment for this form of the disease. By the time it becomes evident, the damage is done.
How can Panleukopenia be Prevented?
Prevention of Panleukopenia is the easiest part of handling this disease. Since vaccines were developed for this virus, the number of cats affected by this condition has dwindled to nearly nothing. The virus is still out there, however, carried by unvaccinated cats, both indoors and out.
Immunity: There are multiple strains of Panleukopenia and immunity to it in the natural way (after infection) is protective, usually for life.
Vaccination: This is the safest and easiest way to mount immunity against Panleukopenia. It should be done before infection to be most effective. Care must be taken with vaccination of kittens, as there would be interference in production of their own antibodies from the antibodies they receive from nursing. A second vaccination plus protection from infection until proper immunity is produced is necessary. Which vaccine to use is of little concern, as all seem to be equally protective. Vaccination itself is beyond the scope of this article, but great references are available on the subject.
Management: Now that it is known that environmental contamination is the major source of virus, it makes good sense that cleaning and disinfecting with bleach is necessary to reduce the load of virus in the environment. Outdoors this would be impossible to control, so indoor lifestyles are definitely important in reducing the exposure to Panleukopenia. Multi-cat catteries/shelters/clinics need to apply principles such as separating sick cats from healthy ones, keeping kittens in separate age groups until 12-16 weeks of age, and creating an environment that can be bleached.
Although there is much more to the subject of vaccination and its effect on this disease, this article will hopefully increase the understanding about Panleukopenia, what it can do and why it is important for those who have cats (especially those with groups of cats) to respect its effects on the general health of felines.