Parvovirus is a highly infectious virus, and one you should hope your cat never catches. So how do cats catch parvo, how bad is it, and can it be treated or prevented?
What causes parvo in cats, and is it serious? Parvo is a kind of viral infection also known as FPV, FIE, FPLV, cat plague and feline distemper. It spreads through bodily fluids like saliva and can be caught either from the environment or directly from another cat. It causes vomiting, variable temperatures (high and low), hunger and thirst and watery diarrhea. It can also cause pregnancy complications in cats. There is no direct cure for parvo but prompt supportive care ensures a survival rate of 50-90%. Vaccination can entirely prevent parvo and is recommended by all vets.
The guide below first looks at what causes parvovirus in cats, how cats catch parvo, and whether some cats are more vulnerable to the condition than others. It will also look at the various symptoms of parvo in turn, whether they’re all displayed together or not, and when to expect them to appear. It will then finish by looking at how parvo is diagnosed, treated and prevented.
What Causes Parvo in Cats?
Parvo is a highly infectious virus known by several names: feline parvovirus, FPV, feline infectious enteritis (FIE) and feline panleukopenia virus (FPLV). Common names for it include ‘cat plague’ and ‘feline distemper’.
Unlike other viruses, FPV is highly resilient. That means it can survive in the environment for a long time (up to a year). This makes it highly infectious, and means that direct contact with an infected cat is not necessary for it to pass on.
FPV has a very high mortality rate. If you suspect your cat has caught it, you must therefore take it to the vet as soon as possible.
What Is Feline Parvovirus?
Feline parvovirus is a virus. Viruses are like bacteria but smaller, and they reproduce in a different way.
Whereas bacteria reproduce by separation—one bacterium splits into two—viruses spread by getting inside an animal’s cells. There, they reprogram the cell to produce copies of the virus rather than copies of the animal’s DNA. The cell then releases the virus particles, which infect other nearby cells.
There are more than a hundred different species of parvovirus grouped together in a family. Some species can infect humans and other animals, but the kind that affects cats cannot spread to people.
How Do Cats Catch Parvo?
Cats catch FPV when they encounter the FPV virus. Unfortunately, the FPV virus is considered ‘ubiquitous’; it’s very common and can be found almost anywhere.
That’s because each individual viral particle is robust and can survive environmental damage, meaning it can survive outside of a cat’s body for an extended period of time. Coupled with the amount of cats that catch the problem—FPV is common—it can be found anywhere you find cats. Cats with the virus routinely shed viral particles in all bodily secretions including vomit, feces, urine, saliva and mucus.
When another cat comes into contact with one of these secretions it is likely to catch the virus. Cats catch the virus when it enters through the mouth or nose.
Because it is so easily transmissible, parvo frequently infects cats housed together or part of a litter. It is one of the leading causes of cat litters failing to thrive or passing away.
Are Some Cats Vulnerable to Parvo?
Kittens are particularly susceptible to parvovirus. That’s because when kittens are first born, they develop their immune systems based on antibodies they get in their mothers’ milk. When the cat weans, their immune systems won’t be at full strength because they aren’t getting antibodies from their milk any more. This is a crucial stage because it takes time for a cat’s immune system to reach full strength from there on out, and parvo is dangerous enough to harm even adult cats.
Cats which have not received the parvo vaccination are also susceptible. There is a vaccination available which makes cats immune to the virus. However, herd immunity is not strong enough to completely get rid of the virus, so unvaccinated cats are still vulnerable.
What Are the Symptoms of Parvo in Cats?
Not all cats that catch parvo will display symptoms. As such, just because your cat doesn’t display all the symptoms described below, that doesn’t mean it doesn’t have the disease.
- Vomiting. The cat will begin by bringing up partially digested food. However, vomiting will continue even if the cat is unable to eat. If this occurs, the cat will bring up froth rather than food.
- Variable Temperature. Your cat’s temperature will intially go up, as typically happens during viral infection. But it’s also common for your cat’s temperature to go down subsequent to initial infection.
- Hunger and Thirst. Your cat will be hungry and thirsty but will feel unable to eat or drink. It may sit near its food or water bowl in a hunched posture.
- Watery Diarrhea. As your cat isn’t eating, its diarrhea will not have much nutritional substance to it. That means it will be watery.
None of these symptoms are necessary for infection to be present. They do not appear in a specific order. They may not all appear.
Because parvo is a serious condition, it is possible that your cat will be seriously ill. Other symptoms are therefore common cat end-of-life symptoms rather than specifically being related to parvo. These include lethargy, complete anorexia and hiding.
If infection occurs in a pregnant cat, it can cause other symptoms too.
When infection occurs during early pregnancy, or even mid pregnancy, the kittens will abort. That’s because the infection is passed on to the kittens in the mother’s womb. The infection stops the kittens from developing properly, and so they become unviable.
When infection occurs during late pregnancy, it can harm the kittens, but won’t necessarily kill them. They will be born with a condition called cerebellar hypoplasia. This stems from damage to the cerebellum, the part of the brain in charge of the central nervous system. It controls balance and movement. The balance and movement of the kittens is thereby affected.
One way in which this becomes obvious is that the kitten will experience tremors, ‘intention tremors’ in particular. These are tremors that occur when the kitten tries to make deliberate movement. The tremors may be so bad that movement becomes impossible. The kittens may also have bobbing heads.
Cats affected by this issue are known as wobbly cats, and while it is presumably a frustrating problem for a cat to experience, it doesn’t significantly affect quality of life.
How is Parvo Diagnosed in Cats?
Parvo can be diagnosed by a vet. There are several ways that a vet can tell whether a cat is infected or not.
The easiest way is for the vet to check for the known symptoms of parvo. While they are not necessary or definitive, they nevertheless provide a clue. Your vet may take either a blood or stool sample to check for the disease; they will send the sample to the lab. This will give a clear result indicating whether the cat is affected or not. If the cat has passed on already, then a sample of intestine may be taken instead.
Another sign that the vet might check for is low white blood cell count. Parvo causes unusually low white blood cell count. The cat may also have low numbers of platelets in the blood.
Alternatively, your vet may be able to run a SNAP test. These tests are like laboratory tests, but are quicker and can be done then-and-there. The SNAP Fecal ELISA test kit is usually used to detect parvo in dogs, but can also be used to test cats.
How Do You Cure Parvo in Cats?
There is no direct cure for FPV, in that there is no pill, salve or other medicine that will completely get rid of the condition.
What veterinarians do instead is treat the symptoms of parvo. This results in better outcomes than leaving the cat to its own devices. By treating the symptoms, the cat’s general condition is somewhat improved, leaving it in a better place to fight the condition off naturally. Even with best treatment it is still possible that your cat will pass away, which is why it’s vital to contact a vet as soon as you suspect it is infected.
How Deadly Is Parvo?
A note before addressing how vets cure parvo—it is an exceedingly dangerous condition. Left without veterinary care, there is an almost 100% chance that an infected cat will pass away. With appropriate treatment the chance of survival rises from 33-50% on average. With novel treatments, the chance of survival may reach 90%, although no definitive cure has yet been found.
No matter what stage of parvo your cat is in, and whether you own any other cats or not, you should isolate your infected cat as soon as possible.
This achieves two ends. The first is that it curbs the spread of infection. If your cat is normally an outdoor cat, then quarantining it will stop it passing the condition on to neighborhood cats. The same applies if you own more than one cat. The second point is that you stop the cat from infecting the whole house. This makes subsequent cleanup a lot easier, lowering the risk of further infections or reinfection. Quarantine protocols include:
- Isolation. The cat must be left alone.
- A minimum of physical contact. Avoid picking up your cat, petting it or touching it in any way as much as possible. If you must touch it, quarantine is more likely to be successful if you use gloves.
- Disinfection of infected surfaces (scientifically known as ‘fomites’). While parvoviruses are resistant to many disinfectants, using them is better than not using them.
In mild cases of FPV, you may be asked to perform this quarantine at home. But in moderate or severe cases, your cat will be admitted to veterinary hospital where the staff will keep it in quarantine there.
Neupogen treatment is a novel treatment that may make survival after parvo more likely.
Neupogen is the brand name of a medicine called filgrastim. Filgrastim is used to correct low neutrophil count, neutrophils being a kind of white blood cell. It’s made artificially in a laboratory, but is the same as a naturally occurring glycoprotein called granulocyte colony-stimulating factor, or G-CSF. G-CSF is found in bone marrow, and stimulates the growth of white blood cells.
Since low white blood cell count is one of the hallmarks of parvo, and part of what makes it so deadly, any treatment that can correct the problem could help. Neupogen was approved for medical use in the U.S. in 1991, and has since been used in people in conditions that cause low white blood cell count, such as HIV. However, it can also be used in cats.
Promising results indicate that Neupogen treatment may significantly improve prognosis in parvo: ‘Our survival rates for felines with FPV using Neupogen are shown in Table 1. We see anecdotally about 33% success using supportive therapies without Neupogen to about 90% survival rate using Neupogen with supportive therapy.’
Ask your vet about Neupogen treatment.
Parvo is a virus, and antibiotics therefore won’t work to curb it. However, your vet may prescribe your cat with antibiotics until its immune system has recovered.
The reason for this isn’t the virus, but your cat’s gut bacteria. In the absence of a functioning immune system your cat’s gut flora could get out of control and cause secondary infection. Antibiotics will preserve regular levels of gut bacteria until your cat is back at full health.
Fluid therapy is where a patient receives fluids through a drip. These fluids are intended to replace those lost during diarrhea and/or those that the patient could not ingest. Because parvo causes difficulty ingesting both food and water, cats with the condition can become exceedingly dehydrated. Fluid therapy, similarly to antibiotics, therefore helps the cat return to normal health so that it can fight off the virus on its own.
Fluid can be administered in several ways:
- Intravenous. This is where the fluid goes into a vein, i.e. the bloodstream.
- Intraperitoneal. This is where the fluid goes into the peritoneum, the abdominal cavity.
- Intraosseous. This is where the fluid goes into the bone marrow (yes, the bones).
- Subcutaneous. This is where the fluid goes just under the skin.
- Oral. Through the mouth.
Fluid therapy in this context will be subcutaneous. When administered subcutaneously, fluid is slowly absorbed, meaning the cat can slowly recover to health without being shocked by too much water in its system.
Prevention is Better than Cure: Parvo Vaccination
The best way to prevent FPV is by vaccinating your cat against it. It is considered one of several core vaccinations that all cats should have alongside those for feline calicivirus, feline herpesvirus, and where relevant, rabies. There is the option either to have a single vaccination that only covers FPV or a combination vaccine that combats respiratory infection (flu).
Vaccination against parvo is recommended from an early age. Kittens, which are especially vulnerable, can be vaccinated as early as four weeks of age. The usual start date is six weeks, then every 3 or 4 weeks until the cat is 16 weeks of age. Booster shots every 1-3 years are recommended also.
How Does the Feline Parvovirus Vaccine Work?
There are several kinds of parvovirus vaccine that can be administered. Some contain active virus particles while others don’t. Some have ingredients added that heighten immune response, helping the cat develop antibodies better, while others don’t. There are also vaccines that can be administered to different parts of the body, e.g. to the eyes and nose or to any part of the body by injection.
Vaccination works in tandem with your cat’s immune system. Your cat has an immune system just like you do. On a microscopic level, the immune system is made up of a network of small cells called white blood cells. These cells police the body, identifying ‘intruders’ like bacteria or viruses and fighting them off.
Crucially, these cells only know about some bacteria and viruses: they know about ones they’ve encountered before. There are many kinds of antibodies, one for each kind of virus or bacteria. When the body identifies an infection, it starts producing lots and lots of antibodies of that specific kind to fight it off. That’s one of the ways in which a cat’s milk is perfect for a kitten, because there are antibodies in it that can ‘teach’ the kitten’s immune system about bacteria and viruses it hasn’t yet seen.
Vaccines work in the same way. A small amount of dead, broken-down or almost-dead bacteria/virus is introduced to the immune system. The immune system then learns how to make antibodies to fight off that particular bacteria or virus. These bacteria are like the weak enemies you encounter in a game tutorial: they can’t hurt your cat, but teach it how to cope with bigger baddies coming later on. When you give your cat a feline parvovirus vaccine, its immune system will then be ready to fight off any parvo infections it comes across.
Is the Feline Parvovirus Vaccination Safe?
The FPV vaccine is safe for cats. As stated above, the virus used in the vaccine is either in such small quantities as to not pose a risk, or has already been killed/neutralized. If you are concerned about giving your cat a live vaccine, that isn’t a problem, as vaccines with inactive viruses are available.
Vets have noted that giving a live vaccine to a pregnant cat can result in the offspring being aborted or failing to thrive. This would occur because the small amounts of virus that the mother can handle would be too much for the kittens. However, a vaccine with inactivated virus particles would be safe.
If you have any concerns with regard to the safety of cat vaccines, talk to your vet.