One of the most common causes of neurological disease in cats is feline infectious peritonitis (FIP). This severe viral illness can affect cats of all ages, though it is most common in those under two years old, particularly those living in multi-cat environments. While, historically, the disease has almost always been fatal, recent advancements in FIP treatment have given new hope to pet parents.
Understanding FIP: Causes and Symptoms
Early detection plays a key role in effective FIP treatment, making it important to understand the disease’s causes and symptoms.
What causes FIP?
FIP is caused by a feline-specific coronavirus that cannot spread to people or other species. This virus typically lives in a cat’s intestines and spreads through contact with feces, most often through shared litter boxes.
However, not all cats exposed to the virus will develop FIP. While nearly all cats carry the coronavirus, FIP only develops when the virus mutates into the harmful form. This only happens in a small percentage of cats when certain immune system interactions trigger the mutation.
Recognizing FIP Symptoms
Early signs of FIP can be vague, including lethargy, loss of appetite, weight loss, and fluctuating fever. However, the disease can take different forms, each with its own set of symptoms.
Effusive (Wet) FIP
This is the most common form, characterized by the buildup of fluid in the abdomen or chest. Symptoms may include:
- A swollen abdomen
- Trouble eating due to pressure on the stomach
- Difficulty breathing due to fluid around the lungs
Non-Effusive (Dry) FIP
In this form, inflammatory masses develop throughout the body, damaging organs and leading to a variety of clinical signs. The most common visible signs of dry FIP appear when the eyes become affected and may include:
- Cloudy or bloodshot eyes
- Differing pupil sizes
- Squinting due to eye pain
- Vision changes
This form of FIP can also affect the nervous system, which can cause:
- Difficulty walking
- Loss of coordination and balance
- Vision impairment
- Seizures in severe cases
FIP Treatment: Challenges, Advancements, and What to Expect
Without treatment, FIP is fatal in nearly all cases. While traditional FIP treatment approaches have focused on symptom management, recent advancements have significantly improved outcomes. However, diagnosing FIP remains a challenge.
How is FIP Diagnosed?
A definitive diagnosis of FIP can only be achieved through a biopsy of tissues infected with the virus, which is highly invasive.
Most veterinarians will evaluate bloodwork for elevated globulin levels (a protein indicating inflammation) and a positive coronavirus titer (indicating prior exposure). But, as Dr. Amanda Taylor, veterinary neurologist at Southeast Veterinary Neurology, explains, standard tests are not always conclusive:
“Diagnosis of FIP is incredibly challenging because FIP is a coronavirus. Cats are actually vaccinated for other coronaviruses in their lifetime, and many cats may have been infected with an enteric, or GI, form of a coronavirus earlier in their lifetime. So when we try to test them for FIP through blood tests that look for previous exposure, those are often positive. And when we look for viral DNA, those tests are not always reliable. So it can become really challenging to make a diagnosis without advanced testing.”
Advanced testing, such as MRI and cerebrospinal fluid (CSF) analysis, can provide additional insight. While these tests cannot definitively diagnose FIP on their own, their results can strongly suggest the presence of the disease when considered alongside the patient’s history, clinical signs, and bloodwork.
Traditional FIP Treatment Methods and Their Limitations
In the past, most cats would survive only weeks after symptoms appeared. FIP treatment was limited to supportive care and medications to decrease inflammation, like steroids. While these treatments temporarily offer comfort, they do not stop the disease from progressing. As a result, the prognosis was extremely poor - until recently.
Revolutionary Antiviral Therapies for FIP Treatment
“Fortunately, there are much better treatment options available to us now that are legal,” says Dr. Taylor. “These consist of antiviral treatments such as GS 441524 and Molnupiravir, which are available legally in the US at compounding pharmacies due to an exception the FDA has made for the licensing of these drugs. Up to 85% of cats will respond to treatment with these drugs over a three month course of treatment,” she reports.
Unlike traditional FIP treatment, which only provides temporary symptom management, these antiviral therapies target the virus itself, offering the potential for significant improvement to both quality of life and survival.
What to Expect After FIP Treatment
While antiviral FIP treatment has dramatically improved survival rates, long-term prognosis remains guarded.
Dr. Taylor weighs in, “Although we have a really good response rate with the antivirals, up to half of cats that are treated can relapse when treatment is discontinued, or can relapse from their signs while treatment is ongoing. So there is concern that this may not be a long term cure for many cats.”
“Additionally, cats with severe disease may not respond to treatment due to how far their disease has progressed,” she warns. “And in some cases, because of the irritation that FIP causes to organs and the nervous system, the body responds by laying down scar tissue. If that scar tissue has caused damage, then the body may not be able to recover from that completely, and you may have residual neurologic deficits,” she adds.
The Future of FIP Treatment and What You Can Do Now
Despite the challenges, the future of FIP treatment looks promising, with ongoing research and clinical trials aimed at discovering even more effective therapies to improve survival rates and quality of life for affected cats.
In the meantime, if you're concerned that your cat is showing signs of FIP, contact your primary veterinarian, as most are now well-informed of antiviral treatment options. If your vet has questions about FIP treatment or feels that a referral is necessary - especially if your cat has neurological signs - Southeast Veterinary Neurology is here to help, with locations in Miami, Boynton Beach, Jupiter, and Virginia Beach.