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Pet Docs: Not yet legal anti-viral medications show promise in fighting feline infection

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Every morning, the first thing I (Perry Jameson) do after arriving at the hospital is to look at my schedule of appointments. For me, a veterinary internist, the day is often varied, not just because I see both dogs and cats but I also deal with diseases of multiple organs.

Cats that have free fluid in their abdomens are not what I like to see listed. Fluid in a cat’s abdomen almost always means there is a problem within that body cavity, and most of the time it is not anything good.

They can have bleeding from an organ, or rupture of the urinary bladder or gall bladder. These cats usually come into the hospital in critical condition and once stabilized are whisked to surgery.

Cats with chronic effusions are the ones I see where basic testing has not provided an answer. Unfortunately, many of these cats have cancer somewhere internally that has not been identified yet.

The other concern, especially, in younger cats, is the viral infection FIP (feline infectious peritonitis). This disease is caused by the feline coronavirus (FCoV), which is a common viral infection in cats. When tested, 80 percent to 90 percent of ones in multi-cat homes will test positive, meaning at some point in their lives they were exposed to this virus. Most cats are never symptomatic or develop only a mild, short-lived diarrhea.

In a small number of cats, however, the virus mutates into a form that causes FIP. It also is believed that in cats that develop FIP, their immune systems are not able to fight off the mutated virus. These two factors are required to develop FIP and would explain why in a home with 90 percent of cats showing evidence of exposure to FCoV, only 5 percent to 10 percent will ever develop it.

The disease can be difficult to diagnose as there is no specific test to rely on. Diagnosis is based on potential for exposure (lives in a cattery or a multi-cat setting, or recently in a shelter), low-grade fever, younger cat and the type of fluid in the abdomen. A newer test that looks for the virus within the cells in the fluid appears to be the best test to date, but it is not perfect.

Not all cats will develop an effusion, and the disease is divided into two main groups, a wet form and a dry form.

The wet form appears to develop sooner after infection or after a stressful event (a new home, surgery, arrival at a shelter). The symptoms usually worsen quickly. This is the form where the cats develop fluid within the abdomen and sometimes thorax.

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The dry form develops more chronically and is more nonspecific in its symptoms. In this form, inflammatory granulomas may develop in almost any organ, including the brain and eyes. So symptoms are related to which organ of the body is involved.

Infection typically is from exposure to infected cat feces. Litter pan sharing is felt to be the most common route of transmission. Approximately 1/3 of cats infected will shed virus in their feces. Most of these shed for only a few months, but 13 percent will shed for their entire lives.

Research is continuing on a vaccine, but none is available to date. This makes decreasing exposure the only way to prevent infection. Since most cats have been exposed, and only a few ever become infected, this is not practical.

Historically, a diagnosis of FIP was a death sentence. Since we think part of the symptoms are related to the cat’s own immune system trying to fight the infection, we would try prednisone to decrease this inflammation and thus symptoms. This never worked for long, if at all.

Then since it also was thought that it was a poor immune response that caused a part of the problem, we would try medications that boost the immune system. These also never helped.

Recently, however, two antiviral drugs have shown promise in providing an effective treatment for symptomatic cats. Initial research performed at the University of California-Davis School of Veterinary Medicine by Dr. Niels C. Pedersen and colleagues was exciting and showed a significant number of cats responded to these medications.

The problem is these drugs have not been thoroughly tested in a large number of cats and are not FDA approved. A drug company has purchased one of the medications from Kansas State University, where it was developed, and hopefully will eventually provide it to U.S. veterinarians.

Several companies, mainly in China, are manufacturing unapproved versions of these anti-viral medications. Pet owners have been obtaining these through the black market for their cats since the therapeutic options we now offer are so poor.

This puts veterinarians, such as me, in a tough situation. I want to help my patients in any way that I can, but legally I am not allowed to recommend or prescribe an unapproved or illegal mediation. For this reason, some veterinarians may stop assisting after the initial diagnosis and turn a blind eye to the parents’ use of these drugs, some may help as long as the parents obtain the drug and some will require the signing of a waiver freeing the veterinarian of any legal or ethical obligations.

For my entire 29-year career, FIP has been a death sentence. Although not yet legal, these newer anti-viral medications are providing some hope that we never had before for this terrible disease.

Dr. Henri Bianucci and Dr. Perry Jameson are with Veterinary Specialty Care LLC. Send questions to

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