New treatment turns the tables on Feline Infectious Peritonitis

Clinicians in the Internal Medicine Service have successfully treated over 50 cats with Feline Infectious Peritonitis (FIP) since March 2021, and have advised vets dealing with hundreds more cases, thanks to the availability of new anti-viral drugs. 

The Specialist-led team report a success rate of over 85 per cent following treatment with a 12-week protocol of GS-441524, the main plasma metabolite of Remdesivir, and occasionally with other antivirals.

This has drastically improved prognosis of FIP as a condition previously considered fatal in almost all cases.

Successful recovery

Archie*, a six-month-old Maine Coon, was referred after losing 25 per cent of his body weight in 10 days. He was lethargic and anorexic, with marked abdominal lymphadenopathy. 

On arrival, Archie was recumbent, anaemic, had severe diarrhoea and significant muscle atrophy. He was hypoalbuminaemic (23g/L) and markedly hyperglobulinaemic (81g/L) making his albumin:globulin ratio less than 0.3 which was highly suggestive of FIP. His serum alpha1-glycoprotein (AGP) concentration was three times the reference interval (1445ug/ml, normal <500ug/ml) which further supported FIP as a differential. 

A fine needle aspirate of the abdominal lymph nodes found pyogranulomatous inflammation, which was further consistent with FIP. Immunohistochemistry for feline coronavirus (FCoV) was positive, which confirmed the diagnosis. 

Supportive treatment including intravenous (IV) fluids, pain medication and medical appetite stimulation was started, followed by a 12-week oral treatment course of the antiviral GS-441524.

Archie was discharged after three days of treatment, without diarrhoea and eating well. His condition was monitored over the next three months, including assessment of the main inflammatory marker (AGP), which decreased with successful treatment. Six months later, he has made a full recovery with no signs of residual disease. 

Challenging disease

FCoV remains a ubiquitous virus in the cat population. It is estimated that 40-50 per cent of cats are carriers and up to 80-100 per cent in a multi-cat household. 

While predicting when enteric FCoV infection develops into the clinical picture of FIP in individual cases remains challenging, treating FIP used to be nearly impossible, with the infection leading to fatal outcomes in the vast majority before the availability of GS-441524. 

The Hospital is one of the leading centres for FIP in the UK and is undertaking key research to improve treatment options.

We are now looking to expand our research further and develop a patient-centred treatment programme that may lower the current treatment duration of 12 weeks in the future, reducing the risk of developing drug resistance and making treatment both easier and more affordable for clients.

Dr Conor O’Halloran, Internal Medicine Resident at the Hospital for Small Animals.

Supporting veterinarians

The Hospital hold stocks of GS-441524/ Remdesivir in tablet, liquid and injectable form and can advise on the use of these and other anti-viral medications for FIP. If you are a referring veterinarian requiring advice on a suspected FIP case, or would like to arrange a referral of a cat with suspected or confirmed FIP, please contact our Feline Medicine Service.

*Patient name has been changed

About the Royal (Dick) School of Veterinary Studies  

The Royal (Dick) School of Veterinary Studies is a one-of-a-kind centre of excellence in clinical activity, teaching and research. Our purpose-built campus, set against the backdrop of the beautiful Pentland Hills Regional Park, is home to more than 800 staff and almost 1400 students, all of whom contribute to our exceptional community ethos.  

The School comprises:  

The Roslin Institute  

The Global Academy of Agriculture and Food Systems  

The Roslin Innovation Centre  

The Hospital for Small Animals  

Equine Veterinary Services  

Farm Animal Services  

Easter Bush Pathology  

The Jeanne Marchig International Centre for Animal Welfare Education  

We represent the largest concentration of animal science-related expertise in Europe, impacting local, regional, national and international communities in terms of economic growth, the provision of clinical services and the advancement of scientific knowledge.