Covid drug turns the tables on fatal cat disease

A drug used to treat humans with Covid-19 has proven extremely successful in treating cats with an otherwise deadly viral disease. 

Clinicians at the Hospital for Small Animals report a success rate of over 85 per cent for cats with feline infectious peritonitis (FIP) following treatment with the anti-viral drug Remdesivir.

Experts at the Hospital, one of the leading centres in the UK for treating this disease, are now developing a tailored treatment programme for individual patients, which may shorten the length of the treatment needed for some cats.

Deadly condition

Five years ago, cats diagnosed with FIP had little hope of survival. 

The disease, which is caused by a mutated feline coronavirus, causes a dangerous build-up of fluid, extreme muscle and weight loss, and ultimately organ failure. Most cats with the condition deteriorate rapidly without prompt treatment. 

However, Remdesivir, which was initially used to treat Covid-19 in humans, was made available to be prescribed by vets in 2021 and is proving highly effective at treating FIP in cats.

Successful treatment

Rebus, a 10-year-old domestic short-haired cat, was one of the first to be treated at the Hospital with the drug. He was referred to the Feline Service, part of the Internal Medicine Service, as he had suffered rapid weight and muscle loss, wasn’t eating and was very lethargic. He was also drinking and urinating excessively. 

When he arrived at the Hospital, Rebus was critically anaemic, had enlarged lymph nodes and a high white blood cell count, indicating that he had a serious infection. He was given fluids and pain relief, and nursing staff helped him to eat. 

A needle biopsy of the cat’s lymph nodes confirmed that Rebus had FIP. He was also found to have kidney damage.

Rebus initially received Remdesivir by injection, then moved on to tablets of the drugs’ active ingredient GS-441524.

Within three months Rebus had made a full recovery from FIP, and nearly three years on he continues to live a full and active life, while receiving ongoing care for his chronic kidney disease.

Challenging disease

FIP is caused by a feline coronavirus that is usually found in the guts of healthy cats. The virus is unrelated to the coronavirus that causes Covid-19 and does not infect humans.

It is estimated that 40 to 50 per cent of cats carry the virus, and up to 80 to 100 per cent of cats in a multi-cat household, with most cats contracting the virus from their mothers. 

The feline coronavirus is usually harmless in the gut, however, in some cats it mutates and migrates to the immune cells. The immune response leads to severe disease including tissue and organ damage and, if left untreated, death. Although FIP is dangerous to cats, the disease is not infectious to humans. 

Vets across the UK have successfully treated hundreds of cats with FIP since the new medications became available. The clinicians at the Hospital are now developing patient-centred treatment programmes that may lower the time cats need to be treated. This should reduce the risk of developing drug resistance and make treatment easier and more affordable for clients. 

“I remember when FIP was a death sentence. The advent of these medications to be able to provide safe and legal treatment has been revolutionary for us as cat-loving vets.” Dr Conor O’Halloran, Resident in Internal Medicine, Hospital for Small Animals.