Feline Infectious Peritonitis (FIP)

There are now legally available antiviral treatments in many countries, and they have been studied in peer- reviewed publications from Taylor, S. et al, 2023, Coggins, S. et al, 2023, Green,J. et al 2023. Antivirals remdesivir (injection SC or IV) and GS-441524 (tablets or suspension) have been shown to be effective in 85%+ cases. Email [email protected] for information on ordering medication in your region.

Yes, they can transition, however, it would be prudent to start the course again so that the correct drug concentration is given for the full treatment period.

GS-441524 can be given in a small amount of food, ideally after a period of fasting (which can also increase appetite and acceptance of medication) and at least an hour before a main meal to help the absorption of the drugs. The tablets (crushed) or suspension can be put into liquid treats for example or other tasty food. Avoid putting it into a main meal. Support owners to give tablets directly into a cat’s mouth if needed (demonstrate and direct owners to https://icatcare.org/advice/how-to-give-your-cat-a-tablet.) Suggest owners make giving medication a positive experience by following with a treat (without medication), a brush or playing with a toy (depending on the cat’s preference).

For most cats, an 84 day/12 week treatment course remains recommended. However, shorter courses of 42 days at 15mg/kg q24hrs (6 weeks) have been used successfully to treat cats with effusive FIP in a recent study (Zuzzi-Krebitz, AM, Buchta K et al, 2024). Importantly, these cats almost all responded rapidly, with clinical (including effusion resolution), haematological and biochemical (including AGP) parameters returning to normal in most cats within 28 days. This is not true of all cats with the disease and hence treatment duration should be decided on the basis of the cat’s response. Shorter courses may be suitable if treated cats respond rapidly, with resolution of clinical signs (including effusions), normalisation of biochemistry abnormalities (and if available normalised serum AGP at 4 and 6 weeks). Cats should be closely monitored for relapse. AGP is not available in many countries and it may be that serum amyloid A (SAA) can be used similarly, but further studies are needed. Communication with owners should discuss that, currently, most published response rates and outcomes are for cats treated for 12 weeks.

The medication is well tolerated. Changes in blood results include mild ALT elevations, eosinophilia, and lymphocytosis which do not require specific treatment. Urolithiasis has been reported with black-market medications. Remdesivir injection may cause pain SC and should be diluted and given slowly IV with hypotension and reduced demeanour possible.

The risk of relapse is around 10% and relapse generally occurs shortly after the treatment course is completed but can occur during treatment. Note that relapse can result in different clinical signs from the original presentation. Late relapse (or reinfection) is possible but current research suggests this is a rare occurrence. Relapses can be successfully treated.

Re-examinations and repeat blood tests are tailored to the individual cat and owner according to clinical condition, response and finances. Clinical improvement should be noted in 3-5 days so contact with owners at this point is recommended along with examination at 6 weeks and before stopping therapy.

No, evidence shows that over 85% of cats respond to once-daily treatment. However, therapeutic drug monitoring (TDM) (unpublished studies) suggests a benefit of twice-daily treatment. For cats challenging to medicate, focusing on consistent once-daily treatment is reasonable, with monitoring of response.

This varies according to type of FIP with ocular and neurological cases requiring higher dosages than cats with the non-effusive or effusive form. However, response is individual and should be adjusted according to clinical and biochemical improvement. Access the document for dosage information and remember to adjust the dosage as the cat gains weight and kittens grow (encourage owners to monitor weight at home).

In this scenario start by reviewing the diagnosis and considering if another condition could be responsible for the clinical signs. If you remain confident of the FIP diagnosis, then a dosage increase may be required. Access the document for further information.

In many cases, no other treatment will be needed, and clinical improvement will be rapid. However, cats with FIP may benefit from supportive treatment such as fluid therapy, nutritional support (including feeding tubes in some cases), analgesia, antiemetics and appetite stimulation. Neurological and ocular cases may require specific treatments such as topical ocular medications and anti-seizure drugs respectively.

Vaccination and neutering should only be considered during the second half or after treatment when the cat is clinically well. Vaccinations should be given according to lifestyle and risk of disease. Relapse after vaccination or neutering has not been reported but is understudied. Stress should be minimised using Cat-Friendly Clinic/Practice principles and analgesia post-neutering optimised. Parasite treatments can be given.

For many owners, the diagnosis is an upsetting one. Direct them to appropriate information about FIP and the antiviral treatment (see below). Support them by giving medications and checking in with them after 24-48 hours to see how they are getting on. Advise on the importance of nutrition and encouraging the cat to eat.