Salem is a 9-month-old, male, Domestic Shorthair cat that initially presented for an exam due to a 2 day history of lethargy. The owner expressed that Salem was just not acting like his normal self but was still eating, drinking, defecating, and urinating normally. The owner did not know of anything that Salem could have consumed around the house (i.e. toys, plants, foreign objects, etc.) to cause his abnormal behavior.
Salem’s physical exam was overall unremarkable other than a fever of 105.2 and lethargy. As owner wanted to be proactive to treat Salem’s fever, he was hospitalized for intravenous fluid therapy and a course of antibiotics. Abdominal radiographs were performed and revealed a generalized loss of detail, which can indicate potential free fluid present within his abdominal cavity. A blood panel was submitted as well, which was within normal limits despite a positive coronavirus titer, meaning Salem has encountered this virus at some point in his life (not uncommon for an adopted cat). An abdominal ultrasound was also performed as owner wanted to figure out why Salem had potential fluid in his abdomen.
The top differentials at that point in time were an intestinal perforation due to a foreign body and feline infectious peritonitis (FIP). The ultrasound revealed a moderate amount of fluid within Salem’s abdomen with no evidence of a foreign body within his gastrointestinal tract. Therefore, Salem’s illness was deemed most suspicious for FIP.
Feline infectious peritonitis (FIP) is a viral disease of cats caused by certain strains of a virus called the feline coronavirus. Most strains of feline coronavirus are avirulent, which means that they do not cause disease. In a small percent of infected cats (5 to 10 percent), either by a mutation of the virus or by an alteration of the immune response, the infection progresses into clinical FIP. It is the interaction between the body’s own immune system and the virus that is responsible for the disease. Once a cat develops clinical FIP, the disease is progressive and is almost always fatal.
Cats that have been exposed to the feline coronavirus usually show no obvious symptoms. Some cats may show mild upper respiratory symptoms such as sneezing, watery eyes, and nasal discharge. Other cats may experience a mild intestinal disease and show symptoms such as diarrhea. Only a small percentage of cats that are exposed to the feline coronavirus develop FIP and this can occur weeks, months, or even years after initial exposure.
There is no way to screen healthy cats for the risk of developing FIP, and the only way to definitively diagnose FIP is by biopsy or examination of tissues at autopsy. Generally, veterinarians rely on a presumptive diagnosis, which can be made with a relatively high degree of confidence by evaluation of the cat’s history, presenting symptoms, examination of fluid if it is present, and the results of supporting laboratory tests including a positive coronavirus antibody titer.
Unfortunately, there is no cure or effective treatment for FIP currently. However, in Salem’s case, possibly due to the owner’s quick action and aggressive treatment, he is almost 3 months out from his hospital stay. The fluid within Salem’s abdomen has also resolved and did so about 1 month after his hospital stay with oral steroid administration at home. Salem is not currently receiving any medications, his temperature has remained normal, his appetite is healthy, and his personality is back. He may not be out of the woods just yet, but the owners and I are hopeful that he will continue to thrive at home.