Comparison of Diagnostic Methods for Identifying Feline Coronavirus in a Captive Population of Cheetahs (Acinonyx jubatus) Affected by Feline Infectious Peritonitis
Cheetahs (Acinonyx jubatus) are susceptible to feline infectious peritonitis (FIP) caused by FIP virus (FIPV), a mutation of feline enteric coronavirus (FECV), both strains of feline coronavirus (FCoV). Antemortem diagnosis remains challenging despite novel tests.
Three adult co-housed cheetah littermates became ill and were euthanized. Cases 1 and 2 had pyogranulomatous peritonitis and were positive for FCoV on immunohistochemistry (IHC). Case 3 had histologic lesions suggestive of FIP, but IHC was negative. Samples from these and apparently healthy cheetahs were evaluated: 11 of 27 tested positive for FCoV by polymerase chain reaction (PCR) on fecal samples, including samples from the three littermates. Serum samples from 20 cheetahs were split and submitted for FCoV IFA at two or three laboratories. Results were consistent among all laboratories in 75% of the cases. No serum was submitted from case 1. Case 2 had the highest serum titer at all three laboratories. Case 3 had the second highest titer at two laboratories but was negative at the third laboratory.
A new commercial real-time RT-PCR test claims to distinguish between FECV and FIPVa. Liver samples were submitted from cases 1, 2, and 3, as well as from three cheetahs previously negative on serum and fecal samples. Cases 1, 2, and one of the presumed negative cheetahs were positive for FCoV, with no FIP biotypes detected. Case 3 and the last two cases tested negative. It is speculated that the biotype causing FIP in cheetahs could differ from those detected in domestic cats.
a. IDEXX Laboratories, Inc., Westbrook, ME, USA
The authors thank Michelle Lovering at the Toronto Zoo for organizing samples and documents for export permits; Dr. Melissa A. Kennedy from University of Tennessee and Dr. Roxanne Chan from IDEXX Laboratories for advice and discussions; and Dr. Roxanne Chan for FCoV RT-PCR testing.