Feline Coronavirus Participation i Diarrhea of Cats

Fecal samples were examined for viruses participated in gastrointestinal disorders of cats, especially focusing on feEine coronavirus <FCoV) by a reverse transcriptase-polymerase chain reaction assay. It was found that a primary viral pathegen was feline panleukopenia parvovirus (FPLV; 28.5% of the positive rate) and the secondary was FCoV "O.7%). Comrnonly reported clinical signs of cats of which feces were FCoV-positive were vomiting, diarrhea and dehydration with an exception of one serious case with concurrent FPLV infection,-KEy woRDs: coronavirus, diarrhea, feline. J. Vet Med. Sci, 61(9). 1071-1073, 1999 In Japan, viruses detected in feline diarrhea c ses include feline panleukopenia parvoyirus (FPLV) as a primary pathogen, feline calicivirus, feline rotavirus, and reovirus [20], Other viruses, on the other hand, such as feline coronavirus (FCoV), feline astrovirus, or feline leukemia virus, are also known to cause clinical enteric diseases in the literature [5]. Furthermore, types 2a and 2b canine parvoviruses (CPV) have been recently recognized as potential pathogens for cats [21, 31]. According to pathobiological properties, FCoV has been classified into two biotypes as feline infectious peritonitis virus (FIPV) and feline enteric coronavirus (FECV), and it has been postulated that FIPV is a highly pathogenic mutant of ubiquitous FECV [28]. The postulation has been evidenced recently by comparative genomic analysis of both biotypes; the order of descent is from FECV to FIPV, suggesting FIPV arises by mutation from endernic FECV in cats [33]. On the other hand, FCoV has been also classified into serotypes I and II defined by neutralization [28]. Type Iyirus is a genuine coronavirus of cats and type II virus has emerged by the genomic recombination between type I FCoV and canine coronavirus [10, 11, 26, 32]. TypeIvirus is a predominant in the field [12, 28], and is generally fastidious in yitro [28], thus the virus isolation by cellculturing method for diagnosis appears to be helpless in most cases, Even by using a celHine fatis c"tus whole fetus (fewf-4) which is highly susceptible to coronaviruses [14, 29], no FCoV was recovered from 335 cat fecal samples examined during the years from 1989 to 1997 (unpublished data). There are only severa1 reports describing spontaneous FCoV enteritis [2, 16, 19], and to the best of our knowledge the FCoV isolation from diarrheal feces of cats has been so far rarely performed in japan. In the present study, we applied a reverse transcriptase-polymerase chain reaction (RT-PCR) assay to elucidate a significance of FCoV in diarrhea of cats. The RT-PCR assay has been used more frequently for FCoVs than ever, and the epidemiological features have become more evident [1, 3, 4, 6, 8, 9, 15, 17]. Rectal swab samples were submitted from veterinary hospitals in various parts of Japan, and a total of 56 samples, 29 from diarrheal cases and 27 from other conditions, were examined during the time from April, 1998 to January, 1999, The swab was placed in 1 mt of Eagle's minimal essential medium as described previously [25], The swab extract was clarified by centrifugation at 8,500 g for 20 min and the resulting supernatant was inoculated into a cell culture ciish which contained either Crandell feline kidney or fCwf4 cell monolayer. The supernatant was additionally examined for FCoV by the RT-PCR assay [8], for parvovirus by the PCR assay [24], and for rotavirus by the reverse passive HA assay [22]. When cytopathic effect was observed in the cell culture, the cells were stained by Giemsa solution and examined cytopathologically, For an identification f the isolate in the cell culture, the infected cells were exarnined by an indirect immunofluorescence assay (IFA) by using monoclonal antibodies (MAb) against cith¢ r FPLV [23] or FCoV [13], Sixteen isolates, 12 from diarrheal and four from the other conditions, of FPLV type parvoyirus and one isolate of FCoV were recovered frorn the samples, but no other viruses were detected. As shown in Tab]e 1, five swab extracts were positive for FCoV by the RT-PCR assay (8.9%) but no FCoV was recovered from them in the fewfl4 ce]1 culture. On the other hand, the RT-PCR assay was negative for one swab extract from which FCoV was recoverecl in the cell culture, though the isolate (C427) was reactive by the RTPCR assay, This may be explained by a probable reason that some PCR-inhibitor existed in the fecal sample, Thus, a total of six samples (10,7%), five from kittens with gastrointestinal and one from a kitten with respiratory disorders, were positive for FCoV in the present survey, Except for the case C427 which was a mixed infection with FPLV and died, the clinical conditions were generally mild and the cats recovered soon. Prirnary clinical signs reported were vomiting, diarrhea and dehydration. Although the RT-PCR assay applied in the present study has been already approved to be specific for FCoV [8], we sequenced an RT-PCR product to make sure that the assay was specific. Sequencing was perforrned by the method described previously [7], Approximately 220 bp product was expected to be generatcd by the amplification [8], lhe product obtained from the sample C408 was composed of 223 bp and a restriction enzyme Dra I site existed inside of it as describect previously [8]. The obtained sequence were Japanese Society of Veterinary Science NII-Electronic Library Service apaneseSociety fVeterinary cience 1072 M, MOCHIZUKI. N. OSAWAAND T, ISHIDA