An outbreak of feline infectious peritonitis in a Taiwanese shelter: epidemiologic and molecular evidence for horizontal transmission of a novel type II feline coronavirus
Veterinary Research
An outbreak of feline infectious peritonitis in a Taiwanese shelter: epidemiologic and molecular evidence for horizontal transmission of a novel type II feline coronavirus
Ying-Ting Wang 0
Bi-Ling Su 1
Li-En Hsieh 0
Ling-Ling Chueh 0
0 Graduate Institute of Veterinary Medicine, School of Veterinary Medicine, National Taiwan University , Taipei 10617 , Taiwan
1 Graduate Institute of Veterinary Clinical Sciences, School of Veterinary Medicine, National Taiwan University , Taipei 10617 , Taiwan
Feline infectious peritonitis (FIP) is a fatal disease caused by feline coronavirus (FCoV) infection. FCoV can be divided into serotypes I and II. The virus that causes FIP (FIPV) is believed to occur sporadically and spread infrequently from cat to cat. Recently, an FIP outbreak from an animal shelter was confirmed in Taiwan. FCoV from all the cats in this shelter were analyzed to determine the epidemiology of this outbreak. Thirteen of 46 (28.2%) cats with typical signs of FIP were identified. Among them, seven cats were confirmed by necropsy and/or histopathological examinations. Despite the fact that more than one FCoV was identified in this multi-cat environment, the eight FIP cats were invariably found to be infected with a type II FCoV. Sequence analysis revealed that the type II FIPV detected from fecal samples, body effusions and granulomatous tissue homogenates from the cats that succumbed to FIP all harbored an identical recombination site in their S gene. Two of the cats that succumbed to FIP were found to harbor an identical nonsense mutation in the 3c gene. Fecal shedding of this type II virus in the effusive form of FIP can be detected up to six days before death. Taken together, our data demonstrate that horizontal transmission of FIPV is possible and that FIP cats can pose a potential risk to other cats living in the same environment.
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Introduction
Feline infectious peritonitis (FIP) is a fatal disease in cats
caused by feline coronavirus (FCoV). FCoV is an
enveloped, positive-stranded RNA virus belonging to
genus Alphacoronavirus, family Coronaviridae, within
the order Nidovirales. The genome size of FCoV is
approximately 28.9 kb, including a non-structural replicase
gene; four structural genes encoding the spike (S),
envelope, membrane and nucleocapsid proteins; and five
accessory genes 3abc and 7ab [1].
Feline coronaviruses cause mild to inapparent and
transient infections of the gut and are ubiquitous in cat
populations worldwide [2]. They exist in two serotypes, I
and II [3]. Type I FCoV is predominant in the field,
whereas type II virus represents only 2-30% of infection
[4-8]. Accumulating genetic evidence indicates that type
II FCoV have arisen by two homologous recombinations
between type I FCoV and canine CoV (CCoV) [9,10].
Both serotypes can mutate in the host to acquire
macrophage tropism and cause a systemic disease known as
feline infectious peritonitis [2,11,12]. Due to a lack of
virus-shedding in studies of FIP cats, the mutant FIP
viruses (FIP causing FCoV, FIPV) are presumably
contained only within the diseased tissues and not
transmitted by cat-to-cat contact under natural circumstances
[2,11,13,14].
In this paper, we report herein on an epizootic of FIP
in a Taiwanese shelter that was caused by a novel type II
FCoV. Epidemiological and molecular studies of isolates
from various healthy and affected cats in this shelter
strongly suggest that this virus was brought in by the
introduction of kittens from another shelter with
subsequent horizontal spread to co-housed adult cats.
Materials and methods
Animals and specimen collection
A total of 46 cats from a private cat shelter were
subjected to this study from September 2011 to August
2012. The shelter houses adult cats and occasionally
some kittens. All of the cats were either stray animals or
had been rescued, and some of them were being
temporally raised at the homes of various private cat rescuers.
Before this outbreak, all cats were living together in a
cageless indoor environment and shared food, water
bowls and litter boxes. Some of the cats were siblings,
and the others were unrelated (Table 1).
Feces or rectal swab samples of all asymptomatic cats
were collected at least once to monitor the presence of
FCoV. For cats showing signs of illness suspected to be
FIP, body effusions, whole blood and swab samples,
including rectal, nasal, oral and conjuctival swabs, were
collected routinely. In addition to supportive care, these
FIP-suspected animals were subjected to treatment with
prednisolone (Prelon, YF Chemical Corp., New Taipei
City, Taiwan), benazepril (Cibacen, Novartis, Barbera
del Valles, Spain) and recombinant human interferon
alpha (Roferon-A, Roche, Basel, Switzerland). Cats that
succumbed to illness were subjected to necropsy for
pathological confirmation. Upon necropsy, body effusions
were first drawn by needle and syringe, followed by
collecting swabs, whole blood, urine and granulomatous
le (...truncated)