Introduction
The Chinese pangolin (Manis
pentadactyla ) is a scale-covered mammal belonging to the order
Pholidota, which also contains the
congeneric Sunda or Malayan pangolin (M. javanica ), the
Philippine pangolin (M. culioensis ), and the Indian or
thick-tailed pangolin (M. crassicaudata ) as co-occurring Asian
species (Gaudin, Emry, & Wible, 2009).
Pangolins have been established to
play pivotal ecological roles in the structure and function of forests
in southern China, and have accordingly been identified as key indicator
species, the status of which closely reflects
that of ecosystem health. However, as
a consequence of widespread poaching and trafficking, the number of
pangolins has decreased substantially in recent years, and across much
of their distribution range, these mammals are believed to be critically
endangered.
The continued survival of wild pangolin populations is further
jeopardized by their generally poor state of health state, which is
believed to be attributable to pathogen infection. In this regard, it
has been reported that common etiological agents, such as canine
parvovirus (CPV), canine distemper virus (CDV), and parainfluenza virus
5 (PIV5), which are highly prevalent among mammals in the families in
Felidae and Canidae, can infect Pangolins (Chin et
al., 2015; S. L. Wang et al., 2020; X. Wang et al., 2019). Moreover,
viral metagenomic analyses have revealed the presence of coronavirus and
Sendai virus sequences in pangolins. (Liu, Chen, & Chen, 2019).
CPV, a member of the family Parvoviridae , genusProtoparvovirus, and Carnivore protoparvovirus species 1(Cotmore et al., 2014), has been characterized as an autonomously
replicable negative-sense single-stranded non-enveloped DNA virus, with
an icosahedral capsid protein of approximately 20 nm in diameter
(Organtini et al., 2015). The viral genome is approximately 5200 bases
in length and consists of two open reading frames (ORFs) with
palindromic structures at the 3ʹ and 5ʹ ends. ORF2 encodes the VP1 and
VP2 viral capsid proteins, the latter of which, consisting of 584 amino
acids, is the major capsid proteins that determines viral host range,
antigenicity, and hemagglutination properties (Sehata et al., 2017).
With respect to infectivity, it has been established that the residue at
position 300 of VP2 contributes to determining the host range (Allison
et al., 2016).
Given its rapid rate of nucleotide replacement, CPV is continually
evolving as a globally spreading virus (Shackelton et al., 2005), and at
present, four major CPV subtypes, namely, CPV-2, CPV-2a, CPV-2b, and
CPV-2c, are recognized worldwide (Behdenna et al., 2019, Mira et al.,
2019, Geng et al., 2015, Decaro et al., 2009, Li et al., 2019, De la
Torre et al., 2018).
Whereas transmission of subtype CPV-2 and its variants among wild
carnivores, particularly those in the families
Felidae and Canidae, are commonplace (Hoelzer &
Parrish, 2010; Voorhees et al., 2019), CPV-2 infections in animals
belonging to the order Pholidota are rarely reported. Recently, however,
Wang et al. (2020) have reported that CPV-2c subtype parvovirus can
cause severe diarrhea-associated diseases in Taiwanese pangolins, and in
this study, we describe the discovery of fatal CPV-2a and CPV-2c
infection in two Chinese pangolins rescued from forests in southern
China.