Papillomavirdae.
Despite the relatively small sample size, several viruses were significantly more likely to be detected in FPV-cases compared with healthy controls including feline kobuvirus, feline astroviruses,Feline calicivirus , feline bocaparvovirus 2 and feline bocaparvovirus 3. Indeed, it is notable that feline kobuvirus was only detected in FPV-cases (Figure 2) and the prevalence of detection (39.1%) is the highest reported to date (Chung et al., 2013; Di Martino et al., 2015; Lu et al., 2018). In previous reports, co-infections of FPV, feline coronavirus and/or feline bocavirus 1 were common in cats naturally infected with feline kobuvirus (Chung et al., 2013; Di Martino et al., 2015; Lu et al., 2018; Niu et al., 2019). However, in those investigations targeted conventional PCR was used to screen for a few common enteric viruses only. The use of unbiased sequencing techniques, as performed here, demonstrates that other enteric viruses including feline astroviruses, feline bocaparvovirus 2 and feline bocaparvovirus 3, as well as Feline calicivirus are also common co-infections (Figure 2). The feline kobuvirus sequences detected here are the first in Australia, suggesting active circulation among Australian cats and highlighting the importance of screening for this virus in Australian cats with gastroenteritis of unknown cause. Similarly, here we documented the first Australian sequences of Feline picornavirus .
Feline astrovirus infections have been identified in both healthy and sick cats (Brussel et al., 2020; Zhang et al., 2019; Zhang et al., 2014), although experimental infection of specific-pathogen kittens with feline astrovirus induces acute enteritis and viral shedding (Harbour et al., 1987). Here, although astrovirus shedding was detected in healthy controls, the prevalence of astrovirus in FPV-cases was significantly higher. Recently feline astrovirus infection was associated with acute gastroenteritis in shelter-housed cats, where 91% of affected cats and 56% of healthy cats were found to be shedding feline astrovirus, using a metagenomics approach (Li et al., 2021).
We detected Feline calicivirus at a significantly higher rate in FPV-cases than in healthy control cats. Although primarily a feline respiratory pathogen, evidence is mounting for an aetiological role in naturally occurring viral gastroenteritis (Castro et al., 2015; Di Martino et al., 2020). Experimental infection of cats with Felinecalicivirus causes diarrhoea (Povey et al., 1974) and enteric strains of Feline calicivirus are resistant to low pH, trypsin and bile salts (Di Martino et al., 2020). In a previous study,Feline calicivirus was not detected in healthy cat faeces but was found in 25.9% of diarrhoeic faeces and co-infections with FPV or feline coronavirus were common (Di Martino et al., 2020). In the cats shedding Feline calicivirus here, enteric co-infections, especially with feline astroviruses were common in both FPV-cases and healthy control cats (Figure 2).
There are conflicting reports on the prevalence of detection of bocaparvoviruses in cats with enteritis. These viruses have been detected in the faeces of cats with and without diarrhoea and in the oropharynx of healthy cats (Abayli et al., 2021; Li et al., 2020; Yi et al., 2018). Here, feline bocaparvovirus 2 and feline bocaparvovirus 3 were both detected at a significantly higher prevalence in the faeces of FPV-cases compared to healthy controls. Although, evidence for an association between feline bocavirus 1 infection and gastroenteritis in cats is accumulating, we found no significant difference in the prevalence of feline bocavirus 1 in FPV-cases and healthy control cats. One study reported a prevalence of 24.8% in 105 cats with diarrhoea compared to 9.8% in 92 healthy cats (Yi et al., 2018). Two other reports concluded there was an association between feline bocavirus 1 infection and severe gastroenteritis in cats, although sample numbers were small and co-infections with other pathogenic enteric viruses including FPV were common (Liu et al., 2018; Piewbang et al., 2019).