1. Introduction
Feline parvovirus (FPV), a small non-enveloped linear ssDNA virus with a 5.1 kb genome is a variant of the species Carnivore Protoparvovirus 1 ( family Parvoviridae). Feline parvovirus causes an enteric and systemic disease known as feline panleukopenia (FPL) and can also infect cats subclinically (Barrs 2019). The virus is shed in high copy numbers in all secretions of infected cats and is transmitted faeco-orally, especially via fomites. Infection by this remarkably environmentally resilient virus occurs most commonly in unvaccinated kittens that first encounter the virus, especially in animal shelters, after maternal antibodies wane. Disease in susceptible cats is characterised by vomiting, diarrhoea, dehydration, sepsis and in severe cases, death (Barrs 2019).
Co-infections of FPV with other enteric viruses have been detected in sick and/or healthy cats including viruses in the familiesParvoviridae (Genus Bocaparvovirus andChaphamaparvovirus ), Astroviridae (GenusMamastrovirus ), Coronaviridae (Genus Alphacoronavirus),Caliciviridae (Genus Vesivirus, Norovirus ) andPicornaviridae (Genus Kobuvirus) (Brussel et al., 2020; Castro et al., 2015; Di Profio et al., 2021; Ji et al., 2020; Piewbang et al., 2019).
A host can be exposed to multiple viruses with similar routes of transmission and high prevalence at the same or within a short space of time. In young children, co-infection and simultaneous detection of enteropathogens is common (Makimaa et al., 2020). Interactions among co-infecting viruses may be synergistically pathogenic and enteric virus co-infections are commonly identified for all viruses linked to acute gastroenteritis in humans (Simsek et al., 2021). Similarly, enteric co-pathogen infections may play a role in determining clinical outcomes in cats infected with FPV. Since FPV damages gastrointestinal epithelium and bone-marrow to cause local and systemic immunocompromise, the abundance of viral co-infections might be higher in cats with FPL than among healthy cats.
We incorporated both metatranscriptomics, the analysis of non-ribosomal RNA (rRNA) transcripts, and viral particle enrichment metagenomics in this study to characterise the enteric virome of sick FPV-infected and clinically healthy cats. Our specific aim was to reveal any differences in the gut virome of FPV-infected cats, particularly enteric viruses that are absent from the enteric virome of healthy control cats.