COVID-19 from veterinary medicine and one health perspectives: What animal coronaviruses have taught us

Abstract

Coronaviruses (CoVs) are enveloped, single-stranded, positive-sense RNA viruses displaying an exceptional genetic plasticity driven by accumulation of point mutations and recombination events. This genetic variation is responsible for continuous emergence of viral strains with increased virulence, different tissue tropism and/or expanded host range (Buonavoglia et al., 2006). CoVs are currently classified within four genera, Alphacoronavirus, Betacoronavirus, Gammacoronavirus and Deltacoronavirus, that recognise bats, birds and likely rodents as natural reservoirs. In December 2019, cases of undiagnosed pneumonia started being reported in Wuhan, Hubei, China. On January 9 2020, the Chinese authorities indicated that a novel CoV was associated with the severe respiratory disease. The first patient with unexplained pneumonia, identified in December 8 2019, came from Wuhan South China Seafood Market. Initially, other patients were linked to the same seafood and live animal market, suggesting an animal origin for the initial spread to humans. Subsequent investigations revealed that the crowded seafood market only boosted circulation of the novel CoV and spread it to the whole city in early December 2019, whereas based on the genome data the virus likely began spreading from person to person in early December or even as early as late November. The first documented human case has been dated back to November 17 2019. The novel human CoV (HCoV) is a betacoronavirus genetically related to Severe acute respiratory syndrome (SARS) CoV and only distantly related to Middle East respiratory syndrome CoV (MERS-CoV) and it was designated as SARS type 2 CoV (SARS-CoV-2). Similar to the other hypervirulent HCoVs, SARS-CoV-2 has a putative animal origin, likely descended from a related bat CoV that spilled over to humans either directly or after adaptation in another animal species, such as the Malayan pangolin (Lam et al., 2020). SARS-CoV-2 is highly related genetically (96% nt) to a SARS-like bat CoV (Zhou et al., 2020) The SARS-CoV-2 induced disease, referred to as CoronaVirus Disease 2019 (COVID-19), affects the respiratory tract, with a number of patients displaying severe pneumonia and requiring hospitalisation and admission to intermediate or intensive care units. Unlike SARS and MERS, COVID-19 is characterised by low lethality rates and high frequency of asymptomatic or paucisymptomatic infections that likely favoured the spread of this new pandemic (Lai et al., 2020). As SARS-CoV-2 started spreading globally, between February and March 2020, potential spill over exposure (viral RNA) was noted in companion animals, likely due to their strict social interactions with humans. SARS-CoV-2 RNA was detected in two dogs and a cat without clinical signs in Hong Kong and in a cat with gastroenteric and respiratory signs in Bruxelles, all which lived in close contact with infected COVID-19 human patients.1 , 2 This noted analogous findings observed during the 2002–2003 spread of SARS-CoV.3