Dogs and cats are less susceptible to the omicron variant of concern of SARS-CoV-2 – a field study

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused a pandemic of unprecedented extent. Beside humans, a number of animal species can be infected, however, in some species differing susceptibilities were observed depending on the virus variant. Here, we serologically investigated cats and dogs living in households with human COVID-19 patients. The study was conducted during the transition period from delta as the dominating variant of concern (VOC) to omicron (BA.1/BA.2) to investigate the frequency of virus transmission of both VOCs from infected owners to their pets. The animal sera were tested by surrogate virus neutralization tests (sVNT) using either the original receptor-binding domain (RBD), enabling the detection of antibodies against the delta variant, or an omicron-specific RBD. Of the 290 canine samples, 20 tested positive by sVNT, but there were marked differences between the sampling time, and, related thereto, the virus variants, the dogs had contact to. While in November 2021 infected owners led to 50% seropositive dogs (18/36), only 0.8% (2/254) of animals with household contacts to SARS-CoV-2 between December 2021 and April 2022 tested positive. In all cases, the positive reaction was recorded against the original RBD. For cats, a similar pattern was seen, as in November 2021 38.1% (16/42) tested positive and between December 2021 and March 2022 only 5.0% (10/199). The markedly reduced ratio of seropositive animals during the period of omicron circulation suggests a considerably lower susceptibility of dogs and cats to this VOC. To examine the effect of BA.2, BA.4 and BA.5 omicron subvariants, sera taken in the second and third quarter of 2022 from randomly selected cats were investigated. 2.3% (11/372) tested seropositive and all of them showed a stronger reaction against the original RBD, further supporting the assumption of a lower susceptibility of companion animals to the omicron VOC.

Detection of SARS-CoV-2 Delta Variant (B.1.617.2) in Domestic Dogs and Zoo Tigers in England and Jersey during 2021

“…Epidemiological and experimental findings have shown that although Omicron and its sublineages have enhanced transmissibility properties, Omicron infection causes less severe disease than Delta in multiple species [78]. A serological field study observed a reduced number of seropositive cats and dogs during the early phases of Omicron circulation in humans [79] and Omicron variant BA.1.1 demonstrated lower pathogenicity compared to earlier variants in a feline experimental model [80]. In hamsters, experimental infections with an Omicron variant showed similar clinical disease compared to Delta variant infection [81]; however, these reports vary depending on the Omicron sublineage [82] and how this reflects natural infection and reverse zoonotic transmission is unclear.…”

Increase in SARS-CoV-2 Seroprevalence in UK Domestic Felids Despite Weak Immunogenicity of Post-Omicron Variants

“…These adaptations are believed to have arisen from alterations in the cell entry mechanism of the virus combined with changes in the antigenicity of the Omicron spike protein [ 36 , 54 ]. In companion animals, Omicron has been reported to be less virulent than previous variants [ 55 ], and cats are also believed to be less susceptible to infection with Omicron compared to pre-Omicron variants [ 56 ]. These combined factors may account for the low number of Omicron-dominant samples observed in this study.…”

Serological Survey of Retrovirus and Coronavirus Infections, including SARS-CoV-2, in Rural Stray Cats in The Netherlands, 2020–2022

“…SARS-CoV-2 Alpha, Delta and Omicron BA.1 variants can infect cats under natural and experimental conditions [ 52 , 54 , 57 , 79 ] Infections in cats with either the Alpha or Delta variant induced antibodies that showed good cross-reactivity in ELISA, s-VNT, pseudo-VNT or PRNT using the ancestral SARS-CoV-2 strain [ 54 , 57 , 80 , 81 , 82 ]. In households with infected humans, human-to-cat spread of Omicron variants was markedly reduced when compared to human-to-cat spread of the Delta variant, suggesting a reduced susceptibility in cats for Omicron variants [ 83 ]. Omicron BA.1 experimental infected cats showed delayed and lower neutralizing antibody titers, which did not neutralize the ancestral SARS-CoV-2 strain [ 54 ].…”