Epsilon Archive for Student Projects

Abstract

COVID-19 is a disease which has had great impact on the world in 2020. It has infected millions of
people during the year, and been confirmed in animals such as cats, dogs and minks. The receptor
ACE2 which is the target for the virus SARS-CoV-2 to use for attachment to the cell, is very similar
between cats and humans. Therefore, there is a risk for cats to become infected with SARS-CoV-2.
Studies have shown that cats can be infected by aerosol transmission, can show symptoms and can
develop antibodies. Prevalence of SARS-CoV-2 antibodies in cats have been investigated in Wuhan,
by using ELISA showing that 14.7% (15/102) of sampled cats were positive. However, there are no
studies done on seroprevalence in Sweden.
The aim of this study was to investigate the prevalence of antibodies against SARS-CoV-2 in cats
in four municipalities in Sweden. This by using a method previously not used for cats, but well
tested for detection of SARS-CoV-2 antibodies in humans, called COVID-19 suspension
immunoassay (SIA). The objective was to adapt the SIA to be able to detect antibodies against
SARS-CoV-2 as well as against feline coronavirus (FCoV), which could have the capability to crossreact in the test. The goal was also to try and connect seroprevalence with different individual traits,
environmental differences and whether the owner had been confirmed infected. The concern in cat
owners regarding COVID-19 and their animals was to be simultaneously studied by a survey.
Blood samples were collected from both sick and healthy cats in Uppsala, Östhammar, Tierp and
Halmstad. They were categorized into two groups, with 56 samples in the first (A) and 147 in the
other (B). In group A, the samples were attached to a survey in which the owner answered 15
questions about their animal, its home environment, closeness to humans and other animals and if
the owner had been sick in COVID-19. In group B, serum samples were collected from the
university hospital for animals in Uppsala (UDS) with no survey administered.
Presence of SARS-CoV-2 antibodies in cat serum was analysed, using part of the spike protein (S1)
as antigen. Six samples out of 203 turned out positive (preliminary cut off at >333 MFI), all in group
B, which translates to a preliminary seropositivity of 3% in our population. Another two samples
had doubtful results (MFI between 174-333), both in group A, why very little could be concluded
from the survey regarding predisposing factors or symptoms. The two doubtfully positive cats did
live very close to their humans, and one of the cats had a family with confirmed COVID-19. The
COVID-19 SIA did unfortunately not work as well for FCoV despite efforts to try and solve a couple
of possible reasons for failure, why it was not possible to examine the possibility for cross-reaction.
However, previous studies have not shown any indications of this.
In conclusion, this study indicates that cats can produce antibodies against SARS-CoV-2, and that
the seropositivity was 3% in the population used for the study. The SIA is reliable for detection of
antibodies against SARS-CoV-2 in human sera and seems to have potential for analysis in cat sera,
but is not yet successfully adapted for FCoV. Owners concern for COVID-19 in cats was low.
In the future, improvements and further studies could be done based on these results. A larger
selection of cats, possibly from more areas of Sweden, should be included. All with information
about their individual traits, environment, symptoms, closeness to humans and if they have been in
contact with someone confirmed infected. A larger number of confirmed seronegative cats could aid
in determining a more accurate cut off value for determining the results from the COVID-19 SIA.
This study was performed in parallel with another study, by Frida Österberg, which investigated the
same subjects as this one, but in dogs.