<div>SARS-CoV-2 is a virus that originated in Wuhan, China, in 2019 and has
since spread worldwide, infecting people and animals. The objective of
this study was to implement the plaque reduction neutralization test
(PRNT90) and microneutralization (MN) to evaluate the presence of
antibodies against SARS-CoV-2 in companion animals. First, a virus was
isolated and sequenced, which showed a similarity of 99.9% with the
original Wuhan strain. This virus had a titer of 3.55 DICC
<sub>50</sub>; for the PRNT90, it was adjusted to 30-40
plaque-forming units (PFU) and for the MN, at 100 DICC
<sub>50</sub>. For both assays, serial double dilutions of the sera
were performed from 1:10 to 1:5120. Serum samples from people with
negative and positive status were used as controls, as well as samples
from companion animals (dogs and cats). In the case of human samples,
the titers were from 1:10 to 1:5120 with PRNT and from 1:10 to 1:1280
with MN (r <sup>2</sup> = 0.957). Analysis of animal samples
(dogs n = 521 and cats n = 29) revealed 10 positive samples, six from
dogs and four from cats. Cats had higher titers than dogs. Titers ranged
from 1:80 to 1:320 by MN and from 1:160 to 1:640 by PRNT90 for cats and
from 1:10 to 1:40 by MN and from 1:10 to 1:80 PRNT90 for dogs (r
<sup>2</sup> = 0.621). In both human and animal samples, the
highest titers were observed with the PRNT90 test; however, the MN test
is easier to perform than the PRNT90 test, so it is suggested as the
test of choice for animal seroprevalence studies.</div>