3.1 Clinical examination and laboratory testing
On D16, all cats and were found bright, alert and responsive, with no
cardiorespiratory signs (including upper respiratory signs) and normal
temperature. According to the owner, their clinical condition remained
unaltered throughout the observation period. Hematology and serum
biochemistry findings were unremarkable (Table 1) and testing results
for FIV and FeLV were negative for all 3 cats. Testing results of all
oropharyngeal and fecal swabs obtained from C1 between D7 and D17 were
negative via both SARS-CoV-2-specific real-time RT-PCR methods. However,
positive results against both targets were obtained by testing of the
other two cats (C2 and C3), and specifically, from the first sampling
time-point (D7), and up to D13.
Daily monitoring of viral load in oropharyngeal and fecal swabs of the
two SARS-CoV-2-positive cats are summarized in Figure 1. High virus
titers (Ct values < 30) were observed in the pharynx of both
C2 and C3 on the first sampling time-point (D7). For C2, 7.03
Log10 RNA copies/swab were determined on D7. A
considerably lower virus titer (3.94 Log10 RNA
copies/swab) was measured on D10. During the subsequent 3 days, a
slightly increasing viral load was measured (4.61, 4.83 and 5.48
Log10 RNA copies/swab, respectively) in this animal’s
pharynx, and it finally tested negative on D14. The oropharyngeal swab
obtained from C3 on D7 was also characterized by a high viral load (8.42
Log10 RNA copies/swab). However, differences were
observed in the kinetics of SARS-CoV-2 presence in the upper respiratory
tract of this animal, since steadily declining virus titers were
measured between D10 and D13 (7.55, 6.72, 4.13 and 4.07
Log10 RNA copies/swab, respectively). All subsequently
collected swabs tested negative.
Fecal swabs obtained from C2 tested positive on the first day of
sampling (D7, 5.31 Log10 RNA copies/swab) and up to D11
with progressively declining virus titers (3.89 Log10RNA copies/swab). Fecal swabs collected on D12 (i.e. 5 days after the
first real-time RT-PCR-positive fecal swab) tested negative. Regarding
C3, the kinetics of viral RNA concentrations in the fecal swabs was
similar to that in its pharynx, although characterized by a time lag
(Figure 1). A virus titer of 4.05 Log10 RNA copies/swab
was measured on D7. Subsequently, a peak was observed on D9 (6.63
Log10 RNA copies/swab), followed by a progressive
decline on D10, D11 and D13 (5.69, 4.23 and 3.89 Log10RNA copies/swab, respectively). Fecal swabs collected on D15 (i.e. 8
days after the first real-time RT-PCR-positive fecal swab) tested
negative.
All sera obtained from C1 and C2 tested negative for SARS-CoV-2-specific
antibodies. On the contrary, serological testing of C3 on D17 (i.e. 10
days after the first real-time RT-PCR-positive oropharyngeal swab)
yielded a positive result (S/P% = 197.3%). Re-testing on D26 indicated
an even stronger positive result (S/P% = 256.7%), with the respective
OD value having reached a plateau (2.934 AU). On D70 an S/P% of 217.6%
was observed, indicating a decline in the respective serum antibody
titer.