3. RESULTS
To evaluate viral spread, viremia, and seroconversion, nasal and rectal
swabs and serum and milk samples were analysed. Milk samples were
collected from 21 out of 24 cows due to the presence of two primiparous
cows (6 and 10) and a dry cow (19) (Table 1).
All nasal and rectal swabs and milk samples tested negative for
SARS-CoV-2 RNA. The results of the analyses performed on the serum
samples are reported in Table 1. All tested samples were BCoV-negative
(MTN ≥ 4). Eight of the 24 samples (33%, 95% CI 14–52) were negative
for SARS-CoV-2. Of the 24 serum samples, 11 (46%, 95% CI 26-66) were
positive for SARS-CoV-2 nucleocapsid protein (range: 1.38–7.40), 14
(58%, 95% CI 38-78) were positive for SARS-CoV-2 spike protein (range:
1.60–249.00), and 13 (54%, 95% CI 34–74) were positive for
SARS-COV-2-neutralising antibodies, with titres ranging from 1:20 to
1:160 (Table 1). Interestingly, six of the samples were from pregnant
cows (46%, 95% CI 19–73) (5, 12, 17, 19, 20, and 23) (Table 1). Of
the 13 animals with neutralising antibodies, 2 of 13 were aged 1–5
years (15%, 95% CI 5–49), 6 of 13 were aged 6–10 years (46%, 95%
CI 36–98), and 5 of 13 were aged >10 years (38%, 95% CI
53–113) (Table 2). Of the six pregnant animals with neutralising
antibodies, one was aged 1–5 years (17%, 95% CI 9–31), four were
aged 6–10 years (67%, 95% CI 12–76), and one was aged over 10 years
(17%, 95% CI 13–47) (Table 2). The correlation between the presence
of SARS-CoV-2-neutralising
antibodies and the age of the cows was analysed using Fisher’s exact
test, which showed a significant relationship (P < 0.05).
Comparison of the 1–5-year-old group to the >10-year-old
group yielded a statistically significant two-sided p value (p = 0.041).
However, no statistically significant difference was observed when
comparing the other groups. In addition, no correlation with pregnancy
status was detected.
Furthermore, evaluating the analysed antibodies and age of the cows via
Pearson correlation analysis showed a significant relationship (P
< 0.05) between anti-S and neutralising antibodies against
SARS-CoV-2 with age (Table 3) and interestingly, Pearson correlation
analysis showed a strongly significant correlation (P < 0.01)
between anti-S and anti-N antibodies (Table 3).
None of the cows with neutralising antibodies displayed fever,
diarrhoea, and/or respiratory signs at sampling.