Longitudinal study on SARS-CoV-2 antibody responses in companion animals, Chile

Abstract

SARS-CoV-2 infection susceptibility in dogs and cats has been documented, with identified risk factors contributing to transmission dynamics. Understanding viral prevalence and the evolution of emerging variants across pandemic waves can clarify the potential role of pets as reservoirs. This study evaluated 3298 serum samples (1921 dogs, 1377 cats) collected from 2020 to 2024. Samples were analyzed using ELISA and viral neutralization assays, revealing a positivity rate of 2.7%. We assessed neutralizing antibody titers (nAbs) against the Wuhan-Hu-1 and Omicron BA.1 strains, finding higher titers in felines compared to canines. A marked reduction in samples exceeding the detection limit was observed after November 2022. Longitudinal data from up to 30 months in a dog and 15 months in two cats demonstrated sustained antibody responses, with increased nAb titers in 7 of 14 monitored animals. Multivariable logistic regression of 275 samples indicated that a pet's vaccination status was associated with an increased risk of infection, while spring season, the owner's number of COVID-19 vaccinations, and the owner's vaccination status were protective factors. These results emphasize the significance of vaccination strategies for both human and animal health, supporting the One Health approach.

Keywords: COVID-19; One-Health; SARS-CoV-2; cats; companion animals; dogs; pandemic; pets.

Figure 1.

NAb titers of ELISA positive animal sera against the ancestral Wuhan-Hu-1 strain or the Omicron BA.1 variant. Antibody titers were assayed by microneutralization using rVSV-SARS2-S-Wuhan-Hu-1 or rVSV-SARS2-S-Omicron BA.1. Results of nAb titers are shown as IC50 on the Y-axis. Canine and feline sera are represented in black and red symbols, respectively, and all correspond to the first samples taken after COVID-19 exposition (M0). (A) NAbs titers against the Wuhan-Hu-1 strain from 77 sera of 31 felines and 46 canines infected in the years 2020–2023 are represented by different symbols: square (2020), cross (2021), rhombus (2022), and hexagon (2023). (B) NAbs titers from 14 felines and 31 canines against the ancestral Wuhan-Hu-1 and Omicron BA.1 variants present in sera from. Antibody titers were assayed by microneutralization using rVSV-SARS2-S-Wuhan-Hu-1 and rVSV-SARS2-S-BA.1. Wuhan-Hu-1 and BA.1 variants are represented by circles and triangles, respectively. The dashed line indicates the limit of detection (LOD) for the microneutralization assay. Each data point represents the results of two technical replicates. The grey lines indicate the nAb titer of a sera from the same individual with the two different variants. The GMT of each species is indicated on the X-axis, which does not consider the samples below the detection limit. The median (P50) titer, including the complete dataset of each group, is indicated below. Statistical analysis was performed of the nAb titers of felines and canines with the different virus variants using the unpaired two-tailed Mann-Whitney test. (ns: not significant).

Figure 2.

Longitudinal dynamics of nAb titers against the ancestral Wuhan-Hu-1 strain present in sera from 7 canines and 7 feline individuals. nAb titers (IC50) were obtained using an rVSV-SARS2-S-Wuhan-Hu-1 microneutralization assay at different time points grouped by months. Results are shown as IC50 on the Y-axis. Felines and canines are represented by red and black circles, respectively. The lines connect antibody titers from the same individual at different time points. The dashed line indicates the limit of detection (LOD) of the assay. Every data point represents results from two technical replicates.