Surveillance and genetic characterization of severe acute respiratory Coronavirus type 2 (SARS-CoV-2) infections in domestic animals and wildlife in Thailand

Abstract

SARS-CoV-2 caused a pandemic outbreak since December 2019 with global implications for public health, economy, and society. This dissertation entitled “Surveillance and genetic characterization of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) infections in domestic animals and wildlife in Thailand” investigates the transmission incidence and characterization of the virus between humans and animals. This thesis comprises 4 studies of the surveillance of SARS-CoV-2 in animals and wildlife species in Thailand from 2017 to 2023. The first investigation (Chapter 2) involved a survey of SARS-CoV-2 in domestic dogs and cats in Samut Sakhon province during the second wave of the COVID-19 outbreak in Thailand in February 2021. Although no viral RNA was detected in the swab samples, 3.14% (5/159) of studied animals tested positive for anti-N-IgG antibody, indicating possible SARS-CoV-2 exposure in high-risk areas. During the third wave of the pandemic, from April to May 2021, the second investigation (Chapter 3) provided active surveillance of SARS-CoV-2 among dogs and cats from COVID-19 households. The detection of SARS-CoV-2 RNA and antibodies in four of the 44 animals confirmed SARS-CoV-2 infection. According to phylogenetic analyses, the viral strains belonged to the Alpha VOCs (B.1.1.7 lineage). The third study (chapter 4) described a cross-sectional survey conducted in Bangkok and vicinities during Thailand’s 4th wave of the COVID-19 outbreak. SARS-CoV-2 infections were discovered in a dog and a cat from COVID-19 positive households. The viral genomes were classified as Delta variant (B.1.617.2 lineage). This study raised awareness of the spillover of variants of concern in domestic animals. The fourth study (Chapter 5), expanded the surveillance of wildlife species in captive and free-ranging habitats during pre and post-COVID-19 (2017 to 2023). Seven lions of a zoo tested positive for SARS-CoV-2 immunity, and a retrospective investigation in the same zoo confirmed the virus infection in a tiger. Human-to-animal transmission has been proposed in the tiger and lions. The finding emphasized the importance of monitoring COVID-19 exposure history in animal species through passive and active surveillance. The summary information of this dissertation contributes to public awareness, risk communication, and the understanding of SARS-CoV-2 dynamics in domestic animals and wildlife populations.