Detection of SARS-CoV-2 in Terrestrial Animals in Southern Nigeria: Potential Cases of Reverse Zoonosis

Abstract

Since SARS-CoV-2 caused the COVID-19 pandemic, records have suggested the occurrence of reverse zoonosis of pets and farm animals in contact with SARS-CoV-2-positive humans in the Occident. However, there is little information on the spread of the virus among animals in contact with humans in Africa. Therefore, this study aimed to investigate the occurrence of SARS-CoV-2 in various animals in Nigeria. Overall, 791 animals from Ebonyi, Ogun, Ondo, and Oyo States, Nigeria were screened for SARS-CoV-2 using RT-qPCR (n = 364) and IgG ELISA (n = 654). SARS-CoV-2 positivity rates were 45.9% (RT-qPCR) and 1.4% (ELISA). SARS-CoV-2 RNA was detected in almost all animal taxa and sampling locations except Oyo State. SARS-CoV-2 IgGs were detected only in goats from Ebonyi and pigs from Ogun States. Overall, SARS-CoV-2 infectivity rates were higher in 2021 than in 2022. Our study highlights the ability of the virus to infect various animals. It presents the first report of natural SARS-CoV-2 infection in poultry, pigs, domestic ruminants, and lizards. The close human–animal interactions in these settings suggest ongoing reverse zoonosis, highlighting the role of behavioral factors of transmission and the potential for SARS-CoV-2 to spread among animals. These underscore the importance of continuous monitoring to detect and intervene in any eventual upsurge.

Features of SARS-CoV-2 Replication in Various Types of Reptilian and Fish Cell Cultures

“…Thus, continuous FHM cells can adsorb SARS-CoV-2 on their surface while maintaining its viability under certain conditions. The preservation of the infectious properties of SARS-CoV-2 in various types of water during this time has been shown for temperatures of 20-24 • C [45,67,68], which may be sufficient for the virus adsorption, for example, on the gill epithelium of some fish species. The results obtained show that the ability to adsorb SARS-CoV-2 is significantly higher in epithelial-like FHM cells compared to CGIB diploid fibroblasts, which may also be due to differences in the cell receptor apparatus and a greater presence of ACE2 on FHM.…”

“…SARS-CoV-2 infection of zebrafish larvae (Danio rerio) [43] and adults of three spot gourami (Trichopodus trichopterus) [44] did not lead to infection. Happi AN et al detected SARS-CoV-2 RNA in oral and cloacal swab samples of common agama (Agama agama) in two states of Nigeria in 2021-2022 [45]. Data on the study of the susceptibility of reptiles to SARS-CoV-2 in vivo and their cells in vitro are not available in accessible sources.…”

Experimental co-infection of calves with SARS-CoV-2 Delta and Omicron variants of concern

“…However, in Italy, Fiorito et al [ 28 ] reported 13/24 lactating cattle which were sampled on a single farm had neutralizing antibodies against SARS-CoV-2; the latter data are suggestive of transmission occurring within the herd. Interestingly, SARS-CoV-2 RNA was isolated from nasal and/or rectal swabs collected from cattle during the human Delta VOC wave of transmission in both India and Nigeria, suggesting Delta VOC susceptibility and recent exposure [ 27 , 30 ]. Together, these data support the conclusion that during the Delta VOC wave of transmission in humans, there were instances of spillover of SARS-CoV-2 Delta VOC from humans into cattle.…”

Five Things Clinicians Need to Know About Zoonotic Viral Spillover and Spillback

“…44,45 Current evidence suggests that SARS-CoV-2 has adapted to new mink and white tail deer hosts and at least some mink-associated novel variants are capable of spilling back to humans. 46 Although current evidence suggests that pigs 47,48,49,50,51,52,53 and cattle 54,55,56 are not routinely susceptible to infection with circulating strains of SAR-CoV-2, were SARS-CoV-2 strains to adapt to infect livestock, other circulating strains of enzootic coronaviruses in livestock might increase the risk of novel virus generation through recombination. When confronted with a patient with unexplained illness and negative diagnostic tests, clinicians are wise to ask questions about a patient's exposure to animals and to consider animal pathogen involvement in the patient's signs and symptoms.…”