Research led by the Universidade Federal de Minas Gerais at the Belo Horizonte Zoo in Minas Gerais, Brazil, has uncovered evidence of SARS-CoV-2 transmission in captive wild mammals, highlighting significant concerns about zoonotic spread and the potential for viral evolution in new hosts. This study is crucial because it indicates that wild animals, traditionally considered less vulnerable to viral infection, can harbor the virus and potentially contribute to its mutation and spread, adding complexity to efforts to track and control the pandemic.
The Belo Horizonte Zoo, home to more than 3,500 animals representing over 235 species, is an important facility for the study of wildlife health. Among the zoo’s diverse population are 117 mammals across 36 species. These animals live in a controlled environment that allows researchers to study them under close observation, providing insights into the dynamics of disease transmission between humans and animals.
SARS-CoV-2, the virus responsible for COVID-19, has primarily impacted humans but has also raised alarms about its potential to spread to wild animals, creating new reservoirs. These reservoirs could become breeding grounds for mutations, potentially leading to new viral variants that are harder to detect or control. Understanding how SARS-CoV-2 transmits between humans and animals is crucial for preventing future pandemics, particularly by identifying potential animal hosts that could harbor the virus outside of regular surveillance systems.
The study, titled “SARS-CoV-2 surveillance in captive animals at the Belo Horizonte Zoo, Minas Gerais, Brazil,” was published in the Virology Journal. It focused on examining the virus’s evolution and zoonotic potential within the zoo’s controlled environment, where researchers could closely monitor animal health and potential virus spread. The research team collected throat, rectal, and nasal swabs from 47 mammals between November 2021 and March 2023. These samples were then analyzed for the presence of SARS-CoV-2 using RT-PCR testing, a method known for its accuracy in detecting the virus’s genetic material.
Out of the 47 animals tested, 19.1% (nine animals) tested positive for SARS-CoV-2. The samples came from a variety of animals, and the virus was detected in throat, rectal, and nasal swabs. Notably, rectal swabs showed the highest positivity rate, suggesting that the virus might have a higher replication rate in the gastrointestinal tract of certain animals. This finding may provide new insights into how the virus behaves in different species and could guide future research into animal-human transmission.
For those samples that tested positive, sequencing was performed to identify the viral strain and track its evolution. Three animals— a fallow deer, a maned wolf, and a western lowland gorilla—yielded successful viral genomes for sequencing. The phylogenetic analysis of these genomes revealed the presence of two variants of concern (VOC): alpha in the wolf and deer, and omicron in the gorilla. These variants are significant because they are associated with increased transmissibility and could potentially lead to more severe infections in both humans and animals.
The phylogenetic data also suggested that the transmission of SARS-CoV-2 from humans to animals occurred in these cases. The genomes of the virus found in the animals were closely related to samples from humans in the same region, confirming that the virus had likely been transmitted from humans to the animals. This is consistent with other studies that have found similar patterns of transmission in wild and domestic mammals, reinforcing the idea that animals can serve as a bridge for the virus to move between human populations.
One of the most concerning findings of this study is the potential for viral mutations to occur in animal populations. As the virus spreads through new hosts, it may evolve in ways that make it more difficult for humans or other animals to resist infection. This possibility highlights the need for vigilant surveillance of both human and wildlife populations, especially in areas where zoonotic transmission is more likely. Monitoring these animal reservoirs could provide early warning signals about the emergence of new viral variants that might evade current vaccines or treatments.
In addition to documenting the presence of SARS-CoV-2 in zoo animals, this research underscores the need for comprehensive and integrated public health strategies that consider both human and wildlife health. In particular, it emphasizes the importance of genomic surveillance across both species to track viral evolution. Such surveillance could help scientists quickly identify new variants and assess their potential impact on public health. Furthermore, it calls for a better understanding of how wildlife can act as intermediaries in the transmission of viruses, especially in a post-pandemic world where zoonotic diseases may become an increasingly common threat.
SARS-CoV-2 has demonstrated its ability to infect a wide range of mammals, both domestic and wild, and this study highlights the risk of interspecies transmission in zoo settings. The findings suggest that zoos, as places where animals and humans frequently come into close contact, may be particularly vulnerable to outbreaks of zoonotic diseases. Although captive animals are not the primary source of COVID-19 in the general population, their role in the evolution and spread of the virus cannot be overlooked.
The detection of variants like alpha and omicron in zoo animals raises additional concerns about the potential for these variants to evolve in animals and be reintroduced into human populations. This reinforces the importance of maintaining strict biosecurity measures in places where humans and animals interact closely, such as zoos, wildlife sanctuaries, and farms.