Detection of Coronavirus-like Particles in Wild, Exotic and Captive Animals by Transmission Electron Microscopy
Abstract
Coronaviruses infect humans and a wide diversity of mammalian and bird species causing respiratory, enteric, neurologic and hepatic disorders. Due to their facility of adapting to new species and establishing sppilover events, coronaviruses pose a risk to global public health. Considering the zoonotic risk of coronaviruses, their role in wild species that host wild animals, as well as their ability to adapt to new species, seems to be the fundamental key to understanding their pathophysiology. The objective of this work was to report the presence of coronavirus-like particles in wild, exotic and captive animal species, in fecal or small intestine samples, using negative staining technique for transmission electron microscopy. Under the transmission electron microscope, particles with coronavirus-like morphology, pleomorphic, rounded or elongated with radial projections forming a corona and measuring 80-140 nm in diameter, were visualized in all examined samples. This report is the first worldwide occurrence of coronaviruses in Falco peregrinus, Tayassu tajacu and Tayassu pecari and the first occurrence in Brazilin Sus scrofa, Nosua nosua, Puma concolor and in Rhea Americana.
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Introduction
The transmission of pathogens from wild animals to humans is called zoonotic spillover, which indicates that this phenomenon plays an important role in the emergence of new infectious diseases, representing a global burden on public health. Although associated with several outbreaks, it is still a poorly understood phenomenon. Coronaviruses circulate in nature in several animal species. There is a consensus that the possible origin of the virus comes from a wild animal, considering that most of the new viruses that crossed the evolutionary barrier and infected humans throughout the epidemiological history of viral diseases, were of animal origin, such as SARS and MARS that caused worldwide epidemics [1]. While still preliminary, current data suggest bats are the most likely initial source of the current Covid-19 outbreak, which began in December 2019 in Wuhan, China [2; 3].
Activities and processes that increase human interaction with the different animal species and pathogens they host, which include handling, poaching and indiscriminate consumption of wild animal meat and by-products without sanitary measures, are associated with an increased risk of spillover events[4]. These factors associated with habitat degradation and fragmentation, climate change and infectious diseases contribute to the extinction of many species of wild animals [5]. Coronaviruses have crossed these species barriers and during the last two decades, three zoonotic coronaviruses have been identified as the cause of large-scale disease outbreaks, Severe Acute Respiratory Syndrome (SARS), Middle Eastern Respiratory Syndrome (MERS) and Syndrome of Acute Swine Diarrhea (SADS) [6]. Coronavirus infection results in respiratory, enteric, neurological, and liver disorders [7]. All pathogenic human coronaviruses have their origin in animals [8], and studies have been carried out in an attempt to obtain clarification on the capacity of domestic and wild animals to be potential reservoirs [9].
Considering the zoonotic risk of coronaviruses, their role in wild species that host wild animals, as well as their ability to adapt to new species, seems to be the fundamental key to understanding their pathophysiology [8].
Coronaviruses are positive-stranded RNA viruses, belong to the order Nidovirales, family Coronaviridae and have four genera, Alphacoronavirus (human coronavírus NL63 (HCoV-NL63), porcine transmissible gastroenteritis coronavírus (TGEV), PEDV, and porcine respiratory coronavírus-PRCV), Betacoronavirus (SARS-CoV, MERS-Cov, bat coronavírus HKU4, mouse hepatites coronavírus (MHV), bovine coronavírus (BCoV), and human coronavírus OC43, Gammacoronavirus (avian (infectious bronchitis coronavírus-IBV) e Deltacoronavirus (porcine deltacoronavirus (PdCV) [10].
Coronaviruses infect humans and a wide diversity of mammalian and bird species causing respiratory, enteric, neurologic and hepatic disorders [7]. Most coronaviruses replicate in epithelial cells of the respiratory tract producing respiratory symptoms while others infect epithelial cells of the enteric tract, causing diarrhea severely, sometime fatal, in young farm animals, causing serious damage to livestock [11; 12].
The objective of this work was to report the presence of coronavirus particles in wild, captive and companion animal species, in fecal or small intestine samples sent to the Electron Microscopy Laboratory of the Biological Institute for identification of the viral agent.
Conclusion
Studies aimed at determining the presence of the coronavirus in wild animals should be continued to better characterize the interspecies barrier transmission between these viruses and different animal species in order to avoid possible losses, mainly due to the fact that many species are included in the list endangered species official. Attention should be given to public health and veterinary surveillance programs, including monitoring of wild animals in order to contribute information to assist prevent future emergencies, outbreaks and pandemics [90].
This report is the first worldwide occurrence of coronaviruses in Falco peregrinus, Tayassu tajacu and Tayassu pecari and the first occurrence in Brazilin Sus scrofa, Nosua nosua, Puma concolor and in Rhea Americana.