Transmission of infectious viruses in the natural setting at human-animal interface

Abstract

Most viral pathogens causing epidemics and pandemics are zoonotic, emerging from wildlife reservoirs like SARS CoV2 causing the global Covid-19 pandemic, although animal origin of this virus remains a mystery. Cross-species transmission of pathogens from animals to humans is known as zoonosis. However, pathogens are also transmitted from humans to animals in regions where there is a close interaction between animals and humans by 'reverse transmission' (anthroponosis). Molecular evidence for the transmission of two zoonotic RNA viruses at the human-monkey interface in Rajasthan forests is presented here: a) the apathogenic Simian Foamy Viruses (SFV), and b): Influenza A viruses (IAV)-like virus, etiologic agent for human flu infecting wild Indian rhesus monkeys inhabiting Rajasthan forests. The data provide critical information on ecology and evolution of viruses of Public Health relevance. During replication, viral genomes mutate along the transmission route to adapt to the new hosts, generating new variants that are likely to have properties different from the founder viruses. Wild Indian monkeys are under-sampled for monitoring infectious diseases mainly because of the difficulties with sample collection. Monkeys are perceived as religious icons by the Hindus in India. It is extremely difficult to obtain permission from the Forest and Wildlife Department government authorities to collect wild simian blood samples for surveillance of infectious diseases caused by viral pathogens. Reducing animal-human contact and affordable vaccination are two relevant anti-viral strategies to counteract the spread of infectious zoonotic pathogens. Genbank Accession numbers: Indian SFVmac: ADN94420, IAV like virus: MZ298601.

Graphical abstract

Fig. 1

A population of wild rhesus monkeys (Macaca mulatta) from the natural habitats close to the cities of Jodhpur and Jaipur was included in the investigation. Cases of monkey bites as shown here, are routinely reported in the local press. Viral pathogens are transmitted not only from wild monkeys to humans, but also from humans to wild monkeys via ‘reverse transmission'. Analyses of partial sequence data of genomes of two different viruses are included in the report, Simian Foamy Viruses (SFV) and human H1N1 Influenza A Virus, that were found to infect wild Indian rhesus monkeys. While SFV infection of different species of nonhuman primates is well documented, natural infection of wild Indian rhesus monkeys by SFV was not reported before. In vitro infection of normal PBMCs by Indian SFV caused typical syncytia formation, as shown here. Natural infection of wild rhesus monkeys by human H1N1 IAV-like virus from the natural habitat in Rajasthan is suggestive of human to simian ‘reverse transmission’ of pathogens. Sequence analyses of the hemagglutinin (HA) gene of ‘IAV like’ virus infecting wild rhesus monkeys revealed several point mutations and deletion of 9 ​amino acid residues at the Carboxy terminal end of the translated amino acid sequence compared to the human IAVs. These changes are likely related to adaptation of the human virus in the simian host.

Fig. 2

SFV sequence analyses: three wild Indian rhesus monkeys M1, M2 and M4 were infected with novel SFV based on the analysis of the highly conserved Integrase gene of the pol region of SFV genome. Alignment of translated amino acid sequences revealed the presence of the conserved His 2, Cys 2 motif. Equivalent sequences from different African and Asian SFVs including SFVmac (X83292) from the Genbank database confirmed that Indian SFV reported here constitute a separate and distinct cluster, related to published Asian SFVs but different from African SFVs.

Fig. 3

Partial sequence data from the hemagglutination gene (HA) of novel ‘IAV-like virus' infecting wild Indian rhesus monkey M3 is suggestive of human to simian reverse transmission at the man-monkey interface. Alignment of translated amino acid sequences reveal high homology in the equivalent sequences of different human IAV sequences available in the Genbank. (HA) protein. Sequence of IAV-like virus infecting Indian wild rhesus monkey is shown in red on the top line in the alignment figure. Genbank Accession numbers of different human IAV sequences are provided. We also included equivalent sequences from swine influenza virus from Ireland, indicated by a green arrow which showed lesser homology and belonged to a different cluster in the phylogenetic tree.