March 24th, 2018
Parvoviruses (family Parvoviridae) are small, single-stranded DNA viruses. Several pathogenic parvoviruses of medical and veterinary importance have been identified.
We recently published the findings of a field study in which we describe our investigation into parvoviruses circulating among wild and domestic animals in Brazil. Genomic analysis of these novel viruses provided insights into general aspects of parvovirus ecology and evolution.
We performed metagenomic analysis of animal samples obtained at several distinct sites in Brazil (see map at bottom of page), encompassing Pernambuco, São Paulo, Paraná and Rio Grande do Sul states. Sampling was carried out by a team comprised of PhD students and posdocs from Brazilian universities.
Brazil has a great diversity and abundance of wildlife, and is consequently considered a hotspot for the potential emergence of novel zoonotic viruses. Moreover, many rural communities in Brazil live in close proximity to wildlife species, as can be appreciated in the photo below, taken near a sampling site in Isla de Marajó in the North of Brazil.
In our study, we sampled both wild and domestic animals. Among wild animals, we focussed in particular on species that might be considered likely vectors of human and/or domestic animal viruses.
We identified eight parvovirus species in total (six of which have not been described previously). The novel parvovirus species were identified in songbirds, marsupials and rodents. None of the infections were associated with obvious disease symptoms in sampled animals.
We detected strains of ungulate tetraparvovirus 1 —a virus in the genus Tetraparvovirus—in cattle from the South of Brazil, demonstrating that this virus is present in cattle populations in South America. It’s presence in farmed cattle in South America, as well as domestic yak in Asia indicates it circulates widely among bovids and is likely to be present in cattle populations throughout the world.
We also recovered the genome of a novel tetraparvovirus from a white-eared opossum. Assuming the genome sequence we recovered from this sample is indeed derived from a parvovirus that infects opossum, it represents the first example of a marsupial tetraparvovirus.
The "Dependoparvovirus" genus of parvoviruses have attracted interest as potential gene therapy vectors We provide the first report of a dependoparvovirus in a New World bat—the vampire bat (Desmodus rotundus). The grouping of this novel virus in phylogenetic trees was consistent with an ancestral origin in bats for the Dependoparvovirus genus, as has been proposed previously. However, as sampling remains quite limited, we should perhaps withhold judgement on this for now. Further sampling of Dependoparvovirus diversity (including paleoviruses as well as contemporary viruses) should allow the evolutionary history of the genus to be reconstructed in greater detail, and with greater confidence.
Besides simply documenting novel parvoviruses, our study offered some revealing insights into the natural biology of parvoviruses in vertebrate species.
We used phylogenetic approaches to reconstruct the evolutionary relationships between the novel parvoviruses described in our study, and those that have been described previously.
We found that viruses from particular host species often grouped together in phylogenies. For example, we recovered identified viruses closely related to the "minute virus of mice" (MVM) in several species of sigmodontine rodent - otherwise known as “New World mice”.
Similarly, we identified a novel aveparvovirus in songbirds, suggesting viruses belonging to the Aveparvovirus genus may circulate widely among wild birds, as well as in poultry. We also identified rodent bocaparvoviruses (genus Bocaparvovirus) that were closely related to bocaparvoviruses recently reported in brown rats in China.
Together, our findings suggest that groups of closely related parvoviruses circulate widely among species in the same order or class, with the barriers to cross-species transmission within these groups being much lower than between them. These kinds of dynamics have previously been described for parvoviruses infecting carnivores.
The awesome power of modern DNA sequencing has finally made it possible to explore the vast diversity of viruses that circulates in wild animals. We are truly living through an age of discovery with respect to viruses. Our study is just one of numerous recent investigations into parvovirus diversity, and these investigations enhance one another - adding to a growing knowledge base that is more than the sum of its parts.
But what is the point of exploring viral diversity? There are many answers to this question, but one of the more important reasons for carrying out descriptive studies of virus distribution and diversity is so that we can make a more informed assessment of risk with respect to the threat posed by the emergence of novel viruses.
It is becoming clear that parvoviruses are very widespread, but it also seems many animals are asymptomatically infected. Through sampling the distribution and diversity of these viruses we can start to gain an understanding of their evolutionary history and ecological dynamics. Understanding these dynamics is key to identifying the factors that determine why some parvovirus infections cause disease, whereas others apparently do not.
Investigations of parvovirus distribution & diversity will also allow an assessment of how recent ecological transitions (e.g. development of industrialised farming methods) have impacted the contemporary distribution of parvoviruses, and the emergence of parvovirus diseases.
de Souza WM, Tristan TPW, Fumagalli MJ, Araujo J, Sabino-Santos Jr. G, Maia FGM, Acrani GO, Carrasco AOT, Romeiro MF, Modha S, Vieira LC, Ometto TL, Queiroz LH, Durigon EL, Nunes MRT, Figueiredo LTM, and RJ Gifford
Viruses , 10(4), 143; doi:10.3390/v10040143
Whole-genome sequencing of parvoviruses from wild and domestic animals in Brazil provides new insights into parvovirus distribution and diversity. view