Puumala hantavirus genetic variability in an endemic region (Northern Sweden)

Dried Blood Spots technology for veterinary applications and biological investigations: technical aspects, retrospective analysis, ongoing status and future perspectives

Dried Blood Spots (DBS) technology has become a valuable tool in medical studies, however, in veterinary and biological research DBS technology applications are still limited. Up-to-date no review has comprehensively integrated all the evidence existing across the fields, technologies and animal species. In this paper we summarize the current applications of DBS technology in the mentioned areas, and provide a scope of different types of dried sample carriers (cellulose and non-cellulose), sampling devices, applicable methods for analyte extraction and detection. Mammals, birds, insects and other species are represented as the study objects. Besides the blood, the review considers a variety of specimens, such as milk, saliva, tissue samples and others. The main applications of dried samples highlighted in the review include epidemiological surveys and monitoring for infections agents or specific antibodies for disease/vaccination control in households and wildlife. Besides the genetic investigations, the paper describes detection of environmental contaminants, pregnancy diagnosis and many other useful applications of animal dried samples. The paper also analyses dried sample stability and storage conditions for antibodies, viruses and other substances. Finally, recent developments and future research for DBS technology in veterinary medicine and biological sciences are discussed.

Orthohantaviruses, Emerging Zoonotic Pathogens

Orthohantaviruses give rise to the emerging infections such as of hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS) in Eurasia and the Americas, respectively. In this review we will provide a comprehensive analysis of orthohantaviruses distribution and circulation in Eurasia and address the genetic diversity and evolution of Puumala orthohantavirus (PUUV), which causes HFRS in this region. Current data indicate that the geographical location and migration of the natural hosts can lead to the orthohantaviruses genetic diversity as the rodents adapt to the new environmental conditions. The data shows that a high level of diversity characterizes the genome of orthohantaviruses, and the PUUV genome is the most divergent. The reasons for the high genome diversity are mainly caused by point mutations and reassortment, which occur in the genome segments. However, it still remains unclear whether this diversity is linked to the disease's severity. We anticipate that the information provided in this review will be useful for optimizing and developing preventive strategies of HFRS, an emerging zoonosis with potentially very high mortality rates.

Detection and Genetic Characterization of Puumala Orthohantavirus S-Segment in Areas of France Non-Endemic for Nephropathia Epidemica

Puumala virus (PUUV) in Europe causes nephropathia epidemica (NE), a mild form of hemorrhagic fever with renal syndrome (HFRS). The incidence of NE is highly heterogeneous spatially, whereas the geographic distribution of the wild reservoir of PUUV, the bank vole, is essentially homogeneous. Our understanding of the processes driving this heterogeneity remains incomplete due to gaps in knowledge. Little is known about the current distribution and genetic variation of PUUV in the areas outside the well-identified zones of NE endemicity. We trapped bank voles in four forests in French regions in which NE is considered non-endemic, but sporadic NE cases have been reported recently. We tested bank voles for anti-PUUV IgG and characterized the S segment sequences of PUUV from seropositive animals. Phylogenetic analyses revealed specific amino-acid signatures and genetic differences between PUUV circulating in non-endemic and nearby NE-endemic areas. We also showed, in temporal surveys, that the amino-acid sequences of PUUV had undergone fewer recent changes in areas non-endemic for NE than in endemic areas. The evolutionary history of the current French PUUV clusters was investigated by phylogeographic approaches, and the results were considered in the context of the history of French forests. Our findings highlight the need to monitor the circulation and genetics of PUUV in a larger array of bank vole populations, to improve our understanding of the risk of NE.

Identifying the patterns and drivers of Puumala hantavirus enzootic dynamics using reservoir sampling

Hantaviruses are zoonotic hemorrhagic fever viruses for which prevention of human spillover remains the first priority in disease management. Tailored intervention measures require an understanding of the drivers of enzootic dynamics, commonly inferred from distorted human incidence data. Here, we use longitudinal sampling of approximately three decades of Puumala orthohantavirus (PUUV) evolution in isolated reservoir populations to estimate PUUV evolutionary rates, and apply these to study the impact of environmental factors on viral spread. We find that PUUV accumulates genetic changes at a rate of ∼10⁻⁴ substitutions per site per year and that land cover type defines the dispersal dynamics of PUUV, with forests facilitating and croplands impeding virus spread. By providing reliable short-term PUUV evolutionary rate estimates, this work facilitates the evaluation of spatial risk heterogeneity starting from timed phylogeographic reconstructions based on virus sampling in its animal reservoir, thereby side-stepping the need for difficult-to-collect human disease incidence data.

Molecular Diagnosis of Hemorrhagic Fever with Renal Syndrome Caused by Puumala Virus

Rodent-borne hantaviruses cause two severe acute diseases: hemorrhagic fever with renal syndrome (HFRS) in Eurasia, and hantavirus pulmonary syndrome (HPS; also called hantavirus cardiopulmonary syndrome [HCPS]) in the Americas. Puumala virus (PUUV) is the most common causative agent of HFRS in Europe. Current routine diagnostic methods are based on serological analyses and can yield inconclusive results. Hantavirus-infected patients are viremic during the early phase of disease; therefore, detection of viral RNA genomes can be a valuable complement to existing serological methods. However, the high genomic sequence diversity of PUUV has hampered the development of molecular diagnostics, and currently no real-time reverse transcription-quantitative (RT)-PCR assay is available for routine diagnosis of HFRS. Here, we present a novel PUUV RT-PCR assay. The assay was validated for routine diagnosis of HFRS on samples collected in Sweden during the winter season from 2013 to 2014. The assay allowed detection of PUUV RNA in 98.7% of confirmed clinical HFRS samples collected within 8 days after symptomatic onset. In summary, this study shows that real-time RT-PCR can be a reliable alternative to serological tests during the early phase of HFRS.

Complete Genome and Phylogeny of Puumala Hantavirus Isolates Circulating in France

Puumala virus (PUUV) is the agent of nephropathia epidemica (NE), a mild form of hemorrhagic fever with renal syndrome (HFRS) in Europe. NE incidence presents a high spatial variation throughout France, while the geographical distribution of the wild reservoir of PUUV, the bank vole, is rather continuous. A missing piece of the puzzle is the current distribution and the genetic variation of PUUV in France, which has been overlooked until now and remains poorly understood. During a population survey, from 2008 to 2011, bank voles were trapped in eight different forests of France located in areas known to be endemic for NE or in area from where no NE case has been reported until now. Bank voles were tested for immunoglobulin (Ig)G ELISA serology and two seropositive animals for each of three different areas (Ardennes, Jura and Orleans) were then subjected to laboratory analyses in order to sequence the whole S, M and L segments of PUUV. Phylogenetic analyses revealed that French PUUV isolates globally belong to the central European (CE) lineage although isolates from Ardennes are clearly distinct from those in Jura and Orleans, suggesting a different evolutionary history and origin of PUUV introduction in France. Sequence analyses revealed specific amino acid signatures along the N protein, including in PUUV from the Orleans region from where NE in humans has never been reported. The relevance of these mutations in term of pathophysiology is discussed.

Spatiotemporal dynamics of Puumala hantavirus associated with its rodent host, Myodes glareolus

Many viruses significantly impact human and animal health. Understanding the population dynamics of these viruses and their hosts can provide important insights for epidemiology and virus evolution. Puumala virus (PUUV) is a European hantavirus that may cause regional outbreaks of hemorrhagic fever with renal syndrome in humans. Here, we analyzed the spatiotemporal dynamics of PUUV circulating in local populations of its rodent reservoir host, the bank vole (Myodes glareolus) during eight years. Phylogenetic and population genetic analyses of all three genome segments of PUUV showed strong geographical structuring at a very local scale. There was a high temporal turnover of virus strains in the local bank vole populations, but several virus strains persisted through multiple years. Phylodynamic analyses showed no significant changes in the local effective population sizes of PUUV, although vole numbers and virus prevalence fluctuated widely. Microsatellite data demonstrated also a temporally persisting subdivision between local vole populations, but these groups did not correspond to the subdivision in the virus strains. We conclude that restricted transmission between vole populations and genetic drift play important roles in shaping the genetic structure and temporal dynamics of PUUV in its natural host which has several implications for zoonotic risks of the human population.

Hantavirus reservoirs: current status with an emphasis on data from Brazil

Since the recognition of hantavirus as the agent responsible for haemorrhagic fever in Eurasia in the 1970s and, 20 years later, the descovery of hantavirus pulmonary syndrome in the Americas, the genus Hantavirus has been continually described throughout the World in a variety of wild animals. The diversity of wild animals infected with hantaviruses has only recently come into focus as a result of expanded wildlife studies. The known reservoirs are more than 80, belonging to 51 species of rodents, 7 bats (order Chiroptera) and 20 shrews and moles (order Soricomorpha). More than 80genetically related viruses have been classified within Hantavirus genus; 25 recognized as human pathogens responsible for a large spectrum of diseases in the Old and New World. In Brazil, where the diversity of mammals and especially rodents is considered one of the largest in the world, 9 hantavirus genotypes have been identified in 12 rodent species belonging to the genus Akodon, Calomys, Holochilus, Oligoryzomys, Oxymycterus, Necromys and Rattus. Considering the increasing number of animals that have been implicated as reservoirs of different hantaviruses, the understanding of this diversity is important for evaluating the risk of distinct hantavirus species as human pathogens.

Co-circulation of two Puumala hantavirus lineages in Latvia: a Russian lineage described previously and a novel Latvian lineage

Puumala hantavirus (PUUV) causes a mild form of haemorrhagic fever with renal syndrome in Europe. Seven genetic lineages of PUUV have thus far been recorded, which exhibit geographic structure within the distribution of its natural host, the bank vole (Myodes glareolus). This study presents evidence for two distinct PUUV lineages co-circulating in Latvia: one previously described from Russia and a novel one that appears to be endemic. The Latvian lineage (LAT) is considerably divergent and several amino acid markers make it easily distinguishable. Phylogenetic analysis suggested a possibility of different evolutionary histories for the PUUV genome segments of LAT.

Genetic diversity and geographic distribution of hantaviruses in Russia

Haemorrhagic fever with renal syndrome (HFRS) is the most prevalent zoonotic disease in Russia. It is caused by several hantavirus species hosted by small rodents. We describe spatial and temporal patterns of HFRS incidence in the Russian Federation, and the geographic distribution of prevalent hantavirus species: Puumala (PUUV) and Dobrava (DOBV). Partial sequencing of nucleocapsid and glycoprotein genes of 117 PUUV strains and 78 DOBV strains revealed several distinct genetic subgroups. The RNA of Volga PUUV subgroup was detected in patients with HFRS and bank voles Myodes glareolus in the Volga Federal District, where the highest HFRS incidence rate has been registered yearly. The RNA of Siberian PUUV subgroup was found in M. glareolus in the trans-Ural Tyumen and Omsk Provinces, where human HFRS cases have been rare. During an HFRS outbreak in 2007 in the Central Federal District, when more than 1000 patients were affected, specific subgroups of DOBV were discovered in patients and rodents, mainly in the striped field mouse Apodemus agrarius. DOBV strains might have 8–9% of nucleotide difference although they were collected at places separated by 30–100 km. The RNA of a unique DOBV subgroup was discovered in the southern semi-desert Astrakhan Province, mainly in A. agrarius and tamarisk jird Meriones tamariscinus. No human HFRS cases were diagnosed in this province. Russian PUUV and DOBV strains have no close homologues among European strains. Our DOBV strains might be genetically grouped together with Central European DOBV strains isolated from A. agrarius, but not from Apodemus flavicollis. The Volga PUUV subgroup is to some extent similar to Baltic PUUV strain, and Finnish PUUV strains resemble the strains from the Siberian PUUV subgroup. Thus, PCRbased monitoring and typing provided the opportunity to delineate and expand the area of hantaviruses in Russia and to identify their new genetic variants.

Hantaviruses and their hosts in Europe: reservoirs here and there, but not everywhere?

Five hantaviruses are known to circulate among rodents in Europe, and at least two among insectivores. Four (Dobrava, Saaremaa, Seoul, and Puumala [PUUV] viruses) are clearly associated with hemorrhagic fever with renal syndrome (HFRS). PUUV, the most common etiological agent of HFRS in Europe, is carried by the bank vole (Myodes glareolus), one of the most widespread and abundant mammal species in Europe. This host-virus system is among hantaviruses also the most studied one in Europe. However, HFRS incidence varies throughout the continent. The spatial as well as temporal variation in the occurrence of HFRS is linked to geographic differences in the population dynamics of the reservoir rodents in different biomes of Europe. While rodent abundance may follow mast seeding events in many parts of temperate Europe, in northern (N) Europe multiannual cycles in population density exist as the result of the interaction between rodent populations and specialist predator populations in a delayed density-dependent manner. The spatial distribution of hantaviruses further depends on parameters such as forest patch size and connectivity of the most suitable rodent habitats, and the conditions for the survival of the virus outside the host, as well as historical distribution patterns (phylogeographies) of hosts and viruses. In multiannually fluctuating populations of rodents, with population increases of great amplitude, one should expect a simultaneous build-up of recently hantavirus-infected (shedding) rodents. The increasing number of infectious, virus-shedding rodents leads to a rapid transmission of hantavirus across the rodent population, and to humans. Our review discusses these aspects for PUUV, the only European hantavirus for which there is a reasonable, yet still far from complete, ecological continental-wide understanding. We discuss how this information could translate to other European hantavirus-host systems, and where the most important questions lie for further research.

Associations between MHC genes and Puumala virus infection in Myodes glareolus are detected in wild populations, but not from experimental infection data

We analysed the influence of MHC class II Dqa and Drb genes on Puumala virus (PUUV) infection in bank voles (Myodes glareolus). We considered voles sampled in five European localities or derived from a previous experiment that showed variable infection success of PUUV. The genetic variation observed in the Dqa and Drb genes was assessed by using single-strand conformation polymorphism and pyrosequencing methods, respectively. Patterns were compared with those obtained from 13 microsatellites. We revealed significant genetic differentiation between PUUV-seronegative and -seropositive bank voles sampled in wild populations, at the Drb gene only. The absence of genetic differentiation observed at neutral microsatellites confirmed the important role of selective pressures in shaping these Drb patterns. Also, we found no significant associations between infection success and MHC alleles among laboratory-colonized bank voles, which is explained by a loss of genetic variability that occurred during the captivity of these voles.

Puumala hantavirus and Myodes glareolus in northern Europe: no evidence of co-divergence between genetic lineages of virus and host

The genus Hantavirus (family Bunyaviridae) includes negative-strand RNA viruses that are carried by persistently infected rodent and insectivore species. Puumala virus (PUUV), carried by bank voles (Myodes glareolus), is a pathogenic hantavirus that causes outbreaks of mild haemorrhagic fever with renal syndrome across Europe. In northern Europe, PUUV is represented by several genetic lineages that are maintained by distinct phylogroups of bank voles. The present study describes sequences of new PUUV strains recovered from northern and southern regions of Scandinavia and compares phylogenetic relationships between north-European PUUV strains and M. glareolus. This analysis revealed contradictions in phylogenetic clustering and remarkable differences in estimated divergence times between the lineages of PUUV and its host, suggesting that the established PUUV lineages did not co-diverge with the distinct phylogroups of M. glareolus that carry them at present.

Analysis of Puumala hantavirus in a bank vole population in northern Finland: evidence for co-circulation of two genetic lineages and frequent reassortment between strains

In this study, for the first time, two distinct genetic lineages of Puumala virus (PUUV) were found within a small sampling area and within a single host genetic lineage (Ural mtDNA) at Pallasjärvi, northern Finland. Lung tissue samples of 171 bank voles (Myodes glareolus) trapped in September 1998 were screened for the presence of PUUV nucleocapsid antigen and 25 were found to be positive. Partial sequences of the PUUV small (S), medium (M) and large (L) genome segments were recovered from these samples using RT-PCR. Phylogenetic analysis revealed two genetic groups of PUUV sequences that belonged to the Finnish and north Scandinavian lineages. This presented a unique opportunity to study inter-lineage reassortment in PUUV; indeed, 32 % of the studied bank voles appeared to carry reassortant virus genomes. Thus, the frequency of inter-lineage reassortment in PUUV was comparable to that of intra-lineage reassortment observed previously (Razzauti, M., Plyusnina, A., Henttonen, H. & Plyusnin, A. (2008). J Gen Virol 89, 1649-1660). Of six possible reassortant S/M/L combinations, only two were found at Pallasjärvi and, notably, in all reassortants, both S and L segments originated from the same genetic lineage, suggesting a non-random pattern for the reassortment. These findings are discussed in connection to PUUV evolution in Fennoscandia.