Human Tula virus infection or rat-bite fever?

Phylogeographic analysis of Tula hantavirus highlights a single introduction to central Europe

Orthohantaviruses are zoonotic pathogens of humans, unique among the bunyaviruses in not being transmitted by an arthropod vector. Tula orthohantavirus (TULV) is an old-world hantavirus, of yet unclear human pathogenicity, with few reported cases of clinically relevant human infection. So far, phylogeographic studies exploring the global pathways of hantaviral migration are scarce and generally do not focus on a specific hantavirus species. The aim of the present study was to reconstruct the dispersal history of TULV lineages across Eurasia based on S segment sequences sampled from different geographic areas. Maximum-likelihood and Bayesian inference methods were used to perform the phylogenetic analysis and phylogeographic reconstructions. Sampling time and trapping localities were obtained for a total of 735 TULV S segment sequences available in public databases at the time of the study. The estimated substitution rate of the analyzed partial S segment alignment was 2.26 × 10-3 substitutions/site/year (95 per cent highest posterior density interval: 1.79 × 10-3 to 2.75 × 10-3). Continuous phylogeography of TULV S segment sequences placed the potential root and origin of TULV spread in the Black Sea region. In our study, we detect a single-lineage introduction of TULV to Europe, followed by local viral circulation further on.

Development of a Comparative European Orthohantavirus Microneutralization Assay With Multi- Species Validation and Evaluation in a Human Diagnostic Cohort

Orthohantaviruses (family Hantaviridae, order Bunyavirales) can cause two serious syndromes in humans: hemorrhagic fever with renal syndrome (HFRS), associated with the Old World orthohantaviruses, and hantavirus cardiopulmonary syndrome (HCPS), associated with orthohantaviruses in the Americas. In Europe, four different orthohantaviruses (DOBV, PUUV, SEOV, and TULV) are associated with human disease. As disease severity and zoonotic source differ between orthohantavirus species, conclusive determination of the infecting species by either RT-PCR or comparative virus neutralization test (VNT) is of importance. Currently, the focus reduction neutralization test (FRNT) is considered the ‘Gold Standard’ for orthohantavirus VNTs, however this test is laborious and time-consuming. Consequently, more high-throughput alternatives are needed. In this study, we developed a comparative orthohantavirus microneutralization test (MNT) including all four human pathogenic orthohantavirus species circulating in Europe. The assay was validated using RT-PCR-confirmed rodent (n=17) and human sera (n=17), DOBV-suspected human sera (n=3) and cohorts of orthohantavirus-negative rodent (n=3) and human sera (n=85). 16/17 RT-PCR-confirmed rodent sera and 18/20 of the RT-PCR-confirmed and DOBV-suspected human sera were serotyped successfully, while for the remaining rodent (n=1) and human sera (n=2) no neutralizing titers could be detected. All negative control sera tested negative in the MNT. The assay was subsequently evaluated using a clinical cohort of 50 orthohantavirus patients. Orthohantavirus infection was confirmed in all 50 patients, and 47/50 (94%) sera were serotyped successfully, confirming PUUV as the major cause of orthohantavirus infections in Netherlands. Notably, two previously unrecognized SEOV cases from 2013 were diagnosed using the MNT, underlining the added value of the MNT in a diagnostic setting. In conclusion, we demonstrate the successful development and clinical implementation of a comparative European orthohantavirus MNT to determine the infecting virus species in European HFRS patients. Identification of the causative species is needed for an adequate Public Health response and can support individual patient care. For many labs, the implementation of orthohantavirus neutralization tests has not been a straightforward procedure. This issue will be addressed by the rollout of the comparative MNT to multiple European laboratories to support patient diagnostics, surveillance and Public Health responses.

Identification and characterization of a novel subtype of Tula virus in Microtus arvalis obscurus voles sampled from Xinjiang, China

Although most of Arvicolinae associated hantaviruses can not cause disease in humans, hemorrhagic fever with renal syndrome (HFRS) cases caused by Tula virus (TULV) have been described in Europe since 2002. In addition to Europe, TULV was also identified in the Microtus arvalis obscurus voles sampled from Kazakhstan, which shares borders with China. To gain more insight into the molecular epidemiology of TULV, a total of 365 rodents representing 7 species of 4 subfamily (Arvicolinae, Murinae, Gerbillinae, and Cricetinae) were captured in Qapqal county, Xinjiang, northwest China. Hantavirus RNA was recovered from 40 lung tissue samples of M. arvalis obscurus, with the prevalence of 10.96%. Genetic analysis revealed that all recovered viral sequences were most closely related to those of TULV, but exhibited >11% nucleotide differences from all currently known TULV, suggesting that they may represent a new subtype of TULV. In the S tree, the newly identified viruses formed a distinct lineage and showed a close evolutionary relationship with those sampled from Southwestern Siberia and Kazakhstan. However, they exhibited a different clustering pattern in both the M and the L trees, suggesting the possibility of genetic reassortment. Finally, the recombination event was also observed in Xinjiang TULV viruses. In sum, all these data reveal a complex evolutionary history of TULV in Central Asia.

High Prevalence of Tula Hantavirus in Common Voles in The Netherlands

Tula virus (TULV) is a zoonotic hantavirus. Knowledge about TULV in the Netherlands is very scarce. Therefore in 2014, 49 common voles (Microtus arvalis) from a region in the south of the Netherlands, and in 2015, 241 common voles from regions in the north of the Netherlands were tested with the TULV quantitative RT-PCR. In the southern region, prevalence of TULV was 41% (20/49). In the northern regions, prevalence ranged from 12% (4/34) to 45% (17/38). Phylogenetic analysis of the obtained sequences showed that the regions fall within different clusters. Voles from the south were also tested on-site for the presence of hantavirus antibodies, but serology results were poorly associated with qRT-PCR results. These findings suggest that TULV may be more widespread than previously thought. No human TULV cases have been reported thus far in the Netherlands, but differentiation between infection by TULV or the closely related Puumala virus is not made in humans in the Netherlands, thus cases may be misdiagnosed.

Tula hantavirus infection in a hospitalised patient, France, June 2015

We report an infection with Tula virus in June 2015, leading to hospitalisation, in a patient living approximately 60 km east of Paris with no previous remarkable medical history. Clinical symptoms were limited to a fever syndrome with severe headache. The main laboratory findings included thrombocytopenia and elevated transaminase levels. Based on S (small) gene sequence analysis, the strain affecting the patient was closely related to strains detected in Central Europe, especially to a south-east German strain.

Tula hantavirus infection in immunocompromised host, Czech Republic

We report molecular evidence of Tula hantavirus as an etiologic agent of pulmonary-renal syndrome in an immunocompromised patient. Acute hantavirus infection was confirmed by using serologic and molecular methods. Sequencing revealed Tula virus genome RNA in the patient’s blood. This case shows that Tula virus can cause serious disease in humans.

Evidence of recombination in Tula virus strains from Serbia

Tula hantavirus (TULV) belongs to Bunyaviridae family, with negative sense RNA genome. Segmented nature of hantaviral genome allows for genetic reassortment, but the evidence of homologous recombination also exists. In this study we analyzed TULV sequences isolated in Serbia on different occasions and from different rodent hosts: 1987 strain from Microtus subterraneus and 2007 strain from Microtus arvalis. Phylogenetic analysis of both L and S segment sequences is suggestive of geographically related clustering, as previously shown for majority of hantaviruses. Reconstruction of phylogenetic tree for TULV S segment showed that both sequences from Serbia clustered together with sequences from East Slovakia, which had previously been shown to be recombinants (Kosice strain). Exploratory recombination analysis, supported by phylogenetic and amino acid pattern analysis, revealed the presence of recombination in the S segment sequences from Serbia, resulting in mosaic-like structure of TULV S segment similar to the one of Kosice strain. Although recombination is considered a rare event in molecular evolution of negative strand RNA viruses, obtained molecular data in this study support evidence of recombination in TULV, in geographically distant regions of Europe.

Tula virus infections in the Eurasian water vole in Central Europe

Recent reports of novel hantaviruses in shrews and moles and the detection of rodent-borne hantaviruses in different rodent species raise important questions about their host range and specificity, evolution, and host adaptation. Tula virus (TULV), a European hantavirus, is believed to be slightly or non-pathogenic in humans and was initially detected in the common vole Microtus arvalis, the East European vole M. levis (formerly rossiaemeridionalis), and subsequently in other Microtus species. Here we report the first multiple RT-PCR detection and sequence analyses of TULV in the Eurasian water vole Arvicola amphibius from different regions in Germany and Switzerland. Additional novel TULV S-, M-, and L-segment sequences were obtained from M. arvalis and M. agrestis trapped in Germany at sites close to trapping sites of TULV-RT-PCR-positive water voles. Serological investigations using a recombinant TULV nucleocapsid protein revealed the presence of TULV-reactive antibodies in RT-PCR-positive and a few RT-PCR-negative water voles. Phylogenetic analyses revealed a geographical clustering of the novel S-, M-, and L-segment sequences from A. amphibius with those of M. arvalis- and M. agrestis-derived TULV lineages, and may suggest multiple TULV spillover or a potential host switch to A. amphibius. Future longitudinal studies of sympatric Microtus and Arvicola populations and experimental infection studies have to prove the potential of A. amphibius as an additional TULV reservoir host.

Rat-bite fever septic arthritis: illustrative case and literature review

Rat-bite fever is a rare zoonotic infection caused by Streptobacillus moniliformis or Spirillum minus, which is characterised by fever, rash and arthritis. The arthritis has previously been described as non-suppurative and isolation of the organism from synovial fluid as very uncommon. This article reports a case of septic arthritis diagnosed as rat-bite fever when the organism was cultured from synovial fluid and reviews another 15 cases of S. moniliformis septic arthritis reported in the worldwide literature since 1985. Articles were included in this review if S. moniliformis was cultured from synovial fluid. Of the published cases, 88% presented with polyarthritis, affecting small and large joints although two had monoarticular hip sepsis. Fever was present in 88%, rash in 25% and 56% had extra-articular features. Synovial fluid analysis revealed high cell counts in all cases (mean 51,000 x 10(9)/l) with a predominance of polymorphonuclear leucocytes, and organisms were found on Gram stain in only 50%. Penicillin was used for treatment in 56% of cases and surgery was required in 30%. All patients recovered. Rat-bite fever arthritis can be suppurative and attempts should be made to isolate the organism from synovial fluid. The diagnosis should be considered when there is arthritis and a high synovial fluid cell count but no apparent organism, especially when the patient has had contact with rats.

Occurrence of renal and pulmonary syndrome in a region of northeast Germany where Tula hantavirus circulates

Hantavirus species Tula (TULV) is carried by European common voles (Microtus spp.). Its pathogenic potential for humans is unknown. In a rural region of northeast Germany, a 43-year-old man became ill with fever, renal syndrome, and pneumonia. Typing of late acute- and convalescent-phase sera by focus reduction neutralization assay revealed the presence of neutralizing antibodies against TULV. Moreover, we detected TULV genetic material in Microtus arvalis animals that were trapped at places only a few kilometers from the home village of the patient. Phylogenetic analysis of completely sequenced genomic S segments from three virus strains grouped them within a third genetic lineage of the TULV species. This is the first case of hemorrhagic fever with renal syndrome and pulmonary involvement which can be associated with TULV infection.