Ecology and evolution of shrew-borne orthohantaviruses in Finland

Jiaxin Ling

Research output: ThesisDoctoral ThesisCollection of Articles

Abstract

More than 60% of human emerging infectious diseases (EIDs) are zoonotic. Zoonoses are infectious diseases of animals (usually vertebrates) that can be transmitted to humans. Hantaviruses are emerging zoonotic pathogens that belong to the genus Orthohantavirus and family Hantaviridae in order Bunyavirales. Hantaviruses pose a serious threat to human health because their infection causes two highly fatal diseases: haemorrhagic fever with renal syndrome (HFRS) and hantavirus cardiopulmonary syndrome (HCPS). Rodents have been regarded as the main reservoir and evolutionary scene of hantaviruses. In the last three decades, our knowledge of hantaviruses has broadened significantly. In contrast to the initial assumption that hantaviruses are mainly carried by rodents, many novel hantaviruses have been detected in shrews, moles and bats during the last few years. These findings raise a number of significant questions about the evolutionary history of hantaviruses, their host association and adaptation, the role and frequency of spillover infections and host-switch events, and most importantly, their pathogenicity. In Finland, Puumala virus (PUUV) has been regarded as the only rodent-borne hantavirus present in the country. To search for novel hantaviruses other than PUUV, various novel hantaviruses were molecularly identified in different species of Soricomorpha ("shrew-form"). Genetic analyses revealed that four soricomorph-borne hantaviruses circulate in Finland, including Boginia virus (BOGV) in Neomys fodiens and Asikkala virus (ASIV) in Sorex minutus. Common shrews (Sorex araneus) harboured two different hantaviruses: Seewis virus (SWSV) and an Altai-like virus, showing the first evidence of co-existence of two distinct hantavirus species circulating simultaneously in one host species population. This host sharing of two divergent hantaviruses in the European common shrews contradicts hantavirus-host specificity, further implying the complexity of hantavirus evolution. After screening hundreds of S. araneus from all of Finland, we obtained a large data set of new SWSV sequences that enabled phylogeographic analyses of SWSV. The results demonstrated that this shrew-borne hantavirus is similar to rodent-borne hantaviruses, and the post-glacial spread of SWSV into Finland mirrors that of the host, S. araneus: these shrews colonized Finland from the east after the last ice age (12,000–8,000 years ago) and then subsequently spread along emerging land bridges towards the west or north. Most new hantaviruses discovered in soricomorph and bat hosts instead of rodents have raised questions as to whether any of them will emerge as human pathogens. Therefore, to predict human exposure risk, novel laboratory techniques for molecular and serological hantavirus detection were developed. No evidence of SWSV infection was found among a panel of 486 patient serum samples; however, we demonstrated a cross-reaction of anti-PUUV serum with shrew-borne hantavirus nucleocapsid (N) protein. This thesis focused on the diversity, host maintenance and cross-species transmission dynamics of soricomorph-borne hantaviruses. The study presented innovative methods to investigate this pertinent topic at the interface of wildlife diseases and human health. The results provided new insights about the ecology, evolutionary origins and phylogeography, and most importantly, the potential pathogenicity of soricomorph-borne hantaviruses. This knowledge in combination with future studies will hopefully lead to a better understanding of host-parasite relationships.
Original languageEnglish
Supervisors/Advisors
  • Sironen, Tarja, Supervisor
  • Vaheri, Antti, Supervisor
Place of PublicationHelsinki
Publisher
Print ISBNs978-951-51-4080-7
Electronic ISBNs978-951-51-4081-4
Publication statusPublished - 2018
MoE publication typeG5 Doctoral dissertation (article)

Fields of Science

  • Antibodies, Viral
  • Biological Evolution
  • Chiroptera
  • Communicable Diseases, Emerging
  • Cross Reactions
  • Disease Transmission, Infectious
  • Hantavirus
  • +pathogenicity
  • Hantavirus Infections
  • +immunology
  • +transmission
  • Hemorrhagic Fever with Renal Syndrome
  • Host Specificity
  • Moles
  • Nucleocapsid Proteins
  • Puumala virus
  • RNA
  • Shrews
  • Virulence
  • Zoonoses
  • 3111 Biomedicine

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