Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
The Origin of the Genus Flavivirus and the Ecology of Tick-Borne Pathogens
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Organismal Biology, Systematic Biology.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present thesis examines questions related to the temporal origin of the Flavivirus genus and the ecology of tick-borne pathogens. In the first study, we date the origin and divergence time of the Flavivirus genus. It has been argued that the first flaviviruses originated after the last glacial maximum. This has been contradicted by recent analyses estimating that the tick-borne flaviviruses emerged at least before 16,000 years ago. It has also been argued that the Powassan virus was introduced into North America at the time between the opening and splitting of the Beringian land bridge. Supported by tip date and biogeographical calibration, our results suggest that this genus originated circa 120,000 (156,100–322,700) years ago if the Tamana bat virus is included in the genus, or circa 85,000 (63,700–109,600) years ago excluding the Tamana bat virus. In the second study we estimate the prevalence of tick-borne encephalitis virus (TBEV) in host-seeking Ixodes ricinus from 29 localities in Sweden and compare our data with those of neighbouring countries. Nymphs and adult ticks were screened for TBEV using a real-time PCR assay. The mean TBEV prevalence for all tick stages combined was 0.26% for Sweden and 0.28% for all Scandinavian countries, excluding Iceland. The low prevalence of TBEV in nature may partly be explained by the fact that TBEV occurs in spatially small foci and that the inclusion of ticks from non-infected foci will reduce the prevalence estimate. In the third and fourth study, we conducted the first large-scale investigations to estimate the prevalence and geographical distribution of Anaplasma spp. and Rickettsia spp. in host-seeking larvae, nymphs and adults of I. ricinus ticks in Sweden. Ticks were collected from several localities in central and southern Sweden and were subsequently screened for the presence of Anaplasma spp. and Rickettsia spp. using a real-time PCR assay. For all active tick stages combined, the mean prevalence of Anaplasma spp. and Rickettsia spp. in I. ricinus in Sweden was estimated to 1.1% and 4.8%, respectively. It was also shown that A. phagocytophilum and R. helvetica are the main Anaplasma and Rickettsia species occurring in Sweden.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. , 60 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1100
Keyword [en]
Flavivirus, Virus dating, Molecular dating, Biogeography, Ixodes ricinus, Minimum infection rate, TBE, Tick-borne encephalitis virus, Rickettsia helvetica, Anaplasma phagocytophilum, Infection prevalence, RT-PCR
National Category
Biological Sciences
Research subject
Biology with specialization in Systematics
Identifiers
URN: urn:nbn:se:uu:diva-211090ISBN: 978-91-554-8814-7 (print)OAI: oai:DiVA.org:uu-211090DiVA: diva2:665331
Public defence
2014-01-10, Zootissalen, EBC, Villavägen 9, Uppsala, 13:00 (English)
Opponent
Supervisors
Available from: 2013-12-10 Created: 2013-11-19 Last updated: 2014-01-24
List of papers
1. Dating the origin of the genus Flavivirus in the light of Beringian biogeography
Open this publication in new window or tab >>Dating the origin of the genus Flavivirus in the light of Beringian biogeography
2014 (English)In: Journal of General Virology, ISSN 0022-1317, E-ISSN 1465-2099, Vol. 95, 1969-1982 p.Article in journal (Refereed) Published
Abstract [en]

The genus Flavivirus includes some of the most important human viral pathogens, and itsmembers are found in all parts of the populated world. The temporal origin of diversification of thegenus has long been debated due to the inherent problems with dating deep RNA virus evolution.A generally accepted hypothesis suggests that Flavivirus emerged within the last 10 000 years.However, it has been argued that the tick-borne Powassan flavivirus was introduced into NorthAmerica some time between the opening and closing of the Beringian land bridge that connectedAsia and North America 15 000–11 000 years ago, indicating an even older origin for Flavivirus.To determine the temporal origin of Flavivirus, we performed Bayesian relaxed molecular clockdating on a dataset with high coverage of the presently available Flavivirus diversity by combiningtip date calibrations and internal node calibration, based on the Powassan virus and Beringianland bridge biogeographical event. Our analysis suggested that Flavivirus originated ~85 000(64 000–110 000) or 120 000 (87 000–159 000) years ago, depending on the circumscriptionof the genus. This is significantly older than estimated previously. In light of our results, wepropose that it is likely that modern humans came in contact with several members of the genusFlavivirus much earlier than suggested previously, and that it is possible that the spread of severalflaviviruses coincided with, and was facilitated by, the migration and population expansion ofmodern humans out of Africa.

Keyword
Flavivirus, virus evolution, virus dating, Beringia, POWV, molecular clock, molecular dating
National Category
Biological Systematics Microbiology
Identifiers
urn:nbn:se:uu:diva-210860 (URN)10.1099/vir.0.065227-0 (DOI)000341800500012 ()24914065 (PubMedID)
Available from: 2013-11-19 Created: 2013-11-15 Last updated: 2017-12-06Bibliographically approved
2. Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in northern Europe with particular reference to southern Sweden
Open this publication in new window or tab >>Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in northern Europe with particular reference to southern Sweden
2014 (English)In: Parasites & Vectors, ISSN 1756-3305, E-ISSN 1756-3305, Vol. 7, 102- p.Article in journal (Other academic) Published
Keyword
Ixodes ricinus, minimum infection rate, RT-PCR, Sweden, Norway, Denmark, Finland, TBE, tick-borne encephalitis virus, virus prevalence.
National Category
Biological Sciences Microbiology in the medical area Microbiology
Identifiers
urn:nbn:se:uu:diva-210857 (URN)10.1186/1756-3305-7-102 (DOI)000335074400002 ()
Available from: 2013-11-19 Created: 2013-11-15 Last updated: 2017-12-06Bibliographically approved
3. Detection and prevalence of Anaplasma phagocytophilum and Rickettsia helvetica in Ixodes ricinus ticks in seven study areas in Sweden
Open this publication in new window or tab >>Detection and prevalence of Anaplasma phagocytophilum and Rickettsia helvetica in Ixodes ricinus ticks in seven study areas in Sweden
Show others...
2010 (English)In: Parasites & Vectors, ISSN 1756-3305, E-ISSN 1756-3305, Vol. 3, no 1, 66- p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Tick-borne Anaplasma phagocytophilum and Rickettsia spp. are considered to be emerging human pathogens, but only limited data are available on their occurrence in Sweden. Two real-time PCR assays followed by nested PCR and sequence analysis were carried out to investigate the prevalence of A. phagocytophilum and spotted fever rickettsiae in ticks from seven areas in Sweden.

RESULTS: In 139 pooled samples, representing a total of 1245 Ixodes ricinus ticks (204 larvae, 963 nymphs, 38 males, 40 females), the overall positive mean infection prevalence was 1.3-15.0% for A. phagocytophilum and 1.5-17.3% for R. helvetica. A. phagocytophilum was only detected in nymphs (1.7-19.4%), whereas R. helvetica was detected in all three tick stages. Support for vertical and transstadial transmission was only obtained for R. helvetica. Both agents showed similar infection rates across study areas, although infection rates were greater in coastal areas.

CONCLUSIONS: The results show that both pathogens occurred in all seven locations, indicating that they are prevalent in Sweden and should be considered etiological agents in patients recently bitten by ticks.

Place, publisher, year, edition, pages
BioMed Central, 2010
Keyword
Rickettsia, Anaplasma, Ehrlichia, Ixodes ricinus, Ticks, Sweden, anaplasmosis, rickettsiosis
National Category
Microbiology in the medical area Infectious Medicine Biological Systematics
Research subject
Clinical Bacteriology; Biology with specialization in Systematics
Identifiers
urn:nbn:se:uu:diva-133700 (URN)10.1186/1756-3305-3-66 (DOI)000282495500001 ()20684755 (PubMedID)
Projects
Medicinsk entomologi
Available from: 2010-11-16 Created: 2010-11-15 Last updated: 2017-12-12Bibliographically approved
4. Prevalence of Rickettsia spp., Anaplasma phagocytophilum and Coxiella burnetii in adult Ixodes ricinus ticks from 29 study areas in central and southern Sweden
Open this publication in new window or tab >>Prevalence of Rickettsia spp., Anaplasma phagocytophilum and Coxiella burnetii in adult Ixodes ricinus ticks from 29 study areas in central and southern Sweden
2012 (English)In: Ticks and Tick-borne Diseases, ISSN 1877-959X, E-ISSN 1877-9603, Vol. 3, no 2, 100-106 p.Article in journal (Refereed) Published
Abstract [en]

A total of 887 adult Ixodes ricinus ticks (469 females and 418 males) from 29 different localities in Sweden were screened for Rickettsia, Anaplasma, and Coxiella DNA using PCR and then subjected to gene sequencing. Rickettsial DNA was detected in 9.5–9.6% of the ticks. Most of the positive ticks were infected with Rickettsia helvetica. One tick harbored another spotted fever rickettsia, closely related to or identical with R. sibirica not previously found in I. ricinus nor in Sweden. Six of the ticks (0.7%) were infected with an Anaplasma sp., presumably A. phagocytophilum. Coxiella burnetii DNA was not detected in any of the ticks. The detection of R. helvetica and A. phagocytophilum in several of the localities sampled suggests that these potentially human-pathogenic agents are common in Sweden.

Keyword
Ixodes ricinus, Rickettsia, Anaplasma, Coxiella, PCR
National Category
Microbiology in the medical area
Research subject
Microbiology
Identifiers
urn:nbn:se:uu:diva-168814 (URN)10.1016/j.ttbdis.2011.11.003 (DOI)000304570200006 ()
Note

De två första författarna delar förstaförfattarskapet.

Available from: 2012-02-15 Created: 2012-02-15 Last updated: 2017-12-07Bibliographically approved

Open Access in DiVA

fulltext(2375 kB)980 downloads
File information
File name FULLTEXT01.pdfFile size 2375 kBChecksum SHA-512
04149c7d99e06bfa935ab17592b0806bcc44a85950b94305e15a27045d387ff27178ca3db860779819b0ee910b9ce1d906c0e520c748dbd788fb2075fdbd236c
Type fulltextMimetype application/pdf
Buy this publication >>

Search in DiVA

By author/editor
Pettersson, John H.-O.
By organisation
Systematic Biology
Biological Sciences

Search outside of DiVA

GoogleGoogle Scholar
Total: 980 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

isbn
urn-nbn

Altmetric score

isbn
urn-nbn
Total: 855 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf