Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in northern Europe with particular reference to Southern Sweden
Abstract Background In northern Europe, the tick-borne encephalitis virus (TBEV) of the European subtype is usually transmitted to humans by the common tick Ixodes ricinus. The aims of the present study are (i) to obtain up-to-date information on the TBEV prevalence in host-seeking I. ricinus in sou...
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| Format: | Article |
| Language: | English |
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BMC
2014-03-01
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| Series: | Parasites & Vectors |
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| Online Access: | https://doi.org/10.1186/1756-3305-7-102 |
| _version_ | 1797811703714414592 |
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| author | John H-O Pettersson Irina Golovljova Sirkka Vene Thomas GT Jaenson |
| author_facet | John H-O Pettersson Irina Golovljova Sirkka Vene Thomas GT Jaenson |
| author_sort | John H-O Pettersson |
| collection | DOAJ |
| description | Abstract Background In northern Europe, the tick-borne encephalitis virus (TBEV) of the European subtype is usually transmitted to humans by the common tick Ixodes ricinus. The aims of the present study are (i) to obtain up-to-date information on the TBEV prevalence in host-seeking I. ricinus in southern and central Sweden; (ii) to compile and review all relevant published records on the prevalence of TBEV in ticks in northern Europe; and (iii) to analyse and try to explain how the TBE virus can be maintained in natural foci despite an apparently low TBEV infection prevalence in the vector population. Methods To estimate the mean minimum infection rate (MIR) of TBEV in I. ricinus in northern Europe (i.e. Denmark, Norway, Sweden and Finland) we reviewed all published TBEV prevalence data for host-seeking I. ricinus collected during 1958–2011. Moreover, we collected 2,074 nymphs and 906 adults of I. ricinus from 29 localities in Sweden during 2008. These ticks were screened for TBEV by RT-PCR. Results The MIR for TBEV in nymphal and adult I. ricinus was 0.28% for northern Europe and 0.23% for southern Sweden. The infection prevalence of TBEV was significantly lower in nymphs (0.10%) than in adult ticks (0.55%). At a well-known TBEV-endemic locality, Torö island south-east of Stockholm, the TBEV prevalence (MIR) was 0.51% in nymphs and 4.48% in adults of I. ricinus. Conclusions If the ratio of nymphs to adult ticks in the TBEV-analysed sample differs from that in the I. ricinus population in the field, the MIR obtained will not necessarily reflect the TBEV prevalence in the field. The relatively low TBEV prevalence in the potential vector population recorded in most studies may partly be due to: (i) inclusion of uninfected ticks from the ‘uninfected areas’ surrounding the TBEV endemic foci; (ii) inclusion of an unrepresentative, too large proportion of immature ticks, compared to adult ticks, in the analysed tick pools; and (iii) shortcomings in the laboratory techniques used to detect the virus that may be present in a very low concentration or undetectable state in ticks which have not recently fed. |
| first_indexed | 2024-03-13T07:26:38Z |
| format | Article |
| id | doaj.art-ac33b09224fc47d7a5433581d81ede2e |
| institution | Directory Open Access Journal |
| issn | 1756-3305 |
| language | English |
| last_indexed | 2024-03-13T07:26:38Z |
| publishDate | 2014-03-01 |
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| series | Parasites & Vectors |
| spelling | doaj.art-ac33b09224fc47d7a5433581d81ede2e2023-06-04T11:20:14ZengBMCParasites & Vectors1756-33052014-03-017111110.1186/1756-3305-7-102Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in northern Europe with particular reference to Southern SwedenJohn H-O Pettersson0Irina Golovljova1Sirkka Vene2Thomas GT Jaenson3Medical Entomology Unit, Subdepartment of Systematic Biology, Department of Organismal Biology, Evolutionary Biology Centre, Uppsala UniversityDepartment of Virology, National Institute for Health DevelopmentPublic Health Agency of SwedenMedical Entomology Unit, Subdepartment of Systematic Biology, Department of Organismal Biology, Evolutionary Biology Centre, Uppsala UniversityAbstract Background In northern Europe, the tick-borne encephalitis virus (TBEV) of the European subtype is usually transmitted to humans by the common tick Ixodes ricinus. The aims of the present study are (i) to obtain up-to-date information on the TBEV prevalence in host-seeking I. ricinus in southern and central Sweden; (ii) to compile and review all relevant published records on the prevalence of TBEV in ticks in northern Europe; and (iii) to analyse and try to explain how the TBE virus can be maintained in natural foci despite an apparently low TBEV infection prevalence in the vector population. Methods To estimate the mean minimum infection rate (MIR) of TBEV in I. ricinus in northern Europe (i.e. Denmark, Norway, Sweden and Finland) we reviewed all published TBEV prevalence data for host-seeking I. ricinus collected during 1958–2011. Moreover, we collected 2,074 nymphs and 906 adults of I. ricinus from 29 localities in Sweden during 2008. These ticks were screened for TBEV by RT-PCR. Results The MIR for TBEV in nymphal and adult I. ricinus was 0.28% for northern Europe and 0.23% for southern Sweden. The infection prevalence of TBEV was significantly lower in nymphs (0.10%) than in adult ticks (0.55%). At a well-known TBEV-endemic locality, Torö island south-east of Stockholm, the TBEV prevalence (MIR) was 0.51% in nymphs and 4.48% in adults of I. ricinus. Conclusions If the ratio of nymphs to adult ticks in the TBEV-analysed sample differs from that in the I. ricinus population in the field, the MIR obtained will not necessarily reflect the TBEV prevalence in the field. The relatively low TBEV prevalence in the potential vector population recorded in most studies may partly be due to: (i) inclusion of uninfected ticks from the ‘uninfected areas’ surrounding the TBEV endemic foci; (ii) inclusion of an unrepresentative, too large proportion of immature ticks, compared to adult ticks, in the analysed tick pools; and (iii) shortcomings in the laboratory techniques used to detect the virus that may be present in a very low concentration or undetectable state in ticks which have not recently fed.https://doi.org/10.1186/1756-3305-7-102Ixodes ricinusMinimum infection rateReal-time PCRSwedenNorwayDenmark |
| spellingShingle | John H-O Pettersson Irina Golovljova Sirkka Vene Thomas GT Jaenson Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in northern Europe with particular reference to Southern Sweden Parasites & Vectors Ixodes ricinus Minimum infection rate Real-time PCR Sweden Norway Denmark |
| title | Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in northern Europe with particular reference to Southern Sweden |
| title_full | Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in northern Europe with particular reference to Southern Sweden |
| title_fullStr | Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in northern Europe with particular reference to Southern Sweden |
| title_full_unstemmed | Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in northern Europe with particular reference to Southern Sweden |
| title_short | Prevalence of tick-borne encephalitis virus in Ixodes ricinus ticks in northern Europe with particular reference to Southern Sweden |
| title_sort | prevalence of tick borne encephalitis virus in ixodes ricinus ticks in northern europe with particular reference to southern sweden |
| topic | Ixodes ricinus Minimum infection rate Real-time PCR Sweden Norway Denmark |
| url | https://doi.org/10.1186/1756-3305-7-102 |
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