| 1. |
- Jaenson, Thomas G.T. 1948-, et al.
(author)
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The importance of wildlife in the ecology and epidemiology of the TBE virus in Sweden: incidence of human TBE correlates with abundance of deer and hares
- 2018
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In: Parasites & Vectors. - : Springer Science and Business Media LLC. - 1756-3305. ; 11
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Journal article (peer-reviewed)abstract
- Background: Tick-borne encephalitis (TBE) is one tick-transmitted disease where the human incidence has increased in some European regions during the last two decades. We aim to find the most important factors causing the increasing incidence of human TBE in Sweden. Based on a review of published data we presume that certain temperature-related variables and the population densities of transmission hosts, i.e. small mammals, and of primary tick maintenance hosts, i.e. cervids and lagomorphs, of the TBE virus vector Ixodes ricinus, are among the potentially most important factors affecting the TBE incidence. Therefore, we compare hunting data of the major tick maintenance hosts and two of their important predators, and four climatic variables with the annual numbers of human cases of neuroinvasive TBE. Data for six Swedish regions where human TBE incidence is high or has recently increased are examined by a time-series analysis. Results from the six regions are combined using a meta-analytical method.Results: With a one-year time lag, the roe deer (Capreolus capreolus), red deer (Cervus elaphus), mountain hare (Lepus timidus) and European hare (Lepus europaeus) showed positive covariance; the Eurasian elk (moose, Alces alces) and fallow deer (Dama dama) negative covariance; whereas the wild boar (Sus scrofa), lynx (Lynx lynx), red fox (Vulpes vulpes) and the four climate parameters showed no significant covariance with TBE incidence. All game species combined showed positive covariance.Conclusions: The epidemiology of TBE varies with time and geography and depends on numerous factors, i.a. climate, virus genotypes, and densities of vectors, tick maintenance hosts and transmission hosts. This study suggests that the increased availability of deer to I. ricinus over large areas of potential tick habitats in southern Sweden increased the density and range of I. ricinus and created new TBEV foci, which resulted in increased incidence of human TBE. New foci may be established by TBE virus-infected birds, or by birds or migrating mammals infested with TBEV-infected ticks. Generally, persistence of TBE virus foci appears to require presence of transmission-competent small mammals, especially mice (Apodemus spp.) or bank voles (Myodes glareolus).
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| 2. |
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| 3. |
- Hoffman, Tove, et al.
(author)
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Association between guilds of birds in the African-Western Palaearctic region and the tick species Hyalomma rufipes, one of the main vectors of Crimean-Congo hemorrhagic fever virus
- 2021
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In: One Health. - : Elsevier. - 2352-7714. ; 13
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Journal article (peer-reviewed)abstract
- IntroductionThe ecology of the vertebrate host contributes to the geographical range expansion of ticks. In this study, we investigated which tick taxa that infest and are dispersed by birds along African-Western Palaearctic flyways during northward migration, and whether bird ecology was associated with tick taxa.Materials and methodsTicks were collected from birds trapped at bird observatories in Spain, Italy, Greece, and Israel during the spring migration of 2014 and 2015, using mist nets. The tick-infested bird species were classified into guilds, using different combinations of the variables: migration distance, wintering region, foraging behaviour, and winter habitat. Ticks were molecularly determined to genus and species level by sequencing fragments of the 12S ribosomal DNA (rDNA) gene and by phylogenetic inference, using the Maximum Likelihood algorithm. Data were analysed using descriptive measures, graphs, Chi2 tests, the Tukey-Kramer test, and a parametric linear model (generalized linear model) in order to analyse and adjust for characteristics in the bird guilds and their relationship to collected tick taxa.ResultsMost (84.2%) of the 10,209 trapped birds were long-distance migrants, of which 2.4% were infested by ticks. The most common tick species was Hyalomma rufipes (77.7%; 447/575), a known vector and reservoir of Crimean-Congo hemorrhagic fever virus. Bird guilds containing only long-distance migrants with wintering areas in Africa were associated with the tick species H. rufipes (p < 0.0001). Furthermore, bird winter habitat was associated with H. rufipes (p = 0.003); with bird species overwintering in open habitat (p = 0.014) and wetlands (p = 0.046) having significantly more H. rufipes as compared to birds with a winter habitat comprising forest and shrubs (p = 0.82).ConclusionsWith climate change, the likelihood of establishment of permanent Hyalomma populations in central and northern Europe is increasing. Thus, surveillance programs for monitoring the risk of introduction and establishment of H. rufipes in the Western-Palaearctic should be established. Our study suggests that migratory bird species wintering in African open habitats and wetlands are good candidates for monitoring potential introduction.
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| 4. |
- Hoffman, Tove, et al.
(author)
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Association between guilds of birds in the African-Western Palaearctic region and the tick species Hyalomma rufipes, one of the main vectors of Crimean-Congo hemorrhagic fever virus.
- 2022
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In: Microorganisms. - : MDPI AG. - 2076-2607. ; 10
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Journal article (peer-reviewed)abstract
- The migratory behavior of wild birds contributes to the geographical spread of ticks and their microorganisms. In this study, we aimed to investigate the dispersal and co-occurrence of Francisella and spotted fever group Rickettsia (SFGR) in ticks infesting birds migrating northward in the African-Western Palaearctic region (AWPR). Birds were trapped with mist nests across the Mediterranean basin during the 2014 and 2015 spring migration. In total, 575 ticks were collected from 244 birds. We screened the ticks for the species Francisella tularensis, the genus Francisella, and SFGR by microfluidic real-time PCR. Confirmatory analyses and metagenomic sequencing were performed on tick samples that putatively tested positive for F. tularensis during initial screenings. Hyalomma rufipes was the most common tick species and had a high prevalence of Francisella, including co-occurrence of Francisella and SFGR. Metagenomic analysis of total DNA extracted from two H. rufipes confirmed the presence of Francisella, Rickettsia, and Midichloria. Average nucleotide identity and phylogenetic inference indicated the highest identity of the metagenome-assembled genomes to a Francisella-like endosymbiont (FLE), Rickettsia aeschlimannii, and Midichloria mitochondrii. The results of this study suggest that (i) FLE- and SFGR-containing ticks are dispersed by northbound migratory birds in the AWPR, (ii) H. rufipes likely is not involved in transmission of F. tularensis in the AWPR, and (iii) a dual endosymbiosis of FLEs and Midichloria may support some of the nutritional requirements of H. rufipes.
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| 5. |
- Hoffman, Tove, et al.
(author)
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Co-occurrence of Francisella and spotted fever group Rickettsia in avian-associated Hyalomma rufipes
- 2022
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In: Microorganisms. - : MDPI. - 2076-2607. ; 10:7
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Journal article (peer-reviewed)abstract
- Introduction: The migratory behaviour of wild birds aids in the geographical spread of ticks and their microorganisms. Ticks are known to harbor both pathogenic and symbiotic bacteria - such as species of the genera Francisella, Rickettsia,and Midichloria - and multiple bacterial species may occur within them. Francisella occurs in different tick taxa andconsists of closely related pathogenic and non-pathogenic species. Spotted fever group Rickettsia are transmitted to humans by different tick genera and are emerging human pathogens in Europe. The aims of this study were to investigate dispersal of Francisella as well as co-occurrence of Francisella and spotted fever group Rickettsia in ticks infesting northward migrating birds in the African-Western Palaearctic region.Materials and methods: Birds were trapped using mist nets at bird observatories in Spain, Italy, Greece, and Israel during their spring migration of 2014 and 2015. Ticks were screened for the genus Francisella, the species Francisella tularensis, and spotted fever group Rickettsia by microfluidic qPCR. Ticks with putative positive results for F. tularensiswere subjected to confirmation analyses, metagenomics analysis, enrichment, and whole genome sequencing.Results: There was a high prevalence of Francisella species (76.7%) and co-occurrence of Francisella species and spotted fever group Rickettsia (50.6%) in the tick species Hyalomma rufipes. Two H. rufipes yielded putative positive test results for the human pathogen F. tularensis during initial screening. Metagenomics analysis revealed presence of Francisella sp., Rickettsia sp., and Midichloria sp. DNA in the two H. rufipes ticks. The levels of Rickettsia and Midichloria DNA were relatively high while the level of Francisella DNA was low and required enrichment for the construction of metagenome-assembled genomes. Phylogenetic inference and calculations of the average nucleotide identity (ANI) indicated that: i) the Francisella genomes belonged to the Francisella-like endosymbiont (FLE) group in Clade 1 of Francisella and had highest sequence identity to an FLE found in Ornithodoros moubata (ANI: 96.7/97.0%), ii) the Rickettsia genomes had highest resemblance to Rickettsia aeschlimannii (ANI: 98.8 - 99.9%), and iii) the Midichloria genomes resembled Midichloria mitochondrii (ANI: 91.5 - 92.3%).Conclusions: The results of this study suggest ticks containing Francisella species, FLEs, and spotted fever groupRickettsia are dispersed by northbound migratory birds in the African-Western Palaearctic and suggest H. rufipes may not be involved in the transmission of F. tularensis in the study region. Future studies should aim at confirming the prevalence of Francisella spp. and spotted fever group Rickettsia in H. rufipes, in addition to focusing on the influence of FLEs on H. rufipes and their interaction with pathogenic and symbiotic bacteria of the genera Rickettsia and Midichloria.
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| 6. |
- Lilja, T., et al.
(author)
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Single nucleotide polymorphism analysis of the ITS2 region of two sympatric malaria mosquito species in Sweden : Anopheles daciaeandAnopheles messeae
- 2020
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In: Medical and Veterinary Entomology. - : WILEY. - 0269-283X .- 1365-2915. ; 34:3, s. 364-368
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Journal article (peer-reviewed)abstract
- Four species of theAnopheles maculipenniscomplex have previously been recorded in Sweden. A recent addition to the complex isAnopheles daciae, which is considered to be closely related to, but distinct fromAnopheles messeae. The original designation ofAn. daciaewas based on five genetic differences (161, 165, 167, 362 and 382) in the second internal transcribed spacer (ITS) 2 of the ribosomal RNA. Further studies have shown that only two nucleotide differences (362 and 382) robustly separate the species. Thirty-threeAn. maculipenniscomplex mosquitoes were collected in the province of Uppland, Sweden. All wereAn. daciaebut showed double peaks for three variable positions (161, 165 and 167). When cloned, the intra-individual nucleotide variation was almost exclusively fixed with either TTC or AAT, originally diagnostic forAn. messaeandAn. daciae, respectively. To further investigate the intra-individual variation, nineAn. daciaeand 11An. messeaewere collected in southern Sweden and their ITS2 fragments were amplified and sequenced using Illumina MiSeq sequencing (Illumina, Inc., San Diego, CA, USA). For the diagnostic nucleotide 382 no intra-individual variation could be detected. However, although eachAn. daciaespecimen carried several ITS2 sequence variants for the four other nucleotides, there was no intra-individual variation in theAn. messeaespecimens.
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| 7. |
- Labbé, Lisa Sandelin, et al.
(author)
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Candidatus Neoehrlichia mikurensis in Ticks from Migrating Birds in Sweden
- 2015
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In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 10:7
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Journal article (peer-reviewed)abstract
- Candidatus Neoehrlichia mikurensis (CNM; family Anaplasmataceae) was recently recognized as a potential tick-borne human pathogen. The presence of CNM in mammals, in host-seeking Ixodes ticks and in ticks attached to mammals and birds has been reported recently. We investigated the presence of CNM in ornithophagous ticks from migrating birds. A total of 1,150 ticks (582 nymphs, 548 larvae, 18 undetermined ticks and two adult females) collected from 5,365 birds captured in south-eastern Sweden was screened for CNM by molecular methods. The birds represented 65 different species, of which 35 species were infested with one or more ticks. Based on a combination of morphological and molecular species identification, the majority of the ticks were identified as Ixodes ricinus. Samples were initially screened by real-time PCR targeting the CNM 16S rRNA gene, and confirmed by a second real-time PCR targeting the groEL gene. For positive samples, a 1260 base pair fragment of the 16S rRNA gene was sequenced. Based upon bacterial gene sequence identification, 2.1% (24/1150) of the analysed samples were CNM-positive. Twenty-two out of 24 CNM-positive ticks were molecularly identified as I. ricinus nymphs, and the remaining two were identified as I. ricinus based on morphology. The overall CNM prevalence in I. ricinus nymphs was 4.2%. None of the 548 tested larvae was positive. CNM-positive ticks were collected from 10 different bird species. The highest CNM-prevalences were recorded in nymphs collected from common redpoll (Carduelis flammea, 3/7), thrush nightingale (Luscinia luscinia, 2/29) and dunnock (Prunella modularis, 1/17). The 16S rRNA sequences obtained in this study were all identical to each other and to three previously reported European strains, two of which were obtained from humans. It is concluded that ornithophagous ticks may be infected with CNM and that birds most likely can disperse CNM-infected ticks over large geographical areas.
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| 8. |
- Wallmenius, Katarina, et al.
(author)
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Spotted fever Rickettsia species in Hyalomma and Ixodes ticks infesting migratory birds in the European Mediterranean area
- 2014
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In: Parasites & Vectors. - : Springer Science and Business Media LLC. - 1756-3305. ; 7
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Journal article (peer-reviewed)abstract
- Background: A few billion birds migrate annually between their breeding grounds in Europe and their wintering grounds in Africa. Many bird species are tick-infested, and as a result of their innate migratory behavior, they contribute significantly to the geographic distribution of pathogens, including spotted fever rickettsiae. The aim of the present study was to characterize, in samples from two consecutive years, the potential role of migrant birds captured in Europe as disseminators of Rickettsia-infected ticks. Methods: Ticks were collected from a total of 14,789 birds during their seasonal migration northwards in spring 2009 and 2010 at bird observatories on two Mediterranean islands: Capri and Antikythira. All ticks were subjected to RNA extraction followed by cDNA synthesis and individually assayed with a real-time PCR targeting the citrate synthase (gltA) gene. For species identification of Rickettsia, multiple genes were sequenced. Results: Three hundred and ninety-eight (2.7%) of all captured birds were tick-infested; some birds carried more than one tick. A total number of 734 ticks were analysed of which 353 +/- 1 (48%) were Rickettsia-positive; 96% were infected with Rickettsia aeschlimannii and 4% with Rickettsia africae or unidentified Rickettsia species. The predominant tick taxon, Hyalomma marginatum sensu lato constituted 90% (n = 658) of the ticks collected. The remaining ticks were Ixodes frontalis, Amblyomma sp., Haemaphysalis sp., Rhipicephalus sp. and unidentified ixodids. Most ticks were nymphs (66%) followed by larvae (27%) and adult female ticks (0.5%). The majority (65%) of ticks was engorged and nearly all ticks contained visible blood. Conclusions: Migratory birds appear to have a great impact on the dissemination of Rickettsia-infected ticks, some of which may originate from distant locations. The potential ecological, medical and veterinary implications of such Rickettsia infections need further examination.
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| 9. |
- Hagman, Karl, et al.
(author)
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On the potential roles of ticks and migrating birds in the ecology of West Nile virus
- 2014
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In: Infection Ecology & Epidemiology. - : Informa UK Limited. - 2000-8686 .- 2000-8686. ; 4
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Journal article (peer-reviewed)abstract
- BACKGROUND: Mosquitoes are the primary vectors of West Nile virus (WNV). Ticks have, however, been suggested to be potential reservoirs of WNV. In order to investigate their role in the spread of the virus, ticks, which had been collected from birds migrating northwards from Africa to Europe, were analyzed for the potential presence of WNV-RNA.METHODS: On the Mediterranean islands Capri and Antikythira a total of 14,824 birds were captured and investigated from which 747 ticks were collected.RESULTS AND CONCLUSION: Most of the identified ticks (93%) were nymphs and larvae of Hyalomma marginatum sensu lato, most of which were or appear to be Hyalomma rufipes. Of these ticks 729 were individually screened for WNV-RNA. None of the ticks was found to be WNV positive. Thus, there was no evidence that Hyalomma marginatum s.l. ticks play a role in the spread of WNV from Africa to Europe.
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| 10. |
- Jaenson, Thomas G.T. 1948-, et al.
(author)
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Coinfection of Babesia and Borrelia in the Tick Ixodes ricinus-A Neglected Public Health Issue in Europe?
- 2024
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In: Pathogens. - : MDPI. - 2076-0817. ; 13:1
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Research review (peer-reviewed)abstract
- Ixodes ricinus nymphs and adults removed from humans, and larvae and nymphs from birds, have been analysed for infection with Babesia species and Borrelia species previously in separately published studies. Here, we use the same data set to explore the coinfection pattern of Babesia and Borrelia species in the ticks. We also provide an overview of the ecology and potential public health importance in Sweden of I. ricinus infected both with zoonotic Babesia and Borrelia species. Among 1952 nymphs and adult ticks removed from humans, 3.1% were PCR-positive for Babesia spp. Of these Babesia-positive ticks, 43% were simultaneously Borrelia-positive. Among 1046 immatures of I. ricinus removed from birds, 2.5% were Babesia-positive, of which 38% were coinfected with Borrelia species. This study shows that in I. ricinus infesting humans or birds in Sweden, potentially zoonotic Babesia protozoa sometimes co-occur with human-pathogenic Borrelia spp. Diagnostic tests for Babesia spp. infection are rarely performed in Europe, and the medical significance of this pathogen in Europe could be underestimated.
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