| 1. |
- Gustafson, Rolf, et al.
(författare)
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Prevalence of Borrelia burgdorferi sensu lato infection in Ixodes ricinus in Sweden
- 1995
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Ingår i: Scandinavian Journal of Infectious Diseases. - : Informa UK Limited. - 0036-5548 .- 1651-1980. ; 27:6, s. 597-601
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Tidskriftsartikel (refereegranskat)abstract
- Between 1988-1991, a total of 3,141 Ixodes ricinus ticks, 2,740 adults and 401 nymphs, was collected from different localities in 23 of the 25 provinces of Sweden. The ticks were identified, dissected and examined for the presence of Borrelia spirochetes. Indirect immunofluorescence was performed, using an antiserum obtained from rabbits, immunized with sonicated, whole Borrelia burgdorferi spirochetes isolated from Swedish Ixodes ricinus ticks. Borrelia-positive I. ricinus were found in all 23 provinces. The prevalence of infection in adults ranged from 3% in Jämtland to 23% in Södermanland. In nymphs, the infection prevalence ranged from 0% in 9 provinces to 15% in Södermanland. A significantly greater proportion of the adult ticks were found to be positive for Borrelia in the southern and central parts of Sweden as compared to the northern part (Norrland). No significant difference in prevalence could be demonstrated between the western and eastern parts of Sweden. On average, 10% of the nymphs and 15% of the adult I. ricinus were positive for Borrelia. Of 41 non-I. ricinus ticks, none was positive for Borrelia. This study shows that Borrelia burgdorferi sensu lato is present throughout the distributional area of I. ricinus in Sweden. This should lead to increased awareness of signs and symptoms compatible with Lyme borreliosis in persons living in or visiting areas where I. ricinus is present.
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| 2. |
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| 3. |
- Mejlon, Hans
(författare)
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Diel activity of Ixodes ricinus Acari: Ixodidæ at two locations near Stockholm, Sweden
- 1997
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Ingår i: Experimental and Applied Acarology. - 0168-8162. ; 21:4, s. 247-255
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Tidskriftsartikel (refereegranskat)abstract
- The diel 'activity', i.e. availability, of Ixodes ricinus larvae, nymphs and adults was investigated in a meadow and a forest habitat near Stockholm during 1991-1993. Generally, the immature ticks were more prevalent in the forest than in the meadow. In the meadow, the mean larval and adult numbers varied significantly between 4 h time intervals with the peak activity from 2300 to 0300 h. In the forest, tick numbers did not differ significantly between time intervals. The association of tick activity with certain meteorological variables was strongest in the meadow, where the mean numbers of all tick stages were negatively correlated with temperature.The relative humidity was positively correlated only with the mean numbers of larvae. In contrast, the larval activity in the forest was positively and negatively correlated with temperature and relative humidity, respectively, while the nymphal and adult activity showed no association with these climatic variables. The impact of host activity on tick diel activity is also discussed.
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| 4. |
- Mejlon, Hans, et al.
(författare)
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Questing behaviour of Ixodes ricinus ticks (Acari: Ixodidae)
- 1997
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Ingår i: Experimental & applied acarology. - 0168-8162 .- 1572-9702. ; 21:12, s. 747-754
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Tidskriftsartikel (refereegranskat)abstract
- The vertical distribution in the vegetation of questing Ixodes ricinus ticks was investigated in two different vegetation types ('high' and 'low' vegetation) at two localities in south-central Sweden during 1992-1993 (Torö) and 1995 (Bogesund). Significant correlations were found between the vertical distribution of immature ticks and the height of the vegetation. The greatest mean availabilities of the larvae and nymphs in low vegetation were in the intervals 0-9 and 30-39 cm, respectively. The larval numbers were greatest close to the ground (0-29) in both high and low vegetation. The larval : nymphal ratio, at ground level at localities free of ground vegetation, varied between 8:1 and 32:1. In high vegetation, the greatest mean numbers of nymphal and adult ticks were at height intervals of 50-59 and 60-79 cm, respectively. These ranges are within the estimated height interval (40-100 cm) of the main part of the body surface of their 'preferred' host, the roe deer (Capreolus capreolus). The presence of most questing I. ricinus larvae at ground level would favour the transmission of Borrelia burgdorferi s.l., since this is where the highly reservoir-competent rodents and shrews usually occur.
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| 5. |
- Tälleklint, Lars, et al.
(författare)
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Transmission of the Lyme borreliosis spirochete at the mammal reservoir : tick vector interface in Sweden
- 1995
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Ingår i: Proceedings of the 2:nd International Conference on tick-borne pathogens at the host-vector interface.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- During 1988 to 1995 we examined the density of questing Ixodes ricinus nymphs infected with Borrelia burgdorferi s.l. at 12 areas in southern and southcentral Sweden. There were great differences in the density of questing Borrelia-infected I. ricinus nymphs between these areas, i.e., from <10 to >500 infected nymphs per hectare. The density of I. ricinus nymphs had a greater impact on this variation than the prevalence of Borrelia-infection in the nymphs, suggesting that reservoir incompetent cervids, which are important hosts for adult female I. ricinus, indirectly increase the risk of encountering Borrerlia-infected nymphal ticks despite the ability of cervids to divert larval ticks from reservoir competent mammals. There was a strong correlation between the mean number of Borrelia-infected nymphs per hectare and the mean number of nymphs per hectare, suggesting that it may be possible to assess the risk of encountering Borrelia-infected ticks in different areas without examining the prevalence of spirochetal infection.
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