Johannes P Borde1,2, Klaus Kaier3, Philip Hehn3, Andreas Matzarakis4, Stefan Frey5, Malena Bestehorn6, Gerhard Dobler5,6, Lidia Chitimia-Dobler5,6. 1. Division of Infectious Diseases, Department of Medicine II, University of Freiburg Medical Center and Faculty of Medicine, Freiburg i.Br., Germany. 2. Praxis Dr. J. Borde / Gesundheitszentrum Oberkirch, Oberkirch, Germany. 3. Institute of Medical Biometry and Statistics, Faculty of Medicine and Medical Center - University of Freiburg, University of Freiburg, Freiburg, Germany. 4. Research Centre Human Biometeorology, German Meteorological Service, Freiburg, Germany. 5. Bundeswehr Institute of Microbiology, German National Reference Laboratory for TBEV, München, Germany. 6. Parasitology Unit, University of Hohenheim, Stuttgart, Germany.
Abstract
BACKGROUND: Tick-borne encephalitis (TBE) is the most important tick-borne viral disease in Eurasia and causes disease in humans and in a number of animals, among them dogs and horses. There is still no good correlation between tick numbers, weather conditions and human cases. There is the hypothesis that co-feeding due to simultaneous occurrence of larvae and nymphs may be a factor for the increased transmission of the virus in nature and for human disease. Based on long-term data from a natural TBEV focus, phylogenetic results and meteorological data we sought to challenge this hypothesis. METHODS: Ticks from an identified TBE natural focus were sampled monthly from 04/2009 to 12/2018. Ticks were identified and pooled. Pools were tested by RT-qPCR. Positive pools were confirmed by virus isolation and/or sequencing of additional genes (E gene, NS2 gene). Temperature data such as the decadal (10-day) mean daily maximum air temperature (DMDMAT) were obtained from a nearby weather station and statistical correlations between tick occurrence and minimal infection rates (MIR) were calculated. RESULTS: In the study period from 04/2009 to 12/2018 a total of 15,530 ticks (2,226 females, 2,268 males, 11,036 nymphs) were collected. The overall MIR in nymphs over the whole period was 77/15,530 (0.49%), ranging from 0.09% (2009) to 1.36% (2015). The overall MIR of female ticks was 0.76% (17/2,226 ticks), range 0.14% (2013) to 3.59% (2016). The overall MIR of males was 0.57% (13/2,268 ticks), range from 0.26% (2009) to 0.97% (2015). The number of nymphs was statistically associated with a later start of spring/vegetation period, indicated by the onset of forsythia flowering. CONCLUSION: There was no particular correlation between DMDMAT dynamics in spring and/or autumn and the MIR of nymphs or adult ticks detected. However, there was a positive correlation between the number of nymphs and the number of reported human TBE cases in the following months, but not in the following year. The hypothesis of the importance of co-feeding of larvae and nymphs for the maintenance of transmission cycle of TBEV in nature is not supported by our findings.
BACKGROUND:Tick-borne encephalitis (TBE) is the most important tick-borne viral disease in Eurasia and causes disease in humans and in a number of animals, among them dogs and horses. There is still no good correlation between tick numbers, weather conditions and human cases. There is the hypothesis that co-feeding due to simultaneous occurrence of larvae and nymphs may be a factor for the increased transmission of the virus in nature and for human disease. Based on long-term data from a natural TBEV focus, phylogenetic results and meteorological data we sought to challenge this hypothesis. METHODS: Ticks from an identified TBE natural focus were sampled monthly from 04/2009 to 12/2018. Ticks were identified and pooled. Pools were tested by RT-qPCR. Positive pools were confirmed by virus isolation and/or sequencing of additional genes (E gene, NS2 gene). Temperature data such as the decadal (10-day) mean daily maximum air temperature (DMDMAT) were obtained from a nearby weather station and statistical correlations between tick occurrence and minimal infection rates (MIR) were calculated. RESULTS: In the study period from 04/2009 to 12/2018 a total of 15,530 ticks (2,226 females, 2,268 males, 11,036 nymphs) were collected. The overall MIR in nymphs over the whole period was 77/15,530 (0.49%), ranging from 0.09% (2009) to 1.36% (2015). The overall MIR of female ticks was 0.76% (17/2,226 ticks), range 0.14% (2013) to 3.59% (2016). The overall MIR of males was 0.57% (13/2,268 ticks), range from 0.26% (2009) to 0.97% (2015). The number of nymphs was statistically associated with a later start of spring/vegetation period, indicated by the onset of forsythia flowering. CONCLUSION: There was no particular correlation between DMDMAT dynamics in spring and/or autumn and the MIR of nymphs or adult ticks detected. However, there was a positive correlation between the number of nymphs and the number of reported human TBE cases in the following months, but not in the following year. The hypothesis of the importance of co-feeding of larvae and nymphs for the maintenance of transmission cycle of TBEV in nature is not supported by our findings.
Authors: Daniel Ruzek; Tatjana Avšič Županc; Johannes Borde; Ales Chrdle; Ludek Eyer; Galina Karganova; Ivan Kholodilov; Nataša Knap; Liubov Kozlovskaya; Andrey Matveev; Andrew D Miller; Dmitry I Osolodkin; Anna K Överby; Nina Tikunova; Sergey Tkachev; Joanna Zajkowska Journal: Antiviral Res Date: 2019-01-31 Impact factor: 5.970
Authors: Malena Bestehorn; Sebastian Weigold; Winfried V Kern; Lidia Chitimia-Dobler; Ute Mackenstedt; Gerhard Dobler; Johannes P Borde Journal: PLoS One Date: 2018-10-18 Impact factor: 3.240
Authors: Johannes P Borde; Rüdiger Glaser; Klaus Braun; Nils Riach; Rafael Hologa; Klaus Kaier; Lidia Chitimia-Dobler; Gerhard Dobler Journal: Int J Environ Res Public Health Date: 2022-09-19 Impact factor: 4.614