Publications by authors named "Ankje de Vries"

19 Publications

  • Page 1 of 1

Bayesian Binary Mixture Models as a Flexible Alternative to Cut-Off Analysis of ELISA Results, a Case Study of Seoul Orthohantavirus.

Viruses 2021 Jun 16;13(6). Epub 2021 Jun 16.

Centre for Infectious Disease Control, Centre for Zoonoses and Environmental Microbiology, National Institute for Public Health and the Environment (RIVM), P.O. Box 1, 3720 BA Bilthoven, The Netherlands.

Serological assays, such as the enzyme-linked immunosorbent assay (ELISA), are popular tools for establishing the seroprevalence of various infectious diseases in humans and animals. In the ELISA, the optical density is measured and gives an indication of the antibody level. However, there is variability in optical density values for individuals that have been exposed to the pathogen of interest, as well as individuals that have not been exposed. In general, the distribution of values that can be expected for these two categories partly overlap. Often, a cut-off value is determined to decide which individuals should be considered seropositive or seronegative. However, the classical cut-off approach based on a putative threshold ignores heterogeneity in immune response in the population and is thus not the optimal solution for the analysis of serological data. A binary mixture model does include this heterogeneity, offers measures of uncertainty and the direct estimation of seroprevalence without the need for correction based on sensitivity and specificity. Furthermore, the probability of being seropositive can be estimated for individual samples, and both continuous and categorical covariates (risk-factors) can be included in the analysis. Using ELISA results from rats tested for the Seoul orthohantavirus, we compared the classical cut-off method with a binary mixture model set in a Bayesian framework. We show that it performs similarly or better than cut-off methods, by comparing with real-time quantitative polymerase chain reaction (RT-qPCR) results. We therefore recommend binary mixture models as an analysis tool over classical cut-off methods. An example code is included to facilitate the practical use of binary mixture models in everyday practice.
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http://dx.doi.org/10.3390/v13061155DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8234822PMC
June 2021

Seoul Virus in Pet and Feeder Rats in The Netherlands.

Viruses 2021 03 10;13(3). Epub 2021 Mar 10.

Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Postbus 1, 3720 BA Bilthoven, The Netherlands.

Seoul virus (SEOV) is a zoonotic orthohantavirus carried by rats. In humans, SEOV can cause hemorrhagic fever with renal syndrome. Recent human SEOV cases described in the USA, United Kingdom, France and the Netherlands were associated with contact with pet or feeder rats. The prevalence of SEOV in these types of rats is unknown. We collected 175 pet and feeder rats () from private owners, ratteries and commercial breeders/traders in the Netherlands. Lung tissue of the rats was tested using a SEOV real-time RT-qPCR and heart fluid was tested for the presence of antibodies against SEOV. In all three investigated groups, RT-qPCR-positive rats were found: in 1/29 rats from private owners (3.6%), 2/56 rats from ratteries (3.4%) and 11/90 rats from commercial breeders (12.2%). The seroprevalence was largely similar to the prevalence calculated from RT-qPCR-positive rats. The SEOV sequences found were highly similar to sequences previously found in domesticated rats in Europe. In conclusion, SEOV is spread throughout different populations of domesticated rats.
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http://dx.doi.org/10.3390/v13030443DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8002128PMC
March 2021

Development of a Comparative European Orthohantavirus Microneutralization Assay With Multi- Species Validation and Evaluation in a Human Diagnostic Cohort.

Front Cell Infect Microbiol 2020 22;10:580478. Epub 2020 Dec 22.

Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, Netherlands.

Orthohantaviruses (family , order ) can cause two serious syndromes in humans: hemorrhagic fever with renal syndrome (HFRS), associated with the Old World orthohantaviruses, and hantavirus cardiopulmonary syndrome (HCPS), associated with orthohantaviruses in the Americas. In Europe, four different orthohantaviruses (DOBV, PUUV, SEOV, and TULV) are associated with human disease. As disease severity and zoonotic source differ between orthohantavirus species, conclusive determination of the infecting species by either RT-PCR or comparative virus neutralization test (VNT) is of importance. Currently, the focus reduction neutralization test (FRNT) is considered the 'Gold Standard' for orthohantavirus VNTs, however this test is laborious and time-consuming. Consequently, more high-throughput alternatives are needed. In this study, we developed a comparative orthohantavirus microneutralization test (MNT) including all four human pathogenic orthohantavirus species circulating in Europe. The assay was validated using RT-PCR-confirmed rodent (n=17) and human sera (n=17), DOBV-suspected human sera (n=3) and cohorts of orthohantavirus-negative rodent (n=3) and human sera (n=85). 16/17 RT-PCR-confirmed rodent sera and 18/20 of the RT-PCR-confirmed and DOBV-suspected human sera were serotyped successfully, while for the remaining rodent (n=1) and human sera (n=2) no neutralizing titers could be detected. All negative control sera tested negative in the MNT. The assay was subsequently evaluated using a clinical cohort of 50 orthohantavirus patients. Orthohantavirus infection was confirmed in all 50 patients, and 47/50 (94%) sera were serotyped successfully, confirming PUUV as the major cause of orthohantavirus infections in Netherlands. Notably, two previously unrecognized SEOV cases from 2013 were diagnosed using the MNT, underlining the added value of the MNT in a diagnostic setting. In conclusion, we demonstrate the successful development and clinical implementation of a comparative European orthohantavirus MNT to determine the infecting virus species in European HFRS patients. Identification of the causative species is needed for an adequate Public Health response and can support individual patient care. For many labs, the implementation of orthohantavirus neutralization tests has not been a straightforward procedure. This issue will be addressed by the rollout of the comparative MNT to multiple European laboratories to support patient diagnostics, surveillance and Public Health responses.
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http://dx.doi.org/10.3389/fcimb.2020.580478DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7783042PMC
June 2021

Prosthetic Valve Endocarditis with in a Human European Patient and Its Detection in Red Squirrels ().

J Clin Microbiol 2019 12 23;58(1). Epub 2019 Dec 23.

Department of Medical Microbiology and Hygiene, University of Mainz, Mainz, Germany.

Members of the genus are fastidious Gram-negative facultative intracellular bacteria that are typically transmitted by arthropod vectors. Several spp. have been found to cause culture-negative endocarditis in humans. Here, we report the case of a 75-year-old German woman with prosthetic valve endocarditis due to The infecting agent was characterized by sequencing of six housekeeping genes (16S rRNA, , , , , and ), applying a multilocus sequence typing (MLST) approach. The 5,097 bp of the concatenated housekeeping gene sequence from the patient were 99.0% identical to a sequence from a strain isolated from a red squirrel ( ) from China. A total of 39% (24/62) of red squirrel () samples from the Netherlands were positive for the gene variant detected in the patient. This suggests that the red squirrel is the reservoir host for human infection in Europe.
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http://dx.doi.org/10.1128/JCM.01404-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6935924PMC
December 2019

Seoul Virus Tropism and Pathology in Naturally Infected Feeder Rats.

Viruses 2019 06 7;11(6). Epub 2019 Jun 7.

Department of Viroscience, Erasmus University Medical Center, 3015 GD Rotterdam, The Netherlands.

Seoul virus (SEOV) is a zoonotic orthohantavirus carried by black and brown rats, and can cause hemorrhagic fever with renal syndrome in humans. Human cases of SEOV virus infection have most recently been reported in the USA, United Kingdom, France and the Netherlands and were primarily associated with contact with pet rats and feeder rats. Infection of rats results in an asymptomatic but persistent infection. Little is known about the cell tropism of SEOV in its reservoir and most available data is based on experimental infection studies in which rats were inoculated via a route which does not recapitulate virus transmission in nature. Here we report the histopathological analysis of SEOV cell tropism in key target organs following natural infection of a cohort of feeder rats, comprising 19 adults and 11 juveniles. All adult rats in this study were positive for SEOV specific antibodies and viral RNA in their tissues. One juvenile rat was seropositive, but negative in the rRT-PCR. Of the 19 adult rats of which subsequently additional organs were tested, SEOV RNA was detected in all lungs, followed by kidney (79%) and liver (74%). Histopathologic changes associated with SEOV infection were primarily found in the liver, consistent with a pathological diagnosis of a mild hepatitis. In conclusion, natural SEOV infection results in mild inflammation of the liver in the absence of clinical disease.
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http://dx.doi.org/10.3390/v11060531DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6630879PMC
June 2019

Tick-Borne Encephalitis Virus Antibodies in Roe Deer, the Netherlands.

Emerg Infect Dis 2019 02;25(2):342-345

To increase knowledge of tick-borne encephalitis virus (TBEV) circulation in the Netherlands, we conducted serosurveillance in roe deer (Capreolus capreolus) during 2017 and compared results with those obtained during 2010. Results corroborate a more widespread occurrence of the virus in 2017. Additional precautionary public health measures have been taken.
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http://dx.doi.org/10.3201/eid2502.181386DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6346459PMC
February 2019

Emergence of tick-borne encephalitis (TBE) in the Netherlands.

Ticks Tick Borne Dis 2019 01 25;10(1):176-179. Epub 2018 Oct 25.

Laboratory for Medical Microbiology and Public Health, Hengelo, the Netherlands. Electronic address:

Recently, tick-borne encephalitis virus (TBEV) was detected in the Netherlands for the first time, in ticks collected in 2015 in the National Park Sallandse heuvelrug in response to the detection of anti-TBEV antibodies in roe deer. Hereafter, two human cases of autochthonous TBE have been reported, occurring in 2016. One case was geographically linked to the area of the previously reported ticks, which harbored a genetically divergent TBEV-Eu strain variant (TBEV-NL). So far these are the few reported events that point to endemic transmission of TBEV in the Netherlands and the true prevalence of TBEV and TBE disease in the Netherlands and its impact on the human population remains to be determined. We describe the third human case, identified in 2017, which geographically clusters with the aforementioned case and TBEV-positive ticks. We also describe the identification of another TBEV-NL-positive tick in the Netherlands, collected 2 years after the initial find in that same region (in 2017). These observations support the concept of continued circulation of TBEV-NL and the presence of a possible TBEV hot spot in the Sallandse Heuvelrug region.
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http://dx.doi.org/10.1016/j.ttbdis.2018.10.008DOI Listing
January 2019

Autochthonous Human Case of Seoul Virus Infection, the Netherlands.

Emerg Infect Dis 2018 17;24(12):2158-2163. Epub 2018 Dec 17.

Orthohantaviruses are a group of rodentborne viruses with a worldwide distribution. The orthohantavirus Seoul virus (SEOV) can cause hemorrhagic fever with renal syndrome in humans and is distributed worldwide, like its reservoir host, the rat. Cases of SEOV in wild and pet rats have been described in several countries, and human cases have been reported in the United Kingdom, France, Canada, and the United States. In the Netherlands, SEOV has previously been found in wild brown rats. We describe an autochthonous human case of SEOV infection in the Netherlands. This patient had nonspecific clinical symptoms of an orthohantavirus infection (gastrointestinal symptoms and distinct elevation of liver enzymes). Subsequent source investigation revealed 2 potential sources, the patient's feeder rats and a feeder rat farm. At both sources, a high prevalence of SEOV was found in the rats. The virus closely resembled the Cherwell and Turckheim SEOV strains that were previously found in Europe.
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http://dx.doi.org/10.3201/eid2412.180229DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6256391PMC
April 2019

Prevalence of spp. and Seoul hantavirus in brown rats () in four regions in the Netherlands, 2011-2015.

Infect Ecol Epidemiol 2018 26;8(1):1490135. Epub 2018 Jun 26.

Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands.

Background:   Brown rats () may carry pathogens that can be a risk for public health. Brown rats in the Netherlands were tested for the zoonotic pathogens spp. and Seoul hantavirus (SEOV), in order to obtain insight in their prevalence.

Methods And Results:   Cross-sectional studies were performed at four locations from 2011 to 2015. The rats were tested for spp. using real-time PCR and/or culture resulting in a prevalence ranging between 33-57%. Testing for SEOV was done through an adapted human Seoul hantavirus ELISA and real-time RT-PCR. Although at several locations the ELISA indicated presence of SEOV antibodies, none could be confirmed by focus reduction neutralization testing.

Conclusion:   The results indicate a widespread presence of spp. in brown rats in the Netherlands, including areas with a low leptospirosis incidence in humans. No evidence for circulation of SEOV was found in this study.
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http://dx.doi.org/10.1080/20008686.2018.1490135DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6022222PMC
June 2018

Modelling human Puumala hantavirus infection in relation to bank vole abundance and masting intensity in the Netherlands.

Infect Ecol Epidemiol 2017 24;7(1):1287986. Epub 2017 Mar 24.

Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.

This paper deals with modelling the relationship between human Puumala hantavirus (PUUV) infection, the abundance and prevalence of infection of the host (the bank vole), mast, and temperature. These data were used to build and parametrise generalised regression models, and parametrise them using datasets on these factors pertaining to the Netherlands. The performance of the models was assessed by considering their predictive power. Models including mast and monthly temperature performed well, and showed that mast intensity influences vole abundance and hence human exposure for the following year. Thus, the model can aid in forecasting of human illness cases, since (1) mast intensity influences the vole abundance and hence human exposure for the following year and (2) monitoring of mast is much more feasible than determining bank vole abundance.
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http://dx.doi.org/10.1080/20008686.2017.1287986DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5443058PMC
March 2017

Tick-Borne Encephalitis Virus in Ticks and Roe Deer, the Netherlands.

Emerg Infect Dis 2017 06;23(6):1028-1030

We report the presence of tick-borne encephalitis virus (TBEV) in the Netherlands. Serologic screening of roe deer found TBEV-neutralizing antibodies with a seroprevalence of 2%, and TBEV RNA was detected in 2 ticks from the same location. Enhanced surveillance and awareness among medical professionals has led to the identification of autochthonous cases.
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http://dx.doi.org/10.3201/eid2306.161247DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5443429PMC
June 2017

High Prevalence of Tula Hantavirus in Common Voles in The Netherlands.

Vector Borne Zoonotic Dis 2017 03 23;17(3):200-205. Epub 2017 Jan 23.

Centre for Infectious Disease Control, National Institute for Public Health and the Environment (RIVM) , Bilthoven, the Netherlands .

Tula virus (TULV) is a zoonotic hantavirus. Knowledge about TULV in the Netherlands is very scarce. Therefore in 2014, 49 common voles (Microtus arvalis) from a region in the south of the Netherlands, and in 2015, 241 common voles from regions in the north of the Netherlands were tested with the TULV quantitative RT-PCR. In the southern region, prevalence of TULV was 41% (20/49). In the northern regions, prevalence ranged from 12% (4/34) to 45% (17/38). Phylogenetic analysis of the obtained sequences showed that the regions fall within different clusters. Voles from the south were also tested on-site for the presence of hantavirus antibodies, but serology results were poorly associated with qRT-PCR results. These findings suggest that TULV may be more widespread than previously thought. No human TULV cases have been reported thus far in the Netherlands, but differentiation between infection by TULV or the closely related Puumala virus is not made in humans in the Netherlands, thus cases may be misdiagnosed.
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http://dx.doi.org/10.1089/vbz.2016.1995DOI Listing
March 2017

First human case of tick-borne encephalitis virus infection acquired in the Netherlands, July 2016.

Euro Surveill 2016 Aug;21(33)

Department of Neurology, Zuwe Hofpoort Hospital, Woerden, The Netherlands.

In July 2016, the first autochthonous case of tick-borne encephalitis was diagnosed in the Netherlands, five days after a report that tick-borne encephalitis virus (TBEV) had been found in Dutch ticks. A person in their 60s without recent travel history suffered from neurological symptoms after a tick bite. TBEV serology was positive and the tick was positive in TBEV qRT-PCR. TBEV infection should be considered in patients with compatible symptoms in the Netherlands.
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http://dx.doi.org/10.2807/1560-7917.ES.2016.21.33.30318DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4998423PMC
August 2016

Lack of evidence for zoonotic transmission of Schmallenberg virus.

Emerg Infect Dis 2012 Nov;18(11):1746-54

National Institute for Public Health and the Environment, Bilthoven, the Netherlands.

The emergence of Schmallenberg virus (SBV), a novel orthobunyavirus, in ruminants in Europe triggered a joint veterinary and public health response to address the possible consequences to human health. Use of a risk profiling algorithm enabled the conclusion that the risk for zoonotic transmission of SBV could not be excluded completely. Self-reported health problems were monitored, and a serologic study was initiated among persons living and/or working on SBV-affected farms. In the study set-up, we addressed the vector and direct transmission routes for putative zoonotic transfer. In total, 69 sheep farms, 4 goat farms, and 50 cattle farms were included. No evidence for SBV-neutralizing antibodies was found in serum of 301 participants. The lack of evidence for zoonotic transmission from either syndromic illness monitoring or serologic testing of presumably highly exposed persons suggests that the public health risk for SBV, given the current situation, is absent or extremely low.
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http://dx.doi.org/10.3201/eid1811.120650DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3559138PMC
November 2012

Circulation of group 2 coronaviruses in a bat species common to urban areas in Western Europe.

Vector Borne Zoonotic Dis 2010 Oct 7;10(8):785-91. Epub 2010 Jan 7.

National Institute for Public Health and the Environment, Bilthoven, The Netherlands.

Fecal samples of 211 bats representing 13 different bat species from 31 locations in the Netherlands were analyzed for the presence of coronaviruses (CoV) using a genus-wide reverse transcription (RT)-polymerase chain reaction. CoVs are known for their high potential for interspecies transmission, including zoonotic transmission with bats as reservoir hosts. For the first time, a group 2 CoV was found in a bat, Pipistrellus pipistrellus, in Europe. This is of particular interest for public health as the reservoir host is a species that is common to urban areas in most of Europe and notorious for its close interactions with humans. Four verspertilionid bat species were found to excrete group 1 CoVs, viz. Myotis daubentonii, M. dasycneme, P. pipistrellus, and Nyctalus noctula. The last species is a newly identified reservoir. The overall prevalence was 16.9% and positive bats were found at multiple widespread locations. The circulating group 1 CoV lineages were rather species associated than location associated.
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http://dx.doi.org/10.1089/vbz.2009.0173DOI Listing
October 2010

First genetic detection of Tula hantavirus in wild rodents in the Netherlands.

J Infect 2008 Dec 1;57(6):500-3. Epub 2008 Nov 1.

Centre for Infectious Disease Control Netherlands, National Institute for Public Health and the Environment (RIVM), P.O. Box 1, 3720 BA Bilthoven, The Netherlands.

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http://dx.doi.org/10.1016/j.jinf.2008.09.032DOI Listing
December 2008

Molecular epidemiology of Cryptosporidium in humans and cattle in The Netherlands.

Int J Parasitol 2008 Jun 4;38(7):809-17. Epub 2007 Nov 4.

National Institute for Public Health and the Environment (RIVM), Centre for Infectious Disease Control (Cib), Laboratory for Zoonoses and Environmental Microbiology (LZO), Antonie van Leeuwenhoeklaan 9, Bilthoven, The Netherlands.

The protozoan parasite Cryptosporidium is found world-wide and can cause disease in both humans and animals. To study the zoonotic potential of Cryptosporidium in The Netherlands we isolated this parasite from the faeces of infected humans and cattle and genotyped those isolates for several different markers. The overall genotyping results showed: for humans isolates, 70% Cryptosporidium hominis, 19% Cryptosporidium parvum, 10% a combination of C. hominis and C. parvum, and 1% Cryptosporidium felis; and for cattle isolates 100% C. parvum. Analysis of the genetic variants detected for the HSP70, ML1 and GP60 markers showed: for human isolates, one C. hominis and two C. parvum variants (C. parvum and C. parvum NL) for HSP70, one C. hominis and five C. parvum variants (C1, C2, C3, and C2 NL1 and C2 NL2) for ML1, four C. hominis (mainly IbA10G2) and four C. parvum variants (mainly IIaA15G2R1) for GP60; and the cattle isolates only C. parvum (not C. parvum NL1) for HSP70, C1 and C2 for ML1, and 17 different IIa sub-types (mainly IIaA15G2R1) for GP60. Molecular epidemiological analysis of the human data showed a C. hominis peak in autumn. The majority (80%) of the human cases were children aged between 0 and 9 years and >70% of these were caused by C. hominis. Patients >25 years of age were infected mainly with C. parvum. We conclude that C. hominis IbA10G2 is found at high frequencies in autumn in humans and not in cattle. The high prevalence of C. parvum IIaA15G2R1 in both humans and cattle indicates that cattle may be a reservoir for this sub-type in The Netherlands.
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http://dx.doi.org/10.1016/j.ijpara.2007.10.014DOI Listing
June 2008

Evidence for an increasing presence of Echinococcus multilocularis in foxes in The Netherlands.

Int J Parasitol 2008 Apr 12;38(5):571-8. Epub 2007 Oct 12.

Laboratory for Zoonoses and Environmental Microbiology, Centre for Infectious Disease Control, National Institute for Public Health and Environment (RIVM), Antonie van Leeuwenhoeklaan 9, 3720 BA, Bilthoven, The Netherlands.

Echinococcus multilocularis, a tapeworm causing alveolar echinococcosis which is considered a serious zoonosis known to affect humans, appears to be expanding its geographical range in Europe. We studied the emergence of the parasite in the European westernmost edge of its geographical distribution, based on two consecutive parasitological examinations of red foxes (Vulpes vulpes) sampled between 1996 and 2003 in The Netherlands. The average worm count increased from 2.6 worms per fox in the first surveillance to 16.6 worms per fox in the second. Using a mathematical model for a spatially spreading parasite, we found a strong indication that the parasite population is increasing in number and is spreading northward at the speed of 2.7 km per year. The reproduction number (R0), reflecting the parasite's transmission process, is estimated from the surveillance data and it is likely to be more than 1 but not exceeding a value of 4. We analysed a parasite control strategy by estimating the critical fox density for parasite elimination. We conclude that E. multilocularis is an emerging parasite in The Netherlands and thus in the western part of Europe. Control will be very difficult given the current high fox population density.
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http://dx.doi.org/10.1016/j.ijpara.2007.09.014DOI Listing
April 2008

Longitudinal analysis of tick densities and Borrelia, Anaplasma, and Ehrlichia infections of Ixodes ricinus ticks in different habitat areas in The Netherlands.

Appl Environ Microbiol 2006 Dec 6;72(12):7594-601. Epub 2006 Oct 6.

Microbiological Laboratory for Health Protection, National Institute for Public Health and the Environment, Antonie van Leeuwenhoeklaan 9, Bilthoven 3720 BA, The Netherlands.

From 2000 to 2004, ticks were collected by dragging a blanket in four habitat areas in The Netherlands: dunes, heather, forest, and a city park. Tick densities were calculated, and infection with Borrelia burgdorferi and Anaplasma and Ehrlichia species was investigated by reverse line blot analysis. The lowest tick density was observed in the heather area (1 to 8/100 m2). In the oak forest and city park, the tick densities ranged from 26 to 45/100 m2. The highest tick density was found in the dune area (139 to 551/100 m2). The infection rates varied significantly for the four study areas and years, ranging from 0.8 to 11. 5% for Borrelia spp. and 1 to 16% for Ehrlichia or Anaplasma (Ehrlichia/Anaplasma) spp. Borrelia infection rates were highest in the dunes, followed by the forest, the city park, and heather area. In contrast, Ehrlichia/Anaplasma was found most often in the forest and less often in the city park. The following Borrelia species were found: Borrelia sensu lato strains not identified to the species level (2.5%), B. afzelii (2.5%), B. valaisiana (0.9%), B. burgdorferi sensu stricto (0.13%), and B. garinii (0.13%). For Ehrlichia/Anaplasma species, Ehrlichia and Anaplasma spp. not identified to the species level (2.5%), Anaplasma schotti variant (3.5%), Anaplasma phagocytophilum variant (0.3%), and Ehrlichia canis (0.19%) were found. E. canis is reported for the first time in ticks in The Netherlands in this study. Borrelia lusitaniae, Ehrlichia chaffeensis, and the human granylocytic anaplasmosis agent were not detected. About 1.6% of the ticks were infected with both Borrelia and Ehrlichia/Anaplasma, which was higher than the frequency predicted from the individual infection rates, suggesting hosts with multiple infections or a possible selective advantage of coinfection.
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http://dx.doi.org/10.1128/AEM.01851-06DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1694262PMC
December 2006
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