First autochthonous cases of TBE detected in the Netherlands, July 2016

First autochthonous cases of TBE detected in the Netherlands, July 2016

• 1.
  First autochthonous casesof tick-borne encephalitis detected in the Netherlands, July 2016 B. Schimmer(1) , J. Reimerink(1) , V. Hira(2) , F. Geeraedts(3) , B. Rockx(1) , C. Swaan(1) , S. Spit(4) , D. Brandwagt(5) , C.C. van den Wijngaard(1) , H. Sprong(1) , A. Hofhuis(1) 1. Centre for Infectious Disease Control , National Institute for Public Health and the Environment (RIVM), Bilthoven, the Netherlands. 2. St Antonius Hospital, Nieuwegein, the Netherlands. 3. Laboratory for Medical Microbiology and Public Health, Hengelo, The Netherlands. 4. Municipal Health Service Twente, Enschede, the Netherlands. 5. Municipal Health Service Utrecht region, Zeist, the Netherlands. Contact: [email protected] Background • Until recently, tick-borne encephalitis virus (TBEV) was thought to be absent in the Netherlands. • Imported tick-borne encephalitis (TBE) is considered rare in the Netherlands. During 2010-2015: 6 imported cases, of which 4 with travel history to Austria, 1 to Germany and 1 had an unknown destination. • In 2015, questing Ixodes ricinus ticks (1160 nymphs and 300 adults) were collected from 7 locations at national park “Sallandse heuvelrug”, where deer sera, collected in 2010, tested positive for TBEV antibodies. TBEV-Eu was detected by RT-PCR in the collected ticks (Figure 1) with a prevalence of 0.09% in nymphs and 0.33% in female adult ticks. Methods • On 30 June 2016, this signal was reported through the weekly Communicable Disease Threats Report and (Lab)Inf@ct, creating awareness of possible autochthonous TBE cases and to encourage testing for TBE in patients with compatible symp- toms without recent travel history. Results • In July 2016, 5 days after these mailings were released, the first autochthonous case of TBE was diagnosed in Utrecht province, 9 days later, a second case was detected in Overijssel province. • Both cases - are male (aged 67 and 44) without a recent travel history. - had a characteristic biphasic course with flu-like symptoms starting in June and were hospitalised with neurological symptoms. - were positive for TBEV-specific IgM and IgG and TBEV neutralising antibodies in serum. - were positive for TBEV-specific IgG in cerebrospinal fluid (CSF) and CSF of the second case was borderline IgM-positive. - had a recent tick bite most likely acquired in a national park. First case during a hike in national park ”Utrechtse Heuvelrug”, the second case resides in a house with garden adjacent to national park ”Sallandse Heuvelrug” and frequently runs in this park. • A tick collected from the first case tested TBEV-positive in qRT-PCR. Interestingly, preliminary data showed that this TBEV was genetically distinct from the TBEV found in Dutch ticks from the Sallandse Heuvelrug suggesting circulation of multiple TBEV in the Netherlands. Discussion conclusions • Dutch autochthonous TBE cases were diagnosed shortly after national awareness was raised on TBEV presence in ticks. • TBE should now also be considered in patients with compatible symptoms without recent travel history. • A case register, case definitions based on ECDC guidelines and a case questionnaire have been established for epidemiological surveillance. • Positive TBEV findings in ticks and deer (2010) and 2 autochthonous human cases (2016) strongly suggest TBE is endemic in the Netherlands. • TBE situation on EU level: TBE is on the rise, with regular reports of new natural foci. • In neighboring countries: Germany reported increased TBE incidence in 2016, also in previously unaffected regions. Belgium reports presence of TBEV neutralising antibodies in cattle, deer and wild boar during 2014-2016. Research recommendations • Assess geographic spread of TBEV through serological screening of deer in 2016, followed by tick collection in areas with seropositive deer. • Assess TBEV seroprevalence in free-ranging sheep flocks in the 2 national parks with autochthonous cases. • Determine seroprevalence and risk factors for TBEV IgG antibodies among occupational groups highly exposed to tick bites. • Retrospective screening for TBEV antibodies in sera and CSF of patients negative for neuroborreliosis residing near the “Sallandse heuvelrug” national park area. Further reading: • de Graaf JA et al. First human case of tick-borne encephalitis virus infection acquired in the Netherlands, July 2016. Euro Surveill. 2016 Aug 18;21(33). • Jahfari S et al. Tick-borne encephalitis virus in ticks and roe deer, the Netherlands (submitted). Figure 1. Serological screening of roe deer sera (n=297) collected in 2010. Ixodes ricinus ticks (n=1460) collected from national park “Sallandse heuvelrug” in 2015, where deer sera tested TBEV-positive. (Figure courtesy of S. Jahfari)  6 TBEV-positive deer sera (Vienna Units/ml 125)  7 TBEV-borderline positive deer sera (Vienna Units/ml 64-124) 284 TBEV-negative deer sera (Vienna Units/ml 64)  Ticks tested TBEV-positive by PCR Published by National Institute for Public Health and the Environment (RIVM) Antonie van Leeuwenhoeklaan 9 3721 MA Bilthoven P.O. Box 1 | 3720 BA Bilthoven | The Netherlands www.rivm.nl/en 009400