Field samplings of Ixodus ricinus ticks from a tick-borne encephalitis virus micro-focus in Northern Zealand, Denmark

In 2008-2009 a tick-borne encephalitis virus (TBEV) micro-focus was detected in Northern Zealand, Denmark. No new cases of TBE with an epidemiological link to Northern Zealand has been reported since. Here we undertook to investigate Ixodus ricinus ticks from this endemic micro-focus in 2016 and 2017. In addition to TBEV, I. ricinus ticks may host other pathogens that include Borrelia spp., Babesia spp., Rickettsia spp. and Neoehrlichia mikurensis, together with various endosymbiont microorganisms. To detect multiple organisms we used a metagenomics PanVirus microarray and next-generation sequencing to examine the persistence and evolution of other emerging viruses, bacteria and parasites. Here we report the rise and fall of the Danish TBEV micro-focus in Northern Zealand. However, we identify for the first time in Danish I. ricinus ticks the presence of Uukuniemi virus in addition to a tick-borne phlebovirus and a range of bacteria.