Tick-Borne Encephalitis Virus Habitats in North East Germany: Reemergence of TBEV in Ticks after 15 Years of Inactivity

Abstract

The incidence of tick-borne encephalitis has risen in Europe since 1990 and the tick-borne encephalitis virus (TBEV) has been documented to be spreading into regions where it was not previously endemic. In Mecklenburg-West Pomerania, a federal state in Northern Germany, TBEV was not detectable in over 16,000 collected ticks between 1992 and 2004. Until 2004, the last human case of TBE in the region was reported in 1985. Following the occurrence of three autochthonous human cases of TBE after 2004, however, we collected ticks from the areas in which the infections were contracted. To increase the chance of detecting TBEV-RNA, some of the ticks were fed on mice. Using nested RT-PCR, we were able to confirm the presence of TBEV in ticks for the first time after 15 years. A phylogenetic analysis revealed a close relationship between the sequences we obtained and a TBEV sequence from Mecklenburg-East Pomerania published in 1992 and pointed to the reemergence of a natural focus of TBEV after years of low activity. Our results imply that natural foci of TBEV may either persist at low levels of activity for years or reemerge through the agency of migrating birds.

Borrelia miyamotoi and Borrelia burgdorferi (sensu lato) identification and survey of tick-borne encephalitis virus in ticks from north-eastern Germany

“…Bavaria and Baden-Wuerttemberg) but sporadic cases were also reported from the upper north regions of the country, recently including Mecklenburg-Western Pomerania [26]. Signs of TBEV circulation in this area were also shown in 2007 by detection of TBEV RNA in I. ricinus ticks [28] and identification of anti-TBEV antibodies in small ruminants [30], and wildlife [29]. Even though we did not detect TBEV RNA in the collected ticks, several factors could contribute to a future expansion of the virus foci in Mecklenburg-Western Pomerania.…”

“…In 2004, the first autochthonous human case was registered after 19 years [27]. Furthermore, detection of TBEV in questing I. ricinus was found in 2007 for the first time since 1992 [28]. Later studies found anti-TBEV-IgG antibodies in wild game [29], sheep and goats [30].…”

Disappearance of TBEV Circulation among Rodents in a Natural Focus in Alsace, Eastern France

“…TBEV thus persists under a limited set of biotic and abiotic conditions. Some natural TBEV foci might be unstable over time when the conditions for TBEV persistence are not fulfilled anymore, but such instability has rarely been observed in the field [ 14 ].…”

First detection of tick-borne encephalitis virus in Ixodes ricinus ticks and their rodent hosts in Moscow, Russia

“…Furthermore, the detection of new TBEV foci has been reported in Sweden (Haglund, 2002;Jaenson et al, 2012) and Norway (Csango et al, 2004;Haglund, 2002;Skarpaas et al, 2006Skarpaas et al, , 2004. There is evidence regarding the reactivation of old foci of TBEV, which for a long time (decades) have been inactive, thus turning the places into a risk area (Frimmel et al, 2014;Jääskeläinen et al, 2006;Kristiansen, 2002).…”