Integration of a Tick-Borne Encephalitis Virus andBorrelia burgdorferisensu lato into Mountain Ecosystems, Following a Shift in the Altitudinal Limit of Distribution of Their Vector,Ixodes ricinus(Krkonoše Mountains, Czech Republic)

Abstract

The altitudinal shift in the limit of Ixodes ricinus occurrence above the previously established altitude of 750 m above sea level has been monitored over the long-term (2002-2008) in the Krkonose Mts. (Giant Mts.), the highest in the Czech Republic, along two vertical transects in their eastern and central parts (600-1020 and 600-1270 m). Ticks were collected by flagging three times annually, and examined individually by PCR or RT-PCR for the presence of Borrelia burgdorferi sensu lato or tick-borne encephalitis virus (TBEV). A total of 5999 I. ricinus ticks were tested. TBEV RNA was detected in 26 ticks at up to 1140 m. Demonstration of TBEV in two larvae of I. ricinus indicates transovarial transmission. Similar infection rates in larvae and nymphs show vertical transmission in TBEV circulation to be very important under these mountain conditions. B. burgdorferi sensu stricto was found at up to 1040-1065 m, Borrelia garinii and Borrelia afzelii up to 1080-1140 m, and Borrelia valaisiana up to 1270 m. The total infection rates of nymphs and larvae were 7.3% and 2%, respectively. B. garinii was the most prevalent (37%), followed by B. afzelii (29%), B. burgdorferi s.s. (11%), and B. valaisiana (9%). Double to quadruple coinfections were detected in 32% of the infected ticks, most frequently B. garinii/B. afzelii. Predominance of B. garinii and B. valaisiana over B. afzelii suggests that small passerine birds moving on the ground are responsible for permanent local populations of I. ricinus in mountain localities with low numbers of small terrestrial mammals. The detection of B. burgdorferi sensu lato and TBEV in host-seeking larvae indicates an autochthonic infection. Upon analysis of the local climate we consider climate warming to be responsible for the spreading of ticks and tick-transmitted pathogens to higher altitudes.

Analysis of meteorological effects on the incidence of tick-borne encephalitis in the Czech Republic over a thirty-year period

“…When scarce, the local tick populations only caused sporadic cases of TBE. In the early 1990s, the local I. ricinus populations became more abundant, similarly to other areas at higher altitudes in the Czech Republic [18,24]. The consequently increased circulation of TBEV, at first among wild animal hosts, eventually led to a higher incidence of TBE in humans.…”

“…Detailed field research has demonstrated the predominant role of ambient temperature on both the activity of ticks [17] and its long-term effects on their distribution to areas previously not inhabited by them in the CZ, primarily to higher altitudes [18].…”

The Health Effects of Climate Change in the WHO European Region

“…Observed and Projected Effects (6) Malaria in Portugal [89] Malaria in Germany [92] Malaria in Turkey [90] Aedes albopictus in Europe [98] Malaria in Spain [91] Recent and future Aedes albopictus suitability [99] WNF in Israel [93] Dengue in Europe [100] WNF in Hungary and Austria [94] Dengue in Europe [103] Chikungunya in Italy [96] Dengue and Chikungunya in Europe [101] Dengue in Madeira 2012 [102] Ticks transmit climate-sensitive infectious diseases including Crimean Congo hemorrhagic fever [108,109], Lyme borreliosis [110][111][112], tick-borne encephalitis [113][114][115][116][117][118][119][120] and Tularemia [121]. Several studies identified in the literature review do not report on climate change and tick-transmitted diseases, but instead describe changes in tick distribution, specifically in the United Kingdom [122], Slovenia [123], and the Czech Republic [124].…”

Detection of Borrelia burgdorferi Sensu Stricto ospC Alleles Associated with Human Lyme Borreliosis Worldwide in Non-Human-Biting Tick Ixodes affinis and Rodent Hosts in Southeastern United States

“…ticks belonging to the Ixodes ricinus complex. All parasitic stages of these ticks are able to transmit the pathogen, but the nymphal stage appears to be the most important one (47)(48)(49)(50). A notable exception is the Asian species I. persulcatus, in which the female tick, not the nymph, is a primary vector of B. burgdorferi sensu lato.…”