Survival of Ixodes ricinus (Acari: Ixodidae) Under Challenging Conditions of Temperature and Humidity Is Influenced by Borrelia burgdorferi sensu lato Infection

Abstract

To determine whether Borrelia burgdorferi sensu lato (s.l.) inßuences tick survival under thermohygrometric stress, Ixodes ricinus (L.) (Acari: Ixodidae) questing ticks were tested under various relative humidities (13, 32, 51.5, 61, and 89% RH) at two different temperatures (12.5 and 25ЊC) and investigated for Borrelia infection. Survival rate of females was highest (77.6%), followed by males (51.6%), and nymphs (43.2%). The thermohygrometric factor that most importantly determined survival was saturation deÞcit (SD). As SD increased, tick survival rate decreased in all stages. Among the 1,500 ticks tested for B. burgdorferi s.l., 34.8% (n ϭ 522) were infected. Adult infection rate (39.6%) was higher than that of nymphs (25.5%). Infection load in real-time polymerase chain reaction ranged from 1 to 1.2 million spirochetes per tick. B. afzelii (39.7%), B. burgdorferi sensu stricto (12.1%), B. garinii (37.9%), B. myamotoi (3.6%), and B. valaisiana (23.8%) were recorded. B. garinii infected signiÞcantly less nymphs than adults whereas B. afzelii displayed the opposite trend. Survival rate of nymphal and adult I. ricinus was signiÞcantly enhanced by infection by B. burgdorferi s.l. ( 2 : nymph, P ϭ 0.008; adult, P ϭ 0.021). In adults, a negative effect of infection on tick survival was observed when spirochete load overcame a threshold estimated at 160,000 spirochetes per tick but not in nymphs. Moreover, ticks infected by B. afzelii survived better than other ticks (infected by other genospecies or not). The results here indicate that infection by B. burgdorferi s.l., and more speciÞcally infection by B. afzelii, confers survival advantages to I. ricinus under challenging thermohygrometric conditions.

Rickettsia spp. and its Effects on the Physiology and Behaviour of Dermacentor Variabilis

“…Infection status also did not influence supercooling point. This result is consistent with the research done by Hermann & Gern (2010) who showed that ticks infected with Borrelia are more resistant to inconsistent temperature and humidity environments even though Dermacentor variabilis is a different tick species and has different bacteria species.…”

Do the level of energy reserves, hydration status andBorreliainfection influence walking byIxodes ricinus(Acari: Ixodidae) ticks?

“…3. The percentage of high-fat fully hydrated (H&F), low-fat fully hydrated (L&F), and low-fat moderately hydrated (L&M) Ixodes ricinus ticks that walked towards the wet (light grey bars) or the dry end (white bars) of the arena after 2 h. common one (Casati et al 2004;Jouda et al 2004;Morán Cadenas et al 2007;Gern et al 2010;Herrmann and Gern, 2010). B. bavariensis (6·8%), formerly B. garinii OspA serotype 4, a newly described genospecies (Margos et al 2009), is reported for the first time in the area, although it was already described in Switzerland (Staatswald) (Hu et al 2001;Huegli et al 2002;Pérez et al manuscript submitted ).…”

Zoonotic Peculiarities of Borrelia burgdorferi s.l.: Vectors Competence and Vertebrate Host Specificity

“…In the interface of field collected I. ricinus infected by different quantity of representatives of 4 species Borrelia d e t e r m i n e d b y r e a l t i m e P C R a n d RLB a very interesting fact was discovered: the better surviving of adult ticks infected by mean doses of pathogens (Herrmann & Gern, 2010). This phenomenon was a brilliant confirmation of prof. Alekseev (1984) theory that among other criteria of interface specificity in the couple "vectorpathogen" the existence of optimum pathogen doses (mean ones) do exist not only in the pairs "Leishmania-sand flies", plague agent and fleas (Alekseev, 1984), "Tick-borne encephalitis (TBE) virus -Ixodes persulcatus" (Alekseev & Kondrashova, 1985), but in the couple "Borrelia-Ixodes ticks" (Herrmann & Gern, 2010).…”

“…This phenomenon was a brilliant confirmation of prof. Alekseev (1984) theory that among other criteria of interface specificity in the couple "vectorpathogen" the existence of optimum pathogen doses (mean ones) do exist not only in the pairs "Leishmania-sand flies", plague agent and fleas (Alekseev, 1984), "Tick-borne encephalitis (TBE) virus -Ixodes persulcatus" (Alekseev & Kondrashova, 1985), but in the couple "Borrelia-Ixodes ticks" (Herrmann & Gern, 2010).…”