Influence of saturation deficit and temperature on Ixodes ricinus tick questing activity in a Lyme borreliosis-endemic area (Switzerland)

Abstract

Questing Ixodes ricinus ticks were sampled monthly in a periurban mixed forest at Neuchâtel, Switzerland, in 1996, 1997, and 1998. A total of 5,530 I. ricinus nymphs and 1,385 adults were collected. The emergence of questing tick populations in spring varied among years in relation to the air temperature. The monthly variation in questing nymph density was negatively correlated with the saturation deficit; there was a strong decrease in tick numbers in late spring and summer as soon as the saturation deficit increased. A variation in tick density in relation to the saturation deficit was also observed between years; the tick density was high when the saturation deficit was low during spring and summer (1997) and was low when the saturation deficit was high (1998). During the 3-year study period, marked climatic differences among years highlighted the influence of temperature and saturation deficit on the phenology of ticks.

Meteorological Influences on the Seasonality of Lyme Disease in the United States

“…Newly emerged nymphs of some Ixodes species may undergo a behavioral diapause between emergence and host-seeking activity (questing) that is dependent on climatic conditions such as temperature. 9,[51][52][53][54] In addition, larvae that feed later in the summer or fall may undergo developmental (morphogenetic) diapause and overwinter before molting. 9,52,[55][56][57] In this case larval development and nymphal emergence would likely be subject to cumulative spring temperatures.…”

“…Nymphal I. scapularis activity increases with ambient relative humidity, 10 and the activity and density of other ixodid ticks is also negatively correlated with saturation deficit. 51,58 Ixodes scapularis nymphs also reach higher questing heights at higher relative humidity levels, 11 which may increase their likelihood of encountering humans. Higher saturation deficits may delay the beginning of the Lyme disease season because it decreases questing activity and decreases the likelihood of questing nymphs encountering humans.…”

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

“…makes ticks more resistant to heat and desiccation. Furthermore, in 1998 in Neuchâ tel, Switzerland, a lower density of questing I. ricinus ticks was observed due to high desiccating climatic conditions (Perret et al 2000) and an unexpectedly high percentage of nymphs harboring high numbers of B. burgdorferi s.l. was recorded compared with the previous and following years (L.G., unpublished data).…”

Assessment of the risk of contracting Lyme disease in areas with significant human presence

“…Two peaks were evident in the seasonal abundance of active adults of I. ricinus at the Kljajicevo, Mt. Avala, and Bovan Lake localities; the higher spring peak that occurred during the period of May-June and the lower autumn peak that occurred during the period of September-October, a pattern that is characteristic of populations of this species in the Temperate Zone (Milutinovic, 1992;Milutinovic and Bobic, 1997;Korenberg, 2000;Perret et al, 2000;Milutinovic and Radulovic, 2002). Seasonal dynamics in the abundance of active nymphs of I. ricinus at the investigated localities achieved a peak during the period of June-July.…”