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.

In this study, we measured the phenology of Ixodes ricinus ticks and their infection with Borrelia burgdorferi sensu lato (sl) simultaneously along an altitudinal gradient to assess the impact of climate on the phenology of ticks and on their infection with B. burgdorferi sl. From 1999 to 2001, free-living I. ricinus ticks were collected monthly by flagging vegetation at three different altitudes (620, 740, and 900 m above sea level) on the slope of a mountain in Chaumont (Neuchâtel, Switzerland). I. ricinus ticks were examined for the presence of B. burgdorferi sl by using direct fluorescent antibody assay and isolation of spirochetes. Borrelia species were characterized by polymerase chain reaction followed by restriction fragment-length polymorphism. Tick density and tick phenology varied with altitude. Although the peak tick density decreased and the onset of ticks was delayed with altitude, the phenology was much more stable among years at the highest altitudes than at the lowest. The prevalence of B. burgdorferi infection in nymphs and adults decreased with altitude. The prevalence of infection differed significantly among years, and it was significantly higher in adults (30%) than in nymphs (21%). B. burgdorferi infection in adults was positively related with adult density, but this was not observed for nymphs. Five B. burgdorferi sl genospecies were successfully isolated: B. garinii, B. burgdorferi sensu stricto, B. afzelii, B. valaisiana, and B. lusitaniae. Mixed infections were obtained from five of 140 infected ticks. The greatest diversity in Borrelia species was observed at the lowest altitude where all five Borrelia species were present, whereas at the two highest altitudes, B. lusitaniae was not observed.

SUMMARY The behaviour of Ixodes ricinus nymphs was recorded in 10-day experiments using computer-assisted video-tracking, in the absence of any host stimuli. These ticks switch spontaneously from questing in a desiccating atmosphere to quiescence in a water-saturated atmosphere after dark. Quantification of both questing and quiescence duration demonstrates that questing duration is inversely related to saturation deficit whereas quiescence duration is not. Distance walked after quiescence increased with desiccating conditions, while the distance walked after questing remained unchanged. Almost all locomotor activities of I. ricinus occurred during darkness under either a 14 h:10 h L:D or a 8 h:4 h L:D cycle. We established that all life stages of I. ricinus are equipped to sense shifts in light intensity with bilaterally placed strings of photoreceptors. This permits I. ricinus to use onset of darkness to trigger mobility when desiccation risk is reduced in nature.

We studied the relationship between climate and Ixodes ricinus L. tick behavior by following every day the proportion of ticks questing in a tick population placed in polyamide mesh-delimited arenas in the Þeld. Simultaneously, the phenology of the questing density of nymphs and adults was studied by sampling ticks in a close location. At any time during the year, the proportion of questing adults was signiÞcantly higher (mean 24%) than the proportion of questing nymphs (mean 12%). The proportion of questing nymphs and adults decreased stepwise with time. The proportion of questing adults partially recovered after each decrease. In contrast, the proportion of questing nymphs was strongly reduced during a single short period in June and did not recover even partially. Decrease in the proportion of questing ticks was strongly related either to a peak in saturation deÞcit or to a drop in maximal relative humidity. No increase in the proportion of questing nymphs was observed in the arenas during autumn, although an autumn peak of nymphs was observed at the sampling location close to the arenas. This suggests that the autumn peak of nymphs observed in nature was due to newly emerged spring-fed larvae and not to reactivated spring active nymphs.

Many women of childbearing age from sub-Saharan Africa use topical skin lighteners, some of which present a risk of toxic systemic effects. The goals of this study were to evaluate, in this environment, the frequency of this practice during pregnancy, as well as eventual consequences on pregnancy. Ninety-nine women from 6 to 9 months pregnant were randomly selected among those attending a standard maternal centre in Dakar for a prenatal visit. Investigations consisted of questions about the use of skin lighteners, a standard clinical examination, follow-up until delivery and a morning blood sample for plasma cortisol levels. Sixty-eight of the 99 selected women used skin lighteners during their current pregnancy, the main active ingredients being hydroquinone and highly potent steroids (used by 64 and 28 women, respectively). No difference in the main outcomes of pregnancy were found between skin-lightener users and the others; however, women using highly potent steroids, when compared with those who did not, had a statistically significant lower plasma cortisol level and a smaller placenta, and presented a higher rate of low-birth-weight infants. Skin lightening is a common practice during pregnancy in Dakar, and the use of steroids may result in consequences in the mother and her child.