Prevalence and genotyping of tick-borne encephalitis virus in questing Ixodes ricinus ticks in a new endemic area in western Switzerland.

Tick-borne encephalitis virus (TBEV) is the causative agent of tick-borne encephalitis (TBE) and causes neurological disease in humans in Eurasia. TBEV is transmitted by ticks of the genus Ixodes. Currently 10,000-12,000 clinical cases are reported annually in approximately 30 TBE endemic countries. Since 1990 the epidemiology of TBE is characterized by a global increase of clinical cases and an expansion of risk areas. Similar trends are also observed in Switzerland but few studies confirmed the emergence of new TBE foci by detecting viral RNA in field-collected ticks. In this study, free-living Ixodes ricinus (L.) ticks from one nonendemic and three new TBE endemic regions located in the Western part of Switzerland were screened during four consecutive years (2007-2010) for the presence of TBEV. A total of 9,868 I. ricinus ticks (6,665 nymphs and 3,203 adults) were examined in pools for TBEV by real-time reverse transcription polymerase chain reaction. Our results confirmed the presence of viral RNA in 0.1% (6/6120) of questing ticks collected in one new endemic region. Among TBE endemic sites, the minimal infection rate per 100 ticks tested ranged from 0.21 (1/477) to 0.95 (1/105). Four positive samples were sequenced and phylogenetic analysis of the NS5 gene showed that all TBEV nucleotide sequences belonged to the European subtype and were split into two distinct lineages originating probably independently from two distinct foci located North-East and East of the study region.

Microclimate and the zoonotic cycle of tick-borne encephalitis virus in Switzerland.

The focal distribution of tick-borne encephalitis virus (TBEV; Flaviviridae, Flavivirus) appears to depend mainly on cofeeding transmission between infected Ixodes ricinus L. nymphs and uninfected larvae. To better understand the role of cofeeding ticks in the transmission of TBEV, we investigated tick infestation of rodents and the influence of microclimate on the seasonality of questing I. ricinus ticks. A 3-yr study was carried out at four sites, including two confirmed TBEV foci. Free-living ticks and rodents were collected monthly, and microclimatic data were recorded. A decrease in questing nymph density was observed in 2007, associated with low relative humidity and high temperatures in spring. One site, Thun, did not show this decrease, probably because of microclimatic conditions in spring that favored the questing nymph population. During the same year, the proportion of rodents carrying cofeeding ticks was lower at sites where the questing nymph density decreased, although the proportion of infested hosts was similar among years. TBEV was detected in 0.1% of questing ticks, and in 8.6 and 50.0% of larval ticks feeding on two rodents. TBEV was detected at all but one site, where the proportion of hosts with cofeeding ticks was the lowest. The proportion of hosts with cofeeding ticks seemed to be one of the factors that distinguished a TBEV focus from a non-TBEV focus. The enzootic cycle of TBEV might be disrupted when dry and hot springs occur during consecutive years.

Comparisons of glycosylated and nonglycosylated amniotic fluid prolactins in normal second- and third-trimester pregnancies.

Prolactins in glycosylated and nonglycosylated form were isolated from 218 second- and third-trimester amniotic fluid samples by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, electrotransferred to nitrocellulose paper, and probed with anti-human prolactin serum and protein A labeled with iodine 125. The glycosylated and nonglycosylated prolactin bands were exposed by autoradiography. The bands were analyzed by densitometry, and the ratio of glycosylated to total (glycosylated + nonglycosylated) prolactin was calculated (glycosylated/total ratio) and compared with matched prolactin radioimmunoassay measurements. Both radioimmunoassay-measured and nonglycosylated prolactin decreased from the second to the third trimester whereas glycosylated prolactin concentrations remained unchanged. Concomitantly, glycosylated/total prolactin ratios increased significantly (p less than 0.001). The correlation of radioimmunoassay-measured prolactin was closer to nonglycosylated prolactin (r2 = 0.32, p = 0.00001) than to glycosylated prolactin (r2 = 0.02, p = 0.06). We suggest that the proportion of amniotic fluid glycosylated prolactin increases with length of gestation and that glycosylation of prolactin is inversely related to total prolactin secretion. Furthermore, prolactin's immunoreactivity correlated more closely to the nonglycosylated-prolactin variant, suggesting that radioimmunoassay of prolactin poorly recognizes the glycosylated prolactin form.