Prospective study on the incidence of infection by Borrelia burgdorferi sensu lato after a tick bite in a highly endemic area of Switzerland.

The periurban forest of Neuchâtel (Switzerland) is a high-risk area for Lyme Borreliosis, due to a high density of infected Ixodes ricinus ticks. In this study, we evaluated the risk of subclinical (seroconversion) and clinical infection after a tick bite in Neuchâtel inhabitants from 2003 to 2005. Inhabitants have been invited, through media, to visit a physician after a tick bite. A questionnaire was filled out and two blood samples were taken at 8-week interval. EIA screening tests for IgM and IgG (IMX system, Abbott) were applied for paired sera. In case of a change in antibody titres between both samples, a homemade Western-blot using Borrelia afzelii, B. burgdorferi sensu stricto and B. garinii as antigens was performed. Participants were included into two groups. Group one included asymptomatic participants (n=255). Among them, nine (3.5%) seroconverted with seroconversion rates varying between 6.8% in 2003, 2.1% in 2004 and 2.3% in 2005. Participants who developed clinical symptoms of LB were included into group two (n=14). Erythema migrans (EM) was reported in 5.2% of participants (5.2%), varying between 7.5% in 2003, 5% in 2004 and 3.4% in 2005. Ticks obtained from 186 participants were examined for B. burgdorferi infection by PCR/Reverse Line Blotting, and by Real Time PCR and tick attachment duration was estimated. Among I. ricinus ticks collected from participants, 32.8% were infected by B. burgdorferi sensu lato. B. afzelii predominated among these ticks. Globally, 65.9% of nymphs remained attached for more than 24h whereas only 38.3% of female ticks remained attached for more than 24h. We observed that 6.6% and 2.4% of participants bitten by infected and uninfected ticks, respectively, developed EM.

Tick bites in a Lyme borreliosis highly endemic area in Switzerland.

The duration of tick feeding is an important indicator to evaluate the risk of Borrelia burgdorferi sensu lato transmission, which increases considerably with the blood meal duration. This blood meal duration may be estimated from scutal index, the ratio between body length (idiosoma) and scutum width. For the estimation of blood meal duration in Ixodes ricinus, nymphal and adult female ticks were detached at predetermined intervals (24, 48, 72, and 96h) from laboratory mice and rabbits and their scutal index calculated. From this, non-linear regression equations were developed to determine the duration of attachment for nymphal and adult female I. ricinus ticks. As part of an epidemiological study addressing the risk of subclinical (seroconversion) and clinical infections after a tick bite in the Neuchâtel area (Switzerland) over 3 years (2003-2005), duration of tick attachment and anatomical site of bites collected on participants as well as seasonal distribution of tick bites were studied. Tick attachment duration was estimated in all ticks collected during this study (n=261). Nymphs were attached for a mean (+/- standard error, SE) of 31.6h (+/-2.6) and females for a mean (+/-SE) of 29.6h (+/-3.2). Most nymphs were removed after 24h of blood meal whereas most females were removed before 24h. Legs were the major anatomical sites of bites for women (40.7%), men (44.4%), and almost all age classes. Only children <10 years old were bitten more frequently on the head (41.2%) and on the neck (38.5%) than participants >10 years. The majority of tick bites were recorded from May to July during the 3 years. Attachment sites can influence the discovery of ticks, hence the duration of the tick bite. A detailed body examination after each outing in forest and an early withdrawal of an attached tick is an effective way to prevent Lyme borreliosis.

An outbreak of scabies: a forgotten parasitic disease still present in Switzerland.

INTRODUCTION: Scabies, a contagious parasitic dermatosis, has a worldwide distribution but is considered a "disease of the poor" in resourcerich countries. However, it can cause major public health problems following outbreaks in industrialised countries. The following study describes a large outbreak of scabies involving several health care institutions in the canton of Neuchâtel, Switzerland. PATIENTS AND METHODS: After reporting a case of crusted scabies hospitalised for several months (for other comorbidities) in various health care institutions, a "scabies task force" was created in order to detect further cases by contact tracing. Suspected cases were reported to public health authorities, with notification of the health care institutions where cases or exposed patients had been transferred, and information to general practitioners and dermatologists of the entire area (100,000 inhabitants), RESULTS: Three health care institutions (a rehabilitation clinic, a 200-bed acute care hospital, a small hospital with a haemodialysis unit) were involved. Overall, 24 cases of scabies were detected, 12 among inpatients after exposure within the health care institutions, and 12 among household or other close contacts. 116 health care providers exposed to cases within the health care institutions were investigated with negative results for scabies. After the creation of the task force, no further transmission of scabies was observed. Prolonged misdiagnosis of crusted scabies as well as frequent transfers of cases between various health care institutions facilitated the outbreak. Barrier precautions for health care workers caring for patients with skin lesions even in the absence of a diagnosis of transmissible disease appeared to be efficacious since no transmission to health care workers could be detected. CONCLUSIONS: This is the first reported observation of a large scabies outbreak involving health care institutions in Switzerland. Our outbreak demonstrates that it is not an obsolete disease and that a high index of suspicion must be maintained in order to promptly detect difficult cases and to curb potential outbreaks.