Search

Lyme disease (LD) and other tick-borne diseases are emerging across Canada. Spatial and temporal LD risk is typically estimated using acarological surveillance and reported human cases, the former not considering human behavior leading to tick exposure and the latter occurring after infection.

Lyme disease (LD) risk is emerging rapidly in Canada due to range expansion of its tick vectors, accelerated by climate change. The risk of contracting LD varies geographically due to variability in ecological characteristics that determine the hazard (the densities of infected host-seeking ticks) and vulnerability of the human population determined by their knowledge and adoption of preventive behaviors. Risk maps are commonly used to support public health decision-making on Lyme disease, but the ability of the human public to adopt preventive behaviors is rarely taken into account in their development, which represents a critical gap. The objective of this work was to improve LD risk mapping using an integrated social-behavioral and ecological approach to: (i) compute enhanced integrated risk maps for prioritization of interventions and (ii) develop a spatially-explicit assessment tool to examine the relative contribution of different risk factors.

Public health management of Lyme disease (LD) is a dynamic challenge in Canada. Climate warming is driving the northward expansion of suitable habitat for the tick vector, Ixodes scapularis. Information about tick population establishment is used to inform the risk of LD but is challenged by sampling biases from surveillance data. Misclassifying areas as having no established tick population underestimates the LD risk classification.

Context:In 1994, immunization against hepatitis B was implemented in schools in Quebec, targeting grade 4 students. In 1996–1997 and 1997–1998, one Local Community Service Centre (CLSC) replaced the school-based program in its district with vaccination offered in community clinics after school hours. The aim of the current study was to compare the effectiveness and costs of school-based and clinic-based programs. Methods:Vaccination coverage data were collected in the CLSC with the clinic-based program (CBP), and in three matched CLSCs with a school-based program (SBP), from 1994 to 2000. Surveys were conducted to estimate costs to parents, to schools and to CLSCs in 1997–1998. Results:With the implementation of the CBP, the vaccination coverage fell to 73%, compared with over 90% in the SBPs. Coverage increased to 90% when the CBP was abandoned. Costs to the CLSC were not much lower in the CBP. Societal costs were $63 per student vaccinated in the CBP, and ≤40 in the SBPs. Conclusion:Results demonstrate the advantage of a SBP over a CBP for the immunization of schoolchildren. Contexte:Un programme de vaccination contre l’hépatite B existe au Québec depuis 1994 où les élèves de 4e année sont vaccinés à l’école. En 1996–1997 et 1997–1998, un Centre local des services communautaires (CLSC) a remplacé le programme scolaire dans son territoire par la vaccination offerte lors de cliniques communautaires spéciales, après les heures de classe. Le but de cette étude était de comparer l’efficacité et les coûts sociétaux du programme de vaccination offert à l’école et celui lors de cliniques communautaires. Méthode:L’étude fut réalisée dans le CLSC offrant la vaccination en clinique (VC) et dans trois CLSC appariés offrant la vaccination en milieu scolaire (VS). Les couvertures vaccinales furent comparées de 1994 à 2000. Des enquêtes furent menées pour décrire les coûts assumés par les parents, les écoles et les CLSC pour l’année 1997–1998. Résultats:La couverture vaccinale obtenue par la VC en 1997–1998 a chuté à 73 % alors qu’elle était supérieure à 90 % dans le groupe contrôle. Le taux de vaccination a augmenté à plus de 90 % lorsque la VC a été abandonnée. La VC n’a pas entraîné de réduction importante des coûts pour le CLSC. Le coût sociétal par élève vacciné par la VC a été de 63 $, mais ≤40 $ avec la VS. Conclusion:Ces résultats démontrent les nets avantages d’offrir la vaccination en milieu scolaire.

BACKGROUND: Public health authorities in Quebec have responded to the progressive emergence of Lyme disease (LD) with surveillance activities and education for family physicians (FPs) who are key actors in both vigilance and case management.OBJECTIVES: To describe FPs’ clinical experience with LD, their degree of knowledge, and their practices in two areas, one with known infected tick populations (Montérégie) and one without (regions nearby Montérégie).METHODS: In the present descriptive cross-sectional study, FPs were recruited during educational sessions. They were asked to complete a questionnaire assessing their clinical experience with Lyme disease, their knowledge of signs and symptoms of LD, and their familiarity with accepted guidelines for diagnosing and treating LD in two clinical scenarios (tick bite and erythema migrans).RESULTS: A total of 201 FPs participated, mostly from Montérégie (n=151). Overall, results revealed a moderate lack of knowledge and suboptimal practices rather than systematically insufficient knowledge or inadequate practices. A majority of participants agreed to more education on LD. As expected, FPs from Montérégie had a higher clinical experience with tick bites (57% versus 25%), better knowledge of LD endemic areas in Canada and erythema migrans characteristics, and better management of erythema migrans (72% versus 50%).CONCLUSION: The present study documented the inappropriate intention to order serology tests for tick bites and the unjustified intention to use tick analysis for diagnostic purposes. Such practices should be discouraged because they are unnecessary and overuse collective laboratory and medical resources. In addition, public health authorities must pursue their education efforts regarding FPs to optimize case management.

Lyme disease (LD) is emerging in Canada because of the northward expansion of the geographic range of the tick vector Ixodes scapularis (Say). Early detection of emerging areas of LD risk is critical to public health responses, but the methods to do so on a local scale are lacking. Passive tick surveillance has operated in Canada since 1990 but this method lacks specificity for identifying areas where tick populations are established because of dispersion of ticks from established LD risk areas by migratory birds. Using data from 70 field sites in Quebec visited previously, we developed a logistic regression model for estimating the risk of I. scapularis population establishment based on the number of ticks submitted in passive surveillance and a model-derived environmental suitability index. Sensitivity-specificity plots were used to select an optimal threshold value of the linear predictor from the model as the signal for tick population establishment. This value was used to produce an “Alert Map” identifying areas where the passive surveillance data suggested ticks were establishing in Quebec. Alert Map predictions were validated by field surveillance at 76 sites: the prevalence of established I. scapularis populations was significantly greater in areas predicted as high-risk by the Alert map (29 out of 48) than in areas predicted as moderate-risk (4 out of 30) (P < 0.001). This study suggests that Alert Maps created using this approach can provide a usefully rapid and accurate tool for early identification of emerging areas of LD risk at a geographic scale appropriate for local disease control and prevention activities.

OBJECTIVE: To evaluate the validity of information in the rubella surveillance system in Quebec.DATA AND METHODS: Cases of rubella in the provincial registry of notifiable diseases, "Maladies à declaration obligatoire" (MADO), from 1994 to 1996 were matched with laboratory-identified cases and with cases in a reference file created from all case investigation records of regional departments of public health for the same period. Sensitivity and the proportion of cases in agreement were calculated.RESULTS: Compared with laboratories, the sensitivity of the provincial registry was 56%. Compared with the reference file, global sensitivity (confirmed cases plus clinical cases) was 58% and the positive predictive value was 50%. Of the 356 cases reported to regional public health departments, 65% were classified in the same diagnostic category (confirmed case, clinical case, excluded case) by public health professionals and a group of experts (weighted kappa=0.32). Information on rubella vaccination status was missing in 25% of cases in the MADO file for rubella.CONCLUSIONS: Notification of positive results for immunoglobulin M antibodies and viral cultures should be required of all laboratories. Uniform procedures should be adopted and applied for the validation of cases that are reported to regional departments of public health. In the context of the rarefaction of rubella, any immunoglobulin M-positive result should be interpreted using all available epidemiological information.