Population-based passive tick surveillance and detection of expanding foci of blacklegged ticks Ixodes scapularis and the Lyme disease agent Borrelia burgdorferi in Ontario, Canada.

Mark P. Nelder,Ye Li,Steven Johnson,Badal Dhar,Bradley S. Schneider,L. Robbin Lindsay,Samir N. Patel,Curtis Russell,Stephen Moore,Erik Kristjanson,Filip Ralevski

doi:10.1371/journal.pone.0105358

Abstract

We identified ticks submitted by the public from 2008 through 2012 in Ontario, Canada, and tested blacklegged ticks Ixodes scapularis for Borrelia burgdorferi and Anaplasma phagocytophilum. Among the 18 species of ticks identified, I. scapularis, Dermacentor variabilis, Ixodes cookei and Amblyomma americanum represented 98.1% of the 14,369 ticks submitted. Rates of blacklegged tick submission per 100,000 population were highest in Ontario's Eastern region; D. variabilis in Central West and Eastern regions; I. cookei in Eastern and South West regions; and A. americanum had a scattered distribution. Rates of blacklegged tick submission per 100,000 population were highest from children (0–9 years old) and older adults (55–74 years old). In two health units in the Eastern region (i.e., Leeds, Grenville & Lanark District and Kingston-Frontenac and Lennox & Addington), the rate of submission for engorged and B. burgdorferi-positive blacklegged ticks was 47× higher than the rest of Ontario. Rate of spread for blacklegged ticks was relatively faster and across a larger geographic area along the northern shore of Lake Ontario/St. Lawrence River, compared with slower spread from isolated populations along the northern shore of Lake Erie. The infection prevalence of B. burgdorferi in blacklegged ticks increased in Ontario over the study period from 8.4% in 2008 to 19.1% in 2012. The prevalence of B. burgdorferi-positive blacklegged ticks increased yearly during the surveillance period and, while increases were not uniform across all regions, increases were greatest in the Central West region, followed by Eastern and South West regions. The overall infection prevalence of A. phagocytophilum in blacklegged ticks was 0.3%. This study provides essential information on ticks of medical importance in Ontario, and identifies demographic and geographic areas for focused public education on the prevention of tick bites and tick-borne diseases.

Highlights

Borrelia burgdorferi sensu stricto, the agent of Lyme disease, has emerged since the mid-1970s to become the most common vector-borne human pathogen in the USA; the emergence has lagged in southern Canada [1,2]
The objective of this work is to determine: 1) the species of ticks found on humans in Ontario and to discuss the vector potential of the most abundant species, 2) the geographic and seasonal distribution patterns of these ticks, 3) the sex and age of persons submitting these ticks and 4) the patterns of geographic distribution and incidence of blacklegged ticks infected with B. burgdorferi and Anaplasma phagocytophilum
Travel histories for most of those submitting adventive ticks were not available; for those that were available, the location the submitter visited was within the range of the tick species submitted, for example: A. americanum, A. cajennense (Belize, Brazil, Jamaica), A. inornatum (Florida, USA), D. andersoni (Calgary, Alberta, Canada), H. punctata (Kazakhstan), I. pacificus (California, USA) and I. ricinus (Portugal, Scotland)

Summary

Introduction

The agent of Lyme disease, has emerged since the mid-1970s to become the most common vector-borne human pathogen in the USA; the emergence has lagged in southern Canada [1,2]. Researchers attribute the delayed occurrence of Lyme disease in Ontario and elsewhere in southern Canada to the limited distribution of the primary vector, the blacklegged tick Ixodes scapularis; but from the 1970s through the 1990s, the range of the blacklegged tick gradually expanded northward from the Northeastern and Midwestern USA [3,4,5]. Beginning in the mid-1990s and through the 2000s, additional established populations of blacklegged ticks were detected along the northern shores of Lake Erie (i.e., Point Pelee National Park, Rondeau Provincial Park, Turkey Point Provincial Park and the Wainfleet Conservation Area), Lake Ontario (Prince Edward Point National Wildlife Area) and the St. Lawrence River (St. Lawrence Islands National Park) [2,8,9,10]. Through this period of establishment, detected blacklegged ticks more frequently in localities outside of these established populations

Objectives

Methods

Results

Conclusion