Date Published: June 1, 2018
Publisher: Public Library of Science
Author(s): Karen O. Johnson, Mark P. Nelder, Curtis Russell, Ye Li, Tina Badiani, Beate Sander, Douglas Sider, Samir N. Patel, Catherine A. Brissette.
Lyme disease (LD) is the most common vector-borne disease in Ontario, Canada. We describe the epidemiology and clinical manifestations of LD in Ontario and examine trends in the incidence of non-disseminated and disseminated LD. LD surveillance data from the integrated Public Health Information System (iPHIS) from 2005–2014 were mapped to symptoms according to syndrome groups (erythema migrans (EM), flu-like, cardiac, neurologic or arthritic) and disease stages (early localized, early disseminated or late disseminated). During the study period, 1,230 cases due to Borrelia burgdoferi were reported in Ontario with annual incidence rates ranging from 0.32 (2006) to 2.16 (2013) cases per 100,000 population. Seventy percent of cases had EM and the proportion of cases with EM increased over time. Other clinical manifestations included flu-like (75%), arthritic (42%), neurologic (41%) and cardiac (6%) symptoms. Early localized disease (n = 415) manifested with EM (87%) and flu-like (57%) symptoms; early disseminated disease (n = 216) manifested with neurologic (94%), cardiac (10%) and EM (63%) symptoms; and late disseminated disease (n = 475) manifested with EM (62%), neurologic (55%), cardiac (9%), and arthritic symptoms (i.e., arthralgia (93%) and arthritis (7%)). Early localized and early disseminated cases (88% each) occurred primarily from May through September, compared to late disseminated cases (81%). The proportion of cases reported to public health within 30 days of illness onset increased during the study period, while the proportion of cases reported within 1–3 months and >3 months decreased. Geographical variations characterized by higher incidence of early localized disease and earlier public health notification (within 30 days of illness onset) occurred in regions with established or recently established LD risk areas, while later public health notification (>3 months after illness onset) was reported more frequently in regions with recently established or no identified risk areas. This is the first study to describe the clinical manifestations of LD in Ontario, Canada. The observed geographical variations in the epidemiology of LD in Ontario reinforce the need for regionally focused public health strategies aimed at increasing awareness, promoting earlier recognition and reporting, and encouraging greater uptake of preventive measures.
Infection with Borrelia burgdoferi results in a multi-system disease that is characterized by three clinically defined stages: early localized, early disseminated and late disseminated Lyme disease (LD). Erythema migrans (EM) is the most common manifestation of early localized LD, with up to 80% of infected persons presenting with either the typical bull’s eye rash or an atypical rash without central clearing [1–3]. EM rash occurs two to 30 days after the tick bite and may be accompanied by flu-like illness that includes fever, chills, myalgia, arthralgia and stiff neck. Secondary EM rashes remote to the initial site of EM occur in 50% of cases  and are one of the earliest indications of early disseminated LD, which typically occurs weeks to months after an untreated infection. Early disseminated disease characterized by neurological manifestations including headache, stiff neck, pain or tingling in the extremities, Bell’s palsy, mood disorders, memory deficits and sleep disorders develops in 15–20%  of untreated cases, while Lyme carditis, frequently presenting as atrioventricular block, occurs in 1% of untreated cases . The most common manifestation of late disseminated LD is arthritis, which appears weeks to years after initial infection in up to 50% of people with untreated infection [6, 7]. Lyme arthritis is characteristically intermittent and mainly affects large joints including the shoulders and knees, with pain, effusion and synovitis being the typical presentations.
Despite possible misclassification of the three clinical stages of LD, we were able to elucidate trends. Incidence rates for the three clinical stages of LD increased over time, with the relative proportion of early to late disseminated disease varying spatially across Ontario. The proportion of cases reported to public health within 30 days of illness onset also increased and the proportion reported >3 months after illness onset decreased. Of importance are our findings of higher occurrence of early localized disease and earlier public health notification for regions with well-established or recently established risk areas for LD, and of higher occurrence of later public health notification for regions with no identified risk areas or recently established risk areas. These findings of increasing risk and regional variation in the incidence of LD demonstrates the relevance of targeted measures to increase awareness, promote earlier recognition and encourage greater uptake of preventive measures by the general public. For healthcare professionals, strategies aimed at improving earlier recognition, diagnosis and treatment based on presenting symptoms and exposure histories, and not surveillance case definitions, should also be emphasized. With increasing awareness and familiarity with LD, we expect decreases in exposures, as well as earlier recognition, diagnosis and treatment, which would result in a reduction in overall incidence and a shift in the ratio of disseminated to early localized disease. However, maximizing gains toward these goals must consider the implementation of different strategies for different regions based on the presence of risk that is well established, recently established or not yet identified, as well as on the length of time that an area has been identified as being higher risk for LD.