Occurrence and distribution of Ambylomma americanum as determined by passive surveillance in Ontario, Canada (1999-2016)

The lone star tick, Amblyomma americanum, is spreading northward from its historical stronghold in the southeastern United States. As a vector and biting pest, public and veterinary health officials must remain vigilant of the lone star tick's expanding range. We use ticks submitted to Public Health Ontario Laboratory (1999-2016) to describe the spatial and temporal dynamics of A. americanum in Ontario, Canada, as well as submitter demographics. We identified 847 A. americanum submissions during the surveillance period, with 773 (91.3%) non-travel-related and 74 (8.7%) travel-related submissions. Annual A. americanum submissions increased over the surveillance period. Approximately 91% of non-travel-related submissions were adult ticks and 9% were nymphs. The highest submission rates were from individuals living in the Eastern and South West regions of the province. Adult specimens were primarily submitted from May through July and nymphs from March through September. Higher numbers of submissions were from young children (< 10 years) and older adults (55-74 years), with equal proportions of male and female submitters. The majority of travel-related submissions were from travellers returning from the southeastern United States (i.e., Florida, North Carolina, South Carolina, Tennessee, Texas). Amblyomma americanum distribution is scattered in Ontario and submissions are likely the consequence of ongoing detection of adventive specimens. Further tick dragging is required to confirm the presence of established lone star tick populations in the province. Given the relatively rapid expansion of blacklegged ticks, Ixodes scapularis, populations in Ontario, we expect climate change to facilitate the range of expansion of A. americanum into the province. We propose an algorithm for identifying A. americanum-risk areas, which will aid public and veterinary health officials when assessing the risks posed by lone star ticks.