A refresher on prescribing antibiotic prophylaxis to prevent Lyme disease following a tick bite

In June 2025, Public Health Ontario launched the new Ontario Vector-Borne Disease Tool, which offers comprehensive surveillance data on vector-borne diseases in Ontario.1 The tool can be used to track weekly and year-to-date case counts for all reportable vector-borne diseases in Ontario, including West Nile virus illness, Lyme disease, anaplasmosis, babesiosis and Powassan virus infection. It also allows visualization of mosquito and tick surveillance data, including species distribution and positive test results, using customizable interactive maps.1 Users can also use the interactive tool to access established blacklegged tick risk area maps. In 2025 to date, most of the risk areas are in southern Ontario along the north shores of Lake Erie, Lake Ontario and the St. Lawrence River, but risk areas also exist within the health unit boundaries of Northwestern and Thunder Bay. The public should be made aware that blacklegged ticks can possibly be encountered almost anywhere in Ontario, provided the habitat is suitable (e.g., wooded or brushy areas).1During the week of June 30 to July 6, 2025, 12 cases of Lyme disease were reported in Ontario, bringing the total number of cases in the province to 423 so far in 2025.2 With the increasing frequency of tick bites in Ontario, pharmacists should familiarize themselves with the Public Health Ontario/Ontario Health pharmacists’ assessment and prescribing algorithm for antibiotic prophylaxis to prevent Lyme disease following a tick bite.3If the patient is symptomatic following a tick bite (i.e., has erythema migrans “bull’s-eye” rash, or is experiencing fever, chills, headache, stiff neck, fatigue, decreased appetite, muscle/joint aches, joint swelling or swollen lymph nodes) they should be referred to a physician or nurse practitioner.3If the patient is not symptomatic, the pharmacist should determine whether the patient is at high risk for developing Lyme disease. Patients at high risk must meet all four of the following criteria:Tick has been removed within the past 72 hours. (If the tick is still attached, advise the patient how to safely remove it.)Tick bite occurred in a higher risk area where blacklegged ticks have been identified.Tick was likely attached for 24 hours or more.Doxycycline is not contraindicated (e.g., allergy).3If all four criteria are met, pharmacists should prescribe antibiotic prophylaxis:Adults: doxycycline 200 mg po single doseChildren: doxycycline 4 mg/kg (maximum 200 mg) po single dose (no age restriction).3Note that previously, doxycycline was not recommended for children < 8 years of age; however, this guidance has changed as dental staining is uncommon with short courses of doxycycline. Doxycycline was also previously contraindicated in pregnant and lactating individuals, but a single dose is considered safe for these individuals. If doxycycline is contraindicated (e.g., allergy), no alternative should be prescribed. In this situation, advise the patient to monitor for symptoms for 30 days and see a physician or nurse practitioner if symptoms develop.3Pharmacists should complete documentation of their assessment and prescription, and notify the patient’s physician or nurse practitioner. They should also educate all patients to monitor for signs and symptoms for 30 days and see a physician or nurse practitioner if symptoms develop.3 Patients can also be advised that they have the option to submit photos of ticks to www.etick.ca for identification; the website also includes information on tick removal.4If all four criteria are not met, antibiotic prophylaxis should not be prescribed. Instead, patients should be educated to monitor for symptoms for 30 days and see a physician or nurse practitioner if symptoms develop.3Further details for healthcare professionals about Lyme disease transmission, clinical manifestations, diagnosis, treatment and laboratory testing can be found on the Health Canada website.5 Pharmacists in some other provinces (AB, NB, NS, QC) are also allowed to assess patients and prescribe antibiotic prophylaxis to prevent Lyme disease following a high-risk tick bite.6 They should follow their respective provincial guidelines. References:Public Health Ontario. Public Health Ontario launches new Ontario Vector-Borne Disease Tool. June 5, 2025. (accessed July 10, 2025).Public Health Ontario. Ontario vector-borne disease tool. (accessed July 10, 2025).Public Health Ontario/Ontario Health. Assessment and prescribing algorithm for pharmacists: antibiotic prophylaxis to prevent Lyme disease following a tick bite. 2024. (accessed July 10, 2025). eTick/Gouvernement du Québec. Removing a tick if bitten. (accessed July 10, 2025).Government of Canada. Lyme disease: for health professionals. Modified June 30, 2025. (accessed July 10, 2025).Canadian Pharmacists Association. Prescribing authority of pharmacists across Canada. February 20025. (accessed July 10, 2025).

A refresher on prescribing antibiotic prophylaxis to prevent Lyme disease following a tick bite

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