More than Lyme disease: Be aware of increased risk of tick-borne diseases with climate change

Tick-borne diseases are expected to become more common in Canada with climate change. As temperatures rise, the range of several tick species has expanded into higher latitudes in North America and the duration of the season when people may be exposed to ticks has increased. As a result, tick-borne diseases are likely to rise in Canada. In addition to Lyme disease, four other tick-borne diseases are emerging in Canada and are expected to increase with climate change—anaplasmosis, babesiosis, Powassan virus and Borrelia miyamotoi disease.1 Anaplasmosis is caused by the bacterium Anaplasma phagocytophilum, which is spread by Ixodes scapularis ticks in eastern and central Canada and Ixodes pacificus ticks in British Columbia. Human or animal cases have been reported in most provinces where the ticks occur. People can have asymptomatic infections, but most often have nonspecific symptoms (e.g., fever, headache, muscle aches). The fatality rate is less than 1%.1 Babesiosis is primarily caused by a malaria-like protozoan Babesia microti, which triggers a Lyme-like disease. To date, rare human cases have been reported in Canada (e.g., Manitoba, Nova Scotia). The pathogen has been detected in I. scapularis ticks in Manitoba, Ontario, Quebec, Nova Scotia and New Brunswick.1-3 Asymptomatic infection may persist for months to years and remain subclinical throughout its course in otherwise healthy people, especially those < 40 yr.4 When symptomatic, the illness usually starts after a one- to two-week incubation period with malaise, fatigue, chills, fever, headache, myalgia and arthralgia, which may last for weeks. Hepatosplenomegaly with jaundice, mild to moderately severe hemolytic anemia, mild neutropenia and thrombocytopenia may occur.4 Babesiosis is sometimes fatal, particularly in the elderly, asplenic patients and patients with AIDS.4 The United States reports a case fatality rate of 2%–5%.1 In these situations, babesiosis may resemble falciparum malaria, with high fever, hemolytic anemia, hemoglobinuria, jaundice and renal failure. Splenectomy may cause previously acquired asymptomatic parasitemia to become symptomatic.4 Treatment consists of atovaquone 750 mg twice daily plus azithromycin 500–1000 mg on the first day, followed by 250–1000 mg/day on subsequent days, for at least seven to 10 days.2,5 Alternatively, in severely ill patients, a combination of clindamycin plus quinine is the standard of care.5 Powassan virus, first detected in Powassan, Ontario, can be found in a number of tick species. The presentation of Powassan infection can vary widely, from asymptomatic infection to encephalitis, which has a fatality rate of 10%. Although many tick-associated pathogens require an extended period of tick feeding prior to transmission, Powassan virus can be transmitted within 15–30 minutes of tick attachment. Two lineages have been identified in vector ticks: Lineage I identified in Ixodes in Ontario, Quebec, New Brunswick and PEI; and Lineage II identified in I. scapularis from Manitoba, Ontario and Nova Scotia.1 Borrelia miyamotoi was first identified in Canada in 2013. This pathogen has been found in I. scapularis and I. pacificus ticks. Signs of Borrelia miyamotoi disease are similar to those of Lyme disease, but without a rash. Rarely, it can cause meningoencephalitis.1 Preventing tick exposure/bites Avoiding exposure to tick habitats is the best defence against tick-borne infections. I. scapularis ticks are most often found in wooded, brushy or grassy areas, in certain regions and seasons. During outdoor activities in tick habitats, advise patients to take the following precautions to reduce the risk for tickborne infections: Walk on cleared trails and stay in the centre of the trail, to minimize contact with leaf litter, brush and overgrown grasses, where ticks are most likely to be found. Minimize the amount of exposed skin, by wearing socks, long pants and a long-sleeved shirt. Tuck the pant legs into the socks, so ticks cannot crawl up the inside of the pants. Wear light-coloured clothing, to make it easier to see and remove ticks before they attach to skin. Apply insect repellents (e.g., DEET, icaridin) to skin and clothing. Follow the instructions on the product label. After outdoor activities, conduct tick checks and promptly remove any ticks that are found. Note that people are generally infected through the bite of immature ticks (nymphs) that are about the size of a poppy seed. Adult ticks (about the size of a sesame seed) can also transmit disease. Because of their small size, ticks can easily be overlooked. In addition, tick bites are often painless, so a person might not know that they have been bitten. For most tick-borne infections, ticks must stay attached to a person for more than 36–48 hours to be able to transmit the parasite. Be sure to check for ticks behind the knees, between the legs (groin/thighs), between the toes, under the arms (armpits), around the waist, inside the belly button, the back of the neck, behind and in the ears, as well as in and around the scalp, hairline and hair. Check children and pets, too. Remove ticks that are attached to the skin as soon as possible, preferably by using pointed (fine-tipped) tweezers. Grab the tick’s mouth parts close to the skin and slowly pull the tick straight out (with steady outward pressure), until the tick lets go.5-7 Free resource for identifying ticks Canadians can use the eTick mobile app (eTtick.ca) for free tick identification in Canadian provinces. The eTick.ca website (available in English or French) also includes information on the steps for removing a tick, what to do following a tick bite, how to recognize a tick (and differentiate it from a spider). The website also offers viewing of a real-time interactive map of all tick records submitted by eTick.ca users.8 Pharmacist prescribing for high-risk tick bites Pharmacists in Ontario (and some other provinces) can now prescribe for postexposure prophylaxis to prevent Lyme disease following a high-risk tick bite. In Ontario, a single dose of doxycycline is recommended for children and nonpregnant adults. A patient assessment and prescribing algorithm is available from the Ontario College of Pharmacists.9 References 1. Bouchard C, Dibernardo A, Koffi J, et al. Increased risk of tick-borne diseases with climate and environmental changes. CCDR 2019;45(4). (accessed April 19, 2023). 2. Yang J, Smith C, Battad A. Babesia microti acquired in Canada. CMAJ 2021;193:E1213-7.(accessed April 19, 2023). 3. Allehebi ZO, Khan FM, Robbins M, et al. Lyme disease, anaplasmosis, and babesiosis, Atlantic Canada. Emerg Infect Dis J 2022;28(6). (accessed April 19, 2023). 4. Tick Awareness Canada Association. Babesiosis. (accessed April 19, 2023). 5. Centers for Disease Control and prevention. Parasites – babesiosis. Resources for health professionals. (accessed April 19, 2023). 6. Government of Canada. Personal insect repellents. (accessed April 19, 2023). 7. Government of Canada. Pamphlet: Enjoy the outdoors, without a tick. (accessed April 19, 2023). 8. Murdoch L. eTick mobile app now available for free tick identification in Canadian provinces. July 6, 2022. (accessed April 19, 2023). 9. Ontario College of Pharmacists. Assessment & prescribing algorithm for antibiotic prophylaxis to prevent Lyme disease following a high-risk tick bite. (accessed April 19, 2023).

More than Lyme disease: Be aware of increased risk of tick-borne diseases with climate change

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