Ticks are no longer just an outdoor nuisance, as public health officials now recognise them as a rapidly growing threat across North America and Europe.
Lyme disease remains the most commonly reported vector-borne illness in the United States, with more than 89,000 cases reported to the CDC in 2023 alone.
The CDC estimates that approximately 476,000 people may actually be diagnosed and treated for Lyme disease annually, suggesting significant under-reporting in official surveillance figures.
Beyond Lyme disease, ticks in the United States can transmit pathogens responsible for anaplasmosis, babesiosis, ehrlichiosis, Rocky Mountain spotted fever, Powassan virus disease, and other serious illnesses.
The CDC reports that the number of Americans affected by Alpha-gal syndrome, a potentially life-threatening allergy triggered by a tick bite, may be as high as 450,000 people.
Tick distributions across North America are shifting in ways that render historical assumptions about safe zones increasingly unreliable for consumers and policymakers alike.
Canada reported a Lyme disease incidence rate of 14.1 cases per 100,000 people in 2024, rising from 11.9 per 100,000 in 2023, with blacklegged tick habitat expanding across Manitoba, Ontario, Quebec, and the Maritime provinces.
Canadian public health authorities expressly identify climate change as contributing to increases in tick abundance, longer periods of tick activity, expansion of suitable habitat, and longer seasons of human exposure.
The Asian longhorned tick, first reported in the United States in 2017, has now been found in numerous eastern and midwestern states, illustrating how quickly the vector landscape can change.
Public health authorities recommend layered protection against ticks, including behavioural measures, physical barriers such as long trousers and closed footwear, chemical repellents, and prompt removal of any attached ticks.
The CDC recommends EPA-registered skin-applied repellents containing active ingredients such as DEET, picaridin, IR3535, oil of lemon eucalyptus, para-menthane-diol, or 2-undecanone for effective tick and insect protection.
Products containing 0.5 percent permethrin are recommended for treating clothing and gear, though permethrin should never be applied directly to skin and is toxic to cats and some white-footed dogs.
Under the Federal Insecticide, Fungicide, and Rodenticide Act, known as FIFRA, the EPA holds primary authority to register pesticides in the United States before they can legally be sold or distributed.
Registration of skin-applied repellents is an intensive process, requiring comprehensive data on product chemistry, human health hazards, and efficacy, with tick testing costs alone potentially exceeding $300,000.
The efficacy of repellent products is measured by Complete Protection Time, defined as the period from application until efficacy failure, with a minimum standard of two hours without reapplication required under FIFRA.
A longstanding regulatory concern involves so-called 25(b) minimum risk pesticides, which are exempt from federal registration and face far lower testing standards than fully EPA-registered products.
The Consumer Specialty Products Association petitioned the EPA on this issue back in 2006, arguing that consumers would not appreciate the distinction between registered and minimum risk products when assessing efficacy and safety.
Notably, the CDC’s own recommendations for topical insect repellents include only products containing EPA-registered active ingredients, not minimum risk 25(b) alternatives.
The EU regulates tick and insect repellents under its Biocidal Products Regulation, requiring active substance approval and product authorisation that specifies target organisms, application rates, and claimed protection duration.
Canada’s Pest Management Regulatory Agency similarly evaluates personal repellents for safety and effectiveness before market approval, with approved products including those containing DEET, icaridin, permethrin, and oil of lemon eucalyptus.
Great Britain regulates repellents under the GB Biocidal Products Regulation, with the Health and Safety Executive maintaining efficacy guidance and prohibiting misleading product descriptions.
Across all major regulatory frameworks, the same fundamental questions arise: what organism does the product repel, how long does the protection last, and is the label an accurate reflection of those conditions.
As tick populations expand geographically and human exposure increases, the answers to those questions carry greater public health consequences than at any previous point in recent decades.