Ticks on the Rise: How Climate Change Is Fueling Their Spread and the Public Health Risk

Black-legged Tick

Once an afterthought during summer hikes or walks in the woods, ticks have become a growing concern across North America. As climate change accelerates, these tiny arachnids expand their range, become active earlier in the year, and persist longer into the fall. This trend is more than inconvenient for humans, pets, and wildlife; it’s a mounting public health threat.

What Are Ticks and How Do They Live?

Ticks are small, blood-feeding parasites related to spiders. Unlike fleas or mosquitoes, ticks don’t jump or fly. Instead, they wait in tall grasses or brush, extending their legs to grab onto a passing host. They are patient and can go months without feeding, waiting for the right opportunity.

There are four stages in a tick’s life cycle: egg, larva, nymph, and adult. Each of the three active stages requires a blood meal to move to the next phase. Many species complete this cycle over two to three years. The black-legged tick (Ixodes scapularis), also known as the deer tick, is the most infamous in the eastern U.S.. In contrast, the Lone Star (Amblyomma americanum) and the American dog tick (Dermacentor variabilis) are more common in the South and Midwest.
​
Ticks thrive in moderate temperatures and high-humidity environments, such as wooded areas, overgrown fields, and shaded gardens. Historically, harsh winters and dry conditions limited their population. That’s changing.

Deer Tick Range Changes Over Time

How Climate Change Is Expanding Tick Territory

With rising temperatures and shorter winters, ticks survive in regions once too cold to persist. The black-legged tick, once mainly restricted to the Northeast and Upper Midwest, is now found throughout parts of the Great Plains and well into Canada. The Lone Star tick, long associated with southern states, has surged northward into the Mid-Atlantic and even the lower Midwest.

Climate change not only expands where ticks live—it extends how long they remain active. In warmer areas, ticks can now search for hosts during previously too cold months. Some adult ticks are active well into late fall and early winter. Earlier springs also mean earlier hatches, more feeding opportunities, and larger populations.

Host animals are shifting, too. White-tailed deer, mice, and other mammals that ticks rely on for blood meals also expand into new territories, creating a positive feedback loop that benefits the parasites.

Rising Tick-Borne Diseases in the U.S.

The spread of ticks into new regions has led to a sharp rise in tick-borne illnesses. Lyme disease, caused by the bacterium Borrelia burgdorferi and transmitted by black-legged ticks, now infects an estimated 470,000 people in the U.S. annually. That’s more than double the number reported two decades ago.

Other illnesses are also on the rise, including anaplasmosis, babesiosis, ehrlichiosis, and the potentially fatal Powassan virus. The Lone Star tick, in particular, is associated with alpha-gal syndrome—a strange and sometimes severe red meat allergy triggered by a tick bite.

Areas once thought safe from these diseases now deal with new cases yearly. The long-held assumption that tick season only runs from May to September is no longer accurate. In many places, it now stretches from early spring to late fall.

Ecological Disruption and Wildlife Impact

Ticks don’t just harm people. Wildlife populations are also feeling the effects. In the northern U.S. and Canada, moose calves are being driven to the brink by massive tick infestations. Known as “ghost moose,” these animals become so heavily infested that they lose blood, fur, and body weight—often leading to death.
In livestock, ticks spread diseases that reduce productivity and increase veterinary costs. As tick ranges expand, farmers and ranchers face growing risks to their herds.

What Can Be Done?

There’s no silver bullet for stopping ticks, but several strategies can help. Homeowners can reduce tick habitats by trimming vegetation, removing leaf litter, and mowing lawns. Wearing long clothing, using insect repellents like DEET or permethrin, and checking for ticks after being outdoors are simple but effective personal measures.

On a broader level, climate resilience and disease monitoring are critical. Public health departments in emerging tick zones need resources to track outbreaks and educate the public. Research into vaccines, better diagnostics, and new repellents is underway, including efforts to develop a human Lyme disease vaccine.

Yet, these adaptations will only go so far without action on climate change. As temperatures continue to climb, tick-friendly environments will increase; with them, the risks will increase.

Conclusion

Ticks are on the rise, both in number and in reach. Climate change is transforming the landscape to allow these pests to thrive in new areas and stay active longer. The consequences go far beyond itchy bites, affecting public health and wildlife survival. As the planet warms, the tiny tick may become one of the clearest, and most dangerous, warning signs we can’t afford to ignore.