Tick-Borne Diseases Could Increase with Global Warming

Some scientists believe that global warming could lead to increases in tick-borne diseases due to ticks spreading into previously unoccupied habitats.

There are about 15 tick-borne diseases caused by infection with Rickettsia bacteria. Related bacteria that cause Mediterranean spotted fever and Rocky Mountain spotted fever are transmitted by the brown dog tick, Rhipicephalus sanguineus, distributed widely around the world. The tick is well adapted to human environments and attaches to domestic dogs, but bites humans rarely.

One group of European scientists believe the brown dog tick may bring about the emergence of new human infections as average global temperatures increase, although they acknowledge that the risk of being bitten is small when another host is available to the ticks. But their research showed the ticks became aggressive to people before a domestic dog infested with them dies. This suggests that a lack of another host wasn’t the reason behind their behavior, and additional evidence points to unusually warm temperatures as the likely explanation.

Ticks need a humid environment to survive and are by nature aggressive, always looking for a host on which to attach. In warmer weather, the ticks could complete their life cycle faster, and higher temperatures could also mean that the air has more drying power. This kind of humidity-related stress can make ticks more eager to attach to a readily available source of blood.