Deadly ticks bite man, not his best friend, when temperatures rise: Study

A type of deadly tick that bites dogs is more than twice as likely to feed on humans as temperatures rise, researchers said on Monday, underlining the health risks of climate change.

Ticks that cause Rocky Mountain spotted fever (RMSF), which can be fatal, were 2.5 times more likely to pick humans over dogs in warmer environments, a University of California, Davis School of Veterinary Medicine study found.

Findings in global research have shown that climate change will have a negative impact on human health as heat stress, extreme weather and deadly illnesses become more common, scientists say.

"This study certainly shows that if we have hotter weather, and hotter weather is happening more often, we can expect more tick bites to humans," Laura Backus, a Ph.D. student who led the study, told the Thomson Reuters Foundation.

"This is going to be a bigger and bigger problem."

The number of RMSF cases has risen significantly in the last two decades in North America, including deadly outbreaks in the last 10 years in indigenous communities in Arizona and northern Mexico, the study said.

In the United States, RMSF cases rose to more than 6,200 in 2017 from fewer than 500 in 2000, according to data from the U.S. Centers for Disease Control and Prevention.

When temperatures rise from about 74 to 100 degrees Fahrenheit (23.3 to 37.8 degrees Celsius), ticks that carry the disease were 2.5 times more likely to pick humans over dogs as hosts, the research found.

RMSF is treatable with antibiotics if detected early but can be fatal once the infection takes hold, the research said.

Cases of tick-borne diseases of all kinds in the United States have more than doubled to almost 48,000 cases in 2018 from 2004, according to the CDC.

"What we're seeing is an ongoing large number of cases versus the sporadic little clusters of cases that we tend to see in other places in the U.S.," Backus said, referring to the uptick in Arizona and northern Mexico that was attributed to warm weather and socioeconomic conditions.