EJIDO PADRE KINO, BAJA CALIFORNIA – The boy came home from school weakened by fever, his ears burning hot. Over the next few days, the 7-year-old got sicker – vomiting and complaining of abdominal pain, his mother recalled. Then, the telltale red spots appeared on his hands. But none of the doctors in this rural community along Mexico’s Pacific coast recognized the warning sign for one of the most lethal infectious diseases in the Americas – Rocky Mountain spotted fever. A week later, the boy was dead.
The following year, in 2020, the disease killed a 5-year-old boy in a nearby house. Then last October, a few blocks away, another 7-year-old succumbed to the same scourge.
The disease spread through the bite of an infected tick that lives primarily on dogs, is rare, but its incidence is rising. It has reemerged at epidemic levels in northern Mexico, where more than 2,000 cases, resulting in hundreds of deaths, have been reported in the past five years. Young children have been hit the hardest. In the Mexican state of Baja California, where Ejido Padre Kino is located, there were 92 cases in 2022, more than double the previous year, according to state data.
The outbreak prompted a team of Mexican and U.S. scientists to descend upon this small town more than four hours south of San Diego to pluck ticks off dogs, scour the crevices around homes for larvae, and warn residents to keep their dogs from roaming the dusty streets.
“It’s very, very hard because it’s a totally 100 percent preventable disease,” said Oscar Efrén Zazueta, epidemiologist for Baja California and part of the research team. “Kids are the ones who are in contact with dogs, and they end up dying so very, very quickly . . . in a matter of days.”
The alarm has risen in recent years as warming temperatures intensify tick activity and disease risk. Cases of malaria, dengue fever, West Nile virus, and Lyme disease – infections transmitted by ticks and mosquitoes – have skyrocketed. Scientists worry that Rocky Mountain spotted fever, first identified in western Montana at the beginning of the 20th century, could spread to more regions.
“What’s the tipping point? We don’t know for sure,” said Laura Backus, a postdoctoral researcher at the Laboratory of Infectious Disease Ecology at the University of California at Davis and another member of the research team. “Weather directly affects how fast ticks reproduce. When it’s hot and dry, they get more desperate.”
The brown dog tick, one of the species that transmit Rocky Mountain spotted fever, becomes more aggressive toward humans in seeking blood meals in hotter, drier climates, such as that in northern Mexico and the southwestern United States, said Backus, who led a 2021 study that found that the ticks are twice as likely to choose humans over dogs when temperatures rise.
With the yearly number of days topping 100 degrees expected to increase across most of the continental United States in the next decade, the study warned of an “increasing concern for heat-driven emergence of tick-borne disease.”
Climate change extends the length of time ticks actively feed on humans and animals, enabling ticks to develop and reproduce faster.
“They begin biting people earlier in the year and stay out longer,” said Ben Beard, deputy director of the division of vector-borne diseases at the Centers for Disease Control and Prevention. “More people are being exposed potentially to the bites of infected ticks and, as a result, more cases of tick-borne diseases.”
“Only a few degrees’ difference in annual average temperature can have a huge impact,” he said.
The spread of Rocky Mountain spotted fever is hard to predict, Backus said, because it often simmers undetected, erupts, and then disappears again. Originally called “black measles” – a rash in the disease’s late stages often turns the skin black – it is one of the deadliest tick-borne diseases in the Americas.
The bacterium that causes it – Rickettsia rickettsii, commonly spread by tick species that feed on wildlife in predominantly wooded areas – is present in almost every U.S. state. But scientists were surprised to discover the brown dog tick – which lives around and inside homes where dogs are present – as a new vector for the disease in the United States in 2003.
Since then, nearly 500 cases and 28 deaths have been reported on tribal lands in Arizona, CDC officials said. In California, 88 cases were reported between 2013 and 2022, more than triple the 26 cases reported in the previous decade, according to state data.
Public health authorities are especially alarmed by the deadly outbreaks in low-income communities such as Ejido Padre Kino which have large numbers of free-roaming dogs. Migrant laborers from poorer parts of Mexico, many from Indigenous communities, have flocked here in recent years to work in the raspberry and strawberry fields. The dog population has also boomed after local governments stopped collecting strays – and spaying and neutering them – during the coronavirus pandemic. The increased interaction between dogs and humans is the underlying factor fueling the rise of Rocky Mountain spotted fever here, researchers said.
Ticks carry the bacteria and spread the disease when they bite dogs or humans. Previously uninfected ticks that bite infected dogs can acquire and transfer the pathogen. The disease can also cause serious illness – even death – in dogs. Dogs who do not receive regular veterinary care, as in poorer communities in Mexico or on tribal lands in Arizona, are more likely to perpetuate the disease.
Untreated, the disease kills 4 out of every 10 people infected in Baja California, Zazueta said. Children younger than 10 are at the highest risk because research shows they have more contact with dogs, and the early symptoms of Rocky Mountain spotted fever – fever, pain, malaise – resemble those of so many common childhood illnesses that the disease is often not diagnosed in time to be treated. Deaths can be prevented with the right antibiotic if it’s administered within a few days of an infection taking hold.
For Emmanuel Juárez Flores, the 7-year-old boy who returned home from school with a fever, it was already too late. The local hospital sent the boy to the bustling port city of Ensenada, two hours away, in hopes that a larger hospital might have intravenous doses of doxycycline, the only treatment for the late stages of the disease.
During the ambulance ride, “my son was crying and screaming because he was already in a lot of pain,” his mother, Olivia Flores Legardia, recalled as she brushed tears from her cheek in a recent interview. “He was biting me. . . because he was acting as if he didn’t know me.”
The nurse explained to her that the bacteria, which infects the lining of blood vessels, had already caused massive internal bleeding and damaged her son’s brain and lungs. Medicine would not work.
Source: The Washington Post