Rocky Mountain spotted fever is a bacterial infection spread by biting ticks to humans and dogs. Found on every continent except Antarctica, the infectious disease has been spreading since the early 2000s, most notably in Mexico and Brazil. Of the cases reported, more than half of infected people and dogs die.

A paper led by the University of California, Davis, highlights one of the most effective but often missing solutions to surviving this preventable, deadly disease: awareness. Most fatal cases stem from delays in diagnosis and treatment.

“The No. 1 thing that prevents human death from Rocky Mountain spotted fever is for everyone at high risk to know — including their doctors — and to seek medical care on day one,” said lead author Janet Foley, a professor of medicine and epidemiology in the UC Davis School of Veterinary Medicine.

The paper, published in Currents in One Health, a themed collection of American Veterinary Medical Association Publications, suggests how doctors, veterinarians, public health officials and communities can reduce the spread of Rocky Mountain spotted fever.

An urban epidemic

Symptoms often begin as a fever, headache and rash and, untreated, can lead to organ failure and death. While cases are reported worldwide, the disease has become an urban epidemic in Mexico and Brazil, where it often occurs in highly marginalized neighborhoods. Children and people living in extreme poverty with under-resourced health care systems and little community infrastructure are at the greatest risk.  

The ticks that carry R. rickettsii, the bacterium that causes Rocky Mountain spotted fever, prefer to feast on free-roaming dogs in Mexico and on capybaras in Brazil. 

Docile and water-loving, capybaras are the biggest rodent in the world. Like dogs, they are well-adjusted to urban life in Brazil, with large populations living alongside city parks and waterways. This has created unprecedented numbers of Rocky Mountain spotted fever cases in Brazil, especially in São Paulo.

Recommendations for dogs, capybaras and people

There is no vaccine available to prevent Rocky Mountain spotted fever in dogs, capybaras or people. To reduce ticks and the spread of disease, the authors recommend dog owners keep fewer dogs, restrict them to their property, and spay and neuter them. 

The paper also suggests neutering capybaras in affected areas, either through surgery or chemically. Additionally, intact wild lands and fencing around croplands could reduce capybara interactions with humans. The paper notes that capybaras are extremely territorial, which suggests that sterilizing a large population of urban capybaras would likely prevent other capybaras from reestablishing in the area. 

“We have to protect people and get rid of the ticks,” Foley said. “When you think about dogs and ticks, you’d assume this would be easy. These aren’t obscure animals you have to catch and find. Their ticks often aren’t highly resistant to insecticides. And yet, we have a super serious problem that is deceptively hard to treat. These problems require a real, sustained intervention.” 

Rather than spread limited resources around a city, Foley recommends public health officials prioritize an especially vulnerable neighborhood and treat every single dog over the course of several months until the ticks are gone. 

“One small piece at a time, we can bring down tick numbers, and that will protect people and dogs,” Foley said. 

The authors urge people who think they may have Rocky Mountain spotted fever to seek medical treatment immediately. They said veterinarians and doctors need to learn to recognize the symptoms, understand the treatments, and consider prescribing the antibiotic doxycycline, which can prevent death and severe illness. 

Disease transcends borders

Rocky Mountain spotted fever transcends national borders. As the climate gets hotter and drier, ticks that spread the illness are expected to feed farther and farther north. Health care practitioners globally can learn from experienced doctors in Latin America about how to recognize and treat the disease. 

“The myriad of determinants involved in the causal chain of Rocky Mountain spotted fever needs to be addressed with a comprehensive approach like that of One Health, and with regional perspective in the Americas,” said co-author Gerardo Álvarez Hernández, a professor of medicine and health sciences at the University of Sonora in Mexico. 

The study was funded by UC Davis School of Veterinary Medicine and Conselho Nacional de Desenvolvimento Científico e Regional in Brazil.

Additional co-authors include Andrés M. López-Pérez of Instituto De Ecología Veracruz, Mexico; Marcelo Labruna and Adriano Pinter of Universidade De São Paulo, Brazil; Rodrigo Nogueira Angerami of Universidade Estadual De Campinas, Brazil; Oscar Zazueta of Harvard T.H. Chan School of Public Health; Sergio Bermudez of Gorgas Memorial Institute for Health Research, Panama; Francesca Rubino of UC Davis School of Veterinary Medicine; and Johanna Salzer, Maureen Brophy and Christopher Paddock of Centers for Disease Control and Prevention.