New Tick-Borne Disease Case Reported in Northern California

A person from Northern California has been identified as the fourth individual ever to be diagnosed with a recently recognized tick-borne illness, which shares symptoms with Rocky Mountain spotted fever.

The California Department of Public Health confirmed this latest case of Rickettsia lanei, with the patient being diagnosed in April of this year. Prior cases in California were noted in 2004 and 2023.

Health officials mentioned that the infected individual was quite ill, requiring hospitalization, but has since been discharged and is now recovering.

Details regarding the duration of the hospital stay or specific symptoms remain unclear. The health department hasn’t disclosed the individual’s county of residence, but they indicated the patient worked and lived in Northern California.

The Rickettsia lanei bacteria belong to the spotted fever group Rickettsia and are transmitted to humans through bites from infected ticks.

In California, three types of ticks—the American dog tick, the Pacific Coast tick, and the brown dog tick—are known to carry the bacteria responsible for Rocky Mountain spotted fever in both humans and dogs, as noted by the California Department of Public Health.

Symptoms of Rocky Mountain spotted fever can range widely, from fever and rashes to severe long-term complications, including internal organ damage and neurological issues.

This tick-borne disease has been spreading around the world since the early 2000s, particularly in Mexico and Brazil, with fatality rates that can exceed 50%, according to a study from UC Davis.

What is Rickettsia lanei?

This year, Rickettsia lanei bacteria were found in a few Pacific Coast ticks, including one in Contra Costa County, where the latest case was first reported in April.

The bacterium, which was added to the list of potentially transmittable pathogens in 2024 by the public health agency, was studied after two serious cases occurred nearly two decades apart, as reported in the CDC’s Emerging and Infectious Diseases journal.

According to the California Department of Public Health, continuous investment in public health has supported the creation of advanced molecular tools to identify these infections.

The report highlighted that both men who became ill had spent time outdoors, with one playing golf in several courses in Alameda and Contra Costa counties just before symptoms started. This first patient experienced fever, headaches, muscle pain, and other symptoms, worsening on the third day in the hospital. He ended up hospitalized for 22 days, including 11 days in intensive care, diagnosed with Rocky Mountain spotted fever along with acute kidney injury.

The second infected individual had camped at a county park and state beach in nearby counties. His symptoms included headaches, vomiting, and confusion, and he lost consciousness, requiring intubation. He was released after 13 days, diagnosed with severe Rickettsia.

Although researchers have been aware of Rickettsia lanei since its detection in rabbit ticks in Sonoma County in 2018, the potential human health risks were unclear, as rabbit ticks rarely bite people.

The California health agency suggested that the Pacific Coast tick, which does bite humans more frequently, might occasionally acquire the bacteria from infected rabbits, leading to the few human infections observed.

Should I be concerned about contracting Rickettsia lanei?

Human cases are rare, but it’s possible they go underreported, as the symptoms of Rickettsia lanei are quite similar to those of Rocky Mountain spotted fever, according to Janet Foley, a veterinarian and disease ecologist at UC Davis.

“I think it’s still so new that I’m not sure anyone has received funding to study it thoroughly,” Foley commented.

She added that some cases of Rickettsia lanei may have gone unnoticed because they weren’t severe enough to warrant medical attention.

Foley emphasized that Californians should stay informed about Rickettsia lanei and take precautions against tick bites.

How to reduce the risk of tick bites

Being attentive to your surroundings is crucial for avoiding ticks and tick bites, Foley noted, since ticks can also transmit other diseases like Lyme disease.

To minimize risks, she recommends:

• Wearing long-sleeved shirts and pants while outdoors.
• Avoiding grassy areas where ticks might cling to clothing; stick to cleared paths.
• Opting for light-colored clothing to easily spot ticks.
• After outdoor activities, changing clothes, washing them, and showering.
• Bathing and applying tick medication to pets after outings.