A Northern Californian has been confirmed as the fourth-ever person diagnosed with a newly recognized and rare tick-borne disease that causes symptoms similar to Rocky Mountain spotted fever.
The California Department of Public Health confirmed the latest case of Rickettsia lanei bacteria in a patient who was diagnosed in April of this year. Two other California cases were reported in 2004 and 2023.
Public health officials told The Times that the infected person “was seriously ill, hospitalized and has since been discharged and is recovering.”
It is unclear how long the person was in the hospital or what their symptoms were. The state agency said it could not disclose the home county of the person but confirmed the infected person lived and worked in Northern California.
Rickettsia lanei comes from the spotted fever group Rickettsia, bacteria transmitted to humans from the bite of an infected tick.
In California three types of ticks — the American dog tick (Dermacentor similis), the Pacific Coast tick (Dermacentor occidentalis) and the brown dog tick (Rhipicephalus sanguineus) — can transmit the bacteria that cause Rocky Mountain spotted fever in humans and dogs, according to the California Department of Public Health.
Symptoms of Rocky Mountain spotted fever can range from fever and a rash to long-term effects that include damage to internal organs or neurological disorders.
The tick-borne disease has been spreading globally since the early 2000s, most notably in Mexico and Brazil, with reported fatality rates that can exceed 50%, according to a study published by UC Davis.
What is Rickettsia lanei?
Rickettsia lanei bacteria were identified this year in a few Pacific Coast ticks, including a tick in Contra Costa County, according to SFGate, where the latest case was first reported in April.
The new bacterium was added to the list of potentially transmittable pathogens in 2024 by the state public health department after its severe symptoms were studied in two cases of infected men nearly 20 years apart, according to a report published in the Centers for Disease Control and Prevention Emerging and Infectious Diseases journal.
“Sustained investment in public health has enabled development of the advanced molecular tools that detected these infections,” the California Department of Public Health said in a statement to The Times.
According to the report, both men fell ill after spending time outdoors, one playing golf at five courses in Alameda and Contra Costa counties within 14 days of the onset of his symptoms. This first patient had fever, headaches, muscle pain, malaise, loss of appetite, diarrhea and abdominal pain, among other symptoms. His condition worsened on his third day in the hospital, according to the report. The man was ultimately in the hospital for 22 days, including 11 in the intensive care unit with a primary diagnosis of rocky mountain spotted fever and a secondary diagnosis of acute kidney injury.
The other infected person had visited and camped at a county park and state beach in San Mateo and Marin counties. The second man reported a five-day history of headaches, vomiting, light sensitivity, neck pain and confusion, according to the report. On the third day of hospitalization, the man became comatose and was intubated, the report stated. After 13 days, he was discharged with a primary diagnosis of severe Rickettsia.
Researchers have known about Rickettsia lanei since 2018 when it was detected in rabbit ticks in Sonoma County, but they didn’t know its potential harm to humans because the rabbit tick rarely bites people.
“The Pacific Coast tick, which bites humans more frequently, may occasionally acquire the organism from an infected rabbit, which is the most likely route for the rare human infections that have been identified,” the state health agency said.
Should I be worried about contracting Rickettsia lanei?
Human infections are rare but could be underreported because Rickettsia lanei symptoms are very similar to those of rocky mountain spotted fever, said Janet Foley, veterinarian and disease ecologist at UC Davis.
“I think it’s so new that I don’t know if anybody’s really gotten a grant to study it or put it under a microscope,” Foley said.
Rickettsia lanei bacteria cases could also have gone undetected for so long because some cases were not severe, she said.
Foley said Californians should be aware of Rickettsia lanei and take precautions against tick bites.
How to keep disease-carrying ticks at bay
The best way to avoid ticks and tick bites is to be vigilant in your surroundings, Foley said, noting that ticks can transmit other diseases such as Lyme disease.
To keep a disease-carrying tick at bay, Foley recommends:
- Covering up your arms and legs when outdoors by wearing pants and long-sleeved shirts.
- Staying out of the grass where a tick can latch onto your clothing. Instead stay on a cleared path.
- Wearing light-colored clothing so it’s easier to spot a tick if one jumps on you.
- After an outdoor activity, take off your clothes, toss them in the wash and take a shower.
- If your dog goes with you for outdoor activities, give it a bath and then apply tick medication.