Flea-Borne Zoonotic Disease Reported in California

County public health officials in California are urging San Diego area residents to protect their pets—and themselves—from fleas after a local woman was recently diagnosed with murine typhus.

A bacterial disease, murine typhus is caused by Rickettsia typhi and Rickettsia felis, gram-negative, obligate intracellular bacilli. The zoonotic disease is most often spread by fleas that feed on infected rats, opossums, cats, raccoons, and rodents. Flea bites don’t directly cause infection to humans, but if flea feces come into contact with the bite wound or existing skin abrasion, then the bacteria that cause murine typhus can end up in the bloodstream.

“The woman who became ill had an indoor/outdoor cat and remembered being bitten by fleas before getting sick,” Sayone Thihalolipavan, MD, MPH, San Diego’s deputy public health officer, said. The woman was hospitalized in May and has since fully recovered.

The exact number of annual murine typhus infections is not reported by the Centers for Disease Control and Prevention because it is not a nationally reportable condition. Historically, murine typhus has been concentrated in coastal urban areas, with most cases occurring in Texas, California, and Hawaii.

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According to the Merk Veterinary Manual: “Clinical illness associated with canine and feline infection with R typhi and R felis is not well documented, but evidence of exposure based on presence of antirickettsial antibodies has been noted, particularly in association with outbreaks of human disease. Although a role as a possible reservoir for infection has been suggested, particularly for cats, the importance of domestic animals in maintenance of enzootic cycles has not been well elucidated.”

Last year, the Texas Department of State Health Services reported more than 400 cases of murine typhus in humans. It was the highest rate for the state in 16 years, with increased activity reported most commonly in the Dallas—Fort Worth and Houston areas.

As reiterated by county health officials in California, the best way for pet owners to protect themselves is to use a veterinarian-approved parasite preventive on their cats and dogs. This news also underscores the importance of initiating discussions with clients about flea prevention and the importance of year-round parasite protection.