Bartonella: important infection, complicated “tick-borne” claim

What is proven—and what is not

CDC's 2026 Bartonella overview identifies established routes that include fleas and flea-associated cat exposure for B. henselae, human body lice for B. quintana, and sand flies for B. bacilliformis. For cat-scratch disease, infection usually follows a scratch from a cat—often a kitten—when the claws are contaminated with flea feces carrying B. henselae. CDC Bartonella overview ↗

This matters when interpreting a tick-testing result. If a tick laboratory reports Bartonella DNA, the most accurate wording is: “Bartonella genetic material was detected in the tick.” It is not scientifically justified to turn that result into “the tick transmitted Bartonella to the person.”

No single Bartonella test answers every clinical question.

Diagnosis depends on the syndrome. Typical cat-scratch disease can sometimes be diagnosed clinically from exposure plus characteristic lymphadenopathy. Serology can support some diagnoses, but antibody cross-reactivity and persistence complicate interpretation. Culture is difficult because Bartonella are slow-growing and fastidious. PCR can be useful when the right specimen is available, including tissue, blood or cardiac-valve material in selected settings.

A negative test does not always exclude infection, and a positive antibody test does not by itself prove that nonspecific chronic symptoms are caused by Bartonella. The pretest clinical picture matters.

There is direct laboratory research—but not human proof.

A 2019 peer-reviewed study screened 149 essential oils against stationary-phase Bartonella henselae in vitro. Oregano, cinnamon bark, mountain savory, clove, allspice, geranium, citronella and several other oils showed activity in the culture system. Carvacrol (a major oregano component) and cinnamaldehyde (a major cinnamon component) were among the most active isolated constituents. Read the study ↗

The investigators were explicit about the next steps: intracellular models, pharmacokinetics, animal studies and safety/efficacy studies were still needed. B. henselae can live in protected cellular niches, so killing free bacteria in a laboratory culture does not show that swallowing or applying an essential oil will safely treat human infection.

Some integrative protocols also use herbs such as Japanese knotweed, cryptolepis, cat's claw, Chinese skullcap or houttuynia for people labeled as having Bartonella. At present, those protocols should be described as traditional/integrative or anecdotal use unless a Bartonella-specific experiment is cited. A result from Lyme or Babesia cannot be assumed to apply to Bartonella simply because the same herb appears in multiple integrative protocols.