Up to this point, Bartonella DNA has been found in ticks, there have been positive PCR results in questing ticks which indicate that the bacterium (or at least its DNA) can survive in the tick through the molt from one life stage to another - and there has been evidence that people who have had tick bites have produced antibodies for both Lyme disease and Bartonella concurrently. But his was not taken as evidence that the tick was the vector responsible for transmission of Bartonella.
As it's been said many times before: Correlation is not causation. There needed to be evidence that Bartonella from ticks carrying the pathogenic organism could be directly transmitted to its host.
In light of the research cited below, it appears this evidence has been found: An Ixodes tick has been shown to be a vector for Bartonella in vivo.
My practical response to this one way or the other has been that regardless of source - fleas from one's cat or dog, or tick - that if one has symptoms of Bartonella and positive test results that they definitely should be treated for Bartonella.
Treat first, and let researchers sort out the source over time...
Reis C, Cote M, Le Rhun D, Lecuelle B, Levin ML, Vayssier-Taussat M, Bonnet SI. Vector Competence of the Tick Ixodes ricinus for Transmission of Bartonella birtlesii. PLoS Negl Trop Dis. 2011;5(5):e1186.
Bartonella spp. are facultative intracellular vector-borne bacteria associated with several emerging diseases in humans and animals all over the world. The potential for involvement of ticks in transmission of Bartonella spp. has been heartily debated for many years. However, most of the data supporting bartonellae transmission by ticks come from molecular and serological epidemiological surveys in humans and animals providing only indirect evidences without a direct proof of tick vector competence for transmission of bartonellae. We used a murine model to assess the vector competence of Ixodes ricinus for Bartonella birtlesii.
Larval and nymphal I. ricinus were fed on a B. birtlesii-infected mouse. The nymphs successfully transmitted B. birtlesii to naïve mice as bacteria were recovered from both the mouse blood and liver at seven and 16 days after tick bites. The female adults successfully emitted the bacteria into uninfected blood after three or more days of tick attachment, when fed via membrane feeding system. Histochemical staining showed the presence of bacteria in salivary glands and muscle tissues of partially engorged adult ticks, which had molted from the infected nymphs. These results confirm the vector competence of I. ricinus for B. birtlesii and represent the first in vivo demonstration of a Bartonella sp. transmission by ticks. Consequently, bartonelloses should be now included in the differential diagnosis for patients exposed to tick bites.
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