It has long been known that ticks harbor Bartonella and that humans who have Lyme disease may also have Bartonellosis. However, the actual transmission of Bartonella from tick to host has not been demonstrated until a mouse study by Drs Reis and colleagues was published in May 2011. The study is available free on line for those interested. “This work represents the first in vivo demonstration of a Bartonella sp. transmission by ticks. It . . . corroborate[s] a prospect that ticks play a role in the natural cycles of some of the bartonellae including those pathogenic for humans. Consequently, bartonelloses should be included in the differential diagnosis for patients exposed to tick bites.”
The study also found that transstadial transmission is high.  This means that bartonella  survive in the tick through the molt from one life stage to another, for example from nymphal ticks to adult ticks. It had been thought that the possible mechanism of transmission of bartonella might be through contaminated tick feces. funded a study at UC Davis pursuing this theory. However, this study confirms that transmission to the host occurs with saliva and not through contaminated feces.

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