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Key Gene Identified in Tick-Bite Lyme Disease Transmission

Deactivated bba64 gene in Lyme disease bacterium blocks transmission from ticks to mice

THURSDAY, April 8 (HealthDay News) -- Deactivating a gene in Borrelia burgdorferi, the tick-borne bacterium that causes Lyme disease in humans, may prevent the transmission of the disease by a tick, according to a study of mice published online April 5 in the Proceedings of the National Academy of Sciences.

Robert D. Gilmore Jr., of the U.S. Centers for Disease Control and Prevention in Fort Collins, Colo., and colleagues inoculated mice with a mutant strain of B. burgdorferi that had been modified to disable the bba64 gene. Ticks were allowed to feed on the mice and acquire the mutated Lyme disease bacteria, and then were transferred to 15 mice that did not have Lyme disease. The mice were observed for the development of infection.

The researchers found that, after eight weeks, only two of 15 test mice were infected via tick bites. The researchers then retrieved ticks from an uninfected mouse and re-cultured the bacteria. They injected the re-cultured bacteria directly into a separate group of mice without Lyme disease, all of whom developed infections, demonstrating that the bba64 gene is likely necessary for a tick to infect its host solely by means of a bite.

"In conclusion, we showed that the B. burgdorferi bba64 is involved in a critical mechanism for host infectivity during pathogen delivery and/or survival from the vector. This finding represents a breakthrough in the understanding of vector-borne pathogen transfer and suggests BBA64 may have utility as a putative tick transmission-blocking vaccine candidate against Lyme disease," the authors write.

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