Lyme disease transmission by zombie ticks

Ticks saliva, the putative nearly-miraculous potion full of pharmacologically active proteins, helps to spread Lyme disease-causing Borrelia. Does it really? In our latest article, we aimed to reshuffle the puzzle pieces of the well-established belief of "Salivary-assisted transmission" and tried to produce a new picture from new data. We have generated, using RNAi-mediated silencing of four essential enzymes involved in proteosynthesis, physiologically-frozen ticks (dubbed as "Zombie ticks") producing very little of dilute saliva, if any. What was not known, though, whether these severely handicapped ticks, which manage to attach to their host but further fail to engorge,  are capable of transmitting Borrelia spirochetes. Interestingly, the zombie ticks did not lose their capacity to transmit Borrelia spirochetes. We argue that ticks thus may serve as a mere physical vehicle that mediates bridging between tick and host tissues, where Borrelia eventually disseminate and cause disease. We suggest that arrest in tick feeding is not a sufficient phenotype to prevent B. afzelii transmission. This, to a large extent, negates the ambition to prevent Lyme borreliosis by antibody-mediated targeting of I. ricinus salivary proteins.

RNAi effect on tick feeding capacity. Silencing of the Asparaginyl-tRNA synthetase, Valyl-tRNA synthetase, Leucyl-tRNA synthetase, and Lysyl-tRNA synthetase and their impact on engorgement weight in I. ricinus (A) adult females and (B) nymphs. Photographic images of five individual representative ticks after 8 days (adults) and 3 days (nymphs) of feeding are shown on top. Bottom graphs show weights of all ticks after 8 days (adults) and 3 days (nymphs) of feeding. Bars indicate standard errors of means. Success rate indicates the percentage of how many ticks managed to fully engorge

Perner J., Kučera M., Frantová H., Urbanová V., Kopáček P., Šíma R. 2022: Lyme disease transmission by severely impaired ticks. Open Biology 12: 210244. [IF=6.411] DOI: 10.1098/rsob.210244