Document Type


Publication Date




Publication Title

International Journal of Molecular Sciences






3545 (1-17)


Ixodes scapularis is a medically important tick that transmits several microbes to humans, including rickettsial pathogen Anaplasma phagocytophilum. In nature, these ticks encounter several abiotic factors including changes in temperature, humidity, and light. Many organisms use endogenously generated circadian pathways to encounter abiotic factors. In this study, we provide evidence for the first time to show that A. phagocytophilum modulates the arthropod circadian gene for its transmission to the vertebrate host. We noted a circadian oscillation in the expression of arthropod clock, bmal1, period and timeless genes when ticks or tick cells were exposed to alternate 12 h light: 12 h dark conditions. Moreover, A. phagocytophilum significantly modulates the oscillation pattern of expression of these genes. In addition, increased levels of clock and bmal1 and decreased expression of Toll and JAK/STAT pathway immune genes such as pelle and jak, respectively, were noted during A. phagocytophilum transmission from ticks to the vertebrate host. RNAi-mediated knockdown of clock gene expression in ticks resulted in the reduced expression of jak and pelle that increased bacterial transmission from ticks to the murine host. Furthermore, clock-deficient ticks fed late and had less engorgement weights. These results indicate an important role for circadian modulation of tick gene expression that is critical for arthropod blood feeding and transmission of pathogens from vector to the vertebrate host.


This is an open access article distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Data Availability

Article states: "All data are contained either within the main manuscript or in the supporting information document."

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Original Publication Citation

Khanal, S., Taank, V., Anderson, J. F., Sultana, H., & Neelakanta, G. (2022). Rickettsial pathogen perturbs tick circadian gene to infect the vertebrate host. International Journal of Molecular Sciences, 23(7), 1-17, Article 3545.


0000-0002-8483-9940 (Khanal), 0000-0001-6290-4150 (Taank, Vikas)