Abstract

The tick Dermacentor everestianus is widely distributed on the Tibetan Plateau of China, where adult ticks usually parasitize sheep, yaks and horses. D. everestianus is able to transmit many zoonotic pathogens, including Francisella tularensis, Anaplasma ovis and Rickettsia raoultii-like bacteria, and can cause great damage to animals and human health. However, the symbionts in D. everestianus have not yet been investigated, which has hindered our understanding of the relationships between this tick species and associated tick-borne pathogens. In the current study, the Rickettsia-like and Coxiella-like symbionts in D. everestianus were identified and characterized. The results indicated that both Rickettsia-like (RLS-Des) and Coxiella-like (CLS-Des) symbionts showed 100% infection rates and displayed vertical transmission in D. everestianus. The RLS-Des showed a relatively higher abundance than the CLS-Des in D. everestianus. No tissue specificity was found for the RLS-Des or CLS-Des. These symbionts can inhabit the ovaries, salivary glands, midguts, Malpighian tubules and testes of D. everestianus. During the development of D. everestianus, the density of the RLS-Des showed more obvious changes than did that of the CLS-Des. Dramatic changes in the density of the RLS-Des were detected in the midguts, ovaries, salivary glands and Malpighian tubules when female D. everestianus were engorged and detached from the host, which suggested the potential role of these symbionts in the reproduction and development of D. everestianus. The dynamic changes in the density of the CLS-Des during feeding and reproduction of D. everestianus suggest the involvement of the CLS-Des in the reproduction of D. everestianus.