Transstadial Transmission from Nymph to Adult of Coxiella burnetii by Naturally Infected Hyalomma lusitanicum

Coxiella burnetii (Derrick) Philip, the causative agent of Q fever, is mainly transmitted by aerosols, but ticks can also be a source of infection. Transstadial and transovarical transmission of C. burnetii by Hyalomma lusitanicum (Koch) has been suggested. There is a close relationship between this tick species, wild animals and C. burnetii but the transmission in a natural environment has not been demonstrated. In this study, we collected 80 engorged nymphs of H. lusitanicum from red deer and wild rabbits. They molt to adults under laboratory conditions and we feed them artificially through silicone membranes after a preconditioning period. C. burnetii DNA was tested in ticks, blood and feces samples using real-time PCR. The pathogen was found in 36.25% of fed adults demonstrating that transstadial transmission from nymph to adult occurs in nature. The presence of DNA in the 60% of blood samples confirms that adults transmit the bacteria during feeding. Further studied are needed about co-feeding and other possible transmission routes to define the role of this tick species in the cycle of C. burnetii.