**11. Acknowledgment**

We are grateful to all members from the Centre of Rickettsiosis and Arthropod-Borne Diseases, Hospital San Pedro-Centre of Biomedical Research (CIBIR), Logroño (La Rioja), Spain. Financial support was provided in part by a grant from 'Instituto de Salud Carlos III' (EMER 07 033), Ministerio de Ciencia e Innovación (Spain).
