Understanding host-pathogen-tick interactions remains a vitally important issue that might be better understood by basic research focused on each of the dyad interplays. Pathogens gain access to either the vector or host during tick feeding when ticks are confronted with strong hemostatic, inflammatory and immune responses. A prominent example of this is the Babesia spp.—tick—vertebrate host relationship. Babesia spp. are intraerythrocytic apicomplexan organisms spread worldwide, with a complex life cycle. The presence of transovarial transmission in almost all the Babesia species is the main difference between their life cycle and that of other piroplasmida. With more than 100 species described so far, Babesia are the second most commonly found blood parasite of mammals after trypanosomes. The prevalence of Babesia spp. infection is increasing worldwide and is currently classified as an emerging zoonosis. Babesia microti and Babesia divergens are the most frequent etiological agents associated with human babesiosis in North America and Europe, respectively. Although the Babesia-tick system has been extensively researched, the currently available prophylactic and control methods are not efficient, and chemotherapeutic treatment is limited. Studying the molecular changes induced by the presence of Babesia in the vector will not only elucidate the strategies used by the protozoa to overcome mechanical and immune barriers, but will also contribute toward the discovery of important tick molecules that have a role in vector capacity. This review provides an overview of the identified molecules involved in Babesia-tick interactions, with an emphasis on the fundamentally important ones for pathogen acquisition and transmission.

Rhipicephalus sanguineus sensu lato (s.l.) is a very common ectoparasite of domestic dogs able to transmit several pathogens of human and veterinary importance. Tick infestations and tick-borne diseases (TBDs) remain a serious and persistent problem, due to the lack of efficient control measures. It is therefore vital that novel approaches to control are pursued. Whilst vaccination is recognised as a potential control method to reduce tick infestation, no anti-R. sanguineus vaccine is available. Ticks depend on their blood meals to obtain nutrients and to achieve sexual maturity, which exposes them to vast amounts of iron. Although an essential molecule for several biological processes, its excess can lead to oxidative stress. Iron homeostasis is achieved with the help of iron-binding proteins called ferritins, among others, present in several tick tissues and developmental stages. These evolutionarily conserved proteins regulate iron homeostasis by storing and releasing iron in a controlled manner. In this study the R. sanguineus ferritin 1 gene was silenced through RNA interference (RNAi) in adult females exposed to an experimental infection with Ehrlichia canis. The purpose of this study was to assess the role of this protein in tick feeding, ovary development, oogenesis, and pathogen acquisition. Our data has shown that silencing ferritin 1 alters tick competence to normally engorge and causes morphologic and histochemical changes in the ovaries (OV) and oocytes. Furthermore, our data revealed that no E. canis DNA was found in either experimental group. Determining the function of molecules that act in key biological processes, such as blood digestion or reproduction, and that could be considered potential tick antigens will contribute towards the improvement of current control measures against these ectoparasites and the pathogens they vector.

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