In recent years, the increasing occurrence and diversity of tick-borne rickettsioses (TBR) in mainland Portugal have become a cause for considerable public health concern due to the emerging and neglected nature of these zoonoses. TBR diseases, which are caused by intracellular α-proteobacteria within the genus Rickettsia, particularly those of the spotted-fever group (SFG), pose a growing threat to both human and animal health.
Main Topic
The primary objective of this study was to investigate rickettsial infections in questing ticks collected over a two-year period from four distinct ecological regions in mainland Portugal. By identifying emerging threats and potential vectors, this research contributes valuable data and insights into the epidemiology of TBR in the region, which is crucial for developing effective public health strategies and control measures.
Key Findings
The study identified eight tick species involved in the transmission of rickettsial infections: Dermacentor marginatus, Haemaphysalis inermis, Haemaphysalis punctata, Hyalomma lusitanicum, Ixodes frontalis, Ixodes ricinus, Rhipicephalus pusillus, and Rhipicephalus sanguineus sensu lato. The overall prevalence of rickettsial infection among these ticks was found to be 10.31%. For nymphal ticks, the prevalence was estimated using the minimum infection rate (MIR) method, while for adult ticks, standard methods were employed.
Phylogenetic analysis was utilized to validate the presence of several Rickettsia species, including R. helvetica, R. massiliae, R. monacensis, Candidatus R. rioja, and R. slovaca. Notably, infection was detected in all tick species except I. frontalis. The study reported the first detection of R. slovaca in I. ricinus ticks in Portugal, a previously unknown association, and provided the first molecular characterization of Candidatus R. rioja in D. marginatus within the region.
Consensus Viewpoints and Trends
The study highlights the critical need for ongoing surveillance programs aimed at mapping and monitoring questing and feeding ticks, along with their vertebrate hosts. Such surveillance is essential in tracking the potential public health threats posed by TBR diseases. Health implications of TBR, such as Mediterranean Spotted Fever (MSF) caused by Rickettsia conorii, and other MSF-like diseases, underscore the necessity for effective control strategies. Furthermore, the research emphasizes the importance of understanding the complex tick-host-pathogen relationships and ecological dynamics that influence rickettsial circulation and transmission.
Detailed Interpretation
The presence of various Rickettsia species within different tick species underscores the intricate nature of TBR epidemiology in Portugal. Ixodes ricinus, a significant vector, was found to be infected with R. helvetica, R. monacensis, and R. slovaca. Additionally, the presence of R. massiliae in Rhipicephalus sanguineus s.l. indicates a need for surveillance in domestic and peri-domestic environments, as these ticks pose a zoonotic risk affecting both companion animals and humans.
A noteworthy finding was the unusual interspecific relationship where I. ricinus, typically an anthropophilic tick, was infected by R. slovaca, traditionally associated with Dermacentor species. This suggests possible ecological dynamics that facilitate cross-species pathogen transmission and highlight the adaptability and complexity of tick-host-pathogen interactions.
Conclusion
In recent years, the rise in both the frequency and variety of tick-borne rickettsioses (TBR) in mainland Portugal has become a significant public health concern. Caused by intracellular α-proteobacteria belonging to the genus Rickettsia, these TBR diseases, particularly those within the spotted-fever group (SFG), present a growing threat to the health of both humans and animals. The emergence and neglected status of these zoonotic diseases highlight the urgent need for increased awareness and research. TBR, transmitted by various tick species, can lead to severe health consequences if not promptly diagnosed and treated. These diseases manifest through symptoms ranging from mild fever and rash to more severe conditions, including neurological and cardiac complications. Public health agencies in Portugal are now focusing on better surveillance, improved diagnostic methods, and effective prevention strategies. Enhancing public awareness and encouraging protective measures against tick bites are crucial steps in addressing this emerging public health issue.
