Flea Borne-Rickettsia Surveillance in Nuevo Leon, Mexico: An Unexpected Finding

Fleas represent a neglected group of ectoparasites of significant public health importance, due to their active role in transmitting various infectious agents associated with emerging and re-emerging diseases. In Mexico, flea borne-rickettsioses represent a growing public health concern, driven by the widespread presence of arthropod vectors and a vulnerable population, compounded by limited knowledge of pathogen-vector-host interactions. This study aimed to identify flea species parasitising dogs and cats in the state of Nuevo Leon, Mexico and to detect and characterise Rickettsia species present through molecular sequencing.

Flea samples were collected from dogs and cats in veterinary clinics and private residences during the period of October-May 2022-2023, across nine municipalities in the state of Nuevo Leon. Samples were identified morphologically and the gltA gene for Rickettsia was amplified and sequenced.

Three flea species were identified from dogs and cats: Ctenocephalides felis felis (Bouché, 1835), Pulex simulans (Baker, 1895) and Echidnophaga gallinacea (Westwood, 1875). Rickettsia DNA was detected in 29.47% of the total flea pools through amplification of the citrate synthase (gltA) gene. Sequence analysis revealed the presence of Candidatus Rickettsia senegalensis in C. felis felis collected from dogs in Nuevo León, representing the first record in Mexico. Simultaneously, an unexpected finding of Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever (RMSF), was also identified in the same flea species, marking the first report of this pathogen in fleas worldwide.

Our findings provide for the first time in Mexico, the molecular detection of Ca. R. senegalensis in Ct. felis felis, increases the number of Rickettsia species recorded in the country to 19. Additionally, R. rickettsii DNA was detected in Ct. felis felis. These findings highlight the need for further studies on clarify the epidemiological relevance of fleas-associated Rickettsia and to better understand their role within rickettsial systems.