Canine cases of relapsing fever (RF) borreliosis have been described in Israel and the USA, where two RF species, Borrelia turicatae and Borrelia hermsii, can cause similar clinical signs to the Borrelia persica in dogs and cats reported from Israel, including fever, lethargy, anorexia, thrombocytopenia, and spirochetemia. In this report, we describe the first clinical cases of two dogs and a cat from Spain (Cordoba, Valencia, and Seville) caused by the RF species Borrelia hispanica. Spirochetes were present in the blood smears of all three animals, and clinical signs included lethargy, pale mucosa, anorexia, cachexia, or mild abdominal respiration. Laboratory findings, like thrombocytopenia in both dogs, may have been caused by co-infecting pathogens (i.e., Babesia vogeli, confirmed in one dog). Anemia was noticed in one of the dogs and in the cat. Borrelia hispanica was confirmed as an infecting agent by molecular analysis of the 16S rRNA locus. Molecular analysis of housekeeping genes and phylogenetic analyses, as well as successful in vitro culture of the feline isolate confirmed the causative agent as B. hispanica.
Our feline and canine friends are sentinels for human diseases and these cases are no different.
To date, 23 TBRF-related Borrelia species have been confirmed, but additional species are proposed (2). B. hispanica is the primary TBRF-related Borrelia species identified in Spain (3,4), where it is endemic. It is transmitted mainly through the bite of O. erraticus ticks (5) but also can be transmitted by O. occidentalis ticks (4). B. hispanica also has been found in Portugal (6), Morocco (4,7,8), and Tunisia (4). https://wwwnc.cdc.gov/eid/article/26/5/19-0745_article?deliveryName=USCDC_331-DM26146
As of 2015, B. hispanica is considered an emerging infectious agent causing Neuroborreliosis: https://n.neurology.org/content/84/14_Supplement/P6.310
Please keep in mind that migrating birds and animals are transporting ticks everywhere and spreading the pathogens they carry.
O. erraticus ticks feed nocturnally on multiple warm- blooded vertebrate hosts, including humans, and are found living buried in soil of traditional pigpens: https://repository.uel.ac.uk/download/ef62f8a0e6b1b15a27c35d240d126464385ad171f0be9af9d7768571b17460b0/128662/Portuguese%2520hosts%2520for%2520Ornithodoros%2520erraticus%2520ticks.pdf
Regarding O. occidentals ticks, according to this 2020 article,
“we have not sampled Ornithodoros ticks to evaluate densities and infection rates, nor have we collected samples from small mammals to investigate the reservoir of Borrelia spp.” 19-0745
Because the spirochetemia phase is short and laboratory diagnosis is exclusively dependent on the observer, we believe TBRF is underdiagnosed, even in areas where suspicion should be relatively high. 19-0745