Relapsing fever (RF) is an infectious disease caused by arthropod-borne spirochetes of the genus Borrelia.1 The disease is characterized by recurrent episodes of fever borrelemia.2 The RF borrelioses include louse borne RF caused by Borrelia recurrentis and tick-borne endemic RF transmitted by argasid soft ticks and caused by several Borrelia spp. such as Borrelia crocidurae, Borrelia coriaceae, Borrelia duttoni, Borrelia hermsii, Borrelia hispanica and Borrelia persica. Human infection with B. persica is transmitted by the soft tick Omithodoros tholozani and has been reported from Iran, Israel, Egypt, India, and Central Asia.2 Dogs have been reported to be infected with B. crocidurae, B. hermsii and B. persica while no report of feline RF borreliosis has been published before.3-7
During 2003–2015, five cats and five dogs from Israel were presented for veterinary care and detected with the presence of Borrelia sp. in blood by observation of blood smear microscopy. The causative infective agent in these animals was identified as B. persica and characterized by PCR from blood and sequencing of parts of the flagellin (flab), 16S rRNA and glycerophosphodiester phosphodiestrase (GlpQ) genes. All animals were infected with B. persica genetically identical to the causative agent of human RF. Phylogenetic analysis indicated that DNA sequences from these cats and dogs clustered together with B. persica genotypes I and II from humans and O. tholozani ticks and distinctly from other RF Borrelia spp. The main clinical findings in cats included lethargy, anorexia, anemia in 5/5 cats and thrombocytopenia in 4/5. All dogs were lethargic and anorectic, 4/5 were febrile and anemic and 3/ 5 were thrombocytopenic. Three dogs were co-infected with Babesia spp. The animals were all treated with antibiotics and the survival rate of both dogs and cats was 80%. The cat and dog that succumbed to disease died one day after the initiation of antibiotic treatment, while survival in the others was followed by the rapid disappearance of spirochetemia.
This is the first report of disease due to B. persica infection in cats and the first case series in dogs. Infection was associated with anemia and thrombocytopenia. Fever was more frequently observed in dogs than cats. Domestic canines and felines suffer from clinical disease due to B. persica infection and may also serve as sentinels for human infection.
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