Introduction: Toscana virus (TOSV) is a sandfly-borne bunyavirus with a significant public health impact. Preliminary studies have revealed TOSV exposure in dogs and they were suggested as potential reservoirs. This study was performed to characterize canine TOSV infections in an endemic region. Sequencing of TOSV small (S) segment in several previously identified specimens was also undertaken to reveal viral genealogy.
Materials and methods: Canine and feline plasma were collected in several districts of Mersin province, Mediterranean Anatolia, Turkey, during May-September, 2015. Phlebovirus RNA was screened through two nested polymerase chain reaction (PCR) assays, targeting S and large (L) segments of the viral genome. A kinetoplast minicircle nested PCR was employed for Leishmania DNA detection and typing. Previously collected TOSV-positive specimens from humans, dogs, cats, and sandflies from various regions in Turkey and Cyprus were further evaluated through the S segment PCR. All amplicons were characterized through sequencing.
Results: A total of 210 specimens that comprise canine (76.2%) and feline (23.8%) plasma were screened. In three (1.9%) and two (1.3%) canine specimens, TOSV and Leishmania nucleic acids were detected, respectively. The TOSV strains were characterized as genotype B, and Leishmania infantum was identified in positive specimens. Twenty-four partial S segment sequences were amplified, which demonstrated a maximum intramural diversity of 3.88% in the nucleotide level. Sequence comparisons revealed significant similarities to particular genotype B strains characterized in Spain and France, whereas a notable divergence was observed among several TOSV strains. Single or recurrent amino acid substitutions were noted in eight residues of the viral nucleocapsid.
Discussion: Canine infections of TOSV genotype B, with temporal and spatial association with L. infantum, were detected. Divergent TOSV S segment sequences with amino acid substitutions, presumably associated with host adaptation, were observed.
Keywords: Arbovirus(es); Leishmania; Phebovirus; Toscana virus; Turkey; bunyaviruses; canine; dogs; sandfly (flies).