Canine Infections and Partial S Segment Sequence Analysis of Toscana Virus in Turkey

Abstract

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.

Serological association between Leishmania infantum and sand fly fever Sicilian (but not Toscana) virus in sheltered dogs from southern Portugal

“…In the present study no association between the presence of antibodies to L. infantum and TOSV was detected (only six dogs were seropositive for both pathogens), not corroborating the epidemiological relationship between human [ 22 ] and canine [ 38 ] leishmaniosis and TOSV infection previously suggested. Nevertheless, the seroprevalence rate obtained in dogs in the present study, together with the seroprevalence detected in humans (ranging from 2% in control population to 4.2% in population with central nervous system disease) [ 10 ] and the reports of human cases of TOSV meningitis [ 9 , 10 ] demonstrate the circulation of the virus or TOSV-like viruses in Portugal.…”

“…and different sand fly-borne phleboviruses in the insect on one hand [ 35 , 36 ] and in dogs on the other hand [ 17 ] have been reported. In addition, the detection of L. infantum and TOSV and Massilia virus in phlebotomine sand flies [ 13 , 37 ], humans [ 22 ] or dogs [ 38 ] sharing the same environmental area has also been described. Thus, we evaluated if the seroprevalence to one of the tested pathogens was significantly associated with seroprevalence to the others.…”

Phylodynamic analysis of the historical spread of Toscana virus around the Mediterranean

“…Supplementary Table 5 shows that 43 strains fall into this category, and that three Turkish strains (Thr2012, Ank2012 and pu3) are candidate reassortants with L segments of genotype A and S segments of genotype B. However, this must be treated with caution, since the Turkish sequences concerned were derived in two separate studies (Dincer et al, 2016; Ergunay et al, 2015) and although the authors noted the genotype in each case to be the same as that given in Supplementary Table 5, no mention was made of reassortment. It is not clear from the accompanying papers if the strain designation really indicates that each is derived from a single individual.…”

Broader Geographical Distribution of Toscana Virus in the Mediterranean Region Suggests the Existence of Larger Varieties of Sand Fly Vectors

“…The fact that neutralizing antibodies against TOSV have been repeatedly described in dogs (4.3-8.4% in studies conducted in France, Portugal, Tunisia, Algeria, Greece, and Cyprus) is likely to reflect exposure rather than being indicative of a more peculiar role in the natural cycle [74,[76][77][78][79][80]. However, two studies conducted in dogs from Mediterranean Anatolia (Turkey) reported the presence of TOSV RNA in the blood of approximately 3% and 10% of tested dogs, respectively, of which some were co-infected with Leishmania parasites [82,83]. Co-infection could contribute to this apparent active replication of TOSV.…”