Arboviruses are viruses that circulate in nature between arthropod vectors, mosquitoes, ticks and sandflies, and natural hosts such as birds and small mammals. Humans become infected with arboviruses through the bite of an infected vector when the density of vectors and hosts in the environment is very high. Medically important arboviruses include the Sindbis virus (SINV), which causes fever, rashes and joint pain in humans. SINV has been demonstrated in mosquitoes and birds in many European countries, but the disease in humans is more common in Finland and Sweden. With the master's thesis, we wanted to find out whether SINV also circulates among mosquitoes in Slovenia, which types of
mosquitoes are involved in the enzoonotic cycle of the virus and which genotype of SINV they transmit. We examined 97,859 mosquitoes that were sampled between 2017 and 2023 at 226 locations throughout Slovenia. Mosquitoes were morphologically identified to species and grouped into 10,997 groups based on location, sampling date, species and sex. We isolated RNA from each group of mosquitoes and determined the presence of viral RNA using molecular methods. SINV RNA was detected in two groups of Culex modestus mosquitoes, which we caught in August 2022 by the lake Ledava in Goričko. We calculated that the minimum level of infection in mosquitoes was 0.09. Based on the nucleotide sequence of the nonstructural protein 4 gene, SINV-SLO is classified as genotype IV, which has been described in Russia, Azerbaijan, and China. Based on alignments between different SINV-IV isolates, we designed 400 bp amplicons with which we successfully amplified the entire SINV-SLO genome and thus identified SINV in Slovenia for the first time.
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