Seroprevalence study in humans and molecular detection in Rhipicephalus sanguineus ticks of severe fever with thrombocytopenia syndrome virus in Thailand.

Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging tick-borne virus with a mortality rate of up to 30%. First identified in China in 2009, it was later reported in other Asian countries, including Thailand in 2020. SFTSV has been detected in several tick species, including Rhipicephalus sanguineus, known for infesting dogs. We conducted a seroprevalence study of SFTSV in Bangkok and Nong Khai, Thailand, by analyzing 1162 human samples collected between 2019 and 2023. The testing method relied on IgG detection using ELISA and confirmed though a virus seroneutralization test. The results indicated that out of the participants, 12 (1.1%) tested positive for anti-SFTSV IgG antibodies; however, none exhibited positive results in the seroneutralization assay. Additionally, molecular detection of SFTSV, Crimean-Congo hemorrhagic fever (CCHF), Coxiella spp., Bartonella spp., and Rickettsia spp. was performed on 433 Rh. sanguineus ticks collected from 49 dogs in 2023 in Chachoengsao Province, Thailand. No evidence of these pathogens was found in ticks. These findings highlight the importance of exploring viral cross-reactivity. Furthermore, it is important to conduct additional studies to isolate SFTSV from animals and ticks in order to identify the potential transmission routes contributing to human and animal infections in Thailand.

Geographic dispersal and genetic diversity of tick-borne phleboviruses (Phenuiviridae, Phlebovirus) as revealed by the analysis of L segment sequences.

The large diversity of new tick-borne phleboviruses, and the negative impacts of the virulent viruses on human/animal health have led to a growing interest in their analysis. In this report, new insights are brought out into the diversity of putative phleboviruses circulating in Portugal (both the continental territory and the islands of São Miguel, in the Azores, and Madeira), as well as in the Spanish western regions of Extremadura and Castilla and León. Phlebovirus sequences were frequently detected (L-segment) from both questing and feeding ticks, but especially in Rhipicephalus sanguineus sensu lato (s.l.) specimens. These sequences were detected in adult ticks, as well as nymphs and eggs, supporting the hypothesis of viral maintenance by vertical transmission. Though multiple genetic groups could be identified in phylogenetic trees (AnLuc, KarMa, RiPar virus 1, and Spanish group 1 and 2), all the sequences from Portugal and Spain shared common ancestry with other viral sequence obtained from samples collected over a large geographic coverage. Spatiotemporal analysis placed Middle-East as the geographic origin of the most recent common ancestor (MRCA) of all phleboviruses analysed in the present study. More recent viral transitions might include migrations from Spain to continental Portugal, and from there to the Portuguese Islands. Our findings suggest that the time of the MRCA of phleboviruses was dated around 225 years ago [95% HPD: 124-387 year before the last sampling date].

Molecular detection of Crimean-Congo haemorrhagic fever virus in ticks collected from infested livestock populations in a New Endemic Area, South of Iran.

OBJECTIVE: Crimean-Congo haemorrhagic fever (CCHF) is a viral zoonotic disease with potentially fatal systemic effects on man. We aimed to determine the presence of CCHF virus among collected ticks from domestic livestock from October 2012 to September 2013. METHODS: A total of 1245 hard and soft ticks were collected from naturally infested ruminants in Marvdasht County, Fars Province, south of Iran. Nine tick species and one unidentified species in four disparate genera were detected. A total of 200 ticks were randomly selected and analysed by reverse transcription-polymerase chain reaction (RT-PCR) for the presence of CCHF virus genome. RESULTS: The viral genome was detected in 4.5% (9 samples) of the studied tick population. The infected ticks belonged to the species of Hyalomma marginatum' Hyalomma anatolicum and Rhipicephalus sanguineus. The viruses detected in these three tick species were clustered in the same lineage as Matin and SR3 strains in Pakistan and some other Iranian strains. These results indicate that the ticks were wildly infected with a genetically closely related CCHF virus in the region. CONCLUSION: Regular controls and monitoring of livestock to reduce the dispersion of ticks and providing information to those involved in high-risk occupations are urgently required.