Sandfly-Borne Phleboviruses in Portugal: Four and Still Counting

Epidemiology of Sandfly-Borne Phleboviruses in North Africa: An Overview

Eight sandfly-borne phleboviruses were found to circulate in North Africa. Phleboviruses detected in sandflies were Toscana (TOSV), Sandfly Fever Sicilian (SFSV), Sandfly Fever Naples (SFNV), Cyprus (CYPV), Punique (PUNV), Utique, Saddaguia, and Medjerda Valley (MVV) viruses, yielding an overall infection rate of 0.02-0.6%. Phlebotomus perniciosus and Phlebotomus longicuspis were the most common vector species in the region. TOSV seroprevalence in dogs from Algeria (4.56%) and Tunisia (7.5%) was low and close, unlike SFSV (38.1%) and PUNV (43.5%), which were restricted to Tunisia. SFSV (1.3-21%) and TOSV (3.8-50%) were the most prevalent among humans. TOSV was frequently detected and symptomatically confirmed in both Algeria (3.8%) and Tunisia (12.86%). Other sandfly-borne phleboviruses have also been detected but less importantly, such as SFNV in Morocco (2.9%) and Tunisia (1.1%) and PUNV (8.72%), CYPV (2.9%), and MVV (1.35%) in Tunisia. Their distribution was mainly northern. Overall, 15.9% of the healthy population were seropositive for sandfly-borne phleboviruses, with evidenced cocirculation. Noticeably, studies conducted in Morocco were mostly interested in TOSV in sandflies. Available data from Libya and Egypt were scant or historical. Further elaboration is required to check the sporadic detection of less-prevalent phleboviruses and fully elucidate the epidemiological situation.

Toscana Virus in Wild-Caught Sand Flies in Portugal, Findings from the National Vector Surveillance Network, 2023

Phlebotomine sand flies play a crucial role in both human and veterinary medicine, acting as vectors for Leishmania parasites and most known phleboviruses. In Portugal, the REVIVE program, a comprehensive national surveillance network under the Ministry of Health, has included sand fly surveys since 2016. REVIVE aims to identify existing sand fly species in the country, determine which pathogens are circulating among them, and provide actionable insights for prevention and control measures when necessary. In this way, annually, from May to October, health technicians collect sand flies across mainland Portugal with CDC light traps. The collected sand flies are sent to the Centre for Vectors and Infectious Diseases Research for species identification and molecular screening of pathogens. On 21 September 2023, Toscana virus (TOSV), a well-known phlebovirus in the Mediterranean region due to its capacity to cause neurological disease, was detected in a pool of 30 sand flies collected in Algarve, the southernmost region of Portugal. A 668 bp partial sequence of the nucleoprotein gene shows similarity with TOSV strains from Spain. To our knowledge, this is the first detection of TOSV in its vector in this country, having previously only been reported in vertebrate hosts. These findings highlight the important role of ongoing surveillance efforts in monitoring and understanding the dynamics of sand fly-borne diseases in Portugal.

Co-Circulation of Leishmania Parasites and Phleboviruses in a Population of Sand Flies Collected in the South of Portugal

In the Old World, phlebotomine sand flies from the genus Phlebotomus are implicated in the transmission of Leishmania spp. parasites (Kinetoplastida: Trypanosomatidae) and viruses belonging to the genus Phlebovirus (Bunyavirales: Phenuiviridae). Two of the five sand fly species known to occur in Portugal, Phlebotomus perniciosus and Ph. ariasi, the former being the most ubiquitous, are recognized vectors of Leishmania infantum, which causes visceral leishmaniasis, the most prevalent form of leishmaniasis in the country. Phlebotomus perniciosus is also the vector of the neurotropic Toscana virus, which can cause aseptic meningitis. Entomological surveillance is essential to provide fundamental data about the presence of vectors and the pathogens they can carry. As such, and given the lack of data in Portugal, an entomological survey took place in the Algarve, the southernmost region of the country, from May to October 2018. Polymerase chain reaction assays were performed in order to detect the presence of the above-mentioned pathogens in sand fly pools. Not only were both Leishmania parasites and phleboviruses detected during this study, but more importantly, it was the first time their co-circulation was verified in the same sand fly population collected in Portugal.