Persistence of Toscana virus in sugar and blood meals of phlebotomine sand flies: epidemiological and experimental consequences

Abstract

Many virological studies have tested the persistence of enveloped RNA viruses in various environmental and laboratory conditions and shown their short-term persistence. In this article, we analyzed Toscana virus (TOSV) infectivity, a pathogenic sandfly-borne phlebovirus, in two different conditions: in the sugar meal and blood meal of sand flies. Our results showed that TOSV RNA was detectable up to 15 days in sugar solution at 26°C and up to 6 hours in blood at 37°C. Moreover, TOSV remains infective for 7 days in sugar solution and for minimum 6 hours in rabbit blood. TOSV has shown persistent infectivity/viability under different conditions, which can lead to important epidemiological consequences and raises new hypotheses about its natural cycle.

Sand flies and Toscana virus: intra-vector infection dynamics and impact onPhlebotomus perniciosuslife-history traits

“…This mode of transmission has already been shown experimentally with Massilia virus, another phlebovirus genetically related to TOSV (14). Moreover, TOSV persistence and infectivity in sand fly sugar meal has recently been demonstrated in laboratory conditions (13).…”

“…perniciosus between three and six dpi although this should be confirmed by fine dissection and testing of only the salivary glands. In addition, the release of TOSV into sugar meal together with recent demonstration of long-term persistence of infectious TOSV in sugar meal (up to 7 days at 26°C) (13) suggest that sand fly to sand fly transmission can occur orally during sap feeding in nature. To better understand the transmission dynamics and be able to predict TOSV emergence it would be crucial to investigate further the possible alternative transmission routes of TOSV between sand flies through their sugar meal.…”

“…perniciosus (6), their significance in the natural TOSV cycle remains uncertain and warrants further investigation. Recently it was hypothesized that transmission from infected to uninfected sand flies during sugar feeding might play a significant role in the virus natural cycle (13). This mode of transmission has already been shown experimentally with Massilia virus, another phlebovirus genetically related to TOSV (14).…”

“…Feeding was performed for six hours, with reduced brightness, and regular manual blood mix to avoid clotting. Six hours of blood feeding was chosen as TOSV remains infectious and at the same amount in the blood meal under these conditions as previously described (13). As engorged females are fragile, it is recommended to handle them after the first 24 hours of digestion (63).…”

Human and animal exposure to newly discovered sand fly viruses, China

“…In the Sichuan Jiuzhaigou region of China, pigs are the primary blood source for sandflies, followed by chickens and dogs (Chen et al, 2016). Sandflies also act as reservoir hosts for certain viruses like TOSV (Laroche et al, 2023), the sandfly fever Sicilian virus (SFSV) (Al-Numaani et al, 2023) and sandfly fever Naples virus (SFNV) (Reeves et al, 2015), in addition to being major vectors for Leishmania parasites (Volf et al, 2008). As bloodfeeding insects, sandflies transmit viruses by biting humans and other mammals.…”