Severe fever with thrombocytopenia syndrome virus (SFTSV), an emerging human pathogen naturally transmitted by ticks, has spread widely since it was first detected in 2010. Although SFTSV-specific antibodies have been detected in wild birds, these natural reservoir and amplifying hosts for the virus have not been well studied.
Here we report an experimental infection of spotted doves ( Streptopelia chinensis) with two strains of SFTSV, JS2010-14, a Chinese lineage strain, and JS2014-16, a Japanese lineage strain, which represent the main viral genotypes currently circulating in East Asia. In these studies, we have determined that spotted doves are susceptible to SFTSV and the severity of the viremia is dose-dependent. When challenged with 10 7 and 10 5 PFU, all doves developed viremia which peaked 3–5 days post infection (dpi). Only a subset (25–62.5%) of the birds developed viremia when challenged at 10 3 PFU. Virulence of SFTSV in spotted doves was strain dependent. Infection with 10 7 PFU of strain JS2014-16 resulted in 12.5% mortality over 6.8 days and mean peak viremia titers of 10 6.9 PFU/mL in experimentally inoculated birds. All doves inoculated with 10 7 PFU of the JS2010-14 strain survived infection with relatively lower mean viremia titers (10 5.6 PFU/mL at peak) over 6.1 days.
Our results suggest that spotted doves, one of the most abundant bird species in China, could be a competent amplifying host for SFTSV and play an important role in its ecology. Between the two SFTSV strains, the strain of the Japanese lineage caused mortality, higher viremia titers in infected birds over a longer time period than did the Chinese strain. Our observations shed light on the ecology of SFTSV, which could benefit the implementation of surveillance and control programs.
Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging human pathogen naturally transmitted by ticks. Our recent study has showed that some species of migratory birds, such as swan geese and spotted doves, can be parasitized by Haemaphysalis longicornis, an SFTSV vector, and antibodies against the SFTSV detected in these species. These data demonstrate that migratory birds are infected with SFTSV and may also play a role in the infection of ticks with SFTSV. Other studies have reported that migratory bird routes and the distribution of H. longicornis in East Asia overlap with the geographic distribution of SFTSV. Migratory birds are known to be carriers and transmitters of infectious agents, like the causative agents of influenza, West Nile encephalitis, and Lyme disease. Wild birds often travel long distances carrying various parasites, including ticks, which may be infected with viruses and bacteria. It is therefore reasonable to hypothesize that migratory birds may have played an important role in spreading SFTSV in two potential transmission scenarios: 1) birds are infected with the virus and transmit it back to ticks endemically or in a distal region, or 2) they are carriers of parasitic ticks that are infected with the virus. Here we report an experimental infection of spotted doves ( Streptopelia chinensis) with two strains of SFTSV, JS2010-14 from a Chinese lineage and JS2014-16 from a Japanese lineage, which represent the main viral genotypes currently circulating in East Asia. We determined that spotted doves are susceptible to SFTSV and that the severity of the viremia was dose and strain dependent. Infection with the strain of JS2014-16 led to a death rate of 12.5% and higher viremia titers in experimentally inoculated birds while doves inoculated with the JS2010-14 strain survived infection with relatively lower virus titers in the blood. These findings provide novel insights for understanding the rapid spread of the virus in a short time span, in particular the SFTSV strains from the Japanese lineage (genotype E).