Abstract
BackgroundUsutu virus (USUV) is a rapidly spreading zoonotic arbovirus (arthropod-borne virus) and a considerable threat to the global avifauna and in isolated cases to human health. It is maintained in an enzootic cycle involving ornithophilic mosquitoes as vectors and birds as reservoir hosts. Despite massive die-offs in wild bird populations and the detection of severe neurological symptoms in infected humans, little is known about which mosquito species are involved in the propagation of USUV.MethodsIn the present study, the vector competence of a German (i.e. “Central European”) and a Serbian (i.e. “Southern European”) Culex pipiens biotype molestus laboratory colony was experimentally evaluated. For comparative purposes, Culex torrentium, a frequent species in Northern Europe, and Aedes aegypti, a primarily tropical species, were also tested. Adult female mosquitoes were exposed to bovine blood spiked with USUV Africa 2 and subsequently incubated at 25 °C. After 2 to 3 weeks saliva was collected from each individual mosquito to assess the ability of a mosquito species to transmit USUV.ResultsCulex pipiens biotype molestus mosquitoes originating from Germany and the Republic of Serbia and Cx. torrentium mosquitoes from Germany proved competent for USUV, as indicated by harboring viable virus in their saliva 21 days post infection. By contrast, Ae. aegypti mosquitoes were relatively refractory to an USUV infection, exhibiting low infection rates and lacking virus in their saliva.ConclusionsConsistent with the high prevalences and abundances of Cx. pipiens biotype molestus and Cx. torrentium in Central and Northern Europe, these two species have most likely played a historic role in the spread, maintenance, and introduction of USUV into Germany. Identification of the key USUV vectors enables the establishment and implementation of rigorous entomological surveillance programs and the development of effective, evidence-based vector control interventions.Graphical
Highlights
Usutu virus (USUV) is a rapidly spreading zoonotic arbovirus and a considerable threat to the global avifauna and in isolated cases to human health
Recent studies even indicate that human USUV infections are not as sporadic as previously presumed [6, 10,11,12], with so far 49 reported acute infections over the years (1981–2018) in the Central African Republic, Burkina Faso, Italy, Croatia, Germany, France, and Austria [6]
Culex torrentium females were produced from egg rafts collected in the field from different populations near Berlin and Bonn, Germany, after species identification of two to three larvae hatching from each raft by means of a real-time polymerase chain reaction (PCR) [27]
Summary
Usutu virus (USUV) is a rapidly spreading zoonotic arbovirus (arthropod-borne virus) and a considerable threat to the global avifauna and in isolated cases to human health It is maintained in an enzootic cycle involving ornithophilic mosquitoes as vectors and birds as reservoir hosts. Usutu virus (USUV; Flaviviridae, Flavivirus) is currently considered an emerging zoonotic arbovirus in Europe with an increase in registered cases and observed disease severity in both humans and animals. This flavivirus belongs to the Japanese encephalitis virus serocomplex with birds, mainly Eurasian blackbirds (Turdus merula), Eurasian magpies (Pica pica), house sparrows (Passer domesticus), and great grey owls (Strix nebulosa), as amplifying hosts [6, 7]. Recent studies even indicate that human USUV infections are not as sporadic as previously presumed [6, 10,11,12], with so far 49 reported acute infections over the years (1981–2018) in the Central African Republic, Burkina Faso, Italy, Croatia, Germany, France, and Austria [6]
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