Molecular detection of Setaria tundra (Nematoda: Filarioidea) and an unidentified filarial species in mosquitoes in Germany

<p>Abstract</p> <p>Background</p> <p>Knowledge of the potential vector role of Culicidae mosquitoes in Germany is very scanty, and until recently it was generally assumed that they are not involved in the transmission of anthroponotic or zoonotic pathogens in this country. However, anticipated changes in the course of global warming and globalization may alter their status.</p> <p>Methods</p> <p>We conducted a molecular mass screening of mosquitoes for filarial parasites using mitochondrial 12S rRNA-based real-time PCR.</p> <p>Results</p> <p>No parasites causing disease in humans such as <it>Dirofilaria </it>spp. were detected in about 83,000 mosquitoes tested, which had been collected in 2009 and 2010 in 16 locations throughout Germany. However, minimum infection rates of up to 24 per 1000 mosquitoes were revealed, which could be attributed to mosquito infection with <it>Setaria tundra </it>and a yet unidentified second parasite. <it>Setaria tundra </it>was found to be widespread in southern Germany in various mosquito species, except <it>Culex </it>spp. In contrast, the unidentified filarial species was exclusively found in <it>Culex </it>spp. in northern Baden-Württemberg, and is likely to be a bird parasite.</p> <p>Conclusions</p> <p>Although dirofilariasis appears to be emerging and spreading in Europe, the absence of <it>Dirofilaria </it>spp. or other zoonotic filariae in our sample allows the conclusion that the risk of autochthonous infection in Germany is still very low. Potential vectors of <it>S. tundra </it>in Germany are <it>Ochlerotatus sticticus</it>, <it>Oc. cantans</it>, <it>Aedes vexans </it>and <it>Anopheles claviger</it>. Technically, the synergism between entomologists, virologists and parasitologists, combined with state-of-the-art methods allows a very efficient near-real-time monitoring of a wide spectrum of both human and veterinary pathogens, including new distribution records of parasite species and the incrimination of their potential vectors.</p

Vector Competence of the Invasive Mosquito Species Aedes koreicus for Arboviruses and Interference with a Novel Insect Specific Virus

The global spread of invasive mosquito species increases arbovirus infections. In addition to the invasive species Aedes albopictus and Aedes japonicus, Aedes koreicus has spread within Central Europe. Extensive information on its vector competence is missing. Ae. koreicus from Germany were investigated for their vector competence for chikungunya virus (CHIKV), Zika virus (ZIKV) and West Nile virus (WNV). Experiments were performed under different climate conditions (27 ± 5 °C; 24 ± 5 °C) for fourteen days. Ae. koreicus had the potential to transmit CHIKV and ZIKV but not WNV. Transmission was exclusively observed at the higher temperature, and transmission efficiency was rather low, at 4.6% (CHIKV) or 4.7% (ZIKV). Using a whole virome analysis, a novel mosquito-associated virus, designated Wiesbaden virus (WBDV), was identified in Ae. koreicus. Linking the WBDV infection status of single specimens to their transmission capability for the arboviruses revealed no influence on ZIKV transmission. In contrast, a coinfection of WBDV and CHIKV likely has a boost effect on CHIKV transmission. Due to its current distribution, the risk of arbovirus transmission by Ae. koreicus in Europe is rather low but might gain importance, especially in regions with higher temperatures. The impact of WBDV on arbovirus transmission should be analyzed in more detail

Epizootic Emergence of Usutu Virus in Wild and Captive Birds in Germany

This study aimed to identify the causative agent of mass mortality in wild and captive birds in southwest Germany and to gather insights into the phylogenetic relationship and spatial distribution of the pathogen. Since June 2011, 223 dead birds were collected and tested for the presence of viral pathogens. Usutu virus (USUV) RNA was detected by real-time RT-PCR in 86 birds representing 6 species. The virus was isolated in cell culture from the heart of 18 Blackbirds (Turdus merula). USUV-specific antigen was demonstrated by immunohistochemistry in brain, heart, liver, and lung of infected Blackbirds. The complete polyprotein coding sequence was obtained by deep sequencing of liver and spleen samples of a dead Blackbird from Mannheim (BH65/11-02-03). Phylogenetic analysis of the German USUV strain BH65/11-02-03 revealed a close relationship with strain Vienna that caused mass mortality among birds in Austria in 2001. Wild birds from lowland river valleys in southwest Germany were mainly affected by USUV, but also birds kept in aviaries. Our data suggest that after the initial detection of USUV in German mosquitoes in 2010, the virus spread in 2011 and caused epizootics among wild and captive birds in southwest Germany. The data also indicate an increased risk of USUV infections in humans in Germany

Special Issue &ldquo;Mosquito-Borne Virus Ecology&rdquo;

Mosquito-borne viruses (MBVs), also known as moboviruses, are associated mainly with mosquitoes and are able to infect humans and other vertebrates [...

Experimental transmission of Zika virus by Aedes japonicus japonicus from southwestern Germany

The invasive mosquito species Aedes japonicus japonicus (Ae. japonicus) is widely distributed in Central Europe and is a known vector of various arboviruses in the laboratory, including flaviviruses such as Japanese Encephalitis virus or West Nile virus. However, the vector competence of Ae. japonicus for the recently emerging Zika virus (ZIKV) has not been determined. Therefore, field-caught Ae. japonicus from Germany were orally infected with ZIKV and incubated at 21, 24, or 27 degrees C to evaluate the vector competence under climate conditions representative of the temperate regions (21 degrees C) in the species' main distribution area in Europe and of Mediterranean regions (27 degrees C). Aedes japonicus was susceptible to ZIKV at all temperatures, showing infection rates between 10.0% (21 degrees C) and 66.7% (27 degrees C). However, virus transmission was detected exclusively at 27 degrees C with a transmission rate of 14.3% and a transmission efficiency of 9.5%. Taking into account the present distribution of Ae. japonicus in the temperate regions of Central Europe, the risk of ZIKV transmission by the studied Ae. japonicus population in Central Europe has to be considered as low. Nevertheless, due to the species' vector competence for ZIKV and other mosquito-borne viruses, in combination with the possibility of further spread to Mediterranean regions, Ae. japonicus must be kept in mind as a potential vector of pathogens inside and outside of Europe.Peer reviewe