Molecular detection of Dirofilaria immitis, Dirofilaria repens and Setaria tundra in mosquitoes from Germany

Abstract

BackgroundAs a result of globalization and climate change, Dirofilaria immitis and Dirofilaria repens, the causative agents of dirofilariosis in Europe, continue to spread from endemic areas in the Mediterranean to northern and northeastern regions of Europe where autochthonous cases of dirofilarial infections have increasingly been observed in dogs and humans. Whilst D. repens was recently reported from mosquitoes in putatively non-endemic areas, D. immitis has never been demonstrated in mosquitoes from Europe outside the Mediterranean.MethodsFrom 2011 to 2013, mosquitoes collected within the framework of a German national mosquito monitoring programme were screened for filarial nematodes using a newly designed filarioid-specific real-time PCR assay. Positive samples were further processed by conventional PCR amplification of the cytochrome c oxidase subunit I (COI) gene, amplicons were sequenced and sequences blasted against GenBank.ResultsApproximately 17,000 female mosquitoes were subjected to filarial screening. Out of 955 pools examined, nine tested positive for filariae. Two of the COI sequences indicated D. immitis, one D. repens and four Setaria tundra. Two sequences could not be assigned to a known species due to a lack of similar GenBank entries. Whilst D. immitis and the unknown parasites were detected in Culex pipiens/torrentium, D. repens was found in a single Anopheles daciae and all S. tundra were demonstrated in Aedes vexans. All positive mosquitoes were collected between mid-June and early September.ConclusionThe finding of dirofilariae in German mosquitoes implies the possibility of a local natural transmission cycle. While the routes of introduction to Germany and the origin of the filariae cannot be determined retrospectively, potential culicid vectors and reservoir hosts must prospectively be identified and awareness among physicians, veterinarians and public health personnel be created. The health impact of S. tundra on the indigenous cervid fauna needs further investigation.

Evaluation of the Adulticidal Efficacy of Imidacloprid 10 %/Moxidectin 2.5 % (w/v) Spot-on (Advocate®, Advantage® Multi) against Dirofilaria repens in Experimentally Infected Dogs

“…Recently, Tappe et al (2014) described the first autochthonous human case in Germany, after a series of cases in dogs in previous years had indicated the occurrence of D. repens there (Hermosilla et al 2006, Sassnau et al 2009). Since the parasite has also been repeatedly detected in a local mosquito population in Germany, a stable local transmission is now assumed (Czajka et al 2014;Kronefeld et al 2014). Adult D. repens live and mate mainly in the subcutaneous tissue and perimuscular fasciae and female worms release their offspring, the microfilariae (MF), into the blood stream.…”

Zoonotic Dirofilaria repens (Nematoda: Filarioidea) in Aedes vexans mosquitoes, Czech Republic

“…vexans (Kronefeld et al 2014). However, the pathogenic potential of Setaria for free-living animals (e.g.…”

“…Taking into account the long flying distance (migrations of up to 15 km), this species becomes suitable for local transmission and the spread of zoonotic dirofilariosis into new endemic foci. Outside the traditional Mediterranean distribution area, dirofilarial worms have also recently been described in mosquitoes from Slovakia (Bocková et al 2013), Austria (Silbermayr et al 2014) and Germany (Czaijka et al 2014;Kronefeld et al 2014), the more so as in two of the four cases (Bocková et al 2013;Czajka et al 2014) Ae. vexans was involved.…”

Culex pipiens as a potential vector for transmission of Dirofilaria immitis and other unclassified Filarioidea in Southwest Spain

“…In neighbouring Portugal, Cx. pipiens revealed a higher D. immitis infection rate (0.5%) , while in Italy, the prevalence rates for this species range between 0.05% and 0.54% Latrofa et al, 2012), being lower (0.12%) in Turkey (Yildirim et al, 2011) or in Germany (0.02%) (Kronefeld et al, 2014), but reaching as high as 1.49% in Hungary (Zittra et al, 2015).…”

“…pipiens. Kronefeld et al (2014) suggested the presence of Cardiofilaria pavlovskyi on mosquitoes in Germany. Curiously, this species has also been previously reported in birds in Spain by López-Caballero (1982).…”