Dirofilaria repens infection case in Hungary: a case report

Recent advances on Dirofilaria repens in dogs and humans in Europe

Dirofilaria repens is a nematode affecting domestic and wild canids, transmitted by several species of mosquitoes. It usually causes a non-pathogenic subcutaneous infection in dogs and is the principal agent of human dirofilariosis in the Old World. In the last decades, D. repens has increased in prevalence in areas where it has already been reported and its distribution range has expanded into new areas of Europe, representing a paradigmatic example of an emergent pathogen. Despite its emergence and zoonotic impact, D. repens has received less attention by scientists compared to Dirofilaria immitis. In this review we report the recent advances of D. repens infection in dogs and humans, and transmission by vectors, and discuss possible factors that influence the spread and increase of this zoonotic parasite in Europe. There is evidence that D. repens has spread faster than D. immitis from the endemic areas of southern Europe to northern Europe. Climate change affecting mosquito vectors and the facilitation of pet travel seem to have contributed to this expansion; however, in the authors' opinion, the major factor is likely the rate of undiagnosed dogs continuing to perpetuate the life-cycle of D. repens. Many infected dogs remain undetected due to the subclinical nature of the disease, the lack of rapid and reliable diagnostic tools and the poor knowledge and still low awareness of D. repens in non-endemic areas. Improved diagnostic tools are warranted to bring D. repens diagnosis to the state of D. immitis diagnosis, as well as improved screening of imported dogs and promotion of preventative measures among veterinarians and dog owners. For vector-borne diseases involving pets, veterinarians play a significant role in prevention and should be more aware of their responsibility in reducing the impact of the zoonotic agents. In addition, they should enhance multisectorial collaboration with medical entomologists and the public health experts, under the concept and the actions of One Health-One Medicine.

Circulation of Dirofilaria repens, Setaria tundra, and Onchocercidae species in Hungary during the period 2011-2013

Dirofilaria repens and recently Dirofilaria immitis are known to be endemic in Hungary. Since there is no related research on Dirofilaria carrier mosquito species from Hungary, we conducted a three-year mosquito surveillance study between 2011 and 2013. During the study period we examined 23,139 female mosquitoes with a generic filaria-specific TaqMan PCR assay, and characterized them by sequencing a 500 bp segment of 12S rRNA. An important result of our study was the detection of Setaria tundra and D. repens along with an unidentified Onchocercidae nematode. D. repens is known to be endemic in Hungary, however, the detection of S. tundra in all sampling sites throughout the study period indicates for the first time the endemicity of this parasite in Hungary. The Onchocercidae sp. nematode showed 95% nucleotide identity with previously detected unidentified nematodes from Germany, indicating a broader geographical distribution of this nematode in Europe. D. immitis specific DNA was not detected among the screened mosquitoes in this study. Here we report 11 mosquito species as potential vector organisms for local filarial infections, including Aedes vexans, Ochlerotatus annulipes, Ochlerotatus sticticus, Coquillettidia richiardii, Anopheles hyrcanus and Ochlerotatus rusticus. Dirofilaria development unit was calculated and the potential transmission period was estimated, which ranged between 65 and 113 days between sampling seasons. A relatively high infection rate (36.8%) was identified, which is a notable finding for veterinary and human health professionals. Moreover, the results of our study widen the group of possible mosquito vector species for D. repens and S. tundra in Central Europe.

Description of five dirofilariasis cases in South Hungary and review epidemiology of this disease for the country

BACKGROUND

Dirofilariasis is an emerging zoonosis (supported by climate change) in Central Europe. Human infections are usually caused by Dirofilaria repens and Dirofilaria immitis with mediation of mosquito vectors. Aims of this publication were to report our dirofilariasis cases, and to summarize Hungarian epidemiological data by reviewing literature.

METHODS AND RESULTS

We present five (four ophthalomological, one subcutaneous) cases observed within a 2-year period in Southern Hungary. Ages of infected patients were between 31 and 74 years. First case during pregnancy is also reported. There was no travel history in the anamnesis of patients which could explain acquisition of the infection. Moving, intact worms eliminated by surgical interventions were identified on the basis of morphological features as D. repens. Since the first report of human case, 115 further episodes (in addition to ours) were diagnosed in Hungary. Mean age of the patients was 47 years. Reviewing national reports, the ratio of subcutaneous infections was higher than that of the ocular ones (66 and 45, respectively). Evaluation of the territorial distribution of human episodes revealed that most infections occurred in patients living in the Danube-Tisza interfluvial region and eastern part of the country. However, sporadic cases were also found in western counties during 2014.

CONCLUSION

Most of the Hungarian dirofilariasis cases were autochthonous infections. Occurrence in the western counties may suggest the spreading of this emerging zoonosis to these areas. Comprehensive monitoring and data analysis are desirable, therefore reporting the epidemiologic data in the case of human infections should be made mandatory.

Human and animal dirofilariasis: the emergence of a zoonotic mosaic

Dirofilariasis represents a zoonotic mosaic, which includes two main filarial species (Dirofilaria immitis and D. repens) that have adapted to canine, feline, and human hosts with distinct biological and clinical implications. At the same time, both D. immitis and D. repens are themselves hosts to symbiotic bacteria of the genus Wolbachia, the study of which has resulted in a profound shift in the understanding of filarial biology, the mechanisms of the pathologies that they produce in their hosts, and issues related to dirofilariasis treatment. Moreover, because dirofilariasis is a vector-borne transmitted disease, their distribution and infection rates have undergone significant modifications influenced by global climate change. Despite advances in our knowledge of D. immitis and D. repens and the pathologies that they inflict on different hosts, there are still many unknown aspects of dirofilariasis. This review is focused on human and animal dirofilariasis, including the basic morphology, biology, protein composition, and metabolism of Dirofilaria species; the climate and human behavioral factors that influence distribution dynamics; the disease pathology; the host-parasite relationship; the mechanisms involved in parasite survival; the immune response and pathogenesis; and the clinical management of human and animal infections.

[The first autochthonous case of subcutaneous dirofilariosis in Austria]

Dirofilaria repens, a common parasite of carnivore mammals, is transmitted by mosquitos and may also infect humans accidentally causing a subcutaneous dirofilariosis. Autochthonous infections of dogs, foxes or cats with D. repens has not been found in Austria so far; however, 12 cases of imported subcutaneous dirofilariosis in man were noticed between 1981 and 2005. The recent case report deals with the 13(th) human case, which has to be considered as the first autochthonously acquired in Austria.