Human dirofilariosis in Austria: the past, the present, the future

Abstract

Background Dirofilariosis is a vector-borne parasitosis caused by filarial nematodes of the genus Dirofilaria. In humans, who represent accidental hosts, dirofilariosis is mostly caused by Dirofilaria repens and Dirofilaria immitis. In Austria, the first reported case occurred in 1978. Since then, several (case) reports have been published. Methods A systematic and retrospective review of collected published cases and new, unpublished confirmed cases of human dirofilariosis occurring in Austria was performed. A nematode was extracted from the eyelid of a previously unreported case and subsequently characterized histologically and using molecular biology techniques. Results Data on a total of 39 cases of human dirofilariosis in Austria occurring between 1978 and 2020 are summarized. Over the past four decades the incidence has markedly increased, in particular after 1998. Of the 39 patients, men and women were equally affected, and the mean age was 47.1 years. The area most frequently affected was the head (38.5% of cases). Confined ocular involvement was observed in 23.1% of cases, and nematodes were isolated from the neck/trunk, extremities and the genito-inguinal area in 25.6, 15.4 and 15.4% of patients, respectively. Microfilariae were detected in two cases. Of the 39 patients, only 73.9% tested positive for anti-filarial antibodies and 56.3% for eosinophilia, despite successful isolation of a nematode; consequently, these measures did not represent reliable markers for dirofilariosis. Most patients had a travel history to countries endemic for Dirofilaria species. One patient who had not traveled abroad represented the only autochthonous case recorded to date. Dirofilaria repens was the predominant species, identified in 89.7% of cases. In the newly reported case of subcutaneous dirofilariosis, a live non-gravid Dirofilaria repens adult female of 12 cm length was isolated from the eyelid of the patient, and a video of the extraction is provided. Conclusions The incidence of human dirofilariosis cases has increased strikingly over the last four decades in Austria. More cases can be expected in the foreseeable future due to changes in human behavior and (travel) activities as well as climate changes and the associated alterations in the availability of the natural reservoir, the vectors and the intrinsic characteristics of the parasite.

Dirofilaria spp. and Angiostrongylus vasorum: Current Risk of Spreading in Central and Northern Europe

“…From 1978 to 2014, 33 cases of human dirofilariasis caused by D. repens were reported in Austria (30 cases), and three cases caused by D. immitis, rising to a total of 39 cases in 2020. Over the past four decades, incidence has markedly increased, particularly after 1998 [62,70,71]. In 2018, Austria was classified as endemic for D. repens (but not for D. immitis) with sporadic human cases [9].…”

Autochthonous Human Dirofilaria repens Infection in Austria

“…The first autochthonous case occurred in 2008 when a 34-year-old woman was bitten by a mosquito at the Austrian-Hungarian border [16]. Other Dirofilaria infections in Austria have been associated with a travel history to endemic regions, especially Mediterranean countries and Hungary [1,[23][24][25]. Between 1978 and 2018, 47 of D. repens cases were documented in Austrian dogs, most of which had a travel history to Hungary or the Western Balkans.…”

“…The highest incidence of Dirofilaria infection was collected between 2010 and 2019 (15 cases). Of the reviewed dirofilariosis cases, 89.7% were identified as D. repens infections [ 23 ]. The first autochthonous case occurred in 2008 when a 34-year-old woman was bitten by a mosquito at the Austrian–Hungarian border [ 16 ].…”

Estimated specific antibody-based true sero-prevalences of canine filariosis in dogs in Central Europe and the UK

“…Previous autochthonous cases of D. repens in humans have been described in Poland (Cielecka et al 2012 ), Italy (Pampiglione et al 2001 ), nine countries of the Balkan Peninsula (Tasić-Otašević et al 2015 ), Hungary (Dóczi et al 2015 ) and Slovakia (Babal et al 2008 ; Boldiš et al 2020 ). More recently, between 2017 and 2022, single cases of human D. repens infections were reported again from the Balkan area, in Serbia (Krstic et al 2017 ), Croatia (Skrinjar et al 2022 ), Bulgaria (Velev et al 2019 ) and Romania (Ciuca et al 2018 ), and further cases from Greece (Bozidis et al 2021 ) and Italy (Ahmed et al 2022 ), Interestingly, also in Austria, overall 39 human cases of dirofilariosis were identified between 1978 and 2020, with a general increasing course since 1998 (Riebenbauer et al 2021 ). In addition, single human cases were reported from south-eastern France (Hennocq et al 2020 ) and Germany (Uslu et al 2017 ), confirming a north- and westwards trend in Europe.…”