Subcutaneous tumor of the lower eyelid: a potential manifestation of a Dirofilaria repens infection

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.

Fallbericht und Literaturübersicht kutaner Dirofilariose

Gegenstand und Ziel: Der Fallbericht erörtert das diagnostische Vorgehen und differenzialdiagnostische Überlegungen bei Patienten mit Mikrofilarämie und negativem Dirofilaria-immitis-Antigentest und diskutiert die Infektion mit Dirofilaria repens und deren Therapie. Material und Methode: Bei einem Hund aus Ungarn wurden im Blutausstrich Mikrofilarien gefunden. Die weitere Diagnostik zur Differenzierung der Mikrofilarien umfasste einen Dirofilaria-immitis-Antigentest, eine Polymerasekettenreaktion zum Nachweis von Dirofilaria immitis und Dipetalonema reconditum sowie eine Saure-Phosphatase-Reaktion zur Diagnose einer Infektion mit Dirofilaria repens. Ergebnisse: Mittels der Saure-Phosphatase-Reaktion konnte eine Infektion mit Dirofilaria repens diagnostiziert werden. Die Therapie gegen die Mikrofilarien erfolgte mit Selamectin. Schlussfolgerung und klinische Relevanz: Bei mikrofilarämischen Patienten muss differenzialdiagnostisch neben einer Infektion mit Dirofilaria immitis eine Infektion mit anderen, weniger pathogenen Parasiten in Betracht gezogen werden, da sich die Notwendigkeit einer Therapie und das Therapieregime je nach Infektion deutlich unterscheiden.

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.

Discrete eyelid swelling caused by live subconjunctival Dirofilaria repens

We present a case concerning a 48 year-old man, who had complaints about ocular pains and an unpleasant feeling, which had started two days before admission. It was as if there was “something moving in his left eye.” The examination showed an extremely motile white worm, which was wrapped in concentric circles around the limb in the subconjunctival space of the patient’s left eye. It was identified as the adult female form of Dirofilaria repens. The patient had a normal clinical finding, except eosinophilia. Ocular filariasis is as a possibility to think about, even when the cases are not in a typically endemic area and with no specific subjective complains.

[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.

Human Dirofilaria repens infection in Serbia

Human infection by Dirofilaria repens in Serbia has been increasing steadily. The first case was reported in 1971, presented in the form of a single subcutaneous nodule on the back of a young boy. As established by a literature search, eight additional cases were reported until mid-2001. The most frequent site of infection was subcutaneous tissue, with the exception of two cases, in which parasites were found in subconjunctiva and epididymis. Our study, conducted from 2001 to 2008, encompasses 19 new cases. Most of them (63.1%) presented as ocular or periocular infections, in which the parasite was typically found under the conjunctiva. In other cases a parasitic nodule was localized in the temporal region of the head, epididymis, testicle, abdomen, breast or arm. The diagnosis was made by morphological and histological analysis of the extracted intact worms and parasite sections from the tissue. Morphology of the filarial worms was well preserved in more than half of the cases (12/19) and there was never more than one parasite found inside the lesions. Adult worms and immature nematodes were observed in nine and seven cases, respectively. Furthermore, in two cases microfilariae were discovered inside the pseudocoelom, sections of the female reproductive tubes filled with clearly visible larval stages. Dirofilaria repens infection was diagnosed by its morphological features (17/19) or by performing polymerase chain reactions (PCR) using paraffin-embedded tissues (2/19) in the cases where the morphology was insufficient for identification and the parasites had been determined initially as Dirofilaria spp. The amplified 246 bp PCR product showed that the worms were D. repens.

A case of lacrimal gland dirofilariasis

A patient with a diagnosis of chronic and idiopathic unilateral dacryoadenitis was submitted to our clinic for diagnostic reasons from a regional hospital. Within a period of 1 year, this was the second onset of a swelling in the region of the lacrimal gland which - unlike the first time - showed resistance to antibiotic treatment. The patient's general and ophthalmic condition was good, and his only complaint was of cosmetic nature because of the disfiguring swelling in the lateral part of the left upper eyelid. Basic laboratory findings showed no abnormalities and radiographic imaging showed enlargement of the left lacrimal gland without bony destruction. Guided by epidemiological data for noninfectious dacryoadenitis we decided to perform excisional biopsy of the left lacrimal gland. To our surprise, the pathologist verified the presence of a worm of the genus Dirofilaria, which is, to the best of our knowledge, the second reported case of lacrimal gland dirofilariasis in the literature and the second reported case of such a disease in Croatia.