Subconjunctival infection with Dirofilaria repens: serological confirmation of cure following surgery

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.

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.

Cutaneous dirofilariasis presenting as an eyelid swelling

Dirofilariasis is a common filarial infection occurring in domestic and wild animals as a result of arthropod bites. However, it can be transmitted to humans after mosquito bites. Here, we report a case of a 54-year-old lady who developed an unilateral eyelid swelling secondary to Dirofilaria repens.

[Subconjunctival dirofilariasis: a case report]

INTRODUCTION

Dirofilariasis is a disease rarely seen in humans, occurring commonly in noncarnivorous mammals. The microfilariae are transmitted by a mosquito vector. Ocular dirofilariasis is rarely described in the ophthalmic literature.

CASE REPORT

An 81-year-old woman living in the north of France had a history of sudden pain and swelling of the left orbit. On slit lamp examination, a white worm was seen under the superior bulbar conjunctiva. Excision of the subconjunctival worm was adequate treatment and was important for parasite identification.

DISCUSSION

Dirofilariasis is broad-based and is more common in Italy. Cases in France are found in the south. Ocular symptoms are frequently subconjunctival, but many cases of orbital involvement are found. Treatment is only surgical; systemic medication is not necessary.

CONCLUSION

Ocular dirofilariasis is exceptional. Case reports in ophthalmic literature are rare. This parasite infection is probably underdiagnosed.

Heartworm disease in animals and humans

Heartworm disease due to Dirofilaria immitis continues to cause severe disease and even death in dogs and other animals in many parts of the world, even though safe, highly effective and convenient preventatives have been available for the past two decades. Moreover, the parasite and vector mosquitoes continue to spread into areas where they have not been reported previously. Heartworm societies have been established in the USA and Japan and the First European Dirofilaria Days (FEDD) Conference was held in Zagreb, Croatia, in February of 2007. These organizations promote awareness, encourage research and provide updated guidelines for the diagnosis, treatment and prevention of heartworm disease. The chapter begins with a review of the biology and life cycle of the parasite. It continues with the prevalence and distribution of the disease in domestic and wild animals, with emphasis on more recent data on the spreading of the disease and the use of molecular biology techniques in vector studies. The section on pathogenesis and immunology also includes a discussion of the current knowledge of the potential role of the Wolbachia endosymbiont in inflammatory and immune responses to D. immitis infection, diagnostic use of specific immune responses to the bacteria, immunomodulatory activity and antibiotic treatment of infected animals. Canine, feline and ferret heartworm disease are updated with regard to the clinical presentation, diagnosis, prevention, therapy and management of the disease, with special emphasis on the recently described Heartworm Associated Respiratory Disease (HARD) Syndrome in cats. The section devoted to heartworm infection in humans also includes notes on other epizootic filariae, particularly D. repens in humans in Europe. The chapter concludes with a discussion on emerging strategies in heartworm treatment and control, highlighting the potential role of tetracycline antibiotics in adulticidal therapy.

Isolated optic neuritis from an identified Gnathostoma spinigerum

PURPOSE

To describe a patient with isolated monocular optic neuritis caused by an identified Gnathostoma spinigerum infestation.

CASE REPORT

A 21-year-old man developed a swollen eyelid and painful monocular visual loss of his left eye which did not improve after treatment by intravenous steroid and albendazole. A remarkable eosinophilia in his peripheral blood count was demonstrated. The patient subsequently found a live parasite emerged from his lower eyelid and it was successfully removed by himself. Gross and histopathology examinations of the obtained parasite was undertaken. The parasite was identified as Gnathostoma spinigerum. His blood test for Gnathostoma antibody was positive.

DISCUSSION

The etiology of isolated optic neuritis in this patient was Gnathostoma spinigerum which was confirmed by the histopathology of the obtained parasite and the positive serologic test.

CONCLUSIONS

We could identify the exact parasite that was proven to cause an isolated optic neuritis. The immediate removal of a causative parasite maynot result in an improvement of the injured tissue but is beneficial in preventing further destruction as well as future complications.

What is happening outside North America regarding human dirofilariasis?

The etiologic agents of human dirofilariasis in the Old World are Dirofilaria immitis, which cause pulmonary and subcutaneous nodules, and Dirofilaria repens, which cause ocular lesions. Although reports of new cases of dirofilariasis are sporadic in other parts of the world, a considerable amount of information is generated in Europe regarding human dirofilariasis. Most cases have been detected in the Mediterranean countries, Ukraine, and Russia; however, isolated or short series of cases have been reported in the Balkan Republics and central and northern European countries. Seroepidemiologic studies have provided evidence that humans living in endemic areas present rates of infection similar to those of the autochthonous canine populations. Antibodies against endosymbiont Wolbachia bacteria have been demonstrated recently in human Dirofilaria infections. During D. immitis infections, preadult worms and third- and fourth-stage larvae are often destroyed by the host reaction, releasing a considerable amount of Wolbachia, and a Th1-type response against Wolbachia and/or filarial antigens is mounted. On the contrary, infections with D. repens, in which worms frequently remain intact, no Th1-type response has been observed. As humans are resistant hosts, the Th1-response could have a role in the resistance against parasites. The causes for the rise in the incidence of human dirofilariasis as well as the possible application of Wolbachia antigens in the serodiagnosis of human infections are discussed.

A case of palpebral dirofilariasis

PURPOSE

Dirofilaria repens infection is the most frequent and widespread dirofilariasis in the world. In Italy subcutaneous dirofilariasis is present especially in Northern-Central areas.

METHODS

A woman with a palpebral lump is presented.

RESULTS

After subcutaneous and muscular décollement, the authors found and removed a parasite. The final diagnosis was subcutaneous parasitosis due to D. repens.

CONCLUSIONS

Surgery was both diagnostic and therapeutic.

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

PURPOSE

To report a case of Dirofilaria repens presenting as a subcutaneous tumor of the lower eyelid.

METHODS

Interventional case report.

RESULTS

A 29-year-old man of Greek origin without systemic symptoms presented with a 3-week history of a small painless mass localized in the medial part of the lower eyelid. There was no history of a preceding trauma, injury, or visual impairment; however, the patient had recently been on a holiday in Italy. The lesion persisted after systemic antibiotic treatment. Routine blood tests were normal and the efferent tear ducts were patent. Upon surgical intervention a yellowish, pea-sized cyst-like structure was found beneath the orbicularis muscle and removed in toto. Histologic examination revealed the presence of a wormlike structure with the characteristic features of a single adult Dirofilaria repens nematode.

CONCLUSIONS

Infection with the nematode Dirofilaria repens has to be considered in the differential diagnosis of malignant and benign tumors of subcutaneous periocular tissues in patients who traveled to endemic areas.

Dirofilarial infection presenting as a facial mass: case report of an emerging zoonosis

Dirofilariasis is a parasitic infection caused by nematodes. Human infection remains rare but is increasing in scope, particularly in endemic areas. Dirofilariasis typically presents as a subcutaneous mass or with pulmonary nodules. Here, we present the case of a 73-year-old woman whose asymptomatic facial mass was caused by dirofilarial infection. The pathophysiology, diagnosis, and treatment of dirofilariasis of the head and neck will be discussed. In endemic areas, dirofilariasis must be considered in the differential diagnosis of facial masses.

Dirofilarial infection of the orbit

PURPOSE

We report on two cases of dirofilaria involving the orbit. There have been no previous case reports of superior rectus involvement in the literature.

METHODS

The presenting history, ocular examination, relevant investigations and treatments are discussed.

RESULTS

In both cases the lesion was debulked surgically with subsequent histopathological identification of a dirofilarial worm. Postoperatively both patients were relieved of their presenting symptoms with no recurrence of the lesion.

CONCLUSIONS

Dirofilarial involvement of the orbit is uncommon. It should be considered as a rare infectious form of specific orbital inflammation and considered in the differential diagnosis of orbital inflammatory lesions.

Dirofilaria repens presenting as a premasseteric nodule

Dirofilariasis is a rare zoonosis that is mainly seen with subcutaneous or pulmonary involvement. Natural hosts are dogs, cats, jackals, and raccoons; however, humans can rarely become an accidental host for the parasite. In the reported case, infection manifested as a subcutaneous nodule, representing a significant diagnostic challenge for both the surgeon and the pathologist. A case of a 62-year-old man with a premasseteric soft tissue mass caused by Dirofilaria repens is presented with histopathologic confirmation.

Canine dirofilariosis in two cities of southeastern Spain

Several cases of human subcutaneous/ocular dirofilariosis caused by Dirofilaria repens from an area in the southeastern Spain where previous epidemiological studies have shown a very low prevalence of this species in dogs, have been studied in our laboratory. Since the prevalence of this species in dogs did not correspond to the incidence of human cases in the zone studied, a preliminary epidemiological survey was carried out on 114 dog blood samples from two kennels and one veterinary clinic. Knott, polymerase chain reaction (PCR) with specific primers for Dirofilaria immitis and D. repens, and ELISA with adult E/S D. immitis and adult somatic D. repens antigens for the detection of specific IgG, were used. Fifty-three out of the 114 samples analyzed were positive for Knott and/or PCR to D. immitis or to D. repens. D. repens was the species with the highest prevalence, 84.6 and 37.1%, respectively, in each kennel. IgG antibodies against D. immitis and D. repens, were detected in 11 samples which gave negative results to both Knott and PCR. These results demonstrate a very high prevalence of D. repens that could be associated with the increasing incidence of human subcutaneous/ocular cases recently detected in this zone.