Case Report: Successful Treatment of a Patient with Microfilaremic Dirofilariasis Using Doxycycline

Lesion on the right testicle of 21-year-old patient

Human dirofilariasis is an emerging disease that is rising and driven by increasing travel of both humans and their companion animals and climate change. We report a case of Dirofilaria repens in the scrotum of a 21-year-old patient, who experienced right testicular pain. Ultrasonography revealed a tubular, worm-like lesion extracted successfully and confirmed as an immature D. repens through parasitological and molecular analyses. Post-surgery, the patient underwent anthelmintic treatment and was discharged. Increased awareness of this parasitosis among healthcare professionals is crucial, given the expected rise in dirofilariasis cases. Climate change in Poland, characterized not so much by record high temperatures but by a systematic increase in the number of warm days, affects many aspects of life. Due to the presence of disease vectors, the introduction and reintroduction of exotic and parasitic disease, previously rare or absent in temperate climate zones, is possible.

Pulmonary presentation and coil marcation of dirofilaria lung coin nodes - case report

Clinicians face significant diagnostic challenges when dealing with nodal lesions of the lung. The majority of lung nodules are benign; however, a significant number can be cancerous. Dirofilaria infestation should also be considered in the differential diagnosis of nodal lung lesions. Most patients with Dirofilaria infestation are asymptomatic. To determine the etiology of nodal lung infiltrations, procedures like radiological imaging, bronchoscopy, endobronchial ultrasound transbronchial needle aspiration (EBUS-TBNA), transthoracic biopsy (TTB), tumor markers, nonspecific serological tests, or surgical removal of the lung coin lesions can be performed. Coil marking of the smaller lung lesions under computed tomography (CT) guidance is a helpful tool in determining the position and localization of the nodal lung lesions. Video-assisted thoracoscopic surgery (VATS) or robot-assisted thoracoscopic surgery (RATS) wedge resection is a diagnostic and therapeutic method of choice. No additional treatment of Dirofilaria other than wedge resection of the lung is necessary.

Subconjunctival Dirofilaria masquerading as nodular scleritis

A man in his late 50s presented with a gradually enlarging, painless, reddish mass on the white portion of his left eye for 2 weeks. His best-corrected visual acuity was 20/20 in both eyes. Slit-lamp examination showed a congested, nodular, elevated lesion on the temporal bulbar conjunctiva with two pustule-like elevations. Anterior segment optical coherence tomography showed a subconjunctival solid mass rather than an abscess or a cyst. Scleral deroofing was performed and a long thread-like object resembling a dead worm was identified. The worm was removed intact, and its histopathology confirmed the diagnosis of Dirofilaria Peripheral blood smear did not show any microfilariae. No recurrences or new lesions were observed during the follow-up examinations at 1 and 5 months post-surgery. This case highlights the importance of considering a parasitic aetiology in cases of nodular or infectious scleritis.

Human Subcutaneous Dirofilariasis Behind a Blepharoconjunctivitis: A Case Report and Review of the Literature

The diagnosis of skin lesions involving the eyes can be challenging, especially when uncommon etiologies are considered. We present a case of a 52-year-old female initially diagnosed with blepharoconjunctivitis but later found to have a subcutaneous heartworm infection. The patient experienced recurrent episodes of unilateral palpebral edema, pain, pruritus, and a sensation of a foreign body in her eye. Upon examination, a vermiform structure with peristaltic movements was observed, raising suspicion of subcutaneous dirofilariasis and prompting further investigations. Serological tests confirmed the presence of anti-Dirofilaria spp. antibodies. Surgical removal of the worm led to the resolution of symptoms. This case highlights the importance of considering uncommon etiologies, such as subcutaneous heartworm infection, in patients presenting with atypical migratory skin lesions or ocular manifestations when there is no definite diagnosis and the condition does not respond to usual medical treatment.

Severe and Rare Case of Human Dirofilaria repens Infection with Pleural and Subcutaneous Manifestations, Slovenia

We report a case of human Dirofilaria repens infection in a woman in Slovenia who had concomitant pleural and subcutaneous manifestations of the infection. This case report illustrates the clinical course of a severe symptomatic parasitic infection that had multisystemic manifestations.

Human Dirofilariasis Caused by Dirofilaria repens in Sri Lanka from 1962 to 2020

PURPOSE

Sri Lanka has reported the highest prevalence of human dirofilariasis cases in Asia. Thus far, Dirofilaria repens is the only reported Dirofilaria species that affect humans, dogs, and cats in Sri Lanka. Therefore, this systematic review was carried out to analyse the studies performed on dirofilariasis in Sri Lanka.

METHODS

Peer-reviewed articles were searched on dirofilariasis published on Google Scholar, PubMed, Cochrane, and ResearchGate from January to March 2021. Articles were selected using inclusion and exclusion criteria. Three reviewers assessed the studies and extracted data independently to minimize the risk of bias. Extracted data were compiled, and then the results were compared and discussed in this systematic review.

RESULTS

Twenty-five studies performed in Sri Lanka were analysed, and high prevalence areas, frequent clinical presentations, diagnostic methods, reservoir hosts, and treatment were identified. More than 173 cases of human dirofilariasis caused by D. repens were reported from 1962 to 2020 in 20 districts among 25 investigated. The highest number of cases (n = 80) was recorded during 2010-2012 period. Canine and feline dirofilariasis are reported countrywide, and a large number of potential mosquito breeding sites could be seen in Sri Lanka.

CONCLUSIONS

The number of reported cases of human dirofilariasis has been varied from 1962 to 2020. The highest number of cases has reported in 2010-2012, and then the number of cases has dropped. This may be due to underreporting. Thus, awareness of Dirofilaria repens infection in humans, control measures in endemic areas and further research on dirofilariasis in other districts of Sri Lanka are crucial.

The emergence of Dirofilaria repens in a non-endemic area influenced by climate change: dynamics of transmission using a mathematical model

Dirofilaria repens is a nematode affecting domestic and wild canids, transmitted by several species of mosquitoes of different genera. It usually causes a non-pathogenic subcutaneous infection in dogs and is the principal agent of human dirofilariasis in the Old World. The geographic distribution of D. repens is changing rapidly, and several factors contribute to the spread of the infection to non-endemic areas. A mathematical model for transmission of Dirofilaria spp. was built, using a system of ordinary differential equations that consider the interactions between reservoirs, vectors, and humans. The transmission simulations of D. repens were carried out considering a projection in time, with intervals of 15 and 100 years. For the dynamics of the vector, seasonal variations were presented as series with quarter periodicity during the year. The results of the simulations highlight the peak of contagions in the reservoir and in humans, a product of the action of the vector when it remains active throughout the year. A 300% infection increase in the reservoir was observed during the first decade and remains present in the population with a representative number of cases. When the vector maintains its density and infectivity during the year, the incidence of the infection in humans increases. Accumulated cases amount to 45 per 100,000 inhabitants, which corresponds to a cumulative incidence of 0.05%, in 85 years. This indicates that early prevention of infection in canids would significantly reduce the disease, also reducing the number of accumulated cases of human dirofilariasis by D. repens. The interaction between the simulations generated by the model highlights the sensitivity of the epidemiological curve to the periodicity of seasonality, reaffirming the hypothesis of the probability of movement of the zoonotic disease to non-endemic areas, due to climate change.

New cases of human dirofilariosis on the Balkan Peninsula - "Masked intruders" uncovered by a surgeon

Dirofilaria spp. nematodes are accidental parasites of humans causing mild to serious, superficial or visceral infections. Superficial dirofilariosis is rather common in Europe and is typically manifested as subcutaneous form. Herein we report 46 new cases of human dirofilariosis (19 patients with subcutaneous, 18 patients with ocular, 4 patients wih genital, 2 patients with submucosal, 2 patients with pulmonary and 1 patient with intramuscular form of infection) that were recorded from the beginning of 2015 to May 2021 on the Balkan Peninsula with a goal to update the prevalence of this parasitosis and point out potential problems in diagnosis and treatment. Besides, given the high possibility of misinterpretation as tumor, our second aim was to encourage the inclusion of this pathogen in the differential diagnosis of subcutaneous nodules. Although quite common forms, subcutaneous and ocular dirofilariosis can be very often misdiagnosed in clinical practice due to the absence of specific clinical manifestations. Therefore, raising awareness of clinicians about this zoonosis is needed as well as closer collaboration between physicians and veterinarians.

Dirofilaria repens microfilaremia in humans: Case description and literature review

Introduction

Dirofilaria repens is a vector-borne filaroid helminth of carnivorous animals, primarily domesticated dogs. Humans are considered to be accidental hosts in which D. repens rarely reach sexual maturity but induce local inflammation, mainly in subcutaneous and ocular tissues.

Methods

In the current study, we present the detection of multiple adults of D. repens, endosymbiont Wolbachia sp. and microfilariae by molecular analysis in peripheral tissues and bloodstream of a human host. A subsequent meta-analysis of published literature identified 21 cases of human infection with adult D. repens producing microfilariae.

Results

Within the study population, there were 13 (59.09%) males, eight (36.36%) females and, in one (4.55%) case, sex was not reported. A total of 11 (50.00%) cases had subcutaneous dirofilariasis, six (27.27%) had ocular dirofiliariasis, with single cases (4.55% each) of genital, mammary, lymphatic and a combination of subcutaneous and pulmonary dirofilariasis described. In one (4.55%) case, the primary anatomical site of adult D. repens could not be found. D. repens microfilariae were detected in the local tissue (local microfilariasis) in 11 (50.00%) cases and the peripheral blood (microfilaremia) in 11 (50.50%) cases. Final identification of D. repens microfilariae was based on morphological detection in 14 (63.64%) cases, and molecular detection in eight (36.36%) cases.

Conclusion

The results of this study suggest that humans may act as a final host for D. repens, however its role as a source of D. repens infection is less clear.

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Humans may act as a final host for D. repens

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Immunodeficiency is not a risk factor for human D. repens microfilaremia.

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Surgical extirpation of adult D. repens is a mainstay of treatment.

Recurrent Swelling and Microfilaremia Caused by Dirofilaria repens Infection after Travel to India

Human subcutaneous dirofilariasis is an emerging mosquitoborne zoonosis. A traveler returning to Germany from India experienced Dirofilaria infection with concomitant microfilaremia. Molecular analysis indicated Dirofilaria repens nematodes of an Asian genotype. Microfilaremia showed no clear periodicity. Presence of Wolbachia endosymbionts enabled successful treatment with doxycycline.

Case Report: Molecular Detection of Dirofilaria repens in an Italian Patient after a Stay in Tanzania

A 35-year-old man was admitted to a hospital in the south of Italy because of a periocular nodule and subpalpebral edema. The patient reported having been stayed in Tanzania five months before. Hematologic parameters were within the normality range, the Acanthocheilonema viteae ELISA did not detect significant levels of antifilarial IgG, and no further symptoms were described. The surgical inspection of the nodule led to the isolation of two filarioid parasites, identified as Dirofilaria repens by scanning electron microscope (SEM), and then by molecular assays. Knott’s test did not reveal microfilaremia, whereas loop-mediated isothermal amplification and PCR detected D. repens DNA. The patient was treated with doxycycline, and he was found no more positive at the follow-up.

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

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.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04696-4.

Candidatus Dirofilaria Hongkongensis Infections in Humans During 2005 to 2020, in Kerala, India

We tried to determine the epidemiology and species of human dirofilariasis observed at two tertiary care hospitals in Kerala. We searched the hospital database to identify cases of dirofilariosis from January 2005 to March 2020. Along with human isolates, one dog Dirofilaria isolate was also subjected to PCR and sequencing of pan filarial primers cytochrome oxidase subunits 1 and 12S rDNA. We documented 78 cases of human dirofilariosis. The orbit, eyelid, and conjunctiva were the most commonly affected sites. Molecular characterization identified one dog and five human isolates as Candidatus Dirofilaria Hongkongensis. A rare case of subconjunctival infestation by B. malayi was also documented. Human dirofilariosis is a public health problem in the state of Kerala in India, and it is mostly caused by Candidatus Dirofilaria Hongkongensis. We propose that all diroifilaria isolates are subjected to sequencing for identification.

Dirofilaria repens infection of the eye with concomitant microfilaremia in a traveller

Dirofilaria repens is the main causative agent of human and canine dirofilariosis. This form of zoonotic parasitosis usually manifests with an involvement of the skin or the eye. Human dirofilariosis is considered as an emerging infectious disease. We report the first case of proven microfilariemic dirofilariosis in peripheral blood in Germany.

Case Studies of Severe Microfilaremia in Four Dogs Naturally Infected With Dirofilaria repens as the Primary Disease or a Disease Complicating Factor

Subcutaneous dirofilariosis in dogs, caused by Dirofilaria repens, is an underdiagnosed disease, now recognized for its zoonotic potential, and growing distribution and prevalence across Europe and Asia. Our understanding of the pathogenicity in human and canine host remains unclear, but case reports suggest that microfilariae (Mf) as well as adult D. repens may directly cause internal organs damage or may be a factor complicating the course of other ailments. The purpose of the study was to report high Mf in dogs and to discuss potential relevance with co-morbidity. Our data from a modified Knott's test performed on 62 infected dogs indicate that the median Mf count in D. repens infections is 675 Mf/ml and we consider microfilaremia above 10,000 Mf/ml as high intensity. This collection of case reports discusses 4 cases of high intensity D. repens microfilaremia in companion dogs; one presenting pathology from a very high intensity of adult D. repens with post-treatment complications, and 3 dogs in which high microfilaremia was detected incidentally during the management of other primary illnesses. To our knowledge this report describes the highest D. repens microfilaremia ever detected in a dog, at 178,000 Mf/ml. The issue of high microfilaremic infections in dogs is poorly studied and there is growing need to identify the presentation and understand the mechanisms of associated pathogenesis in the host-parasite relationship.