The trends of human dirofilariasis in Croatia: Yesterday - Today - Tomorrow

Microfilaremic infection in canine filariosis in Colombia: a challenge in morphological and molecular diagnostics

Canine filariosis is caused by filiform nematodes and affects several species of animals as well as humans. The disease produces a wide range of symptoms that can often be confused with other diseases, which increases the complexity of its diagnosis. The search for methodologies to facilitate its diagnosis is a challenge, and specific and differential identification of the parasite species causing the disease holds key to a successful diagnosis. In Colombia, there is a problem of underdiagnosis of filariosis in microfilaremic dogs infected by Dirofilaria immitis and Acanthocheilonema reconditum, and of microfilaremias not related to heartworm disease. The highest prevalences have been reported for D. immitis infections, although new cases of A. reconditum infections are beginning to appear. The aim of this study was to differentiate the microfilariae infections caused by D. immitis and A. reconditum by a morphological and molecular characterization of microfilariae so as to facilitate an accurate diagnosis of canine filariosis in the metropolitan area of Bucaramanga (Colombia). For this purpose, 400 blood samples with anticoagulants were collected from the dogs and analyzed with the help of a commercial immunochromatography kit for the detection of D. immitis circulating antigen. The Woo, Knott, and polymerase chain reaction (PCR) techniques were employed for determining the parasite count, morphological observation, and molecular identification of microfilariae present in the dogs respectively. The prevalence of microfilaremic dogs in Bucaramanga metropolitan area was 18.75% (75/400). The prevalence of dogs that tested positive for D. immitis in the antigen and in PCR tests was 1.25% (5/400) and 1% (4/400), respectively. Furthermore, the PCR test revealed that 17.75% of the microfilaremic dogs tested positive for A. reconditum (71/400) (first report in the metropolitan area of Bucaramanga), with one animal co-infected by both species, and 0% for D. repens (0/400). However, by morphological characterization, 4% of the microfilariae (3/75) corresponded to D. immitis, 20% (15/75) to D. repens, and 76% (57/75) to A. reconditum. The use of molecular diagnostic methods such as PCR aids in the specific identification of the parasite, thus making it a more accurate method than the morphological characterization of microfilariae. The identification of the parasites by PCR helps improve the veterinary diagnosis of canine filariosis in Colombia, which would lead to the establishment of an appropriate treatment protocol for each species of filaria and also to the generation of reliable data to be used at the clinical and epidemiological levels.

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.

Live Intraoral Dirofilaria repens of Lower Lip Mimicking Mucocele-First Reported Case from Croatia

Dirofilariasis is an endemic infestation in tropical and subtropical countries caused by about 40 different species. It rarely occurs in the oral cavity and is mostly presented as mucosal and submucosal nodules. Differential diagnoses include lipoma, mucocele, and pleomorphic adenoma. We report a rare case of oral dirofilariasis mimicking mucocele in a 41-year-old male patient from Croatia without an epidemiological history of travelling outside the country. He came in because of non-painful lower lip swelling that had lasted for two months. The parasite was surgically removed from the lesion. This is the first reported case of oral dirofilariasis in Croatia. It is important to point out this rare diagnosis in order to make dentists aware of the possibility of the presence of such an infestation in common lesions of the oral mucosa.

Dirofilaria Repens in Dogs and Humans in Slovenia

Introduction

The prevalence of Dirofilaria repens in dogs in countries bordering Slovenia ranges from 1.5% to 47.3%. The aim of this study was to estimate its prevalence in Slovenian dogs and to present the cases of dirofilariasis diagnosed in humans from 2010 to 2020.

Material and Methods

Epidemiological data were collected and blood samples were taken from 465 dogs older than one year and born in Slovenia. A real-time PCR was performed on all samples to detect filarioid DNA, and a D. repens-and D. immitis-specific real-time PCR was performed on positive samples. Blood samples from 446 dogs were tested for Dirofilaria spp. using a modified Knott's test. Human cases were diagnosed from histological sections of excised subcutaneous nodules. Descriptive statistics were used to characterise the samples. The one-sample nonparametric chi-squared test was used to assess whether categories of a variable were equally distributed.

Results

Three dogs' samples tested positive for D. repens using the species-specific real-time PCR, while D. immitis DNA was not detected. The modified Knott's test was positive in two of the three PCR-positive dogs, two of which had never travelled outside Slovenia's borders. Four human patients with D. repens dirofilariasis were diagnosed. Since their travel history was unknown, autochthonous transmission could not be confirmed.

Conclusion

Our study demonstrated a 0.64% prevalence of D. repens infection in dogs in Slovenia. Two cases could be autochthonous.

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.

Emergence of Dirofilaria repens (Spirurida: Onchocercidae) in dogs in Eastern Thailand

Background and Aim:

Dirofilaria repens is a zoonotic vector-borne parasite of dogs and cats. It is not commonly found in every part of Thailand, except the southern part. This study was conducted to investigate the prevalence of this parasite in Eastern Thailand in 2019.

Materials and Methods:

A total of 8003 blood samples were collected from private veterinary clinics and animal hospitals in Eastern Thailand. Blood parasites were examined using buffy coat thin blood smears with Wright-Giemsa staining. D. repens was morphologically identified and confirmed using the acid phosphatase activity technique.

Results:

The first case of D. repens was found in March 2019. The prevalence of D. repens from January to December 2019 was 0.44% (35/8003) (95% confidence interval 0.30-0.61).

Conclusion:

The prevalence data of D. repens in Eastern Thailand indicate that this parasitic infection should be considered as a zoonotic vector-borne disease. A strategic plan to control zoonotic transmission alongside a preventive program should be emphasized and encouraged among pet owners and veterinarians.

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.

An epidemiological survey of Dirofilaria spp. and Acanthocheilonema spp. in dogs from the Republic of Moldova

Background

During the last decades, filarial infections caused by Dirofilaria spp. have spread rapidly within dog populations of several European countries. Increasing scientific interest in filariasis, and the availability of new diagnostic tools, has led to improved knowledge of the biology, morphology, and epidemiology of different species of filarial worms. However, data are still scarce for a number of countries, including the Republic of Moldova. Thus, we assessed the epidemiological status of canine filariasis in the Republic of Moldova to address part of this knowledge gap.

Methods

A total of 120 blood samples were collected between June 2018 and July 2019 from dogs originating from the cities of Cahul and Chişinău. The samples were examined microscopically, and multiplex polymerase chain reaction was performed to evaluate filarioid species diversity.

Results

Microscopic examination revealed that 12 dogs (10.0%) were positive for circulating microfilariae. The molecular test showed that one dog was positive for Acanthocheilonema reconditum (0.8%), one for Dirofilariaimmitis (0.8%), six for Dirofilariarepens (5.0%), and four (3.3%) harboured a co-infection with D. immitis and D. repens. Prevalence was significantly higher in dogs aged ≥ 2 years.

Conclusions

The epidemiological survey presented here for the Republic of Moldova confirmed the presence D. immitis, D. repens and A. reconditum in dogs that had not received any heartworm preventive.

Graphical abstract

Different epidemiological pattern of canine dirofilariosis in two neighboring countries in Central Europe-the Czech Republic and Slovakia

The known data resulting from individual surveys of canine dirofilariosis point to the great differences in the epidemiological situation among countries where Dirofilaria parasites emerged approximately at the same time. In this regard, the Czech Republic and Slovakia, neighboring countries situated in Central Europe, could serve as an illustrative example of such a situation. The present study aimed to assess the prevalence of canine dirofilariosis in both countries and to discuss the reasons for potential differences shown. Between October and December 2019, 429 dogs from the Czech Republic and 644 from Slovakia were examined for canine dirofilariosis using the Knott test for microfilariae detection and conventional PCR for the species determination. The results' analyses showed notable differences. While in the Czech Republic autochthonous Dirofilaria repens cases are reported sporadically and Dirofilaria immitis infections have been confirmed only as imported so far, in Slovakia, both Dirofilaria species seem to have become endemic. Concretely, in the Czech Republic, microfilariae were detected in the peripheral blood of 8 dogs (1.86%): in seven, D. repens was confirmed, and in one dog, mixed infection with D. repens and D. immitis was diagnosed. Seven infected animals came from the eastern part of the country neighboring Slovakia. In Slovakia, microfilariae were detected in 68 (10.56%) dogs examined. DNA analysis confirmed D. repens mono-infection in 38 (5.90%) dogs, single D. immitis infection in 21 (3.26%) animals, and both Dirofilaria species were detected in 9 (1.40%) samples. Although we are unable to determine the cause of the differences, our study confirmed that the long-registered low number of canine dirofilariosis cases in the Czech Republic is not due to insufficient investigation (monitoring), but due to a low prevalence of the parasite in this area.