Canine and human Dirofilaria infections in the Balkan Peninsula

Beyond Borders: Dirofilaria immitis Infection in Dogs Spreads to Previously Non-Enzootic Areas in Greece-A Serological Survey

Although Dirofilaria immitis in dogs is considered enzootic in northern Greece, the available data on the occurrence of infection in southern parts of the country demonstrate its scarcity. The aim of this study was to update the current knowledge on D. immitis infection in dogs in areas of Greece previously considered non-enzootic (Central Greece, Attica, Peloponnese, North Aegean, South Aegean, Crete and the Ionian islands). In total, 1528 dog blood samples were collected from the aforementioned areas and examined by Dirochek® ELISA (Synbiotics). Additionally, data published until 2022 on the prevalence of infection in these areas were compared to the data of this study. The 'Wilson' Score interval method (Epitools) was employed. Overall, 10.8% of dogs were positive for D. immitis. In detail, the prevalence was 21.7, 13.7, 10.7, 5.4, 4.7, 6.2 and 17.0% for D. immitis, in Central Greece, Attica, Peloponnese, North Aegean, South Aegean, Crete and the Ionian islands, respectively. Infection with D. immitis is recorded for the first time in Crete. The probability of a dog becoming infected has increased 4.1 times since 2022 in previously non-enzootic areas. This study denotes the spread of D. immitis and highlights the necessity for preventive measures.

Zoonotic dirofilariases: one, no one, or more than one parasite

Dirofilaria spp. are vector-borne filarial nematodes that affect a variety of animal species, including humans. Dirofilaria immitis and Dirofilaria repens are the two main zoonotic species, but also other wildlife-associated Dirofilaria species are occasionally reported as causative agents of human dirofilariasis, including Dirofilaria striata, Dirofilaria tenuis, Dirofilaria ursi, Dirofilaria spectans, and Dirofilaria magnilarvata. Since the etiological identity of most of the species mentioned here is arguable, we summarized and critically discussed data concerning infections in humans, focusing on the reliability of Dirofilaria species identification. We advocate the importance of combined morphological and genomic approaches to provide unequivocal evidence for their zoonotic potential and pathogenicity.

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.

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

Dirofilariosis is a vector-borne disease mainly caused by Dirofilaria immitis and Dirofilaria repens. In contrast to the known endemicity of dirofilariosis in southern and south-eastern Europe, information on the distribution of D. repens in Central-Europe is fragmentary. We tested 8877 serum samples from dogs from Austria, Denmark, Germany, Italy, Lithuania, Poland, Switzerland and the UK using an ELISA detecting filarial-specific antibodies, hypothesising higher occurrence of D. repens. Based on two overlapping frequency distributions, presumed negative samples had a mean optical density (OD) value of 0.097, representing 97.45% of all samples. Presumed positive samples, representing 2.55% of all sera, had a mean OD value of 0.287. Test prevalence based on the calculated cut-off was 3.51% for all sera (4.36% for Austria, 1.94% for Denmark, 1.39% for Germany, 3.37% for Italy, 6.90% for Lithuania, 6.99% for Poland, 0.77% for Switzerland and 0.0% for the UK, respectively). The bimodal distribution, representing overlapping distributions of OD values from positive and negative dogs, enabled the assignment of a probability of true infection status to each dog. Mean probabilities of true infection status across groups, based on the postal codes of origin, allowed us to estimate and map true prevalences. For all countries, except the UK, the true prevalence was lower than the test prevalence. The large number of serum samples and the use of a non-gold standard analytical method allowed us to create a more realistic picture of the distribution of D. repens in Central Europe and the UK.

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.

Occurrence of Dirofilaria immitis in Stray Dogs from Nepal

BACKGROUND

Nematodes of the genus Dirofilaria are widespread vector-borne helminths (VBH) of veterinary relevance. Dirofilariosis caused by D. immitis is frequently diagnosed in dogs often showing a severe clinical condition known as heartworm disease. Assessing the distribution pattern of canine dirofilariosis is pivotal to undertake appropriate control measures and define the risk of infection in animals and humans. This study provides original data on the occurrence of D. immitis in naive stray dogs from Nepal.

METHODS

An epidemiological study was performed on stray dogs from Siddharthanagar, Lumbini region, Nepal. Alive animals were blood sampled and examined for microfilariae using direct microscopy, buffy coat centrifugation and modified Knott's method. In addition, hematobiochemical parameters, including packed cell volume (PCV), alanine aminotransferase (SGPT), aspartate aminotransferase (SGOT), alkaline phosphate (ALP), creatinine, blood urea nitrogen (BUN), urea and total protein were analysed, along with a clinical scoring (body temperature and respiratory rate). During the observation period, data on autopsies performed on stray dogs showing canine heartworm disease were also included.

RESULTS

The overall prevalence of D. immitis in both alive and necropsied dogs was 22.49% (38/169). Out of 150 alive dogs, 29 (19.3%) were positive for D. immitis microfilariae. The prevalence of the infection varied according to the technique used, ranging from 16.0 to 19.3% based on direct blood smear microscopy and modified Knott's technique, respectively. The infection rate was significantly higher (p < 0.05) in dogs aging more than 3 years. A positive correlation was observed between SGPT and SGOT and the presence of microfilariae (p < 0.05). Among the 19 dead stray dogs, 9 animals showed adult D. immitis nematodes.

CONCLUSION

Results of this survey account for the presence of D. immitis in stray dogs from Nepal, thus supporting the existence of a local transmission cycle of diroflariosis in the region. Further investigations are warranted to accurately define the prevalence of the infection in the canine population and to undertake appropriate control measures to reduce the burden on the infection in dogs and, accordingly, the risk of transmission to humans.

Zoonotic Dirofilaria immitis and Dirofilaria repens infection in humans and an integrative approach to the diagnosis

Dirofilariosis by Dirofilaria immitis and Dirofilaria repens is endemic in dogs from countries of the Mediterranean basin. Both species may infect humans, with most of the infected patients remaining asymptomatic. Based on the recent description of the southernmost hyperendemic European focus of heartworm disease in dogs from the Pelagie archipelagos, we performed a serological and molecular survey in human population of that area. Human blood samples were collected in the islands of Linosa (n=101) and Lampedusa (n=296) and tested by ELISA and molecular test for the detection of D. immitis and D. repens. Samples were also screened for filarioid-associated endosymbionts, Wolbachia sp. The seroprevalence of D. immitis and D. repens was, respectively, 7.9% and 3.96% in Linosa, and 7.77% and 19.93% in Lampedusa. Out of 397 human blood samples tested molecularly, 4 scored positive (1%) for Dirofilaria spp. by qPCR (i.e., three for D. immitis and one for D. repens) and 6 (1.5%) for Wolbachia. Of the qPCR positive for Dirofilaria spp., only D. repens was amplified by cPCR and was positive for Wolbachia. In the phylogenetic analysis, the sequence of Wolbachia detected in D. repens positive samples clustered along with other C supergroup filarioids. Our results overlap with the recent prevalence data collected on dogs from the same area, where D. immitis is prevalent in Linosa and D. repens prevails in Lampedusa. Molecular detection of D. immitis in human blood is quite unusual considering that humans are dead-end hosts for dirofilarial infection and most of the human cases described so far in Europe were ascribed to D. repens. An integrative diagnostic approach using serum analysis and Wolbachia detection is also presented. In endemic areas for canine dirofilarioses humans are exposed to the infection, suggesting the importance of One Health approach in diagnosing, treating and controlling this zoonotic parasitosis.

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.

Endoparasites of European Wildcats (Felis silvestris) in Greece

The European wildcat (Felis silvestris) is the only wild felid living in Greece. Wildcat populations are declining due to anthropogenic and phenological unfavourable conditions, and parasites may have an additional negative impact. In the present study, the occurrence of endoparasites in wildcats in Greece and the potential threats posed to wildcats, domestic animals, and humans in the study areas has been investigated. In a six-year period, 23 road-killed wildcats and 62 wildcat faecal samples were collected from different areas of the country. Necropsy for the detection of endoparasites and standard parasitological examinations of faecal samples were performed. Parasites were morphologically identified and, in selected cases, molecularly analysed. All necropsied wildcats (100%) were infected by three to 10 different parasite taxa, with the most prevalent being Taenia taeniaeformis (73.9%), Toxocara cati (60.9%), Angiostrongylus chabaudi (56.5%), Ancylostoma tubaeforme (39.1%), Cylicospirura spp. (34.8%), Troglostrongylus brevior (34.8%), and Capillaria aerophila (33.8%). Of the 62 faecal samples examined, 53 (85.5%) were positive for one or more parasite elements (larvae, eggs, or oocysts). The most frequent were T. cati (45.2%), A. chabaudi (29%), C. aerophila (24.2%), and Ancylostomatidae (17.7%). This is the first survey on endoparasites affecting wildcats in Greece. Some of the parasites here found are frequent in domestic and wild felids, while others, i.e., Oslerus rostratus and Cylicospirura petrowi, were described for the first time in the European wildcat. Most of them have a significant pathogenic potential, causing severe to hazardous diseases to infected felids and some, under specific circumstances, can also threaten human health.

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.

Molecular Identification of New Cases of Human Dirofilariosis (Dirofilaria repens) in Italy

(1) Dirofilariosis is a vector-borne parasitic disease mainly in domestic and wild carnivores caused by Dirofilaria (Noctiella) repens, which is endemic in many countries of the Old World, and D. immitis, which has a worldwide distribution. In recent years, an increase in the number of human cases has been reported, suggesting that dirofilariosis is an emergent zoonosis. Here, we describe further cases (N = 8), observed in Central Italy during the years 2018-2019. (2) Molecular diagnosis was performed on: (i) live worms extracted from ocular conjunctiva, cheek, and calf muscle; (ii) histological sections of surgically removed nodules from parenchymal lung, coccyx, and breast. (3) Sequence analysis (650-bp) of the mitochondrial cytochrome oxidase subunit I gene (mtDNA cox1) showed a match of 100% with the sequences of D. repens previously deposited in GenBank. ELISA test to detect IgG against filarial antigens was performed on four patients' sera and resulted positive in two patients who showed ocular and subcutaneous dirofilariosis, respectively. Microfilariae have been never detected in the peripheral blood of the patients. (4) The occurrence of N = 8 new cases of human D. repens-infections observed in a two-year period suggests an increased circulation of the parasite in Italy. Therefore, dirofilariosis should be included in differential diagnosis in patients presenting subcutaneous and/or pulmonary nodules. Molecular diagnosis of the etiological agents is fundamental. Specific serological diagnosis needs to be improved in future research work.

Ocular Dirofilariasis in Bosnia and Herzegovina: A Case Report and Review of the Literature

Purpose:

To report a rare occurrence of ocular dirofilariasis in Bosnia and Herzegovina and provide a short overview on clinical characteristics and treatment options for ocular dirofilariasis.

Methods:

A 75-year-old woman was admitted to the University Clinical Centre Tuzla with pain and redness in her left eye. A live, white, coiled, and active worm was noticed in subconjunctival space of bulbar conjunctiva.

Results:

After successful surgical extraction, the parasite was identified as the adult form of Dirofilaria repens. There were no signs of intraocular or systemic inflammation.

Conclusion:

Ophthalmologists should have in mind a possible infestation, especially in cases with repeated inflammatory reactions and swelling of the ocular region, which does not respond to conventional therapy.

New insights into the biology, diagnosis and immune response to Dirofilaria repens in the canine host

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Antibody response to D. repens in dogs develops before the onset of patency.

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Wolbachia and D. repens antibodies had peaks of OD values on Days 220, 245, 281.

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The specificity of IgG ELISA against D. repens and Wolbachia must be evaluated.

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If microfilarial counts are too low, PCR can be considered a sensitive alternative.

Dogs are the primary host for Dirofilaria repens, therefore it is mandatory to accurately diagnose the canine infection and to expand our current knowledge on parasite biology and the immune response of the infected host for a better prevention.Thus, the aim of the present study was to provide new insights from experimental infections of dogs with D. repens, focusing on the evaluation of: 1) the pre-patent period and 2) the antibody response against D. repens somatic antigens and against the Wolbachia endosymbiont. Briefly, on Day 0, twenty purpose-bred Beagle dogs were experimentally infected with 50 infective larvae (L3) of D. repens. Starting from Day 58 until the last day of the study (Day 281), blood samples were collected on a monthly basis for detection of antibodies against D. repens (Dr) and recombinant Wolbachia surface protein (rWSP) by non-commercial IgG-ELISAs. Additional samples were collected on Days 220, 245 and 281 for the detection of microfilariae (mff) using the modified Knott’s test and biomolecular analysis, following two PCR protocols: Gioia et al. (2010; protocol A) and Rishniw et al. (2006- protocol B). The results were analysed by univariate statistical analyses using 2 × 2 contingency tables and K Cohen was calculated to assess the agreement among all the diagnostic techniques. Overall, the outcome of the study revealed that out of the 20 dogs experimentally infected with D. repens, 16 (80 %) were microfilaraemic, 17 (85 %) were positive at DNA detection in the blood, 18 (90 %) had D. repens antibodies and 16 (80 %) had Wolbachia antibodies on the last day of the study. The overall k agreement between Knott’s and PCR protocol B was 0.442 (P = 0.0001) and increased throughout the study, reaching 0.828 (P = 0.0001) on Day 281. To the authors knowledge, this is only the second study reporting antibody response to D. repens somatic antigen in experimentally infected dogs. ELISA results showed that an antibody response develops before the onset of patency, and steadily increases with time. Results would suggest that the development of an immunological response to infection could lead to application in epidemiological studies, risk assessment and as an aid in the diagnostic approach in dogs, in particular for early infections without mff.

Focus on Common Small Animal Vector-Borne Diseases in Central and Southeastern Europe

Vector-borne diseases are one of the main causes of morbidity and mortality in small animals in Europe. Many of these diseases are well-known among veterinary practitioners and some of them are called emerging diseases as prevalence, temporal and spatial distribution seem to increase in Europe. The number of newly recognized pathogens, transmitted by a variety of arthropod vectors, that are relevant for dogs and cats, is also increasing every year. The prevalence among infected vectors and hosts is a hot topic in veterinary science throughout the entire continent, as well as the development of efficient diagnostic procedures, therapy and prophylactic measures. Companion animal vector-borne diseases comprise a large group of pathogens including viruses, bacteria, protozoa and helminths. These pathogens are mainly transmitted by bloodsucking arthropods (ticks, fleas, mosquitos, sand flies), and more seldom by direct transmission between vertebrate hosts. Vector prevalence and activity is influenced by local climate conditions, host species density, changes in landscape and land use. Human parameters such as poverty and migration affect the use of prophylactic measures against pathogen transmission and infection as well as increasing the zoonotic risk to introducing pathogens by infected humans. Small animal associated factors such as pet trade and pet travel spread infection and certain vectors such as ticks and fleas. All these factors pose several complex and significant challenges for veterinarians in clinical practice to decide on efficient laboratory work-up and constructive diagnostic procedures.

Molecular survey of Dirofilaria species in stray dogs, red foxes and golden jackals from Vojvodina, Serbia

Cardiopulmonary dirofilariosis in dogs and other carnivores is caused by Dirofilaria immitis, while Dirofilaria repens usually causes a subcutaneous infection. The importance of red foxes and golden jackals in the epidemiology of dirofilariosis remains unknown. Thus, the aim of this study was to conduct a cross-sectional molecular survey of Dirofilaria species in stray dogs, red foxes and golden jackals from the endemic region of Vojvodina, Serbia, in order to determine and update data on their prevalence and provide insight into the epidemiological importance of wild canids. A total of 59 blood samples from stray dogs, 94 from red foxes and 32 from golden jackals were collected and screened by real-time PCR targeting a 115-bp fragment of the mitochondrial 12S gene of filarioids and by conventional PCR assay targeting a 484-524-bp fragment of 5.8S-ITS2-28S locus of filarioids. The cross-sectional molecular survey detected the filarioid mitochondrial 12S gene fragment in stray dogs (27.1 %), red foxes (8.5 %) and golden jackals (6.3 %) in the same endemic region of Vojvodina, Serbia. Only D. immitis was detected in stray dogs, while both D. immitis and D. repens were detected in populations of red foxes and golden jackals. These results outline a possible interaction of D. immitis infection between the dog population and the wild canid populations, while D. repens was found to circulate mostly in golden jackals and red foxes populations.

The current situation of canine dirofilariosis in Hungary

Between April and September 2017, blood samples were collected from 344 randomly selected dogs older than 1 year in 180 settlements of 19 counties in Hungary. The dogs lived exclusively outdoors, had never travelled and had neither been examined for Dirofilaria infection nor treated against mosquitoes with insecticides or/and filarioid worms with macrocyclic lactones. Dirofilaria infection was examined with a modified Knott’s test for microfilariae, DiroCHEK®, for the presence of D. immitis antigen, as well as by multiplex and conventional PCR. Altogether, 77 (22.4%) dogs living in 58 settlements of 17 counties were found to be infected with one or both Dirofilaria species based on the PCR techniques. Twenty-eight (8.1%) and 38 (11.1%) dogs were infected with D. immitis and D. repens, respectively. Coinfections were recorded in 11 samples (3.2%) collected in 11 locations of 8 counties. The results confirmed that both dirofilarioses are endemic in dogs and the eastern areas of the country are hyperendemic for heartworm disease. Temperature showed a significant association with the prevalence of D. immitis (OR 2.41, 95% CI 1.24–4.86, p = 0.012) but not with that of D. repens (OR 1.37, 95% CI 0.78–2.47, p = 0.286). The prevalence of neither D. immitis (OR 0.99, 95% CI 0.98–1.00, p = 0.213) nor D. repens (OR 1.01, 95% CI 0.99–1.01, p = 0.094) showed a significant correlation with precipitation. The number of yearly growing degree days (GDD) based on the lifecycle of Dirofilaria in mosquitoes ranged between 3.73 and 7.57 for the Hungarian districts. The GDD showed a significant positive association with the prevalence of D. immitis (OR 2.38, 95% CI 1.43–4.15, p = 0.001) and a non-significant positive relationship with that of D. repens (OR 1.25, 95% CI 0.83–1.95, p = 0.291).

The prevalence of Dirofilaria immitis and D. repens in the Old World

Dirofilaria immitis and D. repens are endemic throughout Europe and southern eastern regions of Asia and reported with increasing frequency in Africa. Nevertheless, the increased awareness of veterinary practitioners, even in countries where the prevalence is low, has led to a decrease D. immitis prevalence in dogs, especially in previously endemic/hyper-endemic areas. Prevalence has significantly increased, however, in areas where heartworm has apparently spread more recently, such as Central and North Eastern Europe. Furthermore, autochthonous cases have been observed in Siberia. Low seroprevalence has been reported in Croatia, while in Romania it has reached 14%. In Greece, the prevalence ranges between 0.7% and 25% whilst in Turkey is 0-18%. Data for canine dirofilariosis in Africa is scarce, and most are case reports. Overall, the dominant species is Achanthocheilonema dracunculoides, although both D. immitis and D. repens have been reported from some countries. In the Far East, the prevalence ranges from 2% to 15% in northeastern of China. In Hong Kong a novel species has been found in dogs and humans (Candidatus Dirofilaria hongkongensis). In India, the prevalence ranges from 4.7%-29.5% in Northeastern states. The main factors that have influenced the spreading of Dirofilaria infections are the climate changes and the introduction of new, invasive, competent mosquito species such as Aedes albopictus and Ae. koreicus. Other factors include relocation and insufficient prevention in dogs, manly in the new areas of colonization. Feline heartworm infection has been diagnosed in every European country when diagnosed either by the Knott test or by serology for circulating antibodies and antigens of the parasite. However, prevalence is much lower than in dogs. In spite of the continuing spreading of heartworm infection, D. repens is the main concern in Europe, mostly for physicians, while the infection is nearly always asymptomatic in dogs. The infection is spreading from Portugal to the Southeastern regions of Finland and Siberia, and in some areas its prevalence overlaps that of D. immitis. Many reasons make more difficult the control of D. repens than D. immitis: the frequent lack of clinical symptoms of suspicion, the specific diagnosis being possible only by blood examination and the inefficacy of some macrocyclic lactones.

Exposure of humans to the zoonotic nematode Dirofilaria immitis in Northern Portugal

Dirofilariosis caused by Dirofilaria immitis (heartworm) is a zoonosis, considered an endemic disease of dogs and cats in several countries of Western Europe, including Portugal. This study assesses the levels of D. immitis exposure in humans from Northern Portugal, to which end, 668 inhabitants of several districts belonging to two different climate areas (Csa: Bragança, Vila Real and Csb: Aveiro, Braga, Porto, Viseu) were tested for anti-D. immitis and anti-Wolbachia surface proteins (WSP) antibodies. The overall prevalence of seropositivity to both anti-D. immitis and WSP antibodies was 6.1%, which demonstrated the risk of infection with D. immitis in humans living in Northern Portugal. This study, carried out in a Western European country, contributes to the characterisation of the risk of infection with D. immitis among human population in this region of the continent. From a One Health point of view, the results of the current work also support the close relationship between dogs and people as a risk factor for human infection

Human dirofilariosis of buccal mucosa - First molecularly confirmed case and literature review

When presented in unusual manner, human dirofilariosis is hard to recognize and often leads to misdiagnosis and unjustified use of various medications. Herein, we report a rare case of Dirofilaria infection localized in buccal mucosa. A 45-year-old male, residing in the Central Serbia, developed striking edema of buccal mucosa followed by leucocytosis, with both neutrophylia and eosinophylia. Thirty days after first symptoms occurred, nodule was formed along the lateral edge of right maxilla. Therefore, patient underwent surgical extirpation and subsequent histopathological analysis of the specimen revealed the presence of a nematode. Based on morphological characteristics of detected parasite, the diagnosis of submucosal Dirofilaria repens-like infection was made. The diagnosis was confirmed, being the first case in the world analyzed by molecular methods. So far, only 13 such cases have been reported worldwide and our paper brings attention to rare form of this zoonosis and updates the data about human dirofilariosis in buccal mucosa.

Dirofilaria repens Infection Mimicking Lung Melanoma Metastasis

We describe a rare case of Dirofilaria repens infection presenting as peripheral lung nodules and mimicking a metastatic focus from a previously diagnosed cutaneous melanoma. To avoid invasive investigations before arriving at the correct diagnosis, dirofilariasis should be included as a part of the diagnostic process in subjects with lung nodules who live in (or have traveled to) endemic regions.

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.

Seroepidemiological survey of human exposure to Dirofilaria spp. in Romania and Moldova

The present study aimed to evaluate the extent of Dirofilaria immitis and D. repens exposure in humans from eastern and southern areas of Romania and central Moldova by serological methods. The serological screening was performed on a total of 450 serum samples (187 from Romania and 263 from Moldova). The sera were collected using a convenience sampling with the help of physicians from the hospitals of the study areas. All samples were analysed by a non-commercial ELISA test for the detection of IgG antibodies against adult somatic antigens of D. immitis and D. repens. The results showed a total of 49 (10.9%; 95% CI = 8.3-14.1%) individuals from Romania and Moldova with a positive response to IgG antibodies against both adult somatic antigens of D. immitis and D. repens. Specifically, 48 (10.7%; 95% CI = 8.0-14.0%) patients were positive for IgG-antibodies against adult somatic antigens of D. immitis, one (0.2%; 95% CI = 0.4-1.2%) against D. repens antigens, and four (0.9%; 95% CI = 0.4-3.3%). were positive for antigens of both parasites. At country level, out of 187 samples from Romania, 13 (6.9%; 95% CI = 4.1-11.5%) were positive for anti-D. immitis IgG with high exposure in the southern part of the country (Bucharest). Of the 263 people from Moldova, 36 (13.7%; 95% CI = 10.0-18.4%) were positive for D. immitis antigens from which three (1.1%, 95% CI = 0.4-3.3%) were positive for the antibodies against antigens of both parasites. Only one sample was found positive for anti-D. repens IgG. Positive IgG-ELISA results were confirmed by Western blot analysis. In addition, for further confirmation, a complementary ELISA was performed for anti-WSP IgG antibodies against Wolbachia endosymbionts. Our findings showed a noticeable exposure of humans from Romania and Moldova to Dirofilaria parasites. Serology can be useful for indicating exposure to Dirofilaria spp. in a healthy population in order to obtain useful data on the epidemiological scenario of human dirofilariosis in Eastern Europe.

Prevalence of intestinal parasites in companion dogs with diarrhea in Beijing, China, and genetic characteristics of Giardia and Cryptosporidium species

Companion animals including dogs are one of the important components in One Health. Parasites may cause not only diseases in pet animals but also many zoonotic diseases infecting humans. In this study, we performed a survey of intestinal parasites in fecal specimens (n = 485) collected from outpatient pet dogs with diarrhea in Beijing, China, for the entire year of 2015 by microscopic examination (all parasites) and SSU rRNA-based nested PCR detection (Giardia and Cryptosporidium). We observed a total of 124 (25.6%) parasite-positive specimens that contained one or more parasites, including Giardia duodenalis (12.8%), Cryptosporidium spp. (4.9%), Cystoisospora spp. (4.3%), trichomonads (4.3%), Toxocara canis (3.5%), Trichuris vulpis (0.6%), and Dipylidium caninum (0.2%). Among the 55 dog breeds, infection rates were significantly higher in border collies and bulldogs, but lower in poodles (p < 0.05). Risk factor analysis suggested that age was negatively correlated with the infection rate (p < 0.00001), while vaccination and deworming in the past 12 months could significantly reduce the parasite infections (p < 0.01). Among the 62 Giardia-positive specimens, 21 were successfully assigned into assemblages using glutamate dehydrogenase (gdh) and/or beta-giardin (bg) genes, including assemblage D (n = 15), C (n = 5), and F (n = 1). Among the 24 Cryptosporidium-positive specimens by SSU rRNA PCR, 20 PCR amplicons could be sequenced and identified as Cryptosporidium canis (n = 20). Collectively, this study indicates that parasites are a significant group of pathogens in companion dogs in Beijing, and companion dogs may potentially transmit certain zoonotic parasites to humans, particularly those with weak or weakened immunity.

Subcutaneous dirofilariosis (Dirofilaria repens): an infection spreading throughout the old world

Background

Two main Dirofilaria species infect dogs: D. immitis and D. repens. While D. immitis has a worldwide distribution, D. repens is currently found only in Europe, Asia, and Africa. Adult D. repens are located in subcutaneous tissues of natural hosts where they survive for long periods of time. First-stage larvae, microfilariae, circulate in the peripheral bloodstream, where they are taken up by the mosquito intermediate hosts. Infected mosquitoes then transmit infective third-stage (L3) larvae to new hosts through the blood meal. In dogs, most infections are asymptomatic, although cutaneous disorders such as pruritus, dermal swelling, subcutaneous nodules, and ocular conjunctivitis can be observed. Currently, two factors have increased the concerns about this parasitic infection 1) its spread throughout the European countries and to other continents and its prevalence in dog populations, where in some cases it has overcome D. immitis; and 2) its zoonotic potential, which is much greater than that of D. immitis.

Results

Different hypotheses can be put forward to explain these concerns. First, climate change has allowed more favorable conditions for survival of culicid vectors. Second, accidental hosts such as humans may have a less efficient immune reaction against a parasite that is located in subcutaneous tissues, and thus less exposed to the host’s immune response than, for instance, D. immitis. Furthermore, the absence of clinical signs in the majority of canine infections and the difficulty in diagnosing the infection, due to the lack of serologic tests and thus the reliance on the identification of microfilariae and differentiation from D. immitis to confirm the presence of the parasite, favor the further spread of this species. Finally, among the macrocyclic lactones currently used to prevent heartworm infection, only moxidectin has been found to be fully effective against the infective larvae transmitted by mosquitoes and partially effective (efficacy 96%) against adult D. repens in experimental studies.

Conclusions

Dirofilaria repens infection is much more difficult than D. immitis to diagnose and control in the reservoir population (microfilaremic dogs). In addition, lack of familiarity with D. repens infection could lead to lack of vigilance underestimation for this parasite. The number of human cases in Europe and Asia is currently a serious public health concern. Medical doctors and veterinarians must collaborate closely for better control and surveillance of D. repens infection.

Dirofilaria infections in dogs in different areas of Greece

Background

The nematodes Dirofilaria immitis and D. repens are enzootic in Greece. In the light of evidence of dirofilariosis spreading to new areas around the world, the aim of the present study was to update and enrich the current knowledge on the prevalence of Dirofilaria infections in dogs in Greece, to assess the risk factors of heartworm infection, and to initiate the drawing of the epizootiological map of canine dirofilariosis, investigating Dirofilaria infections in five locations along the north-south axis of the country, i.e. municipalities of Thessaloniki, Larissa, Achaia, Attica and Heraklion, associated with the five largest urban centres of Greece.

Methods

Blood samples collected from 750 dogs in total, were examined by the modified Knott’s method and by serology. A questionnaire including information about each examined dog was filled in and statistical analysis of the results was performed using the Chi-square test and a Binary Multiple Univariate Generalized Linear Model.

Results

In total, 31 (4.1 %) out of 750 examined animals were found positive for D. immitis by any of the tests applied (Knott’s method and serological examination). Moreover, microfilariae of D. repens and Acanthocheilonema reconditum were detected by the Knott’s method in 17 (2.3 %) and 10 (1.3 %) of the animals, respectively. At the municipality level, the prevalence of infection was 14, 7, 5.3, 0.7 and 0 % for D. immitis, 1, 2, 8.7, 0.3 and 0 % for D. repens, and 0, 3, 2.7, 0.7 and 1 % for A. reconditum in Thessaloniki, Larissa, Achaia, Attica and Heraklion, respectively. In addition, in three dogs (one each in Thessaloniki, Achaia and Attica) mixed D. immitis - D. repens infections were detected by the Knott’s method. The area of the country, dog’s usage and age were determined as risk factors for heartworm infection.

Conclusions

Northern areas of Greece have higher Dirofilaria prevalence and the prevalence in a western province (Achaia) is recorded for the first time. The mosquito population dynamics recorded in the past is likely to play an important role in the distribution of Dirofilaria infections in Greece, and needs further investigation. Similarly, the role of wild reservoirs of filarial parasites in different areas needs to be clarified. Promotion by veterinarians of preventive treatment and compliance by pet owners is essential in all parts of Greece, regardless of the recorded prevalence of infection.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1797-6) contains supplementary material, which is available to authorized users.

The prevalence of Dirofilaria repens in cats, healthy dogs and dogs with concurrent babesiosis in an expansion zone in central Europe

BACKGROUND

Dirofilaria repens is a mosquito-transmitted, filarial nematode parasitizing dogs, cats and other carnivores. Recently, this parasite has spread in central Europe, including Poland. The aim of the present study was to estimate the prevalence of D. repens in cats and dogs in different regions of the country and to investigate the occurrence and consequences of co-infection with another fast-spreading vector-borne parasite, Babesia canis.

RESULTS

In the period 2013-2015, 147 blood samples from cats from central Poland and 257 blood samples from dogs from central, northern, southern and western Poland were collected. Prevalence of D. repens was determined by amplification and sequencing of the 12S rDNA gene fragment. Among dogs, 94 samples originated from clinically healthy dogs from central Poland (Masovia) and 58 samples originated from dogs that were infected with B. canis. Prevalence of D. repens was compared between these two groups of dogs. For the first time D. repens was identified in a cat from central Europe (0.7 % [95 % CL: 0-4.1 %]). The DNA of the filarial endosymbiotic bacterium Wolbachia was detected in two cats (1.4 % [95 % CL: 0-5.5 %]). In dogs, the parasite was detected only in samples from central Poland (Masovia) (local prevalence = 38 % [95 % CL: 25.9-51.8 %]). Prevalence of D. repens was significantly higher in dogs with babesiosis (90 % [95 % CL: 81.6-94.5 %]). Co-infections of D. repens and B. canis were confirmed by sequencing in 30 dogs with babesiosis, but no co-infections were identified in healthy dogs from Masovia. Statistical analyses of blood parameters revealed that dogs with co-infections suffered more severe anemia and thrombocytopenia, but presented milder changes in biochemical parameters (i.e. less elevated concentration of alkaline phosphatase [ALP] and serum urea) suggesting lower risk of hepatic or renal failure in comparison to dogs infected only with B. canis.

CONCLUSIONS

These findings are important due to the spread of dirofilariosis and babesiosis in central Europe, as microfilaraemic dogs seem to be more prone to babesiosis. The possible protective effect of the nematode infection against hepatic or renal failure in canine babesiosis and its mechanisms require further investigations.

An appraisal of canine and human cases reveals an endemic status of dirofilariosis in parts of Serbia

Dirofilaria immitis and D. repens are mosquito-borne nematodes that primarily infect canids, and can also cause mild to serious superficial or visceral infection in humans. In the present survey, peripheral blood from 150 asymptomatic dogs from Serbia were examined using the modified Knott's technique. Dirofilaria immitis, identified based on morphological and morphometric characteristics, was prevalent in dogs not receiving preventative treatment (in 44% and 60% of pound and pet dogs, respectively). These results, together with findings of autochthonous cases of subcutaneous D. repens infection in human patients from Southeastern Serbia emphasize the need for further investigations of this veterinary and public health problem.

Microfilaricidal efficacy of a single administration of Advocate(®) (Bayer Animal Health) in dogs naturally infected with Dirofilaria immitis or Dirofilaria repens

The present study evaluated the microfilaricidal efficacy of a single application of the spot-on containing imidacloprid 10%/moxidectin 2.5% (Advocate(®), Bayer Animal Health) in dogs naturally infected either by Dirofilaria immitis or Dirofilaria repens. Dogs living in north-eastern and central-southern Italy, endemic for D. immitis and D. repens respectively, were randomly screened. Sixteen animals, eight infected with D. immitis and eight with D. repens, and fulfilling inclusion criteria were enrolled. Dogs infected with D. immitis received an adulticide treatment prior to the study and Advocate(®) 3 weeks after. The animals were divided in blocks of two (1:1, T1:T2) animals each, where Day 0 (D0) had an interval of 15days to compare T2 vs. T1 dogs during the first fortnight of examination (i.e. T2 dogs acted as control animals at each examination). At baseline (Days -15 and 0 for T2 and T1 dogs, respectively) the animals had a range of microfilaraemia of 180-99.700mff/ml (D. immitis) and 60-750 mff/ml (D. repens). All animals received a topical administration of Advocate(®) at D0 and were examined for microfilariae with microscopic and molecular tests at D15, D30, D60 and D90. All animals scored negative for mff at the first control post-treatment and throughout the study, with the exception of two D. immitis- infected animals that had a 2 mff/ml count at D15, and then become negative from Day 30 onwards. No adverse events were observed. The present study demonstrates the safety and the high microfilaricidal efficacy (99.97% and 100% for D. immitis and D. repens, respectively) of a single dose of moxidectin contained in Advocate(®) in naturally infected dogs.

Dirofilaria in Humans, Dogs, and Vectors in Austria (1978-2014)-From Imported Pathogens to the Endemicity of Dirofilaria repens

Background

Dirofilaria repens and D. immitis are filarioid helminths with domestic and wild canids as main hosts and mosquitoes as vectors. Both species are known to cause zoonotic diseases, primarily pulmonary (D. immitis), ocular (D. repens), and subcutaneous (D. repens) dirofilariosis. Both D. immitis and D. repens are known as invasive species, and their distribution seems associated with climate change. Until very recently, both species were known to be nonendemic in Austria.

Methodology and Principal Findings

Metadata on introduced and possibly autochthonous cases of infection with Dirofilaria sp. in dogs and humans in Austria are analysed, together with analyses of mosquito populations from Austria in ongoing studies.

In Austria, most cases of Dirofilaria sp. in humans (30 cases of D. repens—six ocular and 24 subcutaneous) and dogs (approximately 50 cases—both D. immitis and D. repens) were most likely imported. However, occasionally infections with D. repens were discussed to be autochthonous (one human case and seven in dogs). The introduction of D. repens to Austria was confirmed very recently, as the parasite was detected in Burgenland (eastern Austria) for the first time in mosquito vectors during a surveillance program. For D. immitis, this could not be confirmed yet, but data from Germany suggest that the successful establishment of this nematode species in Austria is a credible scenario for the near future.

Conclusions

The first findings of D. repens in mosquito vectors indicate that D. repens presumably invaded in eastern Austria. Climate analyses from central Europe indicate that D. immitis also has the capacity to establish itself in the lowland regions of Austria, given that both canid and culicid hosts are present.

First molecular identification of Dirofilaria spp. (Onchocercidae) in mosquitoes from Serbia

Dirofilariosis is a common and widespread veterinary health issue in several European countries with notable zoonotic potential. The causative agents are Dirofilaria immitis and Dirofilaria repens nematoda species which are transmitted by different mosquito vectors. Similar to other mosquito-borne infections, the knowledge about mosquito species involved in disease transmission is crucial for the complex understanding of local transmission cycles. Since there is no available data on mosquito species, potentially involved in disease transmission from Serbia, 6369 female mosquito individuals were retrospectively tested for Dirofilaria nematodes, collected from 13 localities in Vojvodina province, Serbia, in 2013. Altogether, 8.33 % of tested pools showed positivity, composed of five mosquito species, mainly, Culex pipiens and Aedes vexans. D. immitis and D. repens were both detected from multiple localities, during the whole period of mosquito breeding season, which provides the first data on local transmission characteristics regarding mosquitoes from the Balkans.

Retrospective study on the distribution of Dirofilaria immitis in dogs in Hungary

Europe has experienced the spreading of vector-borne helminths including heartworms (Dirofilaria immitis) from the Mediterranean countries towards the northern ones in the past decades. Recently, the establishment of D. immitis was confirmed in Hungary on the basis of period prevalence studies involving dogs, red foxes (Vulpes vulpes) and golden jackals (Canis aureus). The aim of our retrospective study was to describe the spatial distribution of the parasite and the time course of spreading of D. immitis in Hungary. Necropsy records of 2622 dogs received at our laboratories from 2001 to 2015 were reviewed for heartworm infections. The locality of origin of animals was recorded in a geographic information system database and compared to the results of the period prevalence study involving wild canids. Autochthonous heartworm infection was detected in 27 dogs. The time course analysis indicates that the parasite established in Hungary in 2007. As temperature is one of the most important determinants of the distribution of D. immitis, the climate of the Great Hungarian Plain is the most suitable region for the establishment of D. immitis in Hungary. Our studies revealed that the Great Hungarian Plain became a D. immitis endemic region for 2015. Nevertheless, sporadic cases in wild canids and dogs also occur in other regions of the country.

The Increase of Exotic Zoonotic Helminth Infections: The Impact of Urbanization, Climate Change and Globalization

Zoonotic parasitic diseases are increasingly impacting human populations due to the effects of globalization, urbanization and climate change. Here we review the recent literature on the most important helminth zoonoses, including reports of incidence and prevalence. We discuss those helminth diseases which are increasing in endemic areas and consider their geographical spread into new regions within the framework of globalization, urbanization and climate change to determine the effect these variables are having on disease incidence, transmission and the associated challenges presented for public health initiatives, including control and elimination.

Morphological and molecular detection of canine dirofilarial species of veterinary and medical importance in Morogoro municipality, Tanzania

A descriptive cross-sectional survey of Dirofilaria infections in dogs was carried out from January to March 2015 in Morogoro municipality, Tanzania. One hundred and fifty two blood samples were collected from healthy dogs aged more than 6 months living in different areas of Morogoro, and analyzed by modified Knott's technique for circulating microfilariae. Microfilaraemic samples were further analyzed by Polymerase chain reaction (PCR) and PCR products were sequenced for molecular identification. Microfilariae were detected by microscopy in 9 samples (5.92%), of which 6 tested positive by PCR. The 5.8S-internal transcribed spacer 2 (ITS2)-28S ribosomal DNA (rDNA) sequences generated were 97% identical to Dirofilaria immitis and 86% to 90% identical to D. repens, confirming the presence of D. immitis in Tanzania and showing the presence of D. repens, not previously observed.

The role of wild canids and felids in spreading parasites to dogs and cats in Europe. Part II: Helminths and arthropods

Over the last few decades, ecological factors, combined with everchanging landscapes mainly linked to human activities (e.g. encroachment and tourism) have contributed to modifications in the transmission of parasitic diseases from domestic to wildlife carnivores and vice versa. In the first of this two-part review article, we have provided an account of diseases caused by protozoan parasites characterised by a two-way transmission route between domestic and wild carnivore species. In this second and final part, we focus our attention on parasitic diseases caused by helminth and arthropod parasites shared between domestic and wild canids and felids in Europe. While a complete understanding of the biology, ecology and epidemiology of these parasites is particularly challenging to achieve, especially given the complexity of the environments in which these diseases perpetuate, advancements in current knowledge of transmission routes is crucial to provide policy-makers with clear indications on strategies to reduce the impact of these diseases on changing ecosystems.