Subcutaneous Dirofilariosis Research Articles

Genetic variability of Dirofilaria repens isolates from humans and dogs in Italy

Dirofilaria repens is a paradigmatic example of an emerging vector-borne pathogen (VBP) in both human and veterinary fields. The spatial expansion and the increasing zoonotic impact of this VBP can be related to several drivers including the genetic structure of parasite populations. Italy is one of the European countries traditionally endemic with the highest incidence of canine and human cases of subcutaneous dirofilariosis. The present study aimed to assess the genetic identity and variability of D. repens isolates of human and canine origin from areas of Central Italy, compared with those isolated from different areas of Europe by sequence analysis of mtDNA genes (i.e., 12 S rDNA and cox1). A total of twenty isolates of D. repens were obtained from biopsies of subcutaneous and ocular cases of dirofilariosis occurring in 10 dogs and 10 humans. The sequence analysis of 12 S rDNA showed that all the sequences obtained clustered as a monophyletic group with a strong nodal support, indicating that all sequence types represented D. repens. The cox1 and the 12 S sequence analysis did not show host-related polymorphisms between human and dog-derived specimens. The sequence analysis of cox1 was performed including 8 additional sequences previously obtained from human and canine isolates in the same areas. Out of the 28 sequences analyzed, 20 were grouped in a haplogroup comprising 15 haplotypes (i.e., DR1, DR2, DR4, DR5, DR7, DR8, DR10-DR18), 2 sequences matched to DR9, reported for the first time in Italy, and 6 showed peculiar polymorphisms that were not previously described. The results obtained have implications for a better understanding of the epidemiology and phylogeography of this emerging vector-borne zoonotic parasite.

Occurrence of canine subcutaneous dirofilariosis (Dirofilaria repens) in Switzerland

Infectious diseases are increasingly introduced into Switzerland due to the increased travel activity in recent decades and the import of dogs. Dirofilariasis, caused by Dirofilaria immitis or D. repens, is one of them. An infection with D. repens, the cause of canine subcutaneous dirofilariosis, is often asymptomatic in dogs, but represents a potential zoonotic disease risk for humans. Due to the rapidly increasing number of human cases, D. repens is considered an emerging zoonosis in north-eastern Europe. The prevalence of D. repens infections in dogs and humans in Switzerland is unknown. Since 2016 the analysing diagnostic laboratory provided with the newly introduced filaria PCR a realiable diagnostic test to differentiate betweeen D. immitis and D. repens. Total nucleic acid (DNA and RNA) was extracted from 200 μl EDTA blood without prior enrichment followed by a species-specific real-time PCR assay. The analyses for Dirofilariae in the years 2016 to 2021 were examined in a descriptive retrospective study and the proportion of positive tests per year (prevalence with 95 % confidence interval) was calculated. Furthermore, blood samples of 50 imported dogs to Switzerland were analyzed in an exploratory cross-sectional study for the presence of dirofilaria. No D. repens positive case was found in the first two years after the introduction of the PCR. In 2018 five of 546 analyzed samples (5/546, 0,9 %, 95 % confidence interval [95 % CI]=0,7 - 1,2 %) tested positive for D. repens, in 2019 four of 591 (0,7 %, 95 % CI=0,5 - 0,9 %), in 2020 15 of 783 (1,9 %, 95 % CI=1,6 - 2,3 %) and in 2021 eleven of 1058 samples (1,0 %, 95 % CI=0,8 - 1,3 %). In the exploratory cross-sectional study, four of the 50 examined dogs were positive for D. repens (8 %, 95 % CI=2,6 - 20,1 %). One dog had a concurrent infection with D. immitis and D. repens. All four positive tested dogs were imported from Hungary. Potentially zoonotic infections with D. repens occur in dogs living in Switzerland. This disease should be included in the differential diagnoses of imported dogs and a monitoring during routine health checks should be done more often. The veterinary profession can thus assume its responsibility for the prevention of zoonoses as part of a One Health approach.

Subcutaneous Dirofilariosis of the Eyelid Brought to Poland from the Endemic Territory of Ukraine

We present the case of a 60-year-old man who was diagnosed with a subcutaneous nodule on the upper eyelid of his left eye. The patient reported multiple mosquito bites during numerous work trips to Ukraine. Histopathological examination of the nodule isolated during surgery suggested Dirofilaria repens infestation. The infection was brought to Poland from the territory of Ukraine. Ophthalmologists must be aware of uncommon presentations of parasitic infestations when they consider infections of the ocular adnexa.

Haplotypes of Dirofilaria repens from Poland and selected countries of Central, North-Eastern Europe and the Middle East: An evaluation on the relation between the genetic diversity and the geographic distribution of the fast-spreading parasite

Subcutaneous dirofilariosis is a fast-spreading infection of dogs, and occasionally of other carnivores and humans. Several factors contribute to its spread, including climate change, which facilitates development and survival of Dirofilaria repens in the mosquito vector. Movement/relocation of infected definitive hosts (dogs) from endemic regions to non-endemic regions is another possible cause of local emergence and the presence of a wide variety of wild reservoirs of the parasite may also contribute to its spread. The main aim of this study was to evaluate the genetic diversity of D. repens from different regions of Europe and to evaluate the spread of identified haplotypes and their geographic origin. A total of 95 D. repens isolates were obtained from Central and Eastern Europe (Poland, Belarus, Ukraine, Austria, Romania), NE Europe (Lithuania, Latvia, Estonia), Italy and Israel. All but two positive samples were obtained from the blood of dogs while one positive sample was obtained from an adult worm from a human case from the Lublin area in SE Poland and one sample was obtained from Anopheles plumbeus mosquito from Austria. Genetic diversity in D. repens isolates was evaluated by PCR amplification and sequencing of three genetic markers, including two mitochondrial genes (mtDNA): the cytochrome c oxidase subunit I (COI) and dehydrogenase subunit I (NADH). Additionally, the genomic marker, internal transcribed spacer 1 (ITS-1) was amplified and sequenced. Haplotypes were differentiated based on sequence alignments by identifying Single Nucleotide Polymorphism (SNPs) using DnaSP and Mega X. PopArt was used to construct a haplotype network including all identified haplotypes. Both mtDNA sequences (COI and NADH) were combined together for phylogenetic and network analyses. Altogether 18 haplotypes (DR1-DR18) were identified in combined mtDNA markers among 95 analysed samples. Haplotype DR1 was the most common encompassing 66 isolates: 42 isolates from Poland (41 from dogs and one from a human), 13 from Lithuania, 4 from Latvia, 2 from Ukraine and 5 from Romania. All other haplotypes grouped around haplotype DR1 separated by 1–5 SNPs, forming a star-like shape. Haplotype DR2 was the second most common haplotype, formed by six isolates from Romania. Interestingly, haplotype DR3 was represented only by four isolates from Israel. The remaining 15 haplotypes were represented by 1–4 isolates of different origins. Our study showed that only minor genetic diversity was found in D. repens since all isolates appear to have clustered in or branched out from haplotype DR1 with 1–5 SNP differences. The genetic diversity appears to be governed by geographic origin since isolates from neighbouring populations (countries) appear to share unique haplotypes while other populations that are geographically distant from individual haplotypes.

Canine antibody response against Dirofilaria repens in natural occult and microfilaremic infections

Dirofilaria repens is the causative agent of the zoonotic canine skin condition called subcutaneous dirofilariosis. Despite being endemic throughout much of Europe, little is known about host humoral responses to D. repens. To address this, we analyzed serum immunoglobulin isotypes recognizing D. repens somatic antigens (DrSA) in naturally infected dogs. Titers of anti-DrSA IgG and IgE, but not IgM were significantly higher in dogs infected with D. repens compared to those that were negative. Moreover, microfilaremic infections were associated with higher levels of IgG1 than IgG2, while occult infections occurred with significantly higher levels of IgG2 than IgG1. Finally, the measurement of anti-DrSA IgG antibodies allowed the detection of occult subcutaneous dirofilariosis in dogs.

Dirofilaria spp. and Angiostrongylus vasorum: Current Risk of Spreading in Central and Northern Europe.

In the past few decades, the relevance of Dirofilaria immitis and Dirofilaria repens, causing cardiopulmonary and subcutaneous dirofilariosis in dogs and cats, and of Angiostrongylus vasorum, causing canine angiostrongylosis, has steadily increased in Central and Northern Europe. In this review, a summary of published articles and additional reports dealing with imported or autochthonous cases of these parasites is provided for Central (Austria, Czechia, Germany, Hungary, Luxemburg, Poland, Slovakia, Slovenia, and Switzerland) and Northern (Denmark, Finland, Iceland, Norway, and Sweden) Europe. Research efforts focusing on Dirofilaria spp. and A. vasorum have varied by country, and cross-border studies are few. The housing conditions of dogs, pet movements, the spread of competent vectors, and climate change are important factors in the spread of these nematodes. Dogs kept outside overnight are a major factor for the establishment of Dirofilaria spp. However, the establishment of invasive, diurnal, synanthropic, competent mosquito vectors such as Aedes albopictus may also influence the establishment of Dirofilaria spp. The drivers of the spread of A. vasorum remain not fully understood, but it seems to be influenced by habitats shared with wild canids, dog relocation, and possibly climatic changes; its pattern of spreading appears to be similar in different countries. Both Dirofilaria spp. and A. vasorum merit further monitoring and research focus in Europe.

Evaluation of alternative reagents on the performance of the modified Knott’s test

The aim of the present study was to evaluate the suitability of different reagents as safe alternatives to 2% formalin in the modified Knott’s test for the diagnosis of subcutaneous (Dirofilaria repens) and cardiopulmonary (D. immitis) dirofilariosis. A total of 61 blood samples from dogs naturally infected with D. immitis and D. repens were collected and analysed in two different laboratories (Lab 1, University of Parma and Lab 2, University of Napoli). For each blood sample the modified Knott’s method was performed to identify and measure the mean length and width of the microfilariae (mfs) using 2% formalin (A), 2% acetic acid (B), 2% glacial acetic acid (C), 10% saponin (D) and distilled water (E). When compared to 2% formalin, there was no significant difference (P > 0.05) among the mean length and width of either D. immitis or D. repens mfs with distilled water (E). The lengths and widths of mfs, however, were significantly reduced (P < 0.05) when using B, C, D likely due to more pronounced parasite dehydration. Despite differences in measurements, the morphological features of the head and tail of the two species were maintained, suggesting that all the solutions tested could be a suitable alternative to formalin. All alternative reagents caused more marked haemolysis compared to formalin, improving readability of slides. The values of the mean length and the mean width of D. immitis and the mean width of D. repens mfs obtained with formalin and distilled water were statistically different (P < 0.005) between the two laboratories. The difference in mf measurements between the two labs could be due to the use of reagents purchased from different manufacturing companies.Results suggest that distilled water could replace formalin in the modified Knott’s test, as a safer reagent that allows morphology-based species differentiation of Dirofilaria spp.

Human dirofilariosis in the 21st century: A scoping review of clinical cases reported in the literature.

Human dirofilariosis is a clinical entity caused by infection with nematode species of the genus Dirofilaria. The traditional picture depicts the disease as a sporadic event associated with the presence of a single immature worm causing a nodular lesion. With the aim to reassess this paradigm, establishing a more accurate picture of the disease and homogenize criteria, a scoping review was conducted by searching, screening and analysing published clinical cases of human dirofilariosis worldwide during the 21st century. After extracting data from 305 publications containing 576 case reports, results showed that human dirofilariosis is currently caused by five Dirofilaria species (mainly D. repens). Maturation was not uncommon, since 42.95% of the parasites recovered were described as mature worms, most of them females, 26.42% of which contained micofilariae in the uterus. Moreover, six microfilaremic cases have been described. The predominant clinical manifestation was the presence of a worm encapsulated within a nodule, but there is a considerable variety of accompanying symptoms depending on anatomical location and type of dirofilariosis. Parasites/nodules were found in 71 different anatomical locations, being the traditional nomenclature of human dirofilariosis unable to properly cover this complex situation. Delay in seeking medical assistance (patient perception) and the frequency of wrong clinical suspicions (doctor knowledge), strongly influenced clinical management. The initial suspicion in cases of subcutaneous and pulmonary dirofilariosis is predominantly a tumour, while in the ocular dirofilariosis a parasite (but not directly Dirofilaria) is mostly suspected. Surgery is usually applied, regardless of the use of non-invasive techniques during preoperative management and although its use is still limited, molecular approach is the most accurate technique to establish a species-level diagnosis. Accurate epidemiological, parasitological and clinical information while handling and reporting human clinical cases is a need for physicians and researchers to improve and standardize the clinical management of human dirofilariosis.

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

BackgroundDirofilariosis 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.MethodsA 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.ResultsData 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.ConclusionsThe 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.Graphical

Dirofilaria immitis infection in the Pelagie archipelago: The southernmost hyperendemic focus in Europe.

Dirofilaria immitis and Dirofilaria repens are mosquito-borne filarioids of zoonotic concern, which primarily cause canine heartworm disease (HWD) and subcutaneous dirofilariosis, respectively. The geographical distribution of these nematodes is constantly changing, due to many factors such as the colonization by new invasive mosquito species, the increased movement of animals and the absence of chemoprophylactic strategies in non-endemic regions. Although HWD has always been considered endemic in northern Italy, an increase in the prevalence of this disease has been recorded in the last decades in central and southern regions. We describe the southernmost hyperendemic European focus of heartworm disease in the Pelagie archipelagos. From June to November 2020, 157 dogs and 46 cats were sampled in Linosa and Lampedusa islands for the detection of Dirofilaria immitis and Dirofilaria repens by modified Knott's, rapid antigen and molecular tests. Mosquitoes were collected using CDC light and BG sentinel-2 traps and aspirators, and tested for host blood meal and Dirofilaria spp. DNA. Out of 56 dogs in Linosa and 101 in Lampedusa, 33 (i.e. 58.9%) and 8 (i.e. 7.9%) were positive to D. immitis and D. repens, respectively. Three cats scored positive to D. immitis (i.e. 17.6%) in Linosa. Six mosquito species were identified, and the abdomen of a non-engorged Aedes albopictus was positive for D. immitis and human DNA. The results suggest that D. immitis infection could spread to new previously non-endemic territories in southern Europe, representing a real threat to animal and human health.

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.

Potential Mosquito Vectors of Dirofilaria immitis and Dirofilaira repens (Spirurida: Onchocercidae) in Aras Valley, Turkey.

Dirofilaria immitis (Leidy, 1856) and Dirofilaria repens (Railliet & Henry, 1911) are mosquito-borne filarial nematodes that primarily affect dogs, causing heartworm disease and subcutaneous dirofilariosis. The canine heartworm is reported in different provinces in Turkey. However, studies about the transmitting mosquito species are limited. Hence, this study aimed to investigate potential vectors of D. immitis and D. repens in Aras Valley, Turkey. In total, 17,995 female mosquitoes were collected from eight villages during three mosquito seasons (2012-2014) in Aras Valley, located in north-eastern Turkey. A total of 1,054 DNA pools (527 abdomen and 527 head-thorax) were tested with Dirofilaria primers by multiplex-polymerase chain reaction (PCR). Aedes caspius was the most abundant species in collection sites with 90%; this was followed by Culex theileri Theobald, 1903 (Diptera: Culicidae) (7.31%), Anopheles maculipennis Meigen 1818 (Diptera: Culicidae) (1.28%), Culex pipiens Linnaeus, 1758 (Diptera: Culicidae) (0.43%), (Anopheles) hyrcanus (Pallas, 1771) (Diptera: Culicidae) (0.37%), Aedes vexans (Meigen, 1830) (Diptera: Culicidae) (0.25%), and Culiseta annulata Schrank, 1776 (Diptera:Culicidae) (0.02%). Dirofilaria immitis and D. repens were detected in mosquito pools from five villages. The total Dirofilaria spp. estimated infection rate was 1.33%. The highest estimated infection rate was found in Ae. vexans (6.66%) and the lowest was in Ae. caspius (1.26%). The results show that An. maculipennis sl, Ae. caspius, Ae. vexans, Cx. theileri and Cx. pipiens are potential vectors of D. immitis and D. repens with DNA in head-thorax pools; An. hyrcanus is also a likely vector, but Dirofilaria DNA was found only in abdomen pools for the study area. This study revealed new potential vector species for D. immitis. Mosquitoes with natural infections of D. repens were reported for the first time in Turkey.

Aedes (Stegomyia) aegypti mosquito bite hypersensitivity in a dog: a case report

BackgroundMosquitoes are vectors of several pathogens of considerable importance to humans and companion animals, including nematode helminths such as Dirofilaria immitis and Dirofilaria repens that cause heartworm disease and subcutaneous dirofilariosis, respectively. In addition to mosquito-borne pathogen transmission, mosquito bites can cause discomfort and irritation in pets, and even lead to severe hypersensitivity reactions. In the present study, we report an acute local hypersensitivity reaction in a dog following experimental exposure to Aedes (Stegomyia) aegypti.Case presentationA healthy six-year-old male beagle was included in an efficacy study in which dogs (n = 28) were exposed to Ae. aegypti mosquitoes. On Day − 6, the dog was allocated to one of the study groups, consisting of seven dogs to be treated on Day 0 with an imidacloprid/flumethrin collar. After sedation, animals were exposed to approximately 50 females of Ae. aegypti for 60 (± 5) minutes on Days − 6, 1, 7, 14, 21, 28, 55, and 83. On Day − 6, no allergic reaction to the mosquito bites was observed. However, on Day 1, corresponding to the second challenge, the dog demonstrated an acute allergic reaction characterized by swelling of the face (especially in the base of the muzzle and around the eyes), redness of the eyes, and conjunctival edema of the right eye was also observed. The dog was immediately treated with an intramuscular injection of a commercially available antihistamine treatment, Pen-Hista-Strep® containing a suspension of benzylpenicillin, chlorphenamine, dexamethasone, dihydrostreptomycin, and procaine at a dosage of 1 mL per 10 kg. A few hours after treatment, the dog showed noticeable improvement.ConclusionsThis case provides the first evidence of canine acute local hypersensitivity reaction to mosquito bites under laboratory conditions. This observation suggests that invasive mosquito species such as Aedes spp. may affect the health and comfort of our companion animals, especially for pets with outdoor access without individual protective measures against insect bites.

Hematological and Biochemical Changes in Dogs Naturally Infected With Dirofilaria repens.

Subcutaneous dirofilariosis is a zoonotic disease emerging throughout Europe caused by the filarial nematode Dirofilaria repens. Despite its increasing prevalence, there is a large gap in knowledge of the impact of the parasite on the host. Currently classified as being non-pathogenic, recent evidence suggests that skin dirofilariosis is associated with dermatological conditions including concomitant pruritus, neoplastic processes, inflammation, and even blindness in dogs and humans. The aim of this study was to determine if natural canine D. repens infection leads to biological changes in the canine host. In a real-life veterinary clinic setting, animals are often presented to clinicians for unrelated issues, and D. repens is incidentally identified during inspection. As such, we compared hematological and biochemical parameters of 218 uninfected and 197 dogs naturally infected with D. repens. Interestingly, animals infected with D. repens had lower numbers of lymphocytes (p < 0.001), red blood cells (p < 0.001), and thrombocytes (p = 0.025), decreased hematocrit (p < 0.001), and increased alkaline phosphatase (p = 0.016) and creatinine activity (p = 0.023) compared to uninfected dogs. We further selected a subpopulation of 214 dogs having prima facie hematological and biochemical results within normal reference ranges to evaluate the effect of D. repens infections in seemingly healthy dogs. Among these patients, 93 dogs infected with D. repens had lower numbers of lymphocytes (p = 0.031), red blood cells (p = 0.025), and hematocrit (p = 0.002), higher glucose levels (p = 0.023), and border line elevated alkaline phosphatase levels (p = 0.054) compared to 121 uninfected animals. Despite being categorized as asymptomatic, we have observed hematological and biochemical changes associated with D. repens infections in dogs, and our data suggest that dirofilariosis may induce a state of chronic stress. These results link the presence of skin dirofilariosis to biological changes in the canine host, suggesting a mechanism for pathogenicity and shedding new light on the host–parasite relationship.

First Molecular Detection of Dirofilaria immitis and D. repens in Dogs from Kyrgyzstan.

Dirofilaria immitis and Dirofilaria repens are the causative agents of cardiopulmonary and subcutaneous dirofilariosis, respectively. This neglected disease mainly seen in dogs, cats and wild carnivores is re-emerging recent years. No study was conducted on dirofilariosis in dogs in Kyrgyzstan. The goal of this study was to investigate Dirofilaria species using PCR and sequencing in dogs from Kyrgyzstan. Dirofilaria spp. infection in dogs was screened via convential PCR and sequencing in 337 dogs from Kyrgyzstan. The overall prevalence of Dirofilaria spp. was 0.59% (2/337): DNA of D. immitis was detected in one sample and DNA of D. repens in second positive sample. In second sample, parallel co-infection of D. repens with Wolbachia was also found. While D. immitis sequence showed 98.70-100% similarity with previously reported sequences of D. immitis from dog blood, D. repens shared 100% identity with other sequences of D. repens. These results provided first evidence for Dirofilaria spp. in Kyrgyzstan and emphasized the veterinary and medical importance.

Dirofilarioses in cats: European guidelines from the ABCD on prevention and management.

Dirofilaria immitis and Dirofilaria repens are the most important filarial worms, causing heartworm disease and subcutaneous dirofilariosis, respectively. D repens is currently considered an emerging zoonotic agent in Europe. Filarial worms infect mainly dogs, but also cats, ferrets, wild carnivores and humans. The life cycle involves an intermediate mosquito host. Compared with dogs, cats are imperfect hosts for dirofilarial worms. After inoculation, only a low number of L3 larvae develop to the adult stage in a small percentage of cats. Heartworm disease in cats may be associated with severe pulmonary thromboembolism and an eosinophilic inflammatory response in the lungs, potentially leading to sudden death. Otherwise self-cure occurs in most cases after 18-48 months. Subcutaneous dirofilariosis may present as subcutaneous nodules or dermatitis. Diagnosis in cats is more difficult compared with dogs and needs a multistep approach (antigen and antibody tests, as well as diagnostic imaging). Cats with acute heartworm disease require stabilisation within an intensive care unit. Cats with respiratory signs or suggestive radiographic changes should receive prednisolone and follow-up with a similar multistep approach. Adulticidal therapy is not safe in cats. In endemic areas cats should receive year-round chemoprophylaxis from 2 months of age.

A possible relationship between Thromboxane B2 and Leukotriene B4 and the encapsulation of Dirofilaria repens worms in human subcutaneous dirofilariasis

Human subcutaneous dirofilariosis has several clinical presentations. Many cases present as subcutaneous nodules, as a consequence of a local inflammatory reaction that encapsulates and destroys the worms. In addition, there are cases in which migrating worms located in the ocular area remain unencapsulated. In the present work, the levels of two pro-inflammatory eicosanoids, thromboxane B2 (TxB2) and leukotriene B4 (LTB4) are analysed by commercial Enzime-Linked immunosorbent assay (ELISA) in serum samples from 43 individuals, 28 diagnosed as having subcutaneous dirofilariasis presenting a subcutaneous nodule, five diagnosed as having dirofilariasis, in which the worms remained unencapsulated in the periphery of the eye, and ten healthy individuals living in a non-endemic area, used as controls. The worms were surgically removed, identifying Dirofilaria repens as the causative agent in all cases, by Polymerase Chain Reaction (PCR). Individuals with nodules showed significantly higher levels of TxB2 and LTB4 than healthy controls, whereas significant differences in LTB4 levels were observed between individuals with unencapsulated worms and healthy controls. It is speculated that the absence of LTB4 may contribute to the fact that worms remain unencapsulated as a part of immune evasion mechanisms.

Dirofilaria repens in dogs and humans in Lithuania

BackgroundIn Lithuania, the first case of canine subcutaneous dirofilariosis was recorded in 2010. Since then, an increasing number of cases of canine dirofilariosis have been documented in different veterinary clinics throughout the country. Human dirofilariosis was diagnosed in Lithuania for the first time in September 2011. However, to the authors’ knowledge, there are no published data on the presence and prevalence of autochthonous dirofilariosis in dogs and humans in the country. The present study provides information about the predominant species and prevalence of Dirofilaria in dogs and describes the cases of human dirofilariosis in Lithuania. It also outlines PCR detection of the bacterial endosymbiont Wolbachia that contributes to the inflammatory features of filarioid infection.ResultsA total of 2280 blood samples and six adult worms from pet and shelter dogs were collected in the central and eastern regions of Lithuania in 2013–2015. Based on their morphological appearance, morphometric measurements and molecular analysis, all the adult nematodes were identified as Dirofilaria repens. The diagnosis of microfilariae in blood samples was based on blood smear analysis and Knott’s test. The PCR and sequence analysis of the ribosomal DNA ITS2 region and cox1 gene confirmed the presence of D. repens. Overall, 61 (2.7%) of the 2280 blood samples were found to be positive for the presence of D. repens. The infection rate of D. repens was significantly higher in shelter dogs (19.0%; 19/100) than in pet dogs (1.9%; 42/2180) (χ2 = 100.039, df = 1, P < 0.0001). Forty-nine DNA samples of D. repens-infected dogs were tested for the presence of the bacterial endosymbiont Wolbachia and, of these, 40 samples (81.6%) were found to be positive. Three ocular and six subcutaneous cases of human dirofilariosis were diagnosed in Lithuania in the period 2011–2018.ConclusionsTo the authors’ knowledge, this is the first report of autochthonous D. repens infection in dogs and humans in Lithuania. The present data demonstrate that D. repens is the main etiological agent of dirofilariosis in Lithuania. The DNA of the filarioid endosymbiotic bacterium Wolbachia was detected in the vast majority of dogs infected with D. repens.

A cardiac and subcutaneous canine dirofilariosis outbreak in a kennel in central France.

Canine dirofilarioses are nematode infections caused by two species of the genus Dirofilaria: D. immitis and D. repens. We describe here an outbreak of D. immitis and D. repens infection in military working dogs (MWDs) housed in a kennel in the Indre department (centre of France). Out of a total of 17 dogs, 6 (35.2%) tested positive for D. immitis, D. repens or both parasites. Infested dogs were treated and prophylactic measures were implemented for the entire kennel staff. To our knowledge, this is the first documented description of an outbreak of canine cardiopulmonary dirofilariasis in the center of France, unlike in the south of this country, where D. immitis and D. repens dirofilariasis are enzootic. In France, as mosquito vectors expand their territory and new non-native vectors are introduced, it is likely that the distribution area of these two diseases of domestic and wild carnivores will be wider and underestimated.

First molecular detection of Dirofilaria immitis (Spirurida: Onchocercidae) infection in dogs from Northern Algeria.

Dirofilaria immitis and Dirofilaria repens are mosquito-borne filarioid nematodes that affect dogs and other domestic and wild carnivores, causing heartworm disease and subcutaneous dirofilariosis, respectively. In Algeria, the data about the epidemiology of these infections is largely unknown. The present study was designed to establish the occurrence of D. immitis and D. repens in dogs in Algeria using molecular tools. In 2014 and 2015, a total of 209 dogs over one year of age of different breed and sex, living in Northern Algeria, were examined and blood samples were collected from each dog. The presence of D. immitis and D. repens in these samples was detected by real-time PCR followed by standard PCR and sequencing. Overall, the blood of 209 dogs from two departments was collected and only 3 (1.4%) of the blood samples were found positive for D. immitis DNA. Sequencing of the corresponding amplicon displayed a 99.8% identity to D. immitis, confirming the presence of this mosquito-borne nematode in Algeria. Furthermore, all tested samples were negative for D. repens.