small molecules

2026-09-30 | Efficacy of a combination of fipronil and permethrin in reducing the risk of Dirofilaria immitis transmission to dogs in field conditions.

Dirofilaria immitis is a life-threatening mosquito-borne parasite affecting dogs. Prevention mainly relies on macrocyclic lactones (MLs), but D. immitis resistance to MLs and lack of compliance may occur. Multimodal strategies combining chemoprophylaxis and vector control with insecticide and repellent products are often recommended. This study evaluated the efficacy of Frontline Tri-Act® (IVP), a topical combination of fipronil and permethrin, in preventing the transmission of D. immitis by repelling mosquitoes in naturally exposed dogs. This study was conducted in northern Greece, in an area highly endemic for D. immitis and with seasonal (spring to fall) mosquito season. Dogs were housed in outdoor kennels to allow natural vector exposure throughout the whole study. Twenty-four healthy, heartworm-naive, Beagle dogs were randomly allocated 1:1 to an IVP or an untreated control group. Phase 1 was conducted during the mosquito season, when dogs from the IVP group were treated monthly for seven consecutive months. Phase 2 was conducted after the mosquito season, when all dogs were left untreated and diagnosed for D. immitis infection via SNAP® Leish 4Dx and Knott's test at scheduled intervals. Mosquito traps were also used to verify D. immitis infection rates, mosquito species composition and presence or absence in relation to Phase 1 and Phase 2. At the end of the study, 7 in 12 (58.3%) untreated control dogs were heartworm-positive, while the 12 IVP treated dogs remained negative, indicating 100% preventive efficacy (p < 0.001). Several hundred mosquitoes were trapped during Phase 1 and pooled for D. immitis Polymerase Chain Reaction (PCR) detection, 8 pools in 30 (27%) were positive. No treatment-related adverse events were reported. Frontline Tri-Act® provided 100% protection against D. immitis transmission under natural mosquito challenge. These findings support its inclusion in multimodal strategies for heartworm prevention in endemic areas.

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2026-09-01 | Milbemycin oxime and lotilaner for heartworm prevention in dogs in Korea: a randomized controlled field trial.

Heartworm disease can lead to chronic cardiopulmonary complications in dogs, and treatment is often prolonged and costly. In Korea, Dirofilaria immitis, the causative agent of canine heartworm disease, has been reported in both dogs and mosquitoes and is generally considered endemic. This field study evaluated the effectiveness and safety of a combination of milbemycin oxime and lotilaner (Credelio Plus) for the prevention of heartworm disease in client-owned dogs in the Republic of Korea. This randomized, single-blind, controlled field trial was conducted between June 2023 and February 2024. Client-owned dogs that were at least 8 weeks old, weighed more than 2.0 kg, were walked more than 3 times per week, and tested negative for heartworm at baseline were enrolled. The dogs were allocated in a 1:1 ratio to receive either the investigational veterinary product (milbemycin oxime/lotilaner) or the control veterinary product (milbemycin oxime/afoxolaner) for six consecutive monthly treatments (days 0, 30, 60, 90, 120, and 150). Prevention of D. immitis infection was assessed monthly from days 0 to 180 using a commercial antigen test kit and conventional polymerase chain reaction. Safety was evaluated using body weight, physical examination findings, hematology and serum chemistry analyses, and adverse event monitoring to assess general health status and identify potential treatment-related abnormalities during the study period. A total of 53 dogs were enrolled in the study, of which 52 were included in effectiveness and safety analyses. All dogs remained negative for D. immitis during the study period. In the safety evaluation, no statistically significant changes were observed in body weight, physical examination findings, or hematology and serum chemistry analyses following milbemycin oxime/lotilaner administration (p > 0.05). No adverse events were observed. The results of this study support the use of milbemycin oxime/lotilaner combination as a safe and effective option for the prevention of canine heartworm infections under field conditions in Korea. These findings indicate that this combination product may be a useful option in veterinary parasite control. Animal and Plant Quarantine Agency, Korea (clinical trial number: A221512).

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2026-08-21 | Comparison of two doxycycline dosages on inflammatory and stress response in dogs naturally infected with Dirofilaria immitis.

Canine heartworm disease, caused by Dirofilaria immitis, is characterized by a marked inflammatory response largely driven by its endosymbiotic bacterium Wolbachia pipientis. Doxycycline is routinely incorporated into treatment protocols to reduce Wolbachia burden and the associated pathology. Although the standard recommended dosage is 10 mg/kg every 12 h for 28-30 days, evidence comparing lower dosages under clinical conditions remains limited. This study aimed to compare the effects of two doxycycline dosages on inflammatory and immune markers in dogs naturally infected with D. immitis during the pre-adulticidal phase of treatment. Seventy-seven dogs naturally infected with D. immitis were randomly allocated to receive doxycycline at either 10 mg/kg (n = 39) or 5 mg/kg (n = 38) every 12 h for 30 days, in combination with a single oral dose of ivermectin (6 µg/kg) administered at treatment initiation. Serum concentrations of C-reactive protein (CRP) and cortisol were measured at baseline (day 0) and after treatment completion (day 30). Anti-recombinant Wolbachia surface protein (rWSP) antibody levels were determined by ELISA. Intra- and intergroup comparisons were performed using non-parametric statistical tests. Both doxycycline regimens resulted in a significant reduction in CRP concentrations from day 0 to day 30 (p < 0.05), indicating a decrease in systemic inflammation. No significant differences were observed between dosages in the magnitude of CRP reduction. Cortisol concentrations showed a non-significant downward trend in both groups, while anti-rWSP antibody levels remained stable throughout the study period. No significant intergroup differences were detected for any evaluated parameter. Doxycycline administered at 5 mg/kg every 12 h for 30 days showed a comparable short-term biomarker response to the standard 10 mg/kg regimen during the pre-adulticidal phase. Lower doxycycline dosages may represent a potential alternative with possible benefits in terms of tolerance, compliance, and antimicrobial stewardship, although these aspects were not directly evaluated in the present study.

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2026-08-21 | A retrospective comparison of two-dose and three-dose melarsomine, with doxycycline and a macrocyclic lactone, in 1246 shelter dogs.

Doxycycline and a macrocyclic lactone (ML/doxy) are now standard additions to melarsomine treatment protocols. The safety and efficacy of the two-dose melarsomine protocol have not been revisited since these adjuncts were added to treatment guidelines. This was a retrospective cohort study comparing two-dose and three-dose melarsomine in dogs with class 1 and 2 heartworm disease, treated at Miami-Dade Animal Services from 2014 to 2024. All dogs received ML/doxy. Outcome measures were efficacy 5-10 months after the last melarsomine injection, survival to 8 weeks post-melarsomine, and post-treatment complications. Efficacy was assessed for different MLs administered at intake. Denominators for analyses varied on the basis of available data. There were 889 dogs in the two-dose melarsomine group and 357 in the three-dose group. Follow-up antigen tests were negative in 242/252 dogs (96.0%; confidence interval [CI] 92.9-97.8%) in the two-dose group and 24/24 (100%; CI 86.2-100%) in the three-dose group (P > 0.9999; not significant [NS]). All-cause mortality was 4/491 (0.8%) in the two-dose group and 4/154 (2.6%) in the three-dose group (P = 0.097; NS). Heartworm-related mortality was 1/491 (0.2%) in the two-dose group and remained at 4/154 (2.6%) in the three-dose group (P = 0.013). The deaths in the three-dose group were not considered to be related to the specific treatment protocol. Mild post-melarsomine complications occurred in 66/889 (7.4%) dogs in the two-dose group and 13/357 (3.6%) in the three-dose group (P = 0.014). Severe complications occurred in 3/889 (0.3%) dogs in the two-dose group and 5/357 (1.4%) in the three-dose group (P = 0.047). Two dogs that initially received ivermectin (2/65; 3.1%) and two that received milbemycin (2/35; 5/7%) had a positive follow-up antigen test, compared with none (0/33) for sustained-release moxidectin. The findings suggest that two-dose melarsomine, with ML/doxy, is a potential alternative to three-dose melarsomine for class 1 and 2 heartworm disease. Moxidectin may be the preferred ML in the two-dose protocol.

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2026-08-21 | Blocking Dirofilaria immitis transmission by treatment of heartworm microfilaremic dogs with doxycycline.

This study was conducted to determine whether heartworm infective larvae (L3) from mosquitoes fed earlier on blood from dogs during daily administration of doxycycline at various dosages and treatment schedules and a single prophylactic dose of ivermectin could develop normally in dogs. A total of 20 heartworm microfilaremic Beagles in a separate study allocated to four groups (n = 5/group) of five dogs were used as blood donors for mosquito infection. These donor dogs in groups 4, 5, and 6 had received doxycycline orally at 5.0, 7.5, or 10.0 mg/kg twice daily (BID) × 14 or 21 days, and ivermectin orally (minimum 6 mcg/kg) on day 0. Group 2 served as the untreated control. To produce infective larvae for each study, two sets of four groups of Aedes aegypti mosquitoes fed on blood from these four groups of dogs on day 14 (study A) or 21 (study B), respectively, and, infective third-stage larvae (L3) were recovered 14 days later. In each study, 8 heartworm-naive dogs (4 groups of 2) were inoculated subcutaneously with 50 L3/dog originating from mosquitoes fed on the corresponding donor group, for a total of 16 recipient dogs. Recipient dogs were monitored by antigen testing and microfilaria counts and necropsied for adult heartworm recovery and enumeration. Necropsies were performed on the same day at 252 days postinfection for study A and 245 days postinfection for study B. Overall, 11 of the 12 dogs that had received L3 from mosquitoes fed on blood from treated dogs had no heartworms at necropsy; however, 1 dog that was administered doxycycline orally at the lowest dosage of 5.0 mg/kg BID daily and for the shorter treatment period of 14 days allowed only 1 adult female heartworm to reach the pulmonary arteries. All control dogs had male and female heartworms at necropsy. Treatment of microfilaremic dogs with doxycycline administered daily at 10.0 or 7.5 mg/kg BID for 14 days and one monthly dose of a heartworm preventive (macrocyclic lactone [ML]) renders the L3 incapable of normal development in recipient dogs, which could potentially widen the scope of a multimodal prevention approach to reduce the spread of heartworm disease.

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proteins

2026-09-17 | Efficacy of rDiHAVO as a potential vaccine antigen against heartworm infections in a mouse model

ABSTRACT Dirofilariasis, or heartworm disease, is a life-threatening parasitic infection caused by the nematode parasite Dirofilaria immitis . Mosquito vectors in tropical and subtropical regions transmit the infection. Current treatment options are expensive, have a short-term effect, and depend on anthelminthic therapy. There are no licensed vaccines available for preventing heartworm infections. The primary goal of this study was to identify potential vaccine candidates, develop a tetravalent fusion protein (rDiHAVO) vaccine antigen, and evaluate its immunogenicity and efficacy in a mouse model of D. immitis infection. Results show that the rDiHAVO is highly immunogenic in mice and confers over 95% protection against a challenge infection. These findings suggest that rDiHAVO is a potential vaccine candidate against Dirofilariasis. Additional testing in dogs can advance this vaccine candidate to clinical trials.

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2025-12-08 | Seroprevalence of selected vector-borne agents in pet cats using the SNAP® 4Dx® PLUS, United States, 2022-2025.

Tick-borne diseases predominate among vector-borne diseases of human and veterinary importance in the United States (US). Many of the most important tick-borne agents in people, including Borrelia burgdorferi, Anaplasma spp., and Ehrlichia spp. are zoonoses capable of infecting domestic pets. These infections can impact animal health with widely varying severity, ranging from subclinical to life-threatening disease. Serological testing is essential for screening and diagnosis of these infections in pets, as well as for epidemiological investigations. While vast amounts of data are available on the seroprevalence of antibodies to B. burgdorferi, Anaplasma spp., and Ehrlichia spp. in domestic dogs, comparatively little data is available in domestic cats. The purpose of this study was to evaluate the prevalence of antibodies to B. burgdorferi, Anaplasma spp., and Ehrlichia spp., as well as antigen of D. immitis, the causative agent of heartworm disease, in a population of apparently healthy pet cats from across the US using the point-of-care (POC) SNAP® 4Dx® PLUS test. This POC test does not visually distinguish between antibodies within the Anaplasma genus and antibodies within the Ehrlichia genus. To address this, additional specific peptide testing was conducted at IDEXX Laboratories for Anaplasma spp. and Ehrlichia spp. seropositive samples. In total, n = 1572 feline serum samples were tested using the SNAP® 4Dx® PLUS. All US states were represented by at least 3 samples, and 2.6 % of cats demonstrated evidence of exposure to ≥1 vector-borne pathogen. Cats in the present study were most commonly exposed to Anaplasma spp. (1.40 %), which contrasts previous seroprevalence reports in cats, in which B. burgdorferi predominates. Seroprevalence of Anaplasma spp. was followed by B. burgdorferi (1.15 %), Ehrlichia spp. (0.38 %), and lastly D. immitis antigen detection (0.13 %). Feline exposure to tick-borne agents observed in the present study was compared with canine seroprevalence reported by the Companion Animal Parasite Council over the same time period. We found that feline exposure was 14-28 % of the exposure prevalence reported in dogs. Although less common than canine infection, continued investigation into feline infection with B. burgdorferi, Anaplasma spp., and Ehrlichia spp. is warranted. Feline susceptibility to these agents, transmission dynamics, pathogenicity, and immunologic response remain poorly described.

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2024-07-26 | Wolbachia Promotes an Anti-Angiogenic Response Using an In Vitro Model of Vascular Endothelial Cells in Relation to Heartworm Disease.

Heartworm disease caused by Dirofilaria immitis is a vector-borne zoonotic disease responsible for the infection of mainly domestic dogs and cats, or these are those for which the most data are known. Humans are an accidental host where a benign, asymptomatic pulmonary nodule may originate. Dirofilaria immitis also harbours the endosymbiont bacteria of the genus Wolbachia, which play a role in moulting, embryogenesis, inflammatory pathology, and immune response. When Wolbachia sp. is released into the bloodstream, endothelial and pulmonary damage is exacerbated, further encouraging thrombus formation and pulmonary hypertension, facilitating congestive heart failure and death of the animal. Previous studies have shown that parasite excretory/secretory products are able to activate the pro-angiogenic pathway (formation of new vessels) to facilitate parasite survival. The aim of this study was to analyse the role of Wolbachia sp. and its relationship with the cellular processes and the angiogenic pathway in a model of human endothelial cells in vitro. The use of recombinant Wolbachia Surface Protein (rWSP) showed that its stimulation exerted an anti-angiogenic effect by detecting an increase in the production of VEGFR-1/sFlt1 and sEndoglin and did not affect the production of VEGFR-2 and mEndoglin (pro-angiogenic molecules). Furthermore, it did not stimulate cell proliferation or migration, although it did negatively stimulate the formation of pseudocapillaries, slowing down this process. These cellular processes are directly related to the angiogenic pathway so, with these results, we can conclude that Wolbachia sp. is related to the stimulation of the anti-angiogenic pathway, not facilitating the survival of D. immitis in vascular endothelium.

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2019-04-12 | Molecular Characterization of a Dirofilaria immitis Cysteine Protease Inhibitor (Cystatin) and Its Possible Role in Filarial Immune Evasion

Infection with canine heartworm (Dirofilaria immitis), spread via mosquito vectors, causes coughing, asthma, pneumonia, and bronchitis in humans and other animals. The disease is especially severe and often fatal in dogs and represents a serious threat to public health worldwide. Cysteine protease inhibitors (CPIs), also known as cystatins, are major immunomodulators of the host immune response during nematode infections. Herein, we cloned and expressed the cystatin Di-CPI from D. immitis. Sequence analysis revealed two specific cystatin-like domains, a Q-x-V-x-G motif, and a SND motif. Phylogenetic analysis indicates that Di-CPI is a member of the second subgroup of nematode type II cystatins. Probing of D. immitis total proteins with anti-rDi-CPI polyclonal antibody revealed a weak signal, and immunofluorescence-based histochemical analysis showed that native Di-CPI is mainly localized in the cuticle of male and female worms and the gut of male worms. Treatment of canine peripheral blood mononuclear cells (PMBCs) with recombinant Di-CPI induced a Th2-type immune response characterized by high expression of the anti-inflammatory factor interleukin-10. Proliferation assays showed that Di-CPI inhibits the proliferation of canine PMBCs by 15%. Together, the results indicate that Di-CPI might be related to cellular hyporesponsiveness in dirofilariasis and may help D. immitis to evade the host immune system.

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2007-03-01 | iNOs expression is stimulated by the major surface protein (rWSP) from Wolbachia bacterial endosymbiont of Dirofilaria immitis following subcutaneous injection in mice

The bacterial endosymbiont Wolbachia of several species of filarial nematodes plays an important role in the inflammatory pathology of filariasis. Nitric oxide (NO) production has also been implicated in the immune response during filarial infections. Here we present data indicating that a recombinant Wolbachia surface protein (rWSP) induces iNOs mRNA expression and NO production, as well as IFN-γ and a Th1-type antibody response, in inoculated BALB/c mice. This effect is not observed when mice are inoculated with a recombinant heat shock protein from Wolbachia (GroEL).

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cell therapies

2025-12-15 | Evaluating the therapeutic potential of Wolbachia in controlling mosquito-borne diseases: a systematic review and meta-analysis

Introduction Wolbachia, an endosymbiotic bacterium, has been the subject of intensive research due to its potential as a macrofilaricidal and microfilaricidal agent, especially in the control of diseases transmitted by mosquitoes, such as Dengue Hemorrhagic Fever (DHF), Cardiac Dirofilariasis, and Tropical Pulmonary Eosinophilia (TPE). In addition, associations with phenomena such as Creeping Eruption and Intraocular Filariasis are also the focus of attention. Objective This study aims to systematically evaluate the clinical and entomological outcomes of Wolbachia mosquito vector therapy on DHF, Cardiac Dirofilariasis, and TPE, while also assessing associated symptoms across different age groups. Methods A systematic review and meta-analysis were conducted by searching PubMed, ScienceDirect, Cochrane Library, Embase, and Scopus for original research, systematic reviews, and meta-analyses published in the last five years. Included studies comprised clinical trials and observational designs (cohort and case-control). Thirteen eligible studies were analyzed, including four randomized clinical trials, seven observational studies, one systematic review, and one guideline. Data were extracted independently by three reviewers, and outcomes were synthesized narratively and quantitatively using GRADEpro software, with effect sizes presented as risk ratios (RR) and 95% confidence intervals (CI). Results Wolbachia deployment in Aedes aegypti significantly reduced DHF incidence by 77.1% and hospitalization rates by 86.2%. In cardiac dirofilariasis, Wolbachia’s surface protein (rWSP) modulated angiogenesis by increasing VEGF-A and lowering anti-angiogenic sEndoglin levels. Environmental analyses indicated a microfilaricidal effect in areas with ≥20% wMel prevalence. Wolbachia’s spread is influenced by host biology, demographic, and ecological factors. All key findings were rated as moderate certainty (GRADE: B) meaning the true effect is likely close to the estimate, but further research could change this. Conclusion Wolbachia vector therapy shows promising macrofilaricidal and microfilaricidal properties across multiple mosquito-borne diseases, with moderate-quality evidence supporting its role in reducing transmission and disease burden. Systematic Review Registration https://www.crd.york.ac.uk/prospero/ , identifier PROSPERO (CRD420251016056).

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2025-05-13 | Therapy Effects of Wolbachia as Macrofilaricidal and Microfilaricidal Against Dengue Hemorrhagic Fever, Cardiac Dirofilariasis and Tropical Pulmonary Eosinophilia Accompanied by Creeping Eruption, Intraocular Filariasis, Delirium and Galectin-3

Intoduction: Wolbachia, an endosymbiotic bacterium, has been the subject of intensive research due to its potential as a macrofilaricidal and microfilaricidal agent, especially in the control of diseases transmitted by mosquitoes, such as Dengue Haemorrhagic Fever (DHF), Cardiac Dirofilariasis, and Tropical Pulmonary Eosinophilia (TPE). In addition, associations with phenomena such as Creeping Eruption and Intraocular Filariasis are also the focus of attention. Objective: This research aims to present a comprehensive understanding of the impact of Wolbachia therapy on DHF, Cardiac Dirofilariasis, TPE, as well as other phenomena, considering the variation of impact in different age groups. Methods: Comprehensive searches are carried out in a variety of key databases including PubMed, ScienceDirect, Cochrane Library, Embase, and Scopus. The articles included original research, systematic reviews, and meta-analyses published over the past five years. The design of the research included clinical trials, and observational studies (cohorts, case controls). Data extraction is carried out independently by three evaluators. Similar results from random clinical trials and observational studies were collected using GRADE pro software and presented in the form of a risk ratio (RR), with a 95% confidence interval (95% CI). Results: Vector manipulation using Wolbachia can be an innovative method in efforts to prevent arbovirus disease (Evidence quality: B). Wolbachia surface protein (rWSP) in cardiopulmonary dirofilariasis can increase the pro-angiogenic VEGF- A and reduce the anti-angiogenesis endoglin, potentially affecting angiogenesis depending on the balance between associated mechanisms. (Evidence quality: B). There is an effect of Wolbachia intervention against as an overall microfilaricidal agent in several zones and in an environmental level analysis that considers the quintile prevalence of wMel in the local population. (Evidence quality: B). Wolbachia release to control diseases transmitted by insects may be successful, but its spread is influenced by host fitness, demographic factors, and environmental factors. (Evidence quality: B).

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2011-12-30 | Subconjunctival dirofilariasis mimicking scleritis: First report from Western India

Dear Editor, Dirofialria repens (D. repens) is a nematode which occasionally causes ocular infestation. Commonly known as the dog heartworm, it is a nematode of veterinary importance. It infects man as an accidental host through vectors such as the anopheles and culex mosquitoes.[1 A 48-year-old male from New Mumbai, Western India presented to the Laxmi Eye Institute, Panvel, a tertiary referral centre in Western India, with complaints of a painless swelling and redness over the white portion of the right eye noticed since 18 days. There was no history of similar episodes in the past, ocular trauma or foreign body. There was no history of any systemic illness and recent travel (in the past one year) out of Mumbai. The right eye (OD) revealed localized conjunctival congestion with a yellowish cream, firm, non-mobile, non-tender, scleral nodule measuring 4 mm × 4 mm situated 3 mm away from the temporal limbus. There were no abnormal feeder vessels. Temporal cornea showed dellen [Fig. 1]. Rest of the ocular examination was normal. Ocular examination of the left eye was essentially normal. A provisional diagnosis of OD atypical infective scleritis was made and a scleral deroofing with excision biopsy of the nodule was planned. At operation, after reflecting the overlying conjunctiva, two live thread-like worms were seen; they were coiled amidst a thick granulation tissue. Most of the conjunctiva was also adherent to the granulation tissue below. The worms were retrieved entirely and the conjunctival space was explored all around to rule out presence of any more worms. The whole granulation tissue was excised and sent in 10% formalin for histopathological analysis to the department of microbiology, King Edward Memorial Hospital, Parel, Mumbai. The resultant conjunctival defect was covered with a conjunctival autograft using fibrin glue.Figure 1: Scleral nodule with corneal dellenBlood examination revealed normal hemogram. Peripheral smears did not reveal any microfilariae and stool examination was normal. Analysis of the worms revealed presence of two white worms approximately 3.5 cm long with a maximum thickness of 0.7 mm [Fig. 2]. A thick cuticle with fine transverse striations was present throughout the length of the worms [Fig. 3]. The species were identified as female D. repens based on the presence of longitudinal striae and a thick muscle coat[2] [Fig. 4] and the presence of a prominent uterine pore. The histopathological analysis of the tissue showed a large number of eosinophils.Figure 2: Naked eye appearance of worms of D. repensFigure 3: Microscopic appearance of D. repens showing transverse striations and longitudinal ridgeFigure 4: Microscopic appearance of D. repens showing thick muscle coatThe patient was started on prednisolone acetate 1% eye drops in tapering dose for one month and ofloxacin 0.3% eye drops for one week. The patient had a well-integrated conjunctival autograft with a quiet eye when he followed up after one month. Our case is the first reported case of ocular dirofilariasis from Western India and was managed with adequate surgical excision with conjunctival autograft. This first indigenous, case of ocular dirofilaria from Western India highlights the importance of being aware of this infection for ophthalmologists from this part of the country; this can help in increased recognition and reporting of such infections. The authors wish to thank Dr Madhav Sathe, Dept of Microbiology, Seth G S Medical College, K E M Hospital and Dr Leena Gajbar, Aditya Labs, Panvel for their assistance in microbiological identification of the worm and Dr Maninder Setia, Dept of Clinical research and Epidemiology, Laxmi Eye Institute, Panvel, for editorial comments.

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gene therapies

2026-05-04 | Global Research Trends in Emerging Zoonosis Due to (the Filarial Nematode) Dirofilaria repens (1955-2025): A Bibliometric Analysis of a Climate-Driven Expansion.

Dirofilaria repens is the leading cause of subcutaneous (dogs) and subcutaneous/ocular dirofilariosis (humans) in the Old World. Despite its rapid geographical spread, driven by climate change, the emergence of new invasive vectors (Aedes albopictus) and growing interest in its study due to the emergence of new cases in areas previously free of the parasite, amongst other factors, scientific research into this pathogen remains limited. This study provides the first longitudinal bibliometric analysis of global research on D. repens (1955-2025). Data from Web of Science and Scopus were processed using PRISMA and RAMIBS protocols, resulting in a normalized corpus of 624 documents analyzed via science mapping techniques. The field exhibits a sustained annual growth rate of 3.79%, transitioning into an exponential expansion phase in 2011. While Italy retains historical leadership, spatial analysis confirms a research displacement towards Central and Eastern Europe (Germany, Poland). Thematic evolution reveals a structural shift from isolated clinical case reports to a multidisciplinary ecosystem dominated by molecular epidemiology, vector competence, and surveillance. Dirofilaria repens has gone from being a minor and neglected issue to having a significant number of reports and studies subject to interest in addressing the disease that results from its infection in different hosts. However, the intellectual structure exposes an operational fragmentation between clinical medicine and medical entomology. Future research must overcome national silos and integrate reservoir management with vector control, transforming the current reactive approach into a predictive preventive system aligned with the One Health framework.

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2026-01-24 | Solitary subcutaneous nodule: From mosquito to man – A case report of human dirofilariasis

Human dirofilariasis is a rare zoonotic infection caused by filarial worms of the genus Dirofilaria , commonly transmitted by mosquito vectors. While dogs and other canines serve as the natural hosts, humans are accidental dead-end hosts. The most frequent clinical manifestation is subcutaneous involvement, typically presenting as a solitary nodule. The anterior abdominal wall is an unusual site of presentation. We report a case of subcutaneous human dirofilariasis in a 21-year-old male presenting with an abdominal wall nodule.

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2025-09-27 | Epidemiological Significance of the Fox (Vulpes vulpes) in the Spread of Vector-Transmitted Zoonoses in the Area of Northern Croatia.

Wild animals often serve as reservoirs for vector-borne zoonoses, which are on the rise worldwide but have not yet been sufficiently researched. Vector-borne zoonoses, such as those caused by Anaplasma phagocytophilum, Borrelia burgdorferi sensu lato, and Dirofilaria immitis, are a growing public health concern due to their increasing incidence and broad host range. The aim of this study was to determine the prevalence and risk factors for vector-borne bacterial (borreliosis, anaplasmosis, ehrlichiosis) and parasitic (dirofilariasis) pathogens and to detect some of these pathogens in the red fox (Vulpes vulpes) population in Croatia. A total of 179 blood samples from foxes from nine districts were analysed. The SNAP ® 4Dx ® Plus rapid test was used to detect circulating D. immitis antigen and antibodies against B. burgdorferi, A. phagocytophilum/Anaplasma platys, and Ehrlichia canis/Ehrlichia ewingii. Circulating D. immitis antigen was detected in 6.70% of the samples (95% CI: 3.20-10.19%), while antibodies against A. phagocytophilum/A. platys were found in 10.06% (95% CI: 5.8-14.25%). Only one sample was positive for B. burgdorferi, while no antibodies were detected for E. canis/E. ewingii. Spatial analysis revealed statistically significant differences in prevalence by geographical region (district) and age, while no significant correlations were found. In the standard PCR analysis, DNA of D. immitis was not detected in any of the eight positive and eight negative SNAP ® 4Dx ® Plus samples. D. repens, A. reconditum, or co-infections were also not detected by PCR. Of the nine samples that tested positive for A. phagocytophilum/A. platys antibodies, four were confirmed to be positive for A. phagocytophilum by nested and semi-nested PCR targeting the 16S rRNA and GroEL genes. Phylogenetic analysis revealed similarities with various European strains, including zoonotic strains. This study is the first molecular detection of A. phagocytophilum from blood samples of red foxes in Croatia. The results show that red foxes are not free from infections such as anaplasmosis and dirofilariasis, emphasising their possible role in the maintenance and transmission of these pathogens in certain regions of Croatia. These results underline the need for further research to better understand the epidemiological importance of red foxes in the spread of vector-borne diseases.

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2025-08-28 | Characterization of Emerging Human Dirofilaria repens Infections, Estonia, 2023.

Mosquitoborne diseases are a growing threat to public health worldwide. Human dirofilariasis, caused by the nematode Dirofilaria repens and transmitted by mosquitoes from various genera, has recently expanded into new areas of Europe. In this article, we report molecularly confirmed autochthonous human D. repens infections in Estonia.

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2025-07-03 | Vectors, host range, and spatial distribution of Dirofilaria immitis and D. repens in Europe: a systematic review.

Dirofilaria immitis and D. repens are mosquito-borne nematodes with dogs as primary hosts, but other mammalian species including humans can be also infected. In the last century, circulation of both pathogens was predominantly restricted to Southern Europe. However, different studies indicated a potential establishment in Central, Eastern and Western parts of Europe as an increasing threat to animal and human health. Therefore, we conducted a systematic literature review of Dirofilaria data in Europe to give a comprehensive overview of potential mosquito vectors and vertebrate hosts, including the collection of different metadata (e.g. sampling year and site), allowing to analyse the spread pattern of the parasites in Europe. On 24 January 2022, we conducted a systematic literature review of all available publications in the PubMed database reporting D. immitis and D. repens screening in mosquitoes and mammalian vertebrates in Europe. We only included acute infection of Dirofilaria spp., i.e. excluding studies only screening antibodies, and in addition noted the travel history and the accuracy of the sampling locations. These data were used to analyse the range of potential vectors and hosts and for a comparison of the spatial distribution between the twentieth and twenty-first century. Both nematodes appear to have a high overlap of Aedes, Anopheles and Culex as potential vector species, which are abundant in Europe. Most published D. immitis infections were reported in dogs, while D. repens predominantly were reported in humans. Dirofilaria immitis infections were detected in a wider range of wild and zoo animals. Compared to the last century, many more countries especially in Central Europe were affected by Dirofilaria spp. circulation, illustrating a significant spread over the last 20 years. Our findings suggest that D. immitis and D. repens are a growing health concern for animals and humans in Europe. Continuous globalisation and climate warming will probably lead to a further spread and increased circulation in the future. All data are made available open access, which will enable further analysis.

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