Search Results (64)

We report the first confirmed case of persistent microfilaremia in a human host infected with Dirofilaria repens. A 54-year-old woman from an endemic area in Croatia presented with peripheral eosinophilia and dermatological symptoms. Over four months, microfilariae were repeatedly detected in her blood using thick smears and Knott’s test, and the diagnosis was molecularly confirmed via COI gene sequencing and detection of Wolbachia endosymbionts. This case provides compelling evidence that D. repens can sustain a complete or near-complete life cycle in humans under specific conditions. Our findings have significant implications for clinical diagnostics, One Health surveillance, and public health interventions. Full article

Heartworm disease—caused by Dirofilaria immitis—is an emerging mosquito-borne zoonotic disease with potentially fatal outcomes in dogs. Due to factors such as climate change, animal importation, and animal transport, the prevalence of the infection has increased in countries in Central and Eastern Europe, where the parasite was not detected before. The first autochthonous case of D. immitis in dogs in Hungary was reported in 2009. This study assessed the prevalence of D. immitis infection and the associated risk factors in domestic dogs in Hungary. A total of 1071 blood samples were collected between March 2023 and February 2024 and were tested using Knott’s test, ELISA, and real-time PCR method. The countrywide prevalence of D. immitis was 17.0%, suggesting a continuous increase in the parasite’s spread compared to the previously reported 11.3% prevalence, with age and spending time outdoors being the main risk factors. These results highlight the ongoing need for preventive measures against heartworm disease. Full article

Background/Objectives: Many tropical diseases such as malaria, Chagas, human African Trypanosomiasis, and Lymphatic filariasis coexist in endemic countries, affecting more than 1 billion people worldwide, and are recognised as major global vector-borne diseases. Tackling this disease requires an accurate diagnosis that is sensitive, specific, and rapid. This study aimed to describe and validate a new highly sensitive and specific multiple-analysis system that can effectively detect numerous etiological agents in a single test. Methods: A total of 230 human blood samples were assessed retrospectively for parasite characterisation, as well as 58 stool samples from non-human primates. Primers and probes were designed in the small subunit ribosomal RNA gene, except for Plasmodium spp., for which the novel target was Cytochrome Oxidase Subunit 1. Results: The analytical specificity of the presented method was 100%, with no unspecific amplifications or cross-reactions with other blood parasitic diseases. The detection limit obtained was between 0.6 and 3.01 parasites/µL for Plasmodium species, 1.8 parasites/mL for Trypanosomatidae, and 2 microfilariae/mL in the case of Filariae. The sensitivity, specificity, predictive values, and kappa coefficient reached almost 100%, except for Filariae, whose sensitivity dropped to 93.9% and whose negative predicted value dropped to 89.5%. The operational features described a turnaround and a hands-on time shorter than the compared methods with a lower cost per essay. Conclusions: This work presents a cost-effective and highly sensitive multiplexed tool (RT-PCR-bp) capable of performing simultaneous detection for blood parasitic diseases using specific fluorescence probes, enabling the diagnosis of low parasite loads and coinfections. Full article

Accurate rapid diagnostic tests (RDTs) are needed to diagnose lymphatic filariasis (LF) in global elimination programmes. We evaluated the performance of the new STANDARD Q Filariasis Antigen Test (QFAT) against the Bioline Filariasis Test Strip (FTS) for detecting W. bancrofti antigen (Ag) in laboratory conditions, using serum (n = 195) and plasma (n = 189) from LF-endemic areas (Samoa, American Samoa and Myanmar) and Australian negative controls (n = 46). The prior Ag status of endemic samples (54.9% Ag-positive) was determined by rapid test (ICT or FTS) or Og4C3 ELISA. The proportion of samples testing positive at 10 min was similar for QFAT (44.8%) and FTS (41.3%). Concordance between tests was 93.5% (kappa 0.87, n = 417) at 10 min, and it increased to 98.8% (kappa 0.98) at 24 h. The sensitivities of QFAT and FTS at 10 min compared to the prior results were 92% (95% CI 88.0–96.0) and 86% (95% CI 80.0–90.0), respectively, and they increased to 97% and 99% at 24 h. Specificity was 98% for QFAT and 99% for FTS at 10 min. Both tests showed evidence of cross-reaction with Dirofilaria repens and Onchocerca lupi but not with Acanthochilonema reconditum or Cercopithifilaria bainae. Under laboratory conditions, QFAT is a suitable alternative RDT to FTS. Full article

Dirofilaria immitis and Angiostrongylus vasorum are major parasitic nematodes of dogs. Many environmental and phenological changes have recently modified their geographic patterns in many countries; thus, this study has updated the distribution of D. immitis and A. vasorum in dog populations of selected regions of Central and Southern Italy. Also, collateral data on other endoparasites affecting the study population have been collected. Blood and fecal samples collected from 2000 dogs were tested using Knott’s test and copromicroscopy (i.e., Baermann’s and fecal flotation tests), respectively. Binomial logistic regression was performed to evaluate statistically significant associations between positivity for D. immitis and/or A. vasorum and potential risk factors. Overall, 35 (1.7%) and 62 (3.1%) dogs were positive for microfilariae of D. immitis and first stage larvae (L1) of A. vasorum, respectively, while 3 (0.1%) were co-infected by both nematodes. Microfilariae of Dirofilaria repens were found in 148 (7.4%) dogs, while at the flotation, eggs of Ancylostomatidae, Trichuris vulpis, and ascarids were found in the feces of 323 (16.5%), 249 (12.4%), and 172 (8.6%), dogs, respectively. Overall, 217 (10.8%) and 44 (2.2%) dogs were positive for eggs of Capillaria aerophila and Capillaria boehmi. The presence of cardiorespiratory clinical signs or non-specific signs, history of travel, and an age of >4 years old were significantly associated with positivity for D. immitis, while A. vasorum was significantly recorded in dogs with cardiorespiratory signs, or with a history of mollusk ingestion or permanent outdoor housing. These results confirm that D. immitis is enzootic in the investigated regions of Central and Southern Italy, even where it was rare/undetected until recently. Indeed, although some dogs positive for D. immitis had a history of travel in enzootic areas, the majority of them were never moved, indicating that they acquired the parasite in the region where they live. Additionally, A. vasorum is stably enzootic in the study areas, as also are other extraintestinal nematodes (i.e., D. repens and C. aerophila) that are more frequently detected today than in the past. A high level of vigilance and routine parasitological screening are necessary, considering the high prevalence of intestinal parasites in owned dogs that are also co-infected by respiratory parasites. The implementation of chemoprevention against D. immitis in dogs living in the examined area should be encouraged. Full article

A deterministic model for controlling the neglected tropical filariasis disease known as elephantiasis, caused by a filarial worm, is developed. The model incorporates drug resistance in human and insecticide-resistant vector populations. An investigation into whether the model is of biological importance reveals that it is positively invariant, mathematically well posed, and tractable for epidemiological studies. The filariasis-free and filariasis-present equilibrium points were obtained. The next-generation matrix technique is used to derive the basic reproduction number $R_0$, which is then used to determine the local stability analysis of the model. It is established that the system is locally asymptotically stable when $R_0<1$. The technique by Castillo-Chavez and a Lyapunov function were employed to prove the global stability of the model’s fixed points. The results of this analysis of filariasis-free equilibrium show that the system is globally asymptotically stable when $R_0<1$ and unstable when $R_0>1$. Similarly, the filariasis-present equilibrium point is proved to be globally asymptotically stable when $R_0>1$ and unstable otherwise. This indicates that the fight against the spread of the disease is achievable. It is observed that increasing human-infected mosquito contacts or mosquito-infected human contacts raises the value of $R_0$, whereas decreasing the progression of micro-filaria into infective larva and killing more mosquitoes will decrease the $R_0$ value according to the sensitivity analysis of the model. The variable precision arithmetic technique executed in MATLAB R2014a was used to determine the elasticity indices of the parameters of $R_0$, which showed that the value of $R_0=0.94639$. Further investigations revealed that ${\omega }_2$ has a significant influence on the reproduction number, suggesting that treatment of acute infections is crucial in the control of the disease. Pontryagin’s Maximum Principle (PMP) is used for optimal control analysis. The numerical result revealed that strategy D is the most effective based on the infection averted ratio (IAR) value. Full article

The elimination of lymphatic filariasis (LF) as a public health problem remains an ongoing challenge in the Pacific region. This study reports on antigen (Ag) and microfilaria (Mf) prevalence in Samoa in 2019, 7–9 months after the completion of the first round of triple-drug mass drug administration (MDA). It evaluates the effectiveness of the intervention for reducing Ag prevalence to below a 2% threshold, and how this differs between 5–9-year-olds and ≥10-year-olds. We surveyed 30 randomly selected and five purposefully selected primary sampling units (PSUs) in Samoa in 2018 (1–3 months post-triple-drug MDA) and, again, in 2019. In each PSU, we conducted a community survey of 15–20 households and a convenience survey of 5–9-year-old children. A finger-prick blood sample was collected from all participants to test for Ag and Mf. Demographic details were also collected. There was no significant change in adjusted Ag prevalence in the 30 randomly selected PSUs between 2018 (3.9% [95% CI: 2.7–5.6%]) and 2019 (4.1% [95% CI 2.7–5.9%]). Significantly higher Ag prevalence was observed in participants aged ≥10 years (4.6%, 95% CIs 3.0–6.7%) compared to 5–9-year-olds (1.1%, 95% CIs 0.5–2.2%), supporting existing evidence that post-MDA surveillance should not be based on Ag prevalence among 6–7-year-olds. A single round of triple-drug MDA was insufficient to break LF transmission in Samoa 7–9 months post-MDA. Full article

Background/Objectives: There is an urgent need for new and improved anthelmintics that are not constrained by existing resistance pathways and that can safeguard the health and welfare of animals. Methods: An integrated platform of chemical, bioassay, and cultivation profiling applied to a library of microbes isolated from Australian livestock pasture soil was used to detect and guide the production, isolation, characterization, identification, and evaluation of new natural products with anthelmintic properties. Results: A global natural products social (GNPS) molecular network analysis of 110 Australian pasture-soil-derived microbial extracts prioritized for antiparasitic activity identified unique molecular families in the extract of Streptomyces sp. S4S-00185A06, a strain selectively active against Dirofilaria immitis microfilariae. UPLC-DAD analysis identified metabolites with unique UV-vis chromophores and unprecedented molecular formulas. A chemical investigation of Streptomyces sp. S4S-00185A06 yielded goondicones A–H (1–8) as new examples of a rare class of spiro-isoindolinones, with structures assigned on the basis of detailed spectroscopic analysis, ECD calculations, and biosynthetic considerations. Conclusions: While goondicones 1–8 exhibit little to no in vitro inhibitory activity against Gram-positive, Gram-negative, and/or fungal pathogens, human carcinoma cells, or the livestock gastrointestinal parasite Haemonchus contortus L1–L3 larvae, 5 and 6 (and, to a lesser extent, 1) inhibit the motility of heartworm Dirofilaria immitis microfilaria (IC₅₀ 10–11 μM). A structure activity relationship analysis based on the co-metabolites 1–8 suggests that (i) an 8-OH is preferable to 8–oxo moiety, (ii) 20-NMe and 3-OH moieties are essential, and (iii) C-9 epimerization exerts no discernible impact on in vitro potency. Full article

Background: Diseases in humans caused by amphizoic amoebae that can result in visual impairment and even blindness, have recently been identified more frequently worldwide. Etiologically complex incidents of keratitis, including those connected with Acanthamoeba strains detected in Poland, were evaluated in this study. Methods: Corneal samples from cases resistant to antimicrobial therapy assessed for epidemiological, microbiological and parasitological aspects were investigated by phase-contrast microscope, slit lamp and by confocal microscopy. In vitro techniques were applied for detection of bacteria and fungi, and corneal isolates cultured under axenic condition using BSC medium—for detection of Acanthamoeba spp.; molecular techniques were applied for amoeba species identification. Results: Most etiologically complicated keratitis cases, detected in ~84% of incidents, was due to exposure of contact lenses to tap water or pool water; trophozoites and cysts of Acanthamoeba, concomitant bacteriae, e.g., Pseudomonas aeruginosa, fungi and microfilariae were identified in contact lens users. Conclusions: In samples from contact lens wearers where microbial keratitis is identified along with some connection with the patient’s exposure to contaminated water environments, a risk of Acanthamoeba spp. infections should be considered. Understanding the complicated relationship between Acanthamoeba spp., co-occurring pathogens including associated endosymbionts is needed. In vivo confocal microscopy and in vitro cultivation were necessary to identify potentially contagious concomitant factors affecting the complex course of the keratitis. Full article

An investigation of ×19 soil samples collected under the auspices of the Australian citizen science initiative, Soils for Science, returned ×559 chemically dereplicated microbial isolates, of which ×54 exhibited noteworthy anthelmintic activity against either the heartworm Dirofilaria immitis microfilaria and/or the gastrointestinal parasite Haemonchus contortus L1–L3 larvae. Chemical (GNPS and UPLC-DAD) and cultivation (MATRIX) profiling prompted a detailed chemical investigation of Streptomyces sp. S4S-00196A10, which yielded new anthelmintic polyketide goondapyrones A–J (1–10), together with the known actinopyrones A (11) and C (12). Structures for 1–12 were assigned on the basis of detailed spectroscopic and chemical analysis, with preliminary structure activity relationship analysis revealing selected γ-pyrones >50-fold and >13-fold more potent than isomeric α-pyrones against D. immitis mf motility (e.g., EC₅₀ 0.05 μM for 1; EC₅₀ 2.7 μM for 5) and H. contortus L1–L3 larvae development (e.g., EC₅₀ 0.58 μM for 1; EC₅₀ 8.2 μM for 5), respectively. Full article

Background: Almost the entire country of Burkina Faso was endemic to onchocerciasis. Onchocerciasis control efforts thus brought the prevalence of O. volvulus to a level where the disease was no longer a public health problem in 2002. A resurgence of onchocerciasis cases has been observed in two regions (Cascades and the Southwest) located around several river basins in 2010–2011. In accordance with WHO guidelines for the management of resurgent cases, community-directed treatment with ivermectin (CDTI) was implemented in the affected areas. The aim of this study was to determine the effects of this intervention on parasitological indices of onchocerciasis, depending on the distance between villages and rivers. Methodology: We conducted a paired pre-post study using aggregated village-level data from two cross-sectional surveys conducted in each region. A Wilcoxon signed-rank test was used to compare the standardized microfilarodermia prevalence and community microfilarial load (CMFL). Results: A total of 43 villages in 6 health districts, in the Southwest (18) and Cascades (25) regions were included in the study. The key findings were that standardized microfilaria prevalence and CMFL decreased significantly after the implementation of CDTI in both regions (p < 0.0001). The median standardized microfilaria prevalence was 2.8 [interquartile range (IQR): 0.2–6.6] before CDTI and 0.72 [IQR: 0.0–2.17] after CDTI. The results showed also a decline in standardized microfilaria prevalence and CMFL in all villages, regardless of the distance separating the village from the streams. However, the results were not statistically significant for the villages located 5 km or more from streams (p = 0.0816 and 0.0542 for standardized microfilaria prevalence and CMFL, respectively). Conclusion: Our results thus show that the implementation of effective CDTI could stop the transmission of O. volvulus in these two regions. The main challenge for stopping transmission could be the migration of populations to neighboring countries and migration of the vector from one country to another, as Burkina Faso shares some river basins with neighboring countries. Full article

The mosquito-borne zoonotic nematode parasites Dirofilaria immitis and Dirofilaria repens primarily affect dogs. In recent years, their distribution has expanded due to various factors influencing vector-borne pathogens. This study aimed to investigate the comparative prevalence of infection in dogs and humans within a hyperenzootic region of Europe, and to estimate the proportional relationship between infection prevalence in dogs and humans, within the concept of “One Health”. To this end, 604 blood samples from dogs and 625 serum samples from humans living in the Thrace region of northeastern Greece were collected. The dog samples were examined for Dirofilaria spp. microfilariae using Kott’s test and for D. immitis antigen using a commercial serological test. The human sera were analyzed for both parasites by Western blot. The overall prevalence of infection in dogs was 177 (29.3%), with 173 (28.6%) testing positive for D. immitis and 7 (1.2%) for D. repens, including 6 (1%) cases of mixed infection. Specific IgG antibodies were detected in 42 (6.7%) human samples, with 24 (3.8%) positive for D. immitis and 18 (2.9%) for D. repens. The infection proportion in humans was 23.4% of the corresponding canine infections, indicating a high risk of human infection in this hyperenzootic region. Full article

A bioassay-guided chemical investigation of a bacterium, Streptomyces sp. CMB-MRB032, isolated from sheep feces collected near Bathurst, Victoria, Australia, yielded the known polyketide antimycins A4a (1) and A2a (2) as potent inhibitors of Dirofilaria immitis (heartworm) microfilaria (mf) motility (EC₅₀ 0.0013–0.0021 µg/mL), along with the octapeptide surugamide A (3) and the new N-methylated analog surugamide K (4). With biological data suggesting surugamides may also exhibit activity against D. immitis, a GNPS molecular network analysis of a library of microbes sourced from geographically diverse Australian ecosystems identified a further five taxonomically and chemically distinct surugamide producers. Scaled-up cultivation of one such producer, Streptomyces sp. CMB-M0112 isolated from a marine sediment collected at Shorncliff, Qld, Australia, yielded 3 along with the new acyl-surugamides A1–A4 (5–8). Solid-phase peptide synthesis provided additional synthetic analogs, surugamides S1–S3 (9–11), while derivatization of 3 returned the semi-synthetic surugamide S4 (12) and acyl-surugamides AS1–AS3 (13–15). The natural acyl-surugamide A3 (7) and semi-synthetic acyl-surugamide AS3 (15) were shown to selectively inhibit D. immitis mf motility (EC₅₀ 3.3–3.4 µg/mL), however, unlike antimycins 1 and 2, were inactive against the gastrointestinal nematode Haemonchus contortus L1–L3 larvae (EC₅₀ > 25 µg/mL) and were not cytotoxic to mammalian cells (human colorectal carcinoma SW620, IC₅₀ > 30 µg/mL). A structure–activity relationship (SAR) study on the surugamides 3–15 revealed that selective acylation of the Lys³-ε-NH₂ correlates with anthelmintic activity. Full article

Onchocerciasis and lymphatic filariasis are two neglected tropical diseases caused by filarial nematodes that utilize insect vectors for transmission to their human hosts. Current control strategies are based on annual or biannual mass drug administration (MDA) of the drugs Ivermectin or Ivermectin plus Albendazole, respectively. These drug regimens kill the first-stage larvae of filarial worms (i.e., microfilariae) and interrupt the transmission of infections. MDA programs for these microfilaricidal drugs must be given over the lifetime of the filarial adult worms, which can reach 15 years in the case of Onchocerca volvulus. This is problematic because of suboptimal responses to ivermectin in various endemic regions and inefficient reduction of transmission even after decades of MDA. There is an urgent need for the development of novel alternative treatments to support the 2030 elimination goals of onchocerciasis and lymphatic filariasis. One successful approach has been to target Wolbachia, obligatory endosymbiotic bacteria on which filarial worms are dependent for their survival and reproduction within the human host. A 4–6-week antibiotic therapy with doxycycline, for example, resulted in the loss of Wolbachia that subsequently led to extensive apoptosis of somatic cells, germline, embryos, and microfilariae, as well as inhibition of fourth-stage larval development. However, this long-course regimen has limited use in MDA programs. As an alternative approach to the use of bacteriostatic antibiotics, in this study, we focused on autophagy-inducing compounds, which we hypothesized could disturb various pathways involved in the interdependency between Wolbachia and filarial worms. We demonstrated that several such compounds, including Niclosamide, an FDA-approved drug, Niclosamide ethanolamine (NEN), and Rottlerin, a natural product derived from Kamala trees, significantly reduced the levels of Wolbachia in vitro. Moreover, when these compounds were used in vivo to treat Brugia pahangi-infected gerbils, Niclosamide and NEN significantly decreased adult worm survival, reduced the release of microfilariae, and decreased embryonic development depending on the regimen and dose used. All three drugs given orally significantly reduced Wolbachia loads and induced an increase in levels of lysosome-associated membrane protein in worms from treated animals, suggesting that Niclosamide, NEN, and Rottlerin were effective in causing drug-induced autophagy in these filarial worms. These repurposed drugs provide a new avenue for the clearance of adult worms in filarial infections. Full article

Background: Newer generation ophthalmologists practicing in the developed world are not very familiar with some tropical ocular diseases due to the absence of reports in the ophthalmic literature over the past thirty years. Because of world globalization or due to influx of immigrants from sub-Saharan Africa, exotic retinal diseases are being encountered more often in ophthalmology clinics. Methods: A multicenter case series of chorioretinitis or optic neuritis with obscure etiology that used serial multimodal imaging. Results: Four cases qualified with the diagnosis of presumed ocular onchocerciasis based on their residence near fast rivers in endemic areas, multimodal imaging, long term follow-up showing progressive disease and negative workup for other diseases. Characteristic findings include peripapillary choroiditis with optic neuritis or atrophy, subretinal tracts of the microfilaria, progressive RPE atrophy around heavily pigmented multifocal chorioretinal lesions of varying shapes, subretinal white or crystalline dots, and response to ivermectin. Typical skin findings are often absent in such patients with chorioretinitis rendering the diagnosis more challenging. Conclusions: Familiarity with the myriad ocular findings of onchocerciasis, and a high-degree of suspicion in subjects residing in endemic areas can help in the correct diagnosis and implementation of appropriate therapy. Onchocercal chorioretinitis is a slow, insidious, progressive, and prolonged polymorphous disease. Full article