Human Angiostrongylus cantonensis: an update

Monitoring the trends of Angiostrongylus cantonensis infection in humans and Pomacea spp. Snails in Dali, Yunnan, China, 2007-2021

We summarize historical events related to angiostrongyliasis and analyze surveys of clinically diagnosed and suspected cases of angiostrongyliasis in Dali from 2007 to 2021. We also randomly tested market sold Pomacea spp. snails to detect whether Angiostrongylus cantonensis was present in Dali market stalls from 2008 to 2021. There were a total of 125 cases of angiostrongyliasis (92 clinically diagnosed and 33 suspected) reported in the Dali Prefecture from 2007-2021. Of the 125 cases, 72 patients from 2010 to 2021 were investigated, with the main clinical manifestations being headache (100%), muscle pain (61%), neck stiffness (58.3%), paresthesia (58.3%), fever (55.5%), nausea (48.6%), coughing (26.3%), vomiting (44.4%), photophobia (18%), diplopia (25%), and visual impairment (5.5%). Laboratory testing showed cerebrospinal fluid qualitative protein levels and blood eosinophil levels were abnormal in 100% and 87.5% of patients tested, respectively. Moreover, of the 49,970 Pomacea spp. checked for A. cantonensis infection, 373 (0.75%) were found infected. Our study highlights the importance of enhancing public education, stricter food safety measures, and improved diagnostic methods to help mitigate future outbreaks of angiostrongyliasis.

Pulmonary angiostrongyliasis: Two cases of atypical manifestations of Angiostrongylus costaricensis in Guatemala

Angiostrongyliasis, an infection caused by nematodes of the genus Angiostrongylus spp., includes nine species in the Americas. Angiostrongylus costaricensis induces eosinophilic enteritis in humans and has been documented in Guatemala. Humans are considered accidental or final hosts of A. costaricensis, as they do not release eggs or larvae in their faeces. Most reported cases present with abdominal angiostrongyliasis (AA). Parasitic structures are difficult to identify in inflammatory lesions and larvae can occasionally migrate to extraintestinal organs. The gold standard for diagnosing A. costaricensis is histopathological analysis, confirmed by the identification of eggs, larvae in tissues, and/or adult worms in the vascular lumen. In our department, two cases of A. costaricensis affecting pulmonary vessels were diagnosed histopathologically. Given the rarity of pulmonary involvement, the cases were consulted with Dr. Carlos Graeff-Teixeira.

Halogen Modulation: Novel Fluoropyridylphenylurea Derivatives as Potent Molluscicides Unveiling Snail-Killing Mechanisms

Pomacea canaliculata is an invasive species that poses significant threats to agriculture and human health. The development of environmentally friendly molluscicides is crucial for its management. In this study, we synthesized 17 fluoropyridylphenylurea derivatives using a halogen modulation strategy to explore their potential as molluscicides. Compounds L-1 and L-2 demonstrated notable molluscicidal activity, with LC50 values of 1.377 mg/L and 1.001 mg/L, respectively. Among these, L-2 exhibited superior efficacy while causing minimal harm to other aquatic organisms, particularly fish. The molluscicidal mechanism of L-2 was investigated using Tandem Mass Tags (TMT)-labeled quantitative proteomic analysis and non-targeted metabolic analysis. These analyses revealed that L-2 significantly affected the liver metabolism of P. canaliculata by disrupting the transaminase, gluconeogenesis, and glycolysis pathways. This metabolic disruption is likely a contributing factor to the mortality observed in the snails. Our findings suggest that compound L-2 is a promising molluscicide, offering high efficiency and minimal environmental impact. These insights could guide future research and development in molluscicide applications.

Biomphalaria glabrata (Say, 1818) as a paratenic host of Angiostrongylus vasorum (Baillet,1866) Kamensky, 1905

Angiostrongylus vasorum parasitizes the pulmonary arteries and heart of dogs (definitive hosts - DHs). Various mollusk species act as intermediate hosts (IHs), becoming infected through ingestion and/or penetration of first-stage larvae (L1), which subsequently develop into second-stage larvae (L2) and then third-stage larvae (L3), the latter being infective to DHs. Additionally, paratenic hosts (PHs), such as frogs, chickens, and rats, can harbor L3. This study aimed to assess whether Biomphalaria glabrata could function as a PH for A. vasorum, identifying potential larval penetration routes, migratory routes, and histological alterations at different time points post-infection. L3 larvae were recovered from B. glabrata mollusks 30 days after exposure to 1000 L1 of A. vasorum, using the Baermann technique. The recovered L3 were used to infect B. glabrata, with the number of 100 L3+ (L3 obtained from mollusks previously infected with 100 L3). Viable and motile L3+ of A. vasorum were detected within mollusk tissues, demonstrating their permissiveness to L3+ infection. The other infected mollusks were fixed in 10% formalin for histological analysis, revealing the presence of larvae, with a tendency in the cephalopodal region. Regarding the viability of L3+, two mixed-breed dogs were fed canine pâté containing L3+, and L1 larvae were detected in their feces. This study demonstrates, for the first time, the potential of B. glabrata to function as a PH in the A. vasorum cycle.

Evaluation of Biological Properties and Beneficial Effects for a Sustainable and Conscious Exploitation of Achatina fulica Snails

In recent decades, there has been significant worldwide interest in the emergence of a new invasive species known as Achatina fulica. This is due to its dangerous habits for the environment, its biological characteristics and the fact that it is the intermediate host of several nematode parasites, such as Angiostrongylus cantonensis. This land snail species is native to tropical African countries, but has been introduced, accidentally or deliberately, to other parts of the world to be used for different purposes and is now established in a large part of the tropics. Since the 1980s, hundreds of researchers have been interested in the beneficial properties of its mucus, ranging from the antimicrobial and anticancer properties to the use of its powdered shell as a biocatalyst. This literature review aims to objectively describe the positive and negative aspects associated with the spread of A. fulica, highlighting in particular the opportunities for the local populations deriving from a conscious exploitation of this mollusc.

A cost-effective strategy for identifying Angiostrongylus spp. larvae in Achatina fulica: combined morphological and molecular biology

BACKGROUND

The detection of Angiostrongylus spp. larvae in intermediate host snails is a critical epidemiological investigation, essential for the effective control of disease outbreaks. Compared to molecular biological detection methods, lung microscopy, a traditional pathogen morphological detection approach, is susceptible to oversights and exhibits relatively lower sensitivity. However, we posit that lung microscopy offers irreplaceable advantages in the context of large-scale field surveys and can serve as a vital foundation for use in conjunction with other diagnostic technologies.

METHODS

In this study, 348 Achatina fulica samples were examined using lung microscopy, PCR, and AcanITS1 qPCR. Statistical analysis was conducted to compare detection rates and sensitivities among these methods. DNA from a snail confirmed positive by lung microscopy was diluted and tested using PCR and AcanITS1 qPCR to assess the diagnostic efficacy of the molecular assays. Finally, we combined the highly sensitive AcanITS1 qPCR with lung microscopy for identifying Angiostrongylus spp. larvae in Achatina fulica for the first time to our knowledge and compared its diagnostic efficacy with that of individual testing methods.

RESULTS

The lung microscopy, PCR, AcanITS1 qPCR, and combined test yielded detection rates of 29.31%, 32.18%, 38.22%, and 38.51%, respectively. These differences were statistically significant (X2 = 9.565, p < 0.05). Notably, AcanITS1 qPCR demonstrated superior sensitivity with a detection threshold of 10 pg/μl, outperforming the PCR with a threshold of 10 ng/μl. When PCR was utilized as the gold standard, the sensitivities for lung microscopy, AcanITS1 qPCR, and the combined test were determined to be 88.39%, 97.32%, and 98.21%, respectively. Correspondingly, the specificities were 98.73%, 89.83%, and 89.83%, respectively.

CONCLUSIONS

This novel straregy, the combined test for the detection of Angiostrongylus spp. larvae in Achatina fulica exhibited superior positive detection rates and sensitivity compared to each of the three individual methods. We believe that this novel strategy is not only applicable to large-scale field investigations of Achatina fulica and Pomacea canaliculata but also has potential application value for monitoring the infection of these snails sold at the local farmers' markets with Angiostrongylus spp. larvae. Of course, while qPCR is exceptionally sensitive, the potential for false negatives remains a consideration. Repeated experimentation is also essential to maximize the reliability and accuracy of the outcomes.

Identifying the function of novel cross-species microRNAs from the excretory-secretory products of Angiostrongylus cantonensis fifth-stage larvae

BACKGROUND

Angiostrongylus cantonensis is a significant foodborne zoonotic parasite that causes severe neuropathological damage and symptoms in humans. Excretory-secretory products (ESPs) play a pivotal role in elucidating host-parasite interactions and can aid in penetrating host defensive barriers in helminths. Recently, secreted microRNAs have become important research targets for parasite-host communication. In this study, we determined the expression and function of novel microRNAs from A. cantonensis L5 ESPs and evaluated the effect of target microRNAs on the molecular mechanisms of mouse astrocytes.

METHODS

Here, we employed next-generation sequencing (NGS) to establish the secreted microRNAs dataset. Next, we evaluated the effects of AcESPs-microRNAs in A. cantonensis ESPs treated astrocytes.

RESULTS

First, we established the secreted microRNA dataset, and then comprehensively verified the characteristics. Novel microRNAs were initially detected, and their expression was found. Moreover, the prediction results showed that these secreted microRNAs may regulate Wnt and mTOR signaling. Next, the data showed that the AcNOVEL55 microRNA reduced cell apoptosis generation via regulating the RhoA-Rock signaling pathway in A. cantonensis L5 ESPs treated mouse astrocytes. Moreover, we also demonstrated that the AcNOVEL31 microRNA can affect the inflammation activation via regulating the presenilin-1/GSK3B/β-catenin/NF-κB pathway. Finally, the concentrations of secreted IL-6 and IL-12 proteins were downregulated by AcNOVEL31 microRNA by influencing presenilin-1 expression.

CONCLUSION

This is the first study to verify the molecular functions of novel microRNAs secreted by A. cantonensis. The discovery of the microRNA mechanisms by which cross-species parasitic nematodes influence hosts has advanced research on host-parasitic nematode interactions.

Molecular study of the status of Angiostrongylus cantonensis in rats in Haiti

Angiostrongylus cantonensis, commonly known as the rat lungworm, causes Eosinophilic meningitis in humans. Our study aimed to investigate the prevalence and distribution of this parasite in rats in Haiti. Rats were trapped at 8 sites, 7 in Artibonite (rural region) and one in an urban area of Port-au-Prince. After euthanasia, hearts and lungs were sampled and preserved in 70% ethanol. Subsequently, the organs were dissected to detect adult worms. Parasite DNA was amplified using PCR targeting either the nematode ITS2 gene for rodent lung tissue or cox1 for isolated worms. Subsequent sequencing allowed parasite identification. A total of 70 rats were captured, i.e. 23 Rattus norvegicus and 47 Rattus rattus. Adult nematodes morphologically compatible with A. cantonensis were isolated from 5/70 rats (7%) and identification was confirmed by sequencing. Molecular analysis of lung tissue revealed a parasite prevalence of 31.4% (22/70), and its presence at 4 of the 8 sites investigated, including Port-au-Prince. The molecular approach on lung tissue targeting the ITS2 gene enabled us to detect a prevalence 4 times higher than the visual search for adult worms alone. Only one COX1 haplotype was identified, belonging to genotype II-G, widely distributed in Brazil, the French Antilles (Guadeloupe), French Polynesia, Hawaii, and Japan. These results confirm that A. cantonensis is an endemic parasite in Haiti not only in the capital Port-au-Prince, but also in several rural areas. Direct molecular screening for Angiostrongylus DNA in rat lung tissue showed higher sensitivity than visual detection of worms during dissection and could be useful for further prevalence studies.

First identification of Angiostrongylus spp. in Lissachatina fulica and Cornu aspersum in Antioquia, Colombia

INTRODUCTION

Abdominal and neural angiostrongyliasis caused by Angiostrongylus costaricensis and A. cantonensis, respectively, are zoonotic diseases involving snails as intermediate hosts. Colombia has already reported human cases, and the increasing distribution of Lissachatina fulica and Cornu aspersum raises public health concerns due to the potential risk of disease transmission in areas where parasites and hosts coexist.

OBJECTIVE

To identify the presence of Angiostrongylus spp. in snail species L. fulica and C. aspersum in Antioquia, Colombia.

MATERIALS AND METHODS

This prospective cross-sectional study had a population of 5,855 L. fulica and C. aspersum snails captured in the ten towns of the Valle de Aburrá (Antioquia, Colombia), 169 samples were collected in 28 sampling points. Lung tissues of the collected snails were dissected and analyzed to detect Angiostrongylus spp. through molecular techniques.

RESULTS

Angiostrongylus spp. were identified in both L. fulica and C. aspersum. Angiostrongylus costaricensis was detected in 18 pooled prevalence of 30% (95% CI = 19.2-43.3), and Medellín was the municipality with the highest number of positive samples (33.3%). Seventy-two-point-two percent of the positive places reported the presence of rodents. None of the tests were positive for A. cantonensis.

CONCLUSION

Our findings provide important insights into the epidemiology and distribution of Angiostrongylus spp. in Antioquia, Colombia. The identification of these parasitic nematodes in L. fulica and C. aspersum highlights the potential role of these snails as intermediate hosts in the transmission of Angiostrongylus spp. infections in the Valle de Aburrá, with implications for human and veterinary health.

A new diagnostic technique for identifying Angiostrongylus spp. larvae in intermediate snail species by examining the buccal cavity

BACKGROUND

Angiostrongyliasis is a zoonotic parasitic disease caused by the rat lungworm Angiostrongylus cantonensis. The intermediate hosts of A. cantonensis are gastropods, and snail species such as Pomacea canaliculata play a key role in the transmission of human angiostrongyliasis. Detecting A. cantonensis infection in snails is an important component of epidemiological surveillance and the control of angiostrongyliasis.

METHODS

In this study, a new method for diagnosing A. cantonensis infection in gastropods was developed by recovering larvae from the buccal cavity of three snail species. The entire buccal cavity of a snail was extracted, and the tissue was pressed between two microscope slides to observe whether A. cantonensis larvae were present. Our new method was compared with traditional pathogenic detection methods of lung microscopy, tissue homogenization, and artificial digestion. We artificially infected 160 P. canaliculata, 160 Cipangopaludina chinensis, and 160 Bellamya aeruginosa snails with A. cantonensis. Then, the four different detection methods were used to diagnose infection in each snail species at 7, 14, 21, and 28 days post exposure.

RESULTS

We found no significant difference in the percentages of infected P. canaliculata snails using the four methods to detect A. cantonensis larvae. The radula pressing method had a mean detection rate of 80%, while the lung microscopy (81.3%), tissue homogenization (83.8%), and artificial digestion (85%) methods had slightly greater detection rates. Similarly, the percentages of infected C. chinensis snails that were detected using the radula pressing (80%), tissue homogenization (82.1%), and artificial digestion (83.8%) methods were not significantly different. Finally, the percentages of infected B. aeruginosa snails that were detected using the radula pressing (81.3%), tissue homogenization (81.9%), and artificial digestion (81.4%) methods were not significantly different. These results showed that the radula pressing method had a similar detection rate to traditional lung microscopy, tissue homogenization, or artificial digestion methods.

CONCLUSIONS

This study demonstrates a new method for the qualitative screening of gastropods that act as intermediate hosts of A. cantonensis (and other Angiostrongylus species), provides technical support for the control of human angiostrongyliasis, and furthers research on A. cantonensis.

Inflammatory and immunopathological differences in brains of permissive and non-permissive hosts with Angiostrongylus cantonensis infection can be identified using 18F/FDG/PET-imaging

BACKGROUND

Angiostrongylus cantonensis is a parasite that mainly infects the heart and pulmonary arteries of rats and causes human eosinophilic meningitis or meningoencephalitis in certain geographical areas. Current diagnostic methods include detection of the parasite in cerebrospinal fluid (CSF) and eosinophilic immune examination after lumbar puncture, which may be risky and produce false-positive results. 18F- Fluorodeoxyglucose (FDG), a Positron emission tomography (PET) tracer, has been used to assess different pathological or inflammatory changes in the brains of patients. In this study, we hypothesized that A. cantonensis infection-induced inflammatory and immunomodulatory factors of eosinophils result in localized pathological changes in the brains of non-permissive hosts, which could be analyzed using in vivo 18F-FDG PET imaging.

METHODOLOGY/FINDINGS

Non-permissive host ICR mice and permissive host SD rats were infected with A. cantonensis, and the effects of the resulting inflammation on 18F-FDG uptake were characterized using PET imaging. We also quantitatively measured the distributed uptake values of different brain regions to build an evaluated imaging model of localized neuropathological damage caused by eosinophilic inflammation. Our results showed that the uptake of 18F-FDG increased in the cerebellum, brainstem, and limbic system of mice at three weeks post-infection, whereas the uptake in the rat brain was not significant. Immunohistochemical staining and western blotting revealed that Iba-1, a microglia-specific marker, significantly increased in the hippocampus and its surrounding area in mice after three weeks of infection, and then became pronounced after four weeks of infection; while YM-1, an eosinophilic chemotactic factor, in the hippocampus and midbrain, increased significantly from two weeks post-infection, sharply escalated after three weeks of infection, and peaked after four weeks of infection. Cytometric bead array (CBA) analysis revealed that the expression of TNF in the serum of mice increased concomitantly with the prolongation of infection duration. Furthermore, IFN-γ and IL-4 in rat serum were significantly higher than in mouse serum at two weeks post-infection, indicating significantly different immune responses in the brains of rats and mice. We suggest that 18F-FDG uptake in the host brain may be attributed to the accumulation of large numbers of immune cells, especially the metabolic burst of activated eosinophils, which are attracted to and induced by activated microglia in the brain.

CONCLUSIONS

An in vivo 18F-FDG/PET imaging model can be used to evaluate live neuroinflammatory pathological changes in the brains of A. cantonensis-infected mice and rats.

Angiostrongylus cantonensis induces energy imbalance and dyskinesia in mice by reducing the expression of melanin-concentrating hormone

BACKGROUND

Infection with Angiostrongylus cantonensis (AC) in humans or mice can lead to severe eosinophilic meningitis or encephalitis, resulting in various neurological impairments. Developing effective neuroprotective drugs to improve the quality of life in affected individuals is critical.

METHODS

We conducted a Gene Ontology enrichment analysis on microarray gene expression (GSE159486) in the brains of AC-infected mice. The expression levels of melanin-concentrating hormone (MCH) were confirmed through real-time quantitative PCR (RT-qPCR) and immunofluorescence. Metabolic parameters were assessed using indirect calorimetry, and mice's energy metabolism was evaluated via pathological hematoxylin and eosin (H&E) staining, serum biochemical assays, and immunohistochemistry. Behavioral tests assessed cognitive and motor functions. Western blotting was used to measure the expression of synapse-related proteins. Mice were supplemented with MCH via nasal administration.

RESULTS

Postinfection, a marked decrease in Pmch expression and the encoded MCH was observed. Infected mice exhibited significant weight loss, extensive consumption of sugar and white fat tissue, reduced movement distance, and decreased speed, compared with the control group. Notably, nasal administration of MCH countered the energy imbalance and dyskinesia caused by AC infection, enhancing survival rates. MCH treatment also increased the expression level of postsynaptic density protein 95 (PSD95) and microtubule-associated protein-2 (MAP2), as well as upregulated transcription level of B cell leukemia/lymphoma 2 (Bcl2) in the cortex.

CONCLUSIONS

Our findings suggest that MCH improves dyskinesia by reducing loss of synaptic proteins, indicating its potential as a therapeutic agent for AC infection.

A smartphone-based crowd-sourced real-time surveillance platform (apple snail inspector) for the invasive snails: a design and development study

BACKGROUND

The large amphibious freshwater apple snail is an important invasive species in China, but there is currently no method available for their surveillance. The development and popularization of smartphones provide a new platform for research on surveillance technologies for the early detection and effective control of invasive species.

METHODS

The ASI surveillance system was developed based on the infrastructure of the WeChat platform and Amap. The user can directly enter the game interface through the WeChat port on their mobile phone, and the system automatically obtains their location. The user can then report the location of apple snails. The administrator can audit the reported information, and all information can be exported to Microsoft Excel version 2016 for analysis. The map was generated by ArcGIS 10.2 and was used to characterize the spatial and temporal distribution of apple snails in Jiangsu Province.

RESULTS

The architecture of ASI consists of three parts: a mobile terminal, a server terminal and a desktop terminal. We published more than 10 tweets on the official WeChat account of the system to announce it to the public, and a total of 207 users in 2020 and 2021 correctly reported sightings of apple snails. We identified 550 apple snails breeding sites in 2020 and 2021, featuring ponds (81%), parks (17%) and farmland (2%). In addition, most of the locations contained snail eggs, and the reporting times mainly occurred between May and September.

CONCLUSIONS

The ASI is an effective surveillance system that can be used to identify the breeding locations of apple snails and provides the basis of prevention and control for its dispersal. Its successful development and operation provide new potential avenues for surveillance of other public health issues.

Semperula wallacei (Mollusca, Veronicellidae) um hospedeiro natural recém-descoberto de Angiostrongylus cantonensis (Nematoda, Angiostrongylidae) na Bacia do Pacífico

Semperula wallacei (Issel, 1874) is a species of terrestrial slug that occurs in southeast China and the Pacific Basin and is the only species of its genus that occurs beyond the Oriental region and to the east of Wallace's line in the Australian region, where it has probably been introduced. In this study, we report for the first time S. wallacei as an intermediate host for Angiostrongylus cantonensis (Chen, 1935) based on histological and molecular analyses of slugs from Tuamasaga, Samoa, deposited at the Medical Malacological Collection (Fiocruz-CMM). DNA was obtained from the deparafinized tissues scraped from specimen slides. Polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) targeted to the internal transcribed spacer 2 (ITS2) region were carried out using the restriction enzyme Cla I. The RFLP profile observed for our larval specimen of S. wallacei was identical to the profile previously established for A. cantonensis, demonstrating that S. wallacei can be naturally infected with A. cantonensis and is likely to be an intermediate host for this parasitic nematode species in the field. The potential for geographical range expansion of S. wallacei in the Pacific Basin, its small size, and the general role of veronicellids as crop pests and hosts of nematodes, indicate the significance of S. wallacei as an invasive species in the Pacific Basin. Our work also highlights the importance of biological collections for investigating the environmental impact of invasive species on agriculture, public health, and biodiversity conservation.

A Structural Analysis of Host-Parasite Interactions in Achatina fulica (Giant African Snail) Infected with Angiostrongylus cantonensis

Angiostrongylus cantonensis is a nematode parasite that resides in the pulmonary arteries of rodents, serving as its definitive hosts. The life cycle involves several species of non-marine gastropods as intermediate hosts, and the African giant snail Achatina fulica is considered one of the most important around the world. Experimental data concerning A. cantonensis infection in the African giant snail remains notably limited. This helminth causes eosinophilic meningitis or meningoencephalitis in humans, representing an emergent zoonosis in Brazil. Understanding the host-parasite relationship through the application of new tools is crucial, given the complex interaction between zoonosis and the intricate mechanisms involving wild/human hosts, parasite adaptation, and dispersion. The objective of this study was to employ SEM as a novel methodology to understand the structural organization of the host tissue, particularly the granuloma formation. This sheds light on the complex balance between A. fulica and A. cantonensis. Nine three-month-old snails were randomly selected and exposed for 24 h to a concentration of 2000 L1/dose of A. cantonensis. A necropsy was performed 37 days after the infection, and the samples were examined using light and scanning electron microscopy (SEM). The histopathological results revealed third-stage larvae of A. cantonensis associated with granulomas distributed throughout the head-foot mass, mantle, and kidney. Scanning electron microscopy of the histological section surface showed that the granuloma is surrounded by a cluster of spherical particles, which are distributed in the region bordering the larvae. This reveal details of the nematode structure, demonstrating how this methodology can enhance our understanding of the role of granulomas in molluscan tissue. The structural characteristics of granuloma formation in A. fulica suggest it as an excellent invertebrate host for A. cantonensis. This relationship appears to provide protection to the parasite against the host's immune defense system while isolating the snail's tissue from potential exposure to nematode antigens.

One-health approach on the future application of snails: a focus on snail-transmitted parasitic diseases

Snails are fascinating molluscs with unique morphological and physiological adaptive features to cope with various environments. They have traditionally been utilized as food and feed sources in many regions of the world. The future exploitation of alternative nutrient sources, like snails, is likely to increase further. Snails, however, also serve as an intermediate host for several zoonotic parasites. A category of parasitic infections, known as snail-transmitted parasitic diseases (STPDs), is harmful to humans and animals and is mainly driven by various trematodes, cestodes, and nematodes. The environment plays a crucial role in transmitting these parasites, as suitable habitats and conditions can facilitate their growth and proliferation in snails. In light of diverse environmental settings and biologically categorized snail species, this review evaluates the dynamics of significant STPDs of zoological importance. Additionally, possible diagnostic approaches for the prevention of STPDs are highlighted. One-health measures must be considered when employing snails as an alternative food or feed source to ensure the safety of snail-based products and prevent any adverse effects on humans, animals, and the environment.

IgE antibody responses in cerebrospinal fluids relate to the brain pathologic injury of hosts with Angiostrongylus cantonensis infection

BACKGROUND

The immunoglobulin E (IgE) response to Angiostrongylus cantonensis infection increases in the host. This study analyzed the IgG and IgE responses detected in different body fluids of A. cantonensis-infected mice.

METHODS

BALB/c (high susceptibility), CBA (medium), and C57BL/6 and C57BL/10 (resistance) strain mice were used in this study. The levels of IgM, IgG, and IgE in the serum and cerebrospinal fluid (CSF) from infected mice were compared. A. cantonensis-reactive antigens from BALB/c and C57BL/6 mice CSF were also analyzed.

RESULTS

Antibodies against fifth-stage larvae (L5) antigens increased in mice CSF, particularly IgE, relate to worm rejection and the susceptibility of different mouse strains. The increased IgE level in BALB/c mice CSF is lower than that from others, suggesting IgE response in brain is more important than that in serum. Anti-L5 and anti-excretory/secretory (ES) antigen IgE and IgG responses in CSF were analyzed. In addition, the antibody-dependent eosinophil-mediated cytotoxicity induced by anti-excretory/secretory (ES) antigen antibodies may be the reason of severe brain inflammation in infected BALB/c mice. IgE and IgG antibodies against a 105 kDa protein of L5 antigen was detected at week 3 post-infection in C57BL/6 mice and week 5 post-infection in BALB/c mice. We suggest that 105 kDa protein is related with the antibody response of A. cantonensis-infected mice.

CONCLUSION

We found that IgE antibodies in mice CSF against L5 antigens related to worm rejection in mice brains. This study may help to identify specific angiostrongyliasis markers that can be applied for clinical diagnosis and treatment in future.

First description study on molecular characterization of Hemiclepsis khankiana (Hirudinea: Glossiphoniidae) in China

BACKGROUND

Leeches are an integral component of aquatic biocenosis and can be found in a wide range of ecosystems such as freshwater, saltwater, flowing, and still-water ecosystems. It especially plays an important role in the freshwater benthic community and is an important part of the food web. In this study, a leech species was found in the mantle cavity of wild freshwater mussels in Zigong City, Sichuan Province, China, and its identity was determined through morphological analysis and molecular biological analysis.

RESULTS

The leech is Hemiclepsis khankiana, a new species of Hemiclepsis that has been discovered in Russia in recent years. Through morphological analysis, the current survey observed that the morphological characteristics of Hemiclepsis khankiana eyespots were significantly different from the first reported description. The first pair of eyespots on the leech were separated and clear, while it had been reduced to unclear shadows in the previous report. The phylogenetic tree based on the COI gene showed that the COI gene sequence obtained in this study was in the same evolutionary branch as Hemiclepsis khankiana (MN295420, MN295421). Genetically, it was most closely related to Hemiclepsis kasmiana (mean COI p-distance = 3.98%).

CONCLUSIONS

The current study reported on the new distribution range of Hemiclepsis khankiana, which was initially discovered in China. This study indicates that the distribution range of the leech species has expanded, laying a foundation for further studies in China.

Protective effect of benzaldehyde combined with albendazole against brain injury induced by Angiostrongylus cantonensis infection in mice

Angiostrongylus cantonensis, also known as rat lungworm, is an important food-borne zoonotic parasite that causes severe neuropathological damage and symptoms, including eosinophilic meningitis and eosinophilic meningoencephalitis, in humans. At present, the therapeutic strategy for cerebral angiostrongyliasis remains controversial. Benzaldehyde, an important bioactive constituent of Gastrodia elata (Tianma), reduces oxidative stress by inhibiting the production of reactive oxygen species. This study aimed to evaluate the therapeutic effect of benzaldehyde in combination with albendazole on angiostrongyliasis in animal models. First, the data from body weight monitoring and behavioural analyses demonstrated that benzaldehyde improved body weight and cognitive function changes after A. cantonensis infection. Next, blood‒brain barrier breakdown and pathological changes were reduced after benzaldehyde and albendazole treatment in BALB/c mice infected with A. cantonensis. Subsequently, four RNA-seq datasets were established from mouse brains that had undergone different treatments: normal, infection, infection + albendazole, and infection + albendazole + 3-hydroxybenzaldehyde groups. Ultimately, benzaldehyde was found to regulate cell apoptosis, oxidative stress and Sonic Hedgehog signalling in mouse brains infected with A. cantonensis. This study evaluated the therapeutic effect of benzaldehyde on angiostrongyliasis, and provided a potential therapeutic strategy for human angiostrongyliasis in the clinical setting. Moreover, the molecular mechanism of benzaldehyde in mouse brains infected with A. cantonensis was elucidated.

Clinical Characteristics and Treatment Outcome of Eosinophilic Meningoencephalitis in South Indian Children: Experience From a Prospective Registry

BACKGROUND

To describe the clinical features and therapeutic outcomes of a prospective cohort of children with eosinophilic meningoencephalitis.

METHODS

Children admitted with clinical features suggestive of meningitis along with cerebrospinal fluid (CSF) eosinophilia during the period of 14 years (2008 to 2021) were included. Their baseline characteristics, epidemiologic associations, and treatment outcomes were analyzed and compared with the previous studies.

RESULTS

We identified 25 children (13 males) satisfying the inclusion criteria. The median age at presentation was 3.9 years (range 0.8 to 17 years); 68% were aged less than two years. Fourteen (56%) children had a history of exposure to snails. Most of them presented with fever, headache, irritability, lateral rectus palsy, and early papilledema. Symptoms started three to 42 days (median duration: 14 days) before admission to our center. All children had peripheral eosinophilia, which ranged from 9% to 41%. The mean CSF white blood cell count was 416/mm3 (range 50 to 1245 cells/mm3) with CSF eosinophilia ranging from 11% to 80%. Brain magnetic resonance imaging was done in 24 children and was normal in 15 (62.5%). Leptomeningeal enhancement was seen in two (8.3%) children, and other nonspecific changes were noted in seven (29.1%) children. All children recovered without any neurological deficits with a standard treatment regimen of albendazole and oral steroids. All were asymptomatic at the last follow-up. None of them had any recurrence during the follow-up period.

CONCLUSION

We report one of the largest clinical series of children with eosinophilic meningoencephalitis from an endemic area of South India.

Rat lungworm survives winter: experimental overwintering of Angiostrongylus cantonensis larvae in European slugs

The rat lungworm Angiostrongylus cantonensis is a metastrongyloid nematode that causes neurological disorders in its accidental hosts, including humans. This invasive pathogen is native to Southeast Asia and adjacent regions and is gradually expanding its distribution to tropical and subtropical areas with new foci discovered near temperate regions. The parasite has a complex life cycle with a range of gastropods serving as intermediate hosts. A broad spectrum of poikilotherm vertebrates and invertebrates can serve as paratenic hosts. Since it has already been demonstrated that other, non-zoonotic metastrongyloids can survive in their intermediate hosts during the winter, the aim of our study was to evaluate the survival of A. cantonensis third-stage larvae in experimentally infected slugs (Limax maximus) kept at 4.5–7°C for 60 days. Third-stage larvae of A. cantonensis survived the period of low temperature and remained capable of infecting definitive hosts (laboratory rats) afterwards, even though their numbers dropped significantly. These results suggest that further spread to higher latitudes or altitudes is possible in areas with sufficient abundance of definitive hosts, since low winter temperatures are not necessarily an obstacle to the spread of the parasite.

Identification and genetic characterization of Angiostrongylus cantonensis isolated from the human eye

Angiostrongylus cantonensis, or the rat lungworm, is the causative agent of human angiostrongyliasis associated with eosinophilic meningitis or meningoencephalitis. Additionally, this nematode can cause ocular angiostrongyliasis, though this is rare. The worm can cause permanent damage to the affected eye and sometimes even blindness. Genetic characterization of the worm from clinical samples is limited. In the present study, we investigated the genetics of A. cantonensis recovered from a patient's eye in Thailand. We sequenced two mitochondrial genes (cytochrome c oxidase subunit I, or COI, and cytochrome b, or cytb) and nuclear gene regions (66-kDa protein and internal transcribed spacer 2, or ITS2) from a fifth-stage larva of Angiostrongylus sample that was surgically removed from the human eye. All sequences of the selected nucleotide regions were highly similar (98-100%) to the sequences of A. cantonensis in the GenBank database. The maximum likelihood and neighbor-joining trees of the COI gene indicated that A. cantonensis was closely related to the AC4 haplotype, whereas the cytb and 66-kDa protein genes were closely clustered with the AC6 and Ac66-1 haplotypes, respectively. In addition, the phylogeny of the concatenated nucleotide datasets of the COI and cytb revealed that the worm was closely related to the Thai strain and strains from other countries. This study confirms the identification and genetic variation of the fifth-stage larvae of A. cantonensis recovered from a patient's eye in Thailand. Our findings are important for future research on the genetic variation of A. cantonensis that causes human angiostrongyliasis.

The recent introduction of Angiostrongylus cantonensis and its intermediate host Achatina fulica into Guadeloupe detected by phylogenetic analyses

BACKGROUND

Angiostrongylus cantonensis (rat lungworm) is the main pathogen responsible for eosinophilic meningitis in humans. One of its intermediate snail hosts, Achatina fulica, was already present in many countries around the world before it appeared in the West Indies in the late 1980s. In the French territories in the Caribbean and northern South America, the first cases of human neuroangiostrongyliasis were reported in Martinique, Guadeloupe and French Guiana in 2002, 2013 and 2017, respectively. In order to better characterize angiostrongyliasis in Guadeloupe, particularly its geographical origin and route of introduction, we undertook molecular characterization of adult worms of Angiostrongylus cantonensis and its intermediate host Achatina fulica.

METHODS

Genomic DNA of adult Angiostrongylus cantonensis and Achatina fulica was extracted and amplified by polymerase chain reaction (PCR) targeting the mitochondrial genes cytochrome B and C for A. cantonensis and 16S ribosomal RNA for A. fulica. The PCR products were sequenced and studied by phylogenetic analysis.

RESULTS

Cytochrome B and cytochrome C molecular markers indicate a monophyletic lineage of A. cantonensis adult worms in Guadeloupe. Two sequences of A. fulica were identified.

CONCLUSIONS

These results confirm the recent introduction of both Angiostrongylus cantonensis and Achatina fulica into Guadeloupe. Achatina fulica in Guadeloupe shares a common origin with those in Barbados and New Caledonia, while Angiostrongylus cantonensis in Guadeloupe shares a common origin with those in Brazil, Hawaii and Japan.

In the Dawn of an Early Invasion: No Genetic Diversity of Angiostrongylus cantonensis in Ecuador?

The nematode Angiostrongylus cantonensis has been reported worldwide. However, some basic questions remain unanswered about A. cantonensis in Ecuador: (1) Was the invasion of A. cantonensis in Ecuador unique, or did it occur in different waves? (2) Was this invasion as recent as historical records suggest? (3) Did this invasion come from other regions of South America or elsewhere? To address these issues, we assessed the genetic diversity of MT-CO1 gene sequences from isolates obtained in 11 of Ecuador's 24 provinces. Our Bayesian inference phylogenetic tree recovered A. cantonensis as a well-supported monophyletic group. All 11 sequences from Ecuador were identical and identified as AC17a. The haplotype AC17a, found in Ecuador and the USA, formed a cluster with AC17b (USA), AC13 (Thailand), and AC12a-b (Cambodia). Notably, all the samples obtained in Ecuadorian provinces' different geographic and climatic regions had no genetic difference. Despite the lack of genetic information on A. cantonensis in Latin America, except in Brazil, our finding differs from previous studies by its absence of gene diversity in Ecuador. We concluded that the invasion of A. cantonensis in Ecuador may have occurred: (1) as a one-time event, (2) recently, and (3) from Asia via the USA. Further research should include samples from countries neighboring Ecuador to delve deeper into this.

An Overview of Angiostrongylus cantonensis (Nematoda: Angiostrongylidae), an Emerging Cause of Human Angiostrongylosis on the Indian Subcontinent

Human angiostrongylosis is an emerging zoonosis caused by the larvae of three species of metastrongyloid nematodes of the genus Angiostrongylus, with Angiostrongylus cantonensis (Chen, 1935) being dominant across the world. Its obligatory heteroxenous life cycle includes rats as definitive hosts, mollusks as intermediate hosts, and amphibians and reptiles as paratenic hosts. In humans, the infection manifests as Angiostrongylus eosinophilic meningitis (AEM) or ocular form. Since there is no comprehensive study on the disease in the Indian subcontinent, our study aims at the growing incidence of angiostrongylosis in humans, alongside its clinical course and possible causes. A systematic literature search revealed 28 reports of 45 human cases from 1966 to 2022; eosinophilic meningitis accounted for 33 cases (75.5%), 12 cases were reported as ocular, 1 case was combined, and 1 case was unspecified. The presumed source of infection was reported in 5 cases only. Importantly, 22 AEM patients reported a history of eating raw monitor lizard (Varanus spp.) tissues in the past. As apex predators, monitor lizards accumulate high numbers of L3 responsible for acute illness in humans. For ocular cases, the source was not identified. Most cases were diagnosed based on nematode findings and clinical pathology (primarily eosinophilia in the cerebrospinal fluid). Only two cases were confirmed to be A. cantonensis, one by immunoblot and the other by q-PCR. Cases of angiostrongylosis have been reported in Delhi, Karnataka, Kerala, Maharashtra, Madhya Pradesh, Puducherry, Telangana, and West Bengal. With a population of more than 1.4 billion, India is one of the least studied areas for A. cantonensis. It is likely that many cases remain undetected/unreported. Since most cases have been reported from the state of Kerala, further research may focus on this region. Gastropods, amphibians, and reptiles are commonly consumed in India; however, typical preparation methods involve cooking, which kills the nematode larvae. In addition to studying rodent and mollusk hosts, monitor lizards can be used as effective sentinels. Sequence data are urgently needed to answer the question of the identity of Angiostrongylus-like metastrongylid nematodes isolated from all types of hosts. DNA-based diagnostic methods such as q-PCR and LAMP should be included in clinical diagnosis of suspected cases and in studies of genetic diversity and species identity of nematodes tentatively identified as A. cantonensis.

Rapid Single-Step Immunochromatographic Assay for Angiostrongylus cantonensis Specific Antigen Detection

Angiostrongylus cantonensis is the major etiological nematode parasite causing eosinophilic meningitis and/or eosinophilic meningoencephalitis in humans. The rapid global spread of Angiostrongylus cantonensis and the emerging occurrence of the infection have exposed the shortcomings of traditional/conventional diagnostics. This has spurred efforts to develop faster, simpler and more scalable platforms that can be decentralized for point-of-need laboratory testing. By far, the point-of-care immunoassays such as the lateral flow assay (LFA) are the best-placed. In this work, a LFA in the form of an immunochromatographic test device (designated AcAgQuick^Dx), based on the detection of a circulating Angiostrongylus cantonensis-derived antigen, was established using anti-31 kDa Angiostrongylus cantonensis antibody as the capture reagent and anti-Angiostrongylus cantonensis polyclonal antibody as the indicator reagent. The AcAgQuick^Dx was evaluated for its diagnostic potential with a total of 20 cerebrospinal fluids (CSF) and 105 serum samples from patients with angiostrongyliasis and other clinically related parasitic diseases, as well as serum samples from normal healthy subjects. Three of the ten CSF samples from serologically confirmed angiostrongyliasis cases and two of the five suspected cases with negative anti-Angiostrongylus cantonensis antibodies showed a positive AcAgQuick^Dx reaction. Likewise, the AcAgQuick^Dx was able to detect Angiostrongylus cantonensis specific antigens in four serum samples of the 27 serologically confirmed angiostrongyliasis cases. No positive reaction by AcAgQuick^Dx was observed in any of the CSF (n = 5) and serum (n = 43) samples with other parasitic infections, or the normal healthy controls (n = 35). The AcAgQuick^Dx enabled the rapid detection of active/acute Angiostrongylus cantonensis infection. It is easy to use, can be transported at room temperature and does not require refrigeration for long-term stability over a wide range of climate. It can supplement existing diagnostic tests for neuroangiostrongyliasis under clinical or field environments, particularly in remote and resource-poor areas.

Sublethal effects of niclosamide on the aquatic snail Pomacea canaliculata

Pomacea canaliculata is a malignant invasive aquatic snail found worldwide, and niclosamide (NS) is one of the primary agents used for its control. NS applied to water will exist in non-lethal concentrations for some time due to degradation or water exchange, thus resulting in sublethal effects on environmental organisms. To identify sublethal effects of NS on Pomacea canaliculata, we studied the aspects of histopathology, oxygen-nitrogen ratio (R_O∶N), enzyme activity determination, and gene expression. After LC₃₀ NS treatment (0.310 g/L), many muscle fibers of the feet degenerated and some acinar vesicles of the hepatopancreas collapsed and dissolved. The oxygen-nitrogen ratio (R_O∶N) decreased significantly from 15.0494 to 11.5183, indicating that NS had changed the metabolic mode of Pomacea canaliculata and shifted it primarily to protein catabolism. Transcriptome analysis identified the sublethal effects of LC₃₀ NS on the snails at the transcriptional level. 386, 322, and 583 differentially expressed genes (DEGs) were identified in the hepatopancreas, gills, and feet, respectively. GO (Gene Ontology) functional analysis and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway annotations showed that DEGs in the hepatopancreas were mainly enriched for sugar metabolism, protein biosynthesis, immune response, and amino acid metabolism functional categories; DEGs in the gills were mainly enriched for ion transport and amino acid metabolism; DEGs in the feet were mainly enriched for transmembrane transport and inositol biosynthesis. In the future, we will perform functional validation of key genes to further explain the molecular mechanism of sublethal effects.

High-throughput metagenomics analysis in early and precise diagnosis of eosinophilic meningoencephalitis complicated with respiratory failure: A case report

RATIONALE

Human infection with Angiostrongylus cantonensis is uncommon and has only been sporadically reported in the literature. Patients infected with A cantonensis usually have a delayed diagnosis and sometimes a poor prognosis.

PATIENT CONCERNS

A 70-year-old woman presented to the respiratory department with complaints of headache, chest pain, myalgia, fatigue, and anorexia for 7 days.

DIAGNOSES

Complete blood count showed eosinophilia. The serum was tested showing a positive finding of A cantonensis antibody. Cerebrospinal fluid was tested using high-throughput metagenomics analysis and 16 reads for A cantonensis were mapped. The patient was diagnosed with A cantonensis infection.

INTERVENTIONS

The patient received a 7-day course of albendazole and 4-day course of prednisone.

OUTCOMES

When discharged from the hospital, the patient still suffered from fatigue and poor memory. Aminotransferase levels were high due to albendazole's liver toxicity. In a post-discharge follow-up about 1 month later she had recovered completely both physically and mentally, and peripheral eosinophil count and aminotransferase levels were both normal.

LESSONS

Because the direct identification of parasites is difficult, high-throughput metagenomics analysis may provide a reliable alternative tool for the diagnoses of infection with A cantonensis. When albendazole is prescribed, caution must be taken with respect to its liver toxicity.

Improving the detection of Angiostrongylus cantonensis in the brain tissues of mammalian hosts

Angiostrongylus cantonensis is an invasive nematode parasite that causes eosinophilic meningitis in many vertebrate hosts, including humans. This parasite is spreading rapidly through the six continents, with Europe being the final frontier. Sentinel surveillance may be a cost-effective strategy to monitor the pathogen's arrival to new geographical regions. Necropsy, followed by tissue digestion, is often used to recover helminth parasites from vertebrate host tissues, however, to detect brain parasites, this protocol is poorly utilized. Our brain digestion protocol is easily performed and 1) reduces false positivity and negativity, 2) provides accurate estimates of parasite burden and 3) helps establish a more precise prevalence. Early detection of A. cantonensis increases the efficacy of prevention, treatment, and disease control strategies for susceptible animal populations and humans.

Range of metastrongylids (superfamily Metastrongyloidea) of public health and veterinary concern present in livers of the endemic lizard Gallotia galloti of Tenerife, Canary Islands, Spain

BACKGROUND

Endemic lizards of the genus Gallotia are of high ecological value to the terrestrial ecosystem of the archipelago of the Canary Islands, being potent seed spreaders as well as an important component of the diet of other vertebrates. The endemic lizard Gallotia galloti in Tenerife has recently been reported to be a paratenic host of Angiostrongylus cantonensis, an invasive metastrongylid with zoonotic potential that is associated with rats as definitive hosts. However, microscopic examination of G. galloti tissue samples also revealed the presence of other metastrongylid larvae inside granulomas on the liver of this reptile. The aim of this study was to investigate the presence of helminths other than A. cantonensis in tissues of G. galloti from Tenerife.

METHODS

A multiplex-nested PCR targeting the internal transcribed spacer 1 was designed that enabled the species-specific detection of A. cantonensis, Angiostrongylus vasorum, Aelurostrongylus abstrusus, Crenosoma striatum and Crenosoma vulpis. Liver samples from 39 G. galloti were analysed.

RESULTS

Five metastrongylids were detected: A. cantonensis (15.4% of samples analysed), A. vasorum (5.1%), Ae. abstrusus (30.8%), C. striatum (30.8%) and undetermined metastrongylid sequences (12.8%). Co-infection was highly prevalent among the lizards which tested positive.

CONCLUSIONS

The study provides a new specific tool for the simultaneous detection of a range of metastrongylids of veterinary importance as well as new data on the circulation of metastrongylids in an ecosystem dominated by lizards.

Eosinophilic meningitis epidemiological data from a national database in Thailand's Department of Disease Control: a pragmatic, retrospective analytical study

Background

Eosinophilic meningitis (EOM) is a rare neurological disease that can be misdiagnosed or underdiagnosed. Based on reported cases in the literature, there have been 2,827 cases worldwide since 1945. There are limited data on the prevalence and trends of EOM in a real-world setting, even in Thailand, the country with the highest prevalence of EOM. Therefore, this study aimed to evaluate the prevalence of EOM and EOM epidemiological data in a real-world setting.

Methods

This was a pragmatic, retrospective analytical study using a national database. We retrieved EOM epidemiological data reported from government hospitals to Thailand’s Bureau of Epidemiology, within the Ministry of Public Health’s Department of Disease Control (DDC), between 2014 and 2019. The study was conducted by retrieving the data of all patients diagnosed with EOM and reported to the DDC. Diagnosis of EOM is made clinically by evidence of eosinophils of 10% or more of the total white blood cells in cerebrospinal fluid. Details of each patient were retrieved from the 506 Report Form, including age, month of reported case, zone of country, occupation, and mortality. Data regarding infection rate in each year and each zone were reported in rate/100,000 population, while data regarding age, month of reported case, and occupation were reported by year. Differences between means of age group, month of reported case, and occupation were tested by one-way analysis of variance (ANOVA). For those factors with significant differences among groups, Bonferroni method was used to compute pairwise differences.

Results

There were 1,083 EOM cases reported in Thailand during the six-year study period. The average annual incidence of EOM was 180.5 cases, or 0.27 cases/100,000 population. The northeast zone had the highest rate, with 0.89/100,000 population. The common age groups were 25–54 years, with the highest rate among the 35–44 age group, with a mean of 38.3 persons/year. These age groups were significantly different from other age groups (F value 39.23; p < 0.001). A relatively high cumulative monthly incidence (> 100 cases) was seen in four months, including January (117 cases), September (103 cases), October (112 cases), and November (103 cases), though these rates were not significantly different from the other months’ rates. Regarding occupation, the top two occupations with EOM diagnoses were farmers and laborers, which were significantly different from other occupations (F value 99.95; p < 0.001). There was no reported case of death during the study period.

Conclusion

EOM is common in Northeast Thailand among people of working age. The disease can be found throughout the year but is more common in the last quarter of the year. Farmers and laborers have the highest infection rate. To better understand the burden and outcomes of EOM, a national EOM reporting system with a better reporting form is required in endemic countries. Such a report form should include more details on risk exposure, symptoms, signs, treatment, and outcomes.

Immunoanalysis of different antigenic preparations of Angiostrongylus cantonensis for neuroangiostrongyliasis diagnosis improvement

BACKGROUND

Angiostrongylus cantonensis is the etiological agent of neuroangiostrongyliasis in humans, which is developed in gastropods and vertebrate species, mainly rodents. Human transmission occurs through consumption of molluscs and paratenic hosts infected with L3, and the migration of larvae to the central nervous system causes eosinophilic meningitis. Laboratory diagnosis is based on molecular and immunological tests, using young or adult females as a source of antigens. However, these tests give positive results only after several weeks of symptoms onset and also cross-reactions with others parasite infections may occur.

OBJECTIVES

The purpose of this work was to study different antigenic preparations of distinct evolutionary phases of A. cantonensis, in order to improve serological techniques for disease immunodiagnosis.

METHODS

For this purpose, antigenic fractions of different evolutionary forms were evaluated by Dot-enzyme-linked immunosorbent assay (Dot-ELISA) and Western blot using serum samples.

FINDINGS

All analysed fractions showed reactivity with serum samples from patients with neuroangiostrongyliasis, especially female membrane alkaline (FAM) and female soluble alkaline (FAS) fractions together with female soluble saline (FSS), improving the technique specificity.

MAIN CONCLUSIONS

The results point to the possibility of use of raw female antigens in association with alkaline membrane antigens extracted from adult worms to aid in diagnosis and helps initiate neuroangiostrongyliasis surveillance and control actions.

Improvements of cognitive functions in mice heavily infected by Angiostrongylus cantonensis after treatment with albendazole, dexamethasone, or co-therapy

Angiostrongylus cantonensis, the causative agent of human eosinophilic meningitis and eosinophilic meningoencepalitis, has been reported to cause cognitive impairments in the host. To determine whether drug treatment improves the cognitive functions, BALB/c mice infected with 50 third-stage larvae were treated with albendazole, dexamethasone, or co-therapy since day 7 or 14 post-infection for one or two weeks. Abilities of spatial memory and learning of these animals were assessed with the Morris water maze. Our results showed that body weight was significant higher then infected group in the albendazole and combined therapy groups. Significantly lower worm recovery rates were found in mice treated with the same groups. The mice treated with dexamethasone since day 7 for 14 day had significant longer time in the remaining groups were found in forced swimming test. The animals treated with albendazole and combined therapy since day 7 for 14 days was demonstrated to have significantly shorter latencies to the platform in learning memory on day 3 and 4. Mice in these two groups were demonstrated to have significantly higher sores in spatial memory tests. These results indicate that treatment with albendazole or combined therapy may be more efficient in preventing brain damages and depression as well as preserving their capabilities in learning and memory. Therefore, administration of albendazole alone or combined with dexamethasone should have higher efficacies than dexamethasone alone in treatment of BALB/c mice infected with a heavy dose of 50 third-stage larvae of A. cantonensis.

Paratenic hosts of Angiostrongylus cantonensis and their relation to human neuroangiostrongyliasis globally

The nematode parasite Angiostrongylus cantonensis (rat lungworm) has a complex life cycle involving rats (definitive hosts) and gastropods (intermediate hosts), as well as various paratenic hosts. Humans become infected and develop rat lungworm disease (neuroangiostrongyliasis) when they consume intermediate or paratenic hosts containing the infective parasite larvae. This study synthesizes knowledge of paratenic hosts of A. cantonensis and investigates their role in causing human neuroangiostrongyliasis worldwide. A literature review was conducted by searching PubMed, JSTOR and Scopus, pooling additional information from sources accumulated over many years by RHC, and snowball searching. The review identified 138 relevant articles published between 1962 and 2022. Freshwater prawns/shrimp, crayfish, crabs, flatworms, fish, sea snakes, frogs, toads, newts, lizards, centipedes, cattle, pigs and snails were reported to act as paratenic hosts in various regions including South and Southeast Asia, Pacific islands, the USA and the Caribbean, as well as experimentally. Human cases of neuroangiostrongyliasis have been reported from the 1960s onwards, linked, sometimes speculatively, to consumption of freshwater prawns/shrimp, crabs, flatworms, fish, frogs, toads, lizards and centipedes. The potential of paratenic hosts to cause neuroangiostrongyliasis depends on whether they are eaten, how frequently they are consumed, the preparation method, including whether eaten raw or undercooked, and whether they are consumed intentionally or accidentally. It also depends on infection prevalence in the host populations and probably on how high the parasite load is in the consumed hosts. To prevent human infections, it is crucial to interrupt the transmission of rat lungworm to humans, from both intermediate hosts and frequently consumed paratenic hosts, by adhering to safe food preparation protocols. Educating the general public and the medical community about this largely neglected tropical/subtropical disease is key.

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Neuroangiostrongyliasis, an emerging parasitic disease of humans and wildlife.

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Caused by the nematode Angiostrongylus cantonensis (rat lungworm).

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Infection primarily via ingestion of stage 3 larvae of the parasite.

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People eat raw intermediate or paratenic hosts infected with stage 3 larvae.

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Comprehensive review of paratenic hosts’ role in neuroangiostrongyliasis globally.

Synaptic loss and progression in mice infected with Angiostrongylus cantonensis in the early stage

Background

Angiostrongylus cantonensis is also known as rat lungworm. Infection with this parasite is a zoonosis that can cause eosinophilic meningitis and/or eosinophilic meningoencephalitis in humans and may lead to fatal outcomes in severe cases. In this study, we explored the mechanisms of the impairments in the cognitive functions of mice infected with A. cantonensis.

Methods

In infected mice with different infective intensities at different timepoint postinfection, loss and recovery of cognitive functions such as learning and memory abilities were determined. Neuronal death and damage to synaptic structures were analyzed by Western blotting and IHC in infected mice with different infection intensities at different timepoint postinfection.

Results

The results of behavioral tests, pathological examinations, and Golgi staining showed that nerve damage caused by infection in mice occurred earlier than pathological changes of the brain. BDNF was expressed on 14 day post-infection. Cleaved caspase-3 increased significantly in the late stage of infection. However, IHC on NeuN indicated that no significant changes in the number of neurons were found between the infected and uninfected groups.

Conclusions

The synaptic loss caused by the infection of A. cantonensis provides a possible explanation for the impairment of cognitive functions in mice. The loss of cognitive functions may occur before severe immunological and pathological changes in the infected host.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02436-8.

Rat Lungworm (Angiostrongylus cantonensis) in the Invasive Cuban Treefrog (Osteopilus septentrionalis) in Central Florida, USA

Cuban treefrogs, Osteopilus septentrionalis, were grossly examined for parasites and parasite species confirmed by PCR. Angiostrongylus cantonensis larvae were recovered from the hind leg muscle of O. septentrionalis. This is the first report of the zoonotic rat lungworm in the Cuban treefrog and new geographic location (Volusia County) in Florida, US.

Control of the Invasive Agricultural Pest Pomacea canaliculata with a Novel Molluscicide: Efficacy and Safety to Nontarget Species

The golden apple snail Pomacea canaliculata is an invasive pest that causes extensive damage to agricultural production. P. canaliculata is also an intermediate host of Angiostrongylus cantonensis, which causes human eosinophilic meningitis. In this study, the molluscicidal activity and safety profile of a novel molluscicide PBQ [1-(4-chlorophenyl)-3-(pyridin-3-yl)urea] were evaluated. PBQ exhibited strong molluscicidal potency against adult and juvenile snails (LC₅₀ values of 0.39 and 0.07 mg/L, respectively). In field trials, PBQ killed 99.42% of the snails at 0.25 g a.i./m². An acute toxicity test in rats demonstrated that PBQ is a generally nonhazardous chemical. PBQ is also generally safe for nontarget organisms including Brachydanio rerio, Daphnia magna, and Apis mellifera L. Transcriptomics analysis revealed that PBQ had a significant impact on the carbohydrate and lipid metabolism pathways, which provided insights into its molluscicidal mechanism. These results suggest that PBQ could be developed as an effective and safe molluscicide for P. canaliculata control.

A restored humoral environment ameliorates acute brain injury after Angiostrongylus cantonensis infection

Circulating factors in the circulatory system support important functions of living tissues and the body. Parabiosis is a condition in which two living animals are connected using surgical methods and share a single circulatory system. Angiostrongylus cantonensis is the major cause of infectious eosinophilic meningitis, which causes severe damage to the central nervous system (CNS) and immune system. However, the mechanism of immunopathology remains largely unknown. We hypothesize that a restored humoral environment can help relieve damage to the CNS and immune system. In the present study, we found that administration of normal serum significantly reduced mortality, alleviated thymic atrophy and reduced inflammation in the brains of mice infected with A. cantonensis. We further generated parabiotic pairs between two healthy mice, one of which was then orally infected with A. cantonensis. The results showed that compared with singleton mice, mice connected with a healthy parabiotic partner were protected against CNS and immune system damage, as revealed by significantly reduced inflammation in the brain, alleviated thymic atrophy, and decreased expression of proinflammatory cytokines. These findings revealed that a healthy systemic environment can relieve damage to the CNS and immune system in infected mice, suggesting novel therapeutic approaches for diseases involving severe brain and immune system damage.

Angiostrongilus cantonensis an Atypical Presenilin: Epitope Mapping, Characterization, and Development of an ELISA Peptide Assay for Specific Diagnostic of Angiostrongyliasis

Background: Angiostrongyliasis, the leading cause universal of eosinophilic meningitis, is an emergent disease due to Angiostrongylus cantonensis (rat lungworm) larvae, transmitted accidentally to humans. The diagnosis of human angiostrongyliasis is based on epidemiologic characteristics, clinical symptoms, medical history, and laboratory findings, particularly hypereosinophilia in blood and cerebrospinal fluid. Thus, the diagnosis is difficult and often confused with those produced by other parasitic diseases. Therefore, the development of a fast and specific diagnostic test for angiostrongyliasis is a challenge mainly due to the lack of specificity of the described tests, and therefore, the characterization of a new target is required. Material and Methods: Using bioinformatics tools, the putative presenilin (PS) protein C7BVX5-1 was characterized structurally and phylogenetically. A peptide microarray approach was employed to identify single and specific epitopes, and tetrameric epitope peptides were synthesized to evaluate their performance in an ELISA-peptide assay. Results: The data showed that the A. cantonensis PS protein presents nine transmembrane domains, the catalytic aspartyl domain [(XD (aa 241) and GLGD (aa 332–335)], between TM6 and TM7 and the absence of the PALP and other characteristics domains of the class A22 and homologous presenilin (PSH). These individualities make it an atypical sub-branch of the PS family, located in a separate subgroup along with the enzyme Haemogonchus contournus and separated from other worm subclasses. Twelve B-linear epitopes were identified by microarray of peptides and validated by ELISA using infected rat sera. In addition, their diagnostic performance was demonstrated by an ELISA-MAP4 peptide. Conclusions: Our data show that the putative AgPS is an atypical multi-pass transmembrane protein and indicate that the protein is an excellent immunological target with two (PsAg3 and PsAg9) A. costarisencis cross-reactive epitopes and eight (PsAg1, PsAg2, PsAg6, PsAg7, PsAg8, PsAg10, PsAg11, PsAg12) apparent unique A. cantonensis epitopes. These epitopes could be used in engineered receptacle proteins to develop a specific immunological diagnostic assay for angiostrongyliasis caused by A. cantonensis.

Farming the Edible Aquatic Snail Pomacea canaliculata as a Mini-Livestock

In the present paper, we describe the farming system of Pomacea canaliculata, an edible freshwater snail, as it is practiced by a farmer as mini-livestock in the vicinity of Andong in Korea. We visited the snail farm several times in the summer and winter of the year and conducted interviews with the farm manager using a semi-structured questionnaire. The farm is housed in polythene tunnels and uses a tank pen of trench type made up of propylene and measuring 1 m × 2 m × 0.5 m (length × width × height) in size. A regulated inflow of fresh water and outflow of used water was installed, with water level not exceeding 5 to 7 cm. As feed of snails, commercial fish feed is generally provided. The life cycle of the P. canaliculata might differ in captivity under the controlled environmental conditions than that of an individual in the wild environment. The farming system of snails, particularly P. canaliculata, does not involve high labor-intensive, high capital investment and also does not require high through-put cutting edge technology. In addition to providing nutrient-dense snail meat, establishing a snailery could therefore augment the economic condition of farmers in the poorer regions of the world and encourage sustainability and biodiversity conservation.

Comparative proteomics suggests the mode of action of a novel molluscicide against the invasive apple snail Pomacea canaliculata, intermediate host of Angiostrongylus cantonensis

Angiostrongylus cantonensis is a zoonotic parasitic nematode that is the most common cause of human eosinophilic meningitis. The invasive apple snail Pomacea canaliculata is an important intermediate host of A. cantonensis and contributes to its spread. P. canaliculata control will help prevent its invasion and transmission of A. cantonensis. The new molluscicide PBQ (1-(4-chlorophenyl)-3-(pyridin-3-yl)urea) exhibits great potency against P. canaliculata and has low toxicity against mammals and non-target aquatic organisms. We studied the mode of action of PBQ using TMT-based comparative quantitative proteomics analysis between PBQ-treated and control P. canaliculata snails. A total of 3151 proteins were identified, and 245 of these proteins were significantly differentially expressed with 135 downregulated and 110 upregulated. GO and KEGG enrichment analyses identified GO terms and KEGG pathways involved in de novo purine biosynthesis, ribosome components and translation process were significantly enriched and downregulated. The results indicated that PBQ treatment had substantial effects on the synthesis of genetic material, translation process, and protein synthesis of P. canaliculata and were likely the main cause of snail mortality.

What do we know about Angiostrongylus cantonensis in Spain? Current knowledge and future perspectives in a globalized world

Angiostrongylus cantonensis is an important emerging and zoonotic nematode that has been reported worldwide since its first description in Asia 86 years ago. Among places where this parasite has been recently described, insular regions of northwest Africa seem to be particularly relevant. We performed a systematic review in scientific databases to search and extract information about all reports describing cases of A. cantonensis in Spain until July 2021. As a result, seven surveys about the presence of this pathogen in Spanish insular regions were found, especially in the Canary Islands, as well as a non-autochthonous report of A. cantonensis in the mainland Spain. The lack of reliable information about the presence or absence of this nematode in the Iberian Peninsula highlights the need for further studies concerning this emerging pathogen since rodents acting as competent definitive hosts of A. cantonensis are widely distributed in the mainland. Moreover, the high maritime traffic daily registered in Spanish ports could be a main entrance pathway for A. cantonensis or its intermediate hosts in the country due to the frequent and direct connection between these points and regions where this pathogen is endemic. We encourage to focus further efforts on investigating the current epidemiological situation of A. cantonensis in the Iberian Peninsula, just as in other Mediterranean countries with similar epidemiological, ecological and geographical characteristics. In this sense, the relevant implications of this parasite for animal and public health make necessary to act integrating different viewpoints under the One Health perspective.

The returned traveler with neurologic manifestations: could my patient have a parasite?

PURPOSE OF REVIEW

The present review focuses on parasitic infections of the central nervous system (CNS) that can affect the international traveler.

RECENT FINDINGS

The epidemiology of imported parasitic infections is changing and clinicians are treating increasing numbers of returned travelers with parasitic infections in the CNS with which they are not familiar.

SUMMARY

The epidemiology, life cycle, clinical manifestations, diagnosis, and treatment of parasites that affect the CNS will be discussed.

Genetic Characterization and Detection of Angiostrongylus cantonensis by Molecular Approaches

Angiostrongylus cantonensis constitutes a major etiologic agent of eosinophilic meningoencephalitis. The detection methods for angiostrongyliasis mainly depend on morphology or immunology. A firmer diagnosis could be reached by directly detecting the parasite in the cerebrospinal fluid or through laboratory assays that are specific for Angiostrongylus-induced antibodies or the parasite's DNA. A. cantonensis detection could be carried out by larva release from the tissue upon pepsin digestion. However, the procedure requires live mollusks, which might complicate the analysis of large amounts of samples. Since morphological assays are limited, multiple molecular techniques have been put forward for detecting A. cantonensis, including PCR amplification of targets followed by fragment length or DNA sequence analysis. This allows rapid and accurate identification of A. cantonensis for efficient infection management and epidemiological purposes. In this study, we reviewed the current methods, concepts, and applications of molecular approaches to better understand the genetic characterization, molecular detection methods, and practical application of molecular detection in A. cantonensis.

Eosinophilic Meningitis and Intraocular Infection Caused by Dirofilaria sp. Genotype Hongkong

Eosinophilic meningitis caused by human diroflarial infection is rare. We report a case of eosinophilic meningitis and concomitant intraocular dirofilarial infection in India. Sequencing of the mitochondrial genome identified the worm as Dirofilaria sp. genotype Hongkong, a close relative of D. repens nematodes.

Autochthonous Angiostrongylus cantonensis, Angiostrongylus vasorum and Aelurostrongylus abstrusus infections in native terrestrial gastropods from the Macaronesian Archipelago of Spain

The presence of zoonotic relevant Angiostrongylus cantonensis infections has recently been reported in rat final hosts and gastropod intermediate hosts in Tenerife, Spain. However, data on A. cantonensis, Angiostrongylus vasorum and Aelurostrongylus abstrusus prevalences in endemic gastropods for other islands of the Macaronesian Archipelago are still missing. In order to fill this gap, we conducted an epidemiological study on terrestrial native slug (Plutonia lamarckii) and snail (Cornu aspersum, Theba pisana, Rumina decollata) species in 27 selected locations of Tenerife, Gran Canaria, El Hierro, Lanzarote, La Palma and Fuerteventura. Overall, 131 terrestrial gastropods were collected in winter/spring season 2018/2019 and examined for the presence of metastrongyloid lungworm larvae via artificial digestion. The current data revealed a total prevalence of 4.6% for A. vasorum, 3.8% for A. abstrusus and 0.8% for A. cantonensis. In Tenerife, three lungworm species were detected, thereby re-confirming A. cantonensis endemicity for this island. Prevalences of snails (C. aspersum) originating from El Hierro were 5% for A. abstrusus and 15% for A. vasorum, respectively, with larval burdens up to 290 larvae per specimen. This epidemiological study indicates the presence of human, canine and feline lungworm species in Macaronesia, Spain. The current data-particularly those on anthropozoonotic A. cantonensis-call for a regular large-scale monitoring on intermediate hosts, paratenic hosts and definitive hosts to prevent further spread of lungworm-related diseases in humans and animals.

Cluster of Angiostrongyliasis Cases Following Consumption of Raw Monitor Lizard in the Lao People's Democratic Republic and Review of the Literature

Angiostrongyliasis in humans causes a range of symptoms from mild headache and myalgia to neurological complications, coma and death. Infection is caused by the consumption of raw or undercooked intermediate or paratenic hosts infected with Angiostrongylus cantonensis or via contaminated vegetables or water. We describe a cluster of cases involved in the shared meal of wild raw monitor lizard in the Lao PDR. Seven males, aged 22–36 years, reported headaches, abdominal pain, arthralgia, myalgia, nausea/vomiting, diarrhea, neurological effects and loss of appetite. Five were admitted to hospital. The final diagnosis was made by clinical presentation and case history, and positive A. cantonensis PCR for two cases. All hospitalized patients recovered fully following supportive treatment. The remaining two individuals sought local home remedies and made full recovery. Whilst most published reports concern infections via consumption of molluscs, few detailed reports exist on infections that result from the consumption of reptiles and there exists little awareness in Lao PDR. This case cluster, which originates from a single meal, highlights the potential public health risk of the consumption of raw and wild-caught meat in Lao PDR and the Southeast Asia region. Without specific diagnostics, clinical history and the consideration of recent food consumption are important when evaluating patients.

Genome sequence of the cardiopulmonary canid nematode Angiostrongylus vasorum reveals species-specific genes with potential involvement in coagulopathy

Angiostrongylus vasorum is an emerging parasitic nematode of canids and causes respiratory distress, bleeding, and other signs in dogs. Despite its clinical importance, the molecular toolbox allowing the study of the parasite is incomplete. To address this gap, we have sequenced its nuclear genome using Oxford nanopore sequencing, polished with Illumina reads. The size of the final genome is 280 Mb comprising 468 contigs, with an N50 value of 1.68 Mb and a BUSCO score of 93.5%. Ninety-three percent of 13,766 predicted genes were assigned to putative functions. Three folate carriers were found exclusively in A. vasorum, with potential involvement in host coagulopathy. A screen for previously identified vaccine candidates, the aminopeptidase H11 and the somatic protein rHc23, revealed homologs in A. vasorum. The genome sequence will provide a foundation for the development of new tools against canine angiostrongylosis, supporting the identification of potential drug and vaccine targets.

CX3CL1 Recruits NK Cells Into the Central Nervous System and Aggravates Brain Injury of Mice Caused by Angiostrongylus cantonensis Infection

Background

Angiostrongylus cantonensis (A. cantonensis), is a food-borne zoonotic parasite that can cause central nervous system (CNS) injury characterized by eosinophilic meningitis. However, the pathogenesis of angiostrongylosis remains elusive. Natural killer cells (NK cells) are unique innate lymphocytes important in early defense against pathogens. The aim of this study was to investigate the role of NK cells in A. cantonensis infection and to elucidate the key factors that recruit NK cells into the CNS.

Methods

Mouse model of A. cantonensis infection was established by intragastric administration of third-stage larvae. The expression of cytokines and chemokines at gene and protein levels was analyzed by qRT-PCR and ELISA. Distribution of NK cells was observed by immunohistochemistry and flow cytometry. NK cell-mediated cytotoxicity against YAC-1 cells was detected by LDH release assay. The ability of NK cells to secrete cytokines was determined by intracellular flow cytometry and ELISA. Depletion and adoptive transfer of NK cells in vivo was induced by tail vein injection of anti-asialo GM1 rabbit serum and purified splenic NK cells, respectively. CX₃CL1 neutralization experiment was performed by intraperitoneal injection of anti-CX₃CL1 rat IgG.

Results

The infiltration of NK cells in the CNS of A. cantonensis-infected mice was observed from 14 dpi and reached the peak on 18 and 22 dpi. Compared with uninfected splenic NK cells, the CNS-infiltrated NK cells of infected mice showed enhanced cytotoxicity and increased IFN-γ and TNF-α production ability. Depletion of NK cells alleviated brain injury, whereas adoptive transfer of NK cells exacerbated brain damage in A. cantonensis-infected mice. The expression of CX₃CL1 in the brain tissue and its receptor CX₃CR1 on the CNS-infiltrated NK cells were both elevated after A. cantonensis infection. CX₃CL1 neutralization reduced the percentage and absolute number of the CNS-infiltrated NK cells and relieved brain damage caused by A. cantonensis infection.

Conclusions

Our results demonstrate that the up-regulated CX₃CL1 in the brain tissue recruits NK cells into the CNS and aggravates brain damage caused by A. cantonensis infection. The findings improve the understanding of the pathogenesis of angiostrongyliasis and expand the therapeutic intervention in CNS disease.

A Peculiar Distribution of the Emerging Nematode Angiostrongylus cantonensis in the Canary Islands (Spain): Recent Introduction or Isolation Effect?

Simple Summary

Angiostrongylus cantonensis, commonly known as the rat lungworm, is considered the leading cause of eosinophilic meningitis in humans. It is an emerging zoonotic parasite, endemic to the temperate and tropical zones of the Far East, Southeast Asia and the Pacific Islands, that has expanded to all continents with the exception of Antarctica. Considering the recent finding of this parasite in rats from the Canary Islands, the aim of this study was to determine its current distribution in these islands in order to highlight the risk sources for angiostrongyliasis in the archipelago. We also analyzed the environmental conditions that could determine distribution. A. cantonensis was detected in only one of the eight islands that constitute this archipelago, i.e., in the north part of the island, which presents better environmental conditions than the south for the parasite to establish itself. This limited distribution could indicate a recent introduction of the parasite in the Canaries or an isolation effect that has not allowed the expansion to the other islands. The presence of A. cantonensis implies risks for humans and other animals that justify the need of control measures to prevent the expansion to other similar areas of the archipelago.

Abstract

Angiostrongylus cantonensis is an emerging zoonotic nematode recognized as the leading cause of eosinophilic meningitis in the word. After its discovery in China, it was recorded in 30 countries worldwide. Recently, it has expanded to new areas such as South America and it has been recently found in the Atlantic island of Tenerife (Canary Islands). In order to characterize the distribution of A. cantonensis in the Canary Islands, the lungs of 1462 rodents were sampled in eight islands of the archipelago over 13 years and were then analyzed for A. cantonensis. Remarkably, the parasite was detected only in Tenerife, in Rattus rattus (19.7%) and Rattus norvegicus (7.14%). They were concretely in the northern part of the island, which had a warmer and more humid climate than the south and main cities. The absence of this nematode in other islands with similar environmental conditions could be explained by an isolation effect or by a recent introduction of the parasite in the islands. Besides, the presence in Tenerife of the most invasive lineage of A. cantonensis reinforced the hypothesis of a recent introduction on this island. This study highlights the need to implement control measures to prevent the expansion to other areas in order to avoid the transmission to humans and other animals.