Central nervous system manifestations of Angiostrongylus cantonensis infection

Potential intermediate hosts of Angiostrongylus cantonensis in the European Mediterranean region (Mallorca, Spain)

Angiostrongylus cantonensis is the main etiological agent of eosinophilic meningitis, a disease that often leads to severe neurological manifestations in mammals and birds. In recent years, the prevalence of this zoonotic nematode has dramatically increased as it expands into new territories beyond its native range in Southeast Asia and the Pacific Basin.Its arrival to Europe, the last continent to be invaded, has raised many questions concerning the parasite's life cycle, particularly in the Mediterranean region, where it is now endemic. This study aims to collect evidence about intermediate hosts (snail and slug species) involved in the transmission of the A. cantonensis in Mallorca. We have conducted a systematic surveillance of gastropods within 2 km radius areas, surrounding the specific locations where infected hedgehogs were found. We employed a sequence-based detection approach that included a species-specific PCR amplification followed by DNA sequencing of the internal transcribed spacer I (ITS-1). This conservative approach was essential to avoid cross reactions with the numerous metastrongylid species known to be circulating in Mallorca. Overall, we collected and identified 398 gastropods belonging to 17 species, of which 11% tested positive for A. cantonensis. These gastropods were collected from touristic settlements to agricultural lands. Five gastropod species: Theba pisana, Cornu aspersum, Deroceras reticulatum, Milax gagates and Otala lactea, had been previously incriminated as A. cantonensis intermediate hosts, while 6 species: Papillifera papillaris, Cochlicella acuta, Eobania vermiculata, Ganula lanuginosa, Milax nigricans and Rumina decollata, are newly recorded hosts. The findings of this study have important epidemiological implications, and further measures are discussed to prevent neuroangiostrongylosis cases.

Fatal neural angiostrongyliasis in the Bolivian squirrel monkey (Saimiri boliviensis boliviensis) leading to defining Angiostrongylus cantonensis risk map at a zoo in Australia

Neural angiostrongyliasis (NA) is a parasitic disease caused by Angiostrongylus cantonensis (rat lungworm). This study presents a case of NA in a captive Bolivian squirrel monkey from a zoo in western Sydney, Australia. The objective was to identify the A. cantonensis cox1 haplotype responsible for the infection and compare its mitochondrial DNA (mtDNA) to known Australian mtDNA. An epidemiological investigation was conducted to assess the risk of infection, focusing on the resident rat population in the zoo. Methods involved trapping rats and collecting rat faeces for Angiostrongylus detection, speciation, and cox1 haplotype confirmation. Various techniques were employed, including necropsy, morphological examination, and molecular methods such as ITS-2 qPCR, cox1 sequencing, and ITS-2 metabarcoding. Cluster analysis of rat faeces distribution and Angiostrongylus detection utilised an equal sampling effort (ESE) approach. Gastropods were collected throughout the study for Angiostrongylus surveillance using a hypersensitive qPCR assay. Results revealed significant clustering of rat faeces near exhibits with fresh food provision and absence of predators. Angiostrongylus-positive faeces were uniformly distributed across the zoo property. Mitochondrial DNA analysis confirmed the presence of the Ac13 haplotype of A. cantonensis in the monkey. Morphology, ITS-2 metabarcoding and partial cox1 sequencing detected only A. cantonensis, with the Ac13 cox1 haplotype predominating. A high prevalence of infection (64%, 9/14) was found in brown rats, with quantification of larvae indicating high shedding rates. Co-infections with both Ac13 and local SYD.1 A. cantonensis cox1 haplotypes were observed. Only three gastropods (all of which were Angiostrongylus-negative) were found in the survey. To minimise the risk of exposure for susceptible species, targeted rodent control was implemented in areas with higher exposure risk. A potential strategy (which requires further exploration) to consider for future zoo design was suggested. This study provides insights into the epidemiology and genetic diversity of A. cantonensis in Australia, emphasising the importance of control measures to prevent future outbreaks.

Emerging and Re-Emerging Parasitic Infections of the Central Nervous System (CNS) in Europe

In a rapidly evolving global landscape characterized by increased international travel, migration, and ecological shifts, this study sheds light on the emergence of protozoal and helminthic infections targeting the central nervous system (CNS) within Europe. Despite being traditionally associated with tropical regions, these infections are progressively becoming more prevalent in non-endemic areas. By scrutinizing the inherent risks, potential outcomes, and attendant challenges, this study underscores the intricate interplay between diagnostic limitations, susceptibility of specific population subsets, and the profound influence of climate fluctuations. The contemporary interconnectedness of societies serves as a conduit for introducing and establishing these infections, warranting comprehensive assessment. This study emphasizes the pivotal role of heightened clinician vigilance, judicious public health interventions, and synergistic research collaborations to mitigate the potential consequences of these infections. Though rare, their profound impact on morbidity and mortality underscores the collective urgency required to safeguard the neurological well-being of the European populace. Through this multifaceted approach, Europe can effectively navigate the complex terrain posed with these emergent infections.

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.

The Landscape of Parasitic Infections in the United States

The landscape of parasitic infections in the United States has shifted dramatically over the past century. Although infections such as malaria have been successfully eliminated, others remain endemic and pose a significant public health risk. Numerous parasitic infections are also imported each year. This article focuses on endemic parasitic infections that may be commonly seen in anatomical pathology preparations and discusses their biology, diagnostic histopathological features, and epidemiology.

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.

Comparative biology of parasitic nematodes in the genus Angiostrongylus and related genera

The rise to prominence of some Angiostrongylus species through associated emerging disease in humans and dogs has stimulated calls for a renewed focus on the biology of this genus and three related genera. Although significant research efforts have been made in recent years these have tended to focus on individual species and specific aspects such as diagnosis and treatment of disease or new records of occurrence and hosts. This comprehensive review takes a comparative approach, seeking commonalities and differences among species and asking such questions as: Which species belong to this and to closely related genera and how are they related? Why do only some species appear to be spreading geographically and what factors might underlie range expansion? Which animal species are involved in the life cycles as definitive, intermediate, paratenic and accidental hosts? How do parasite larvae find, infect and develop within these hosts? What are the consequences of infection for host health? How will climate change affect future spread and global health? Appreciating how species resemble and differ from each other shines a spotlight on knowledge gaps and provides provisional guidance on key species characteristics warranting detailed study. Similarities exist among species, including the basic life cycle and transmission processes, but important details such as host range, climatic requirements, migration patterns within hosts and disease mechanisms differ, with much more information available for A. cantonensis and A. vasorum than for other species. Nonetheless, comparison across Angiostrongylus reveals some common patterns. Historically narrow definitive host ranges are expanding with new knowledge, combining with very broad ranges of intermediate gastropod hosts and vertebrate and invertebrate paratenic and accidental hosts to provide the backdrop to complex interactions among climate, ecology and transmission that remain only partly understood, even for the species of dominant concern. Key outstanding questions concern larval dynamics and the potential for transmission outside trophic relations, relations between infection and disease severity in different hosts, and how global change is altering transmission beyond immediate impacts on development rate in gastropods. The concept of encounter and compatibility filters could help to explain differences in the relative importance of different gastropod species as intermediate hosts and determine the importance of host community composition and related environmental factors to transmission and range. Across the group, it remains unclear what, physiologically, immunologically or taxonomically, delimits definitive, accidental and paratenic hosts. Impacts of infection on definitive host fitness and consequences for population dynamics and transmission remain mostly unexplored across the genus. Continual updating and cross-referencing across species of Angiostrongylus and related genera is important to synthesise rapid advances in understanding of key traits and behaviours, especially in important Angiostrongylus species that are emerging causative agents of disease in humans and other animals.

Angie-LAMP for diagnosis of human eosinophilic meningitis using dog as proxy: A LAMP assay for Angiostrongylus cantonensis DNA in cerebrospinal fluid

BACKGROUND

Angiostrongylus cantonensis (rat lungworm) is recognised as the leading cause of human eosinophilic meningitis, a serious condition observed when nematode larvae migrate through the CNS. Canine Neural Angiostrongyliasis (CNA) is the analogous disease in dogs. Both humans and dogs are accidental hosts, and a rapid diagnosis is warranted. A highly sensitive PCR based assay is available but often not readily accessible in many jurisdictions. An alternative DNA amplification assay that would further improve accessibility is needed. This study aimed to assess the diagnostic utility of a newly designed LAMP assay to detect DNA of globally distributed and invasive A. cantonensis and Angiostrongylus mackerrasae, the other neurotropic Angiostrongylus species, which is native to Australia.

METHODOLOGY/PRINCIPAL FINDINGS

Cerebrospinal fluid (CSF) from dogs with a presumptive diagnosis of A. cantonensis infection (2020-2022) were received for confirmatory laboratory testing and processed for DNA isolation and ultrasensitive Angiostrongylus qPCR targeting AcanR3390. A newly designed LAMP assay targeting the same gene target was directly compared to the reference ultrasensitive qPCR in a diagnostic laboratory setting to determine the presence of A. cantonensis DNA to diagnose CNA. The LAMP assay (Angie-LAMP) allowed the sensitive detection of A. cantonensis DNA from archived DNA specimens (Kappa = 0.81, 95%CI 0.69-0.92; n = 93) and rapid single-step lysis of archived CSF samples (Kappa = 0.77, 95%CI 0.59-0.94; n = 52). Only A. cantonensis DNA was detected in canine CSF samples, and co-infection with A. mackerrasae using amplicon deep sequencing (ITS-2 rDNA) was not demonstrated. Both SYD.1 and AC13 haplotypes were detected using sequencing of partial cox1.

CONCLUSIONS/SIGNIFICANCE

The Angie-LAMP assay is a useful molecular tool for detecting Angiostrongylus DNA in canine CSF and performs comparably to a laboratory Angiostrongylus qPCR. Adaptation of single-step sample lysis improved potential applicability for diagnosis of angiostrongyliasis in a clinical setting for dogs and by extension, to humans.

Spatial parasitology and the unmapped human helminthiases

Helminthiases are a class of neglected tropical diseases that affect at least 1 billion people worldwide, with a disproportionate impact on resource-poor areas with limited disease surveillance. Geospatial methods can offer valuable insights into the burden of these infections, particularly given that many are subject to strong ecological influences on the environmental, vector-borne or zoonotic stages of their life cycle. In this study, we screened 6829 abstracts and analysed 485 studies that use maps to document, infer or predict transmission patterns for over 200 species of parasitic worms. We found that quantitative mapping methods are increasingly used in medical parasitology, drawing on One Health surveillance data from the community scale to model geographic distributions and burdens up to the regional or global scale. However, we found that the vast majority of the human helminthiases may be entirely unmapped, with research effort focused disproportionately on a half-dozen infections that are targeted by mass drug administration programmes. Entire regions were also surprisingly under-represented in the literature, particularly southern Asia and the Neotropics. We conclude by proposing a shortlist of possible priorities for future research, including several neglected helminthiases with a burden that may be underestimated.

The application of metagenomic next-generation sequencing for Angiostrongylus eosinophilic meningitis in a pediatric patient: A case report

Background

Angiostrongylus eosinophilic meningitis (AEM) is a rare yet emerging disease caused by Angiostrongylus cantonensis infection. Its atypical symptoms may delay the diagnosis and cause fatal outcomes, especially in the early stages of infection and among children.

Case presentation

Here we reported the use of metagenomic next-generation sequencing (mNGS) to facilitate the diagnosis and treatment of an 8-year-old boy with severe A. cantonensis infection. The mNGS tests consistently identified the infection of A. cantonensis prior to the detection by the immunologic method and confirmed it as AEM. Owing to the multidisciplinary team (MDT)-administrated treatments and close disease monitoring based on regular clinical tests and sequential mNGS tests, the patients eventually fully recovered from severe infectious conditions.

Conclusion

This case demonstrated the advantages of mNGS for early diagnosis of AEM in pediatric patients, highlighting its application for pan-pathogen detection, as well as disease monitoring for severe A. cantonensis infection.

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.

Upregulated galectin-1 in Angiostrongylus cantonensis L5 reduces body fat and increases oxidative stress tolerance

Background

Angiostrongylus cantonensis L5, parasitizing human cerebrospinal fluid, causes eosinophilic meningitis, which is attributed to tissue inflammatory responses caused primarily by the high percentage of eosinophils. Eosinophils are also involved in killing helminths, using the peroxidative oxidation and hydrogen peroxide (H₂O₂) generated by dismutation of superoxide produced during respiratory burst. In contrast, helminthic worms have evolved to attenuate eosinophil-mediated tissue inflammatory responses for their survival. In previous study, we demonstrated the extracellular function of Acan-Gal-1 in inducing the apoptosis of macrophages. Here, the intracellular functions of Acan-Gal-1 were investigated, aiming to further reveal the mechanism involved in A. cantonensis L5 worms surviving inflammatory responses in the human central nervous system.

Methods

In this study, a model organism, Caenorhabditis elegans, was used as a surrogate to investigate the intracellular functions of Acan-Gal-1 in protecting the worm from its host’s immune attacks. First, structural characterization of Acan-Gal-1 was analyzed using bioinformatics; second, qRT-PCR was used to monitor the stage specificity of Acan-gal-1 expression in A. cantonensis. Microinjections were performed to detect the tissue specificity of lec-1 expression, the homolog of Acan-gal-1 in C. elegans. Third, microinjection was performed to develop Acan-gal-1::rfp transgenic worms. Then, oxidative stress assay and Oil Red O fat staining were used to determine the functions of Acan-Gal-1 in C. elegans.

Results

The results of detecting the stage specificity of Acan-gal-1 expression showed that Acan-Gal-1 was upregulated in both L5 and adult worms. Detection of the tissue specificity showed that the homolog of Acan-gal-1 in C. elegans, lec-1 was expressed ubiquitously and mainly localized in cuticle. Investigating the intracellular functions of Acan-Gal-1 in the surrogate C. elegans showed that N2 worms expressing pCe-lec-1::Acan-gal-1::rfp, with lipid deposition reduced, were significantly resistant to oxidative stress; lec-1 mutant worms, where lipid deposition increased, showed susceptible to oxidative stress, and this phenotype could be rescued by expressing pCe-lec-1::Acan-gal-1::rfp. Expressing pCe-lec-1::Acan-gal-1::rfp or lec-1 RNAi in fat-6;fat-7 double-mutant worms, where fat stores were reduced, had no significant effect on the oxidative stress tolerance.

Conclusion

In C. elegans worms, upregulated Acan-Gal-1 plays a defensive role against damage due to oxidative stress for worm survival by reducing fat deposition. This might indicate the mechanism by which A. cantonensis L5 worms, with upregulated Acan-Gal-1, survive the immune attack of eosinophils in the human central nervous system.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05171-4.

Mechanisms of the host immune response and helminth-induced pathology during Trichobilharzia regenti (Schistosomatidae) neuroinvasion in mice

Helminth neuroinfections represent serious medical conditions, but the diversity of the host-parasite interplay within the nervous tissue often remains poorly understood, partially due to the lack of laboratory models. Here, we investigated the neuroinvasion of the mouse spinal cord by Trichobilharzia regenti (Schistosomatidae). Active migration of T. regenti schistosomula through the mouse spinal cord induced motor deficits in hindlimbs but did not affect the general locomotion or working memory. Histological examination of the infected spinal cord revealed eosinophilic meningomyelitis with eosinophil-rich infiltrates entrapping the schistosomula. Flow cytometry and transcriptomic analysis of the spinal cord confirmed massive activation of the host immune response. Of note, we recorded striking upregulation of the major histocompatibility complex II pathway and M2-associated markers, such as arginase or chitinase-like 3. Arginase also dominated the proteins found in the microdissected tissue from the close vicinity of the migrating schistosomula, which unselectively fed on the host nervous tissue. Next, we evaluated the pathological sequelae of T. regenti neuroinvasion. While no demyelination or blood-brain barrier alterations were noticed, our transcriptomic data revealed a remarkable disruption of neurophysiological functions not yet recorded in helminth neuroinfections. We also detected DNA fragmentation at the host-schistosomulum interface, but schistosomula antigens did not affect the viability of neurons and glial cells in vitro. Collectively, altered locomotion, significant disruption of neurophysiological functions, and strong M2 polarization were the most prominent features of T. regenti neuroinvasion, making it a promising candidate for further neuroinfection research. Indeed, understanding the diversity of pathogen-related neuroinflammatory processes is a prerequisite for developing better protective measures, treatment strategies, and diagnostic tools.

The best protection is early detection

This current special issue of the Biomedical Journal provides insights in various cancer forms, and possible ways of prognostic and predictive screening. In detail we learn about lung cancer and tissue samples from ground glass opacifications, liquid biopsy through circulating tumor cells in colon cancer, transcription factor analysis in cervical cancer, and long non-coding RNAs in breast and lung cancer. A prognosis factor in individuals with acute myeloid leukemia and a rare fungal infection are determined. Challenges surrounding transplantation are elucidated, a potential biomarker for allograft dysfunction is presented, as well as a mean to save beta cells after islet transplantation. We get to know more about drug resistance in transplant recipients with tuberculosis, and also in the case of H.pylori infection. Lastly, the possibilities of cardiac shock wave therapy in simultaneous artery and renal disease is explored, we are presented with genetic factors contributing to cancer risk in arseniasis areas, and protocol recommendations for the optimal reproducibility of bladder volume in prostate cancer treatment. Three markers for detecting stages of diabetic retinopathy are covered, as well as a way to mitigate effects of lungworm secretions. Finally we get to see a novel approach for acupuncture needle material, and two management approaches for a form of skeletal malocclusion.

Eosinophilic meningitis in New Caledonia: The role of Angiostrongylus cantonensis?

INTRODUCTION

Eosinophilic meningitis is a rare form of meningitis with sequelae or death occurring in approximately 2-3% of cases. The most frequent etiological agent is the parasite Angiostrongylus cantonensis. The aim of this study was to characterize New Caledonian cases and to assess the extent to which of A. cantonensis was involved.

MATERIAL AND METHODS

We performed a retrospective study of all cases of eosinophilic meningitis (EM) admitted to the Territorial Hospital of New Caledonia, from 2004 to 2019. We performed a descriptive and a multivariate analysis to identify association of variables with severe and fatal cases (or cases with sequelae).

CONCLUSION

Angiostrongyliasis was confirmed as being responsible for 17 of the 92 reported EM cases in New Caledonia from 2004 to 2019 with most being young adults and non-walking infants, and with two peaks of incidence one during the dry season and one during the rainy season. Considering the high incidence and regularity of cases, the potential reservoirs should be identified to target prevention campaigns.

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.

Co-Therapy of Albendazole and Dexamethasone Reduces Pathological Changes in the Cerebral Parenchyma of Th-1 and Th-2 Dominant Mice Heavily Infected with Angiostrongylus cantonensis: Histopathological and RNA-seq Analyses

Administration of albendazole alone was not very suitable for the treatment of cerebral angiostrongyliasis. This study was designed to evaluate the effects of the co-therapy of this drug and dexamethasone in Th-1 and Th-2 dominant mice infected with Angiostrongylus cantonensis. Each of BALB/c and C57BL/6 mice infected with 50 A. cantonensis third-stage larvae were administered albendazole (10 mg/kg/day) alone, dexamethasone (0.5 mg/kg/day) alone, or co-therapy of the two drugs from day 7 or 14 post-infection for 7 or 14 days. After sacrifice, coronal slices were prepared from five brain regions and stained with hematoxylin and eosin. Eight pathological changes were employed to determine the therapeutic effectiveness using a scoring system. RNA-seq analysis was performed to confirm the histopathological findings. The infected BALB/c and C57BL/6 mice had similar patterns in the pathological changes. Meningitis, hemorrhage, size of worms, and encephalitis in the cerebral parenchyma were slighter in the mice treated with co-therapy than the remaining groups. Mice treated from day 14 had more severe changes than those from day 7. The histopathological findings were found to be consistent to immune responses determined by RNA-seq analysis. Co-therapy was determined to reduce pathological changes after administration to mice infected with A. cantonensis.

Chronic neuroangiostrongyliasis: case study of chronic presentations in Hawaii

This paper describes chronic features of neuroangiostrongyliasis (NAS), a long-term outcome of the disease that has not been adequately described. Current and past literature is predominantly limited to acute manifestations of NAS, and mention of chronic, ongoing clinical symptoms is usually limited to brief notes in a discussion of severe cases. This study investigated the long-term outcomes in ten individuals who were diagnosed with acute neuroangiostrongyliasis in Hawaii between 2009 and 2017. The study demonstrates a significant number of persons in Hawaii sustain residual symptoms for many years, including troublesome sensory paresthesia (abnormal spontaneous sensations of skin experienced as 'burning, pricking, pins and needles'; also described as allodynia or hyperesthesia) and extremity muscle pains. As a consequence, employment and economic hardships, domestic relocations, and psychological impairments affecting personal relationships occurred. The study summarizes common features of chronic disease, sensory paresthesia and hyperesthesia, diffuse muscular pain, insomnia, and accompanying emotional distress; highlights the frequently unsuccessful endeavours of individuals struggling to find effective treatment; proposes pathogenic mechanisms responsible for prolonged illness including possible reasons for differences in disease presentation in Hawaii compared to Southeast Asia.

Tetraventricular Hydrocephalus Following Eosinophilic Meningitis due to Angiostrongylus cantonensis in a 14-Month-Old Boy From Mayotte: A Case Report

Angiostrongylus cantonensis is endemic in Mayotte, and cases of meningitis due to angiostrongyliasis are regularly diagnosed in young children. In a 14-month-old boy with slow-onset psychomotor regression, brain magnetic resonance imaging revealed communicating hydrocephalus. Reverse transcription polymerase chain reaction for A. cantonensis on cerebrospinal fluid was positive. The evolution was favorable with repeated lumbar punctures and a 2-week treatment with albendazole and high-dose corticosteroids.

Downregulated RPS-30 in Angiostrongylus cantonensis L5 plays a defensive role against damage due to oxidative stress

Background

Eosinophilic meningitis, caused by fifth-stage larvae of the nematode (roundworm) Angiostrongylus cantonensis, is mainly attributed to the contribution of eosinophils to tissue inflammatory responses in helminthic infections. Eosinophils are associated with the killing of helminths via peroxidative oxidation and hydrogen peroxide generated by the dismutation of superoxide produced during respiratory bursts. In contrast, when residing in the host with high level of eosinophils, helminthic worms have evolved to attenuate eosinophil-mediated tissue inflammatory responses for their survival in the hosts. In a previous study we demonstrated that the expression of the A. cantonensis RPS 30 gene (Acan-rps-30) was significantly downregulated in A. cantonensis L5 roundworms residing in cerebrospinal fluid with a high level of eosinophils. Acan-RPS-30 is a protein homologous to the human Fau protein that plays a pro-apoptotic regulatory role and may function in protecting worms from oxidative stress.

Methods

The isolation and structural characterization of Acan-RPS-30 were performed using rapid amplification of cDNA ends (RACE), genome walking and bioinformatics. Quantitative real-time-PCR and microinjection were used to detect the expression patterns of Acan-rps-30. Feeding RNA interference (RNAi) was used to knockdown the apoptosis gene ced-3. Microinjection was performed to construct transgenic worms. An oxidative stress assay was used to determine the functions of Acan-RPS-30.

Results

Our results showed that Acan-RPS-30 consisted of 130 amino acids. It was grouped into clade V with C. elegans in the phylogenetic analysis. It was expressed ubiquitously in worms and was downregulated in both L5 larvae and adult A. cantonensis. Worms expressing pCe-rps30::Acan-rps-30::rfp, with the refractile “button-like” apoptotic corpses, were susceptible to oxidative stress. Apoptosis genes ced-3 and ced-4 were both upregulated in the transgenic worms. The phenotype susceptible to oxidative stress could be converted with a ced-3 defective mutation and RNAi. rps-30^−/− mutant worms were resistant to oxidative stress, with ced-3 and ced-4 both downregulated. The oxidative stress-resistant phenotype could be rescued and inhibited by through the expression of pCe-rps30::Acan-rps-30::rfp in rps-3^−/− mutant worms.

Conclusion

In C. elegans worms, downregulated RPS-30 plays a defensive role against damage due to oxidative stress, facilitating worm survival by regulating downregulated ced-3. This observation may indicate the mechanism by which A. cantonensis L5 worms, with downregulated Acan-RPS-30, survive in the central nervous system of humans from the immune response of eosinophils.

Graphic abstract

The Use of Adjunctive Steroids in Central Nervous Infections

Central nervous system (CNS) infections continue to be associated with significant neurological morbidity and mortality despite various existing therapies. Adjunctive steroid therapy has been employed clinically to reduce inflammation in the treatment of CNS infections across various causative pathogens. Steroid therapy can potentially improve clinical outcomes including reducing mortality rates, provide no significant benefit, or cause worsened outcomes, based on the causative agent of infection. The data on benefits or harms of adjunctive steroid therapy is not consistent in outcome or density through CNS infections, and varies based on the disease diagnosis and pathogen. We summarize the existing literature on the effects of adjunctive steroid therapy on outcome for a number of CNS infections, including bacterial meningitis, herpes simplex virus, West Nile virus, tuberculosis meningitis, cryptococcal meningitis, Angiostrongylus cantonensis, neurocysticercosis, autoimmune encephalitis, toxoplasmosis, and bacterial brain abscess. We describe that while steroid therapy is beneficial and supported in pathogens such as pneumococcal meningitis and tuberculosis, for other diseases, like Listeria monocytogenes and Cryptococcus neoformans they are associated with worse outcomes. We highlight areas of consistent and proven findings and those which need more evidence for supported beneficial clinical use of adjunctive steroid therapy.

Proteomic Insights into the Biology of the Most Important Foodborne Parasites in Europe

Foodborne parasitoses compared with bacterial and viral-caused diseases seem to be neglected, and their unrecognition is a serious issue. Parasitic diseases transmitted by food are currently becoming more common. Constantly changing eating habits, new culinary trends, and easier access to food make foodborne parasites' transmission effortless, and the increase in the diagnosis of foodborne parasitic diseases in noted worldwide. This work presents the applications of numerous proteomic methods into the studies on foodborne parasites and their possible use in targeted diagnostics. Potential directions for the future are also provided.

The spreading of parasites by human migratory activities

The global spread of parasites is unquestionably linked with human activities. Migration in all its different forms played a major role in the introduction of parasites into new areas. In ancient times, mass migrations were the main causes for the spread of parasites while in the recent past and present, emigration, immigration, displacement, external and internal migration, and labor migration were the reasons for the dispersal of parasites. With the advent of seagoing ships, long-distance trading became another important mode of spreading parasites. This review summarizes the spread of parasites using notable examples. In addition, the different hypotheses explaining the arrival of Plasmodium vivax and soil-transmitted helminths in pre-Columbian America are also discussed.

Guidelines for the diagnosis and treatment of neuroangiostrongyliasis: updated recommendations

A subcommittee of the Hawaii Governor's Joint Task Force on Rat Lungworm Disease developed preliminary guidelines for the diagnosis and treatment of neuroangiostrongyliasis (NAS) in 2018 (Guidelines, 2018). This paper reviews the main points of those guidelines and provides updates in areas where our understanding of the disease has increased. The diagnosis of NAS is described, including confirmation of infection by real-time polymerase chain reaction (RTi-PCR) to detect parasite DNA in the central nervous system (CNS). The treatment literature is reviewed with recommendations for the use of corticosteroids and the anthelminthic drug albendazole. Long-term sequelae of NAS are discussed and recommendations for future research are proposed.

First cases of Angiostrongylus cantonensis infection reported in Martinique, 2002-2017

Neuroangiostrongyliasis is a parasitic disease caused by the accidental ingestion of the nematode Angiostrongylus cantonensis in its larval form. Human infection can lead to eosinophilic meningitis, sometimes complicated by life-threatening radiculomyelitis or encephalitis. Although some cases have been reported from other Caribbean Islands, no cases have been diagnosed in Martinique so far. Here, we report the first eight laboratory-confirmed cases of neuroangiostrongyliasis on the island of Martinique, French West Indies, between 1 January 2002 and 31 December 2017. One case was fatal and five resulted in neurological sequelae. The medical community should consider the risk of A. cantonensis infection in patients living in or returning from Martinique.

Angiostrongylus cantonensis Galectin-1 interacts with Annexin A2 to impair the viability of macrophages via activating JNK pathway

BACKGROUND

Angiostrongylus cantonensis can cause severe symptoms of central nervous system infections. In the host, this parasite localizes in the blood and cerebrospinal fluid, and its secreted components can impact immune responses. Our previous study demonstrated that immune responses were inhibited in A. cantonensis-infected mice immunized with Ac-Galectin-1 (AcGal-1). However, the mechanisms by which AcGal-1 regulates the immune responses remain unclear. Macrophages are innate immune cells that rapidly respond to infection. The direct impact of AcGal-1 on macrophages may affect the immune responses.

METHODS

AcGal-1 protein was purified by nickel ion affinity chromatography. The effect of AcGal-1 on the apoptosis of macrophages was detected using CCK-8 assay, flow cytometry and western blot. Macrophage membrane proteins bound to AcGal-1 were obtained using the His-tag-based pull-down assay and identified via mass spectrometry. Co-localization of AcGal-1 and the macrophage membrane protein Annexin A2 was observed by immunofluorescence microscopy, and their interaction was validated by co-immunoprecipitation experiments. SiRNA-mediated knockdown of Annexin A2 was used to determine if AcGal-1-induced macrophage apoptosis required interaction with Annexin A2. The phosphorylation level of apoptotic signal pathway protein was detected by phospho-antibody microarray and western blot.

RESULTS

Our study showed that AcGal-1 caused apoptosis of the macrophages. AcGal-1 increased the expression of apoptosis proteins caspase-3, caspase-9, Bax, but reduced the expression of anti-apoptosis protein Bcl-2. AcGal-1 interacted with the membrane protein Annexin A2, and knockdown of Annexin A2 expression increased Bcl-2 but decreased Bax levels in AcGal-1-treated cells. Moreover, AcGal-1 increased JNK phosphorylation and the inhibition of JNK phosphorylation in AcGal-1-treated cells decreased the expression of caspase-3, -9, Bax and almost restored Bcl-2 to the level observed in control cells.

CONCLUSIONS

AcGal-1 can induce the apoptosis of macrophages by binding to Annexin A2 and activating JNK downstream the apoptotic signaling pathway.

Zoonotic transmission of intestinal helminths in southeast Asia: Implications for control and elimination

Intestinal helminths are extremely widespread and highly prevalent infections of humans, particularly in rural and poor urban areas of low and middle-income countries. These parasites have chronic and often insidious effects on human health and child development including abdominal problems, anaemia, stunting and wasting. Certain animals play a fundamental role in the transmission of many intestinal helminths to humans. However, the contribution of zoonotic transmission to the overall burden of human intestinal helminth infection and the relative importance of different animal reservoirs remains incomplete. Moreover, control programmes and transmission models for intestinal helminths often do not consider the role of zoonotic reservoirs of infection. Such reservoirs will become increasingly important as control is scaled up and there is a move towards interruption and even elimination of parasite transmission. With a focus on southeast Asia, and the Philippines in particular, this review summarises the major zoonotic intestinal helminths, risk factors for infection and highlights knowledge gaps related to their epidemiology and transmission. Various methodologies are discussed, including parasite genomics, mathematical modelling and socio-economic analysis, that could be employed to improve understanding of intestinal helminth spread, reservoir attribution and the burden associated with infection, as well as assess effectiveness of interventions. For sustainable control and ultimately elimination of intestinal helminths, there is a need to move beyond scheduled mass deworming and to consider animal and environmental reservoirs. A One Health approach to control of intestinal helminths is proposed, integrating interventions targeting humans, animals and the environment, including improved access to water, hygiene and sanitation. This will require coordination and collaboration across different sectors to achieve best health outcomes for all.

A Case Report of Slug Ingestion Causing Eosinophilic Meningitis, Papilledema, and Pronounced Motor Weakness in a US Marine

Angiostrongyliasis is the most common cause of eosinophilic meningitis worldwide and is primarily characterized by eosinophilic meningitis, meningoencephalitis, or myelitis. It is caused by ingestion of the nematode Angiostrongylus cantonensis, the rat lungworm (or apple snail). The most common route of infection is by ingestion of parts of the intermediate hosts like mollusks or food contaminated with infective third stage larvae. Following ingestion, the larvae migrate through the intestinal walls into the bloodstream and further into the central nervous system where they cause meningo-encephalo-myelitis and can have a variety of ocular manifestations. We present a case of a Caucasian United States Marine who suffered severe meningo-encephalo-myelitis with papilledema following ingestion of a raw Giant African Snail (Lissachatina lutica) while stationed in Japan. He developed eosinophilic meningoencephalitis, polyneuropathy, motor weakness, and papilledema. We describe the unique clinical features of this disease in our patient.

Magnetic resonance imaging findings and clinical manifestations in cerebral angiostrongyliasis from Dali, China

PURPOSE

To analyze magnetic resonance imaging (MRI) findings and clinical diagnosis and treatment data relating to Angiostrongylus cantonensis infection to gain insight into the disease.

MATERIALS AND METHODS

We retrospectively analyzed the epidemiology, clinical manifestations, diagnosis and treatment data, imaging manifestations, and outcomes of 27 patients who were clinically diagnosed with angiostrongyliasis and who underwent contrast-enhanced brain MRI.

RESULTS

Patients with A. cantonensis infection had a history of eating raw mollusks in the endemic area, and they mainly presented with dizziness and headache of varying degrees and vomiting (n = 7). Laboratory examinations revealed increased peripheral blood and cerebrospinal fluid (CSF) eosinophils, as well as increased CSF protein levels. Brain MRI findings mainly included eosinophilic meningitis, whereas linear or nodular enhancement of the pia mater was observed in enhanced T1-weighted and fluid-attenuated inversion recovery images, accompanied by encephalitis or vasculitis. Meningitis manifested as multiple, thickened flow voids around the meninges, and contrast-enhanced scans showed substantial enhancement in intracranial dilated and hyperplastic blood vessels.

CONCLUSION

The possibility of A. cantonensis infection should be considered in the effective use of albendazole or mebendazole as a treatment. Combining clinical history with laboratory examination is helpful in diagnosing A. cantonensis infection. A final definite diagnosis can be confirmed by detecting larvae in the CSF. The administration of corticosteroids during pathogen therapy can substantially reduce the therapeutic response.

Angiostrongylus cantonensis in travelers: clinical manifestations, diagnosis, and treatment

PURPOSE OF REVIEW

Angiostrongylus cantonensis eosinophilic meningitis is a neglected, yet important emerging disease, which has been increasingly recognized in travelers. In this review, we describe the occurrence of the disease in travelers, sources of infection, clinical manifestations, diagnosis, and currently recommended treatment.

RECENT FINDINGS

Various intermediate hosts and/or paratenic hosts can be the source of infection in humans. Serological tests for antibody may be negative early in the course of the disease but PCR for antigen detection in the CSF has recently been developed and may help to make the diagnosis at an earlier stage. High-dose corticosteroids (e.g. prednisolone 60 mg per day for at least 1-2 weeks) are currently the recommended treatment. Efficacy and safety of antihelminthic drugs for treatment remains controversial because of theoretical concerns that they may worsen the inflammatory response to dead and dying worms. Previous clinical trials were conducted with small numbers of participants and were underpowered. Further well designed clinical trials are urgently needed.

SUMMARY

Awareness about increasing numbers of A. cantonensis eosinophilic meningitis in travelers is very important. Travelers should be advised about possible sources of infection. Diagnosis should be confirmed by antigen or antibody detection in blood or CSF. High-dose corticosteroids are the recommended treatment. The efficacy of various antihelminthic drugs is unproven. A large-scale, double-blind, randomized, controlled trial of antihelminthic drug involving antihelminthic drugs such as albendazole is necessary to prove the efficacy before formally advocating their use on a regular basis.

Diagnostic approach to encephalitis and meningoencephalitis in adult returning travellers

BACKGROUND

Encephalitis and meningoencephalitis are severe, sometime life-threatening infections of the central nervous system. Travellers may be exposed to a variety of neurotropic pathogens.

AIMS

We propose to review known infectious causes of encephalitis in adults acquired outside Europe, and how to identify them.

SOURCES

We used Pubmed and Embase, to search the most relevant publications over the last years.

CONTENT

Microbiologic tests and radiological tools to best identify the causative pathogen in travellers presenting with encephalitis and ME are presented in this narrative review, as well as a diagnostic approach tailored to the visited area and types of exposures.

IMPLICATIONS

This review highlights the diagnostic difficulties inherent to exotic causes of central nervous system infections, and attempts to guide clinicians with respect to which microbiological tests to consider, in addition to brain MRI, when approaching a returning traveller presenting with encephalitis.

Assessment of the kidney and lung as immune barriers and hematopoietic sites in the invasive apple snail Pomacea canaliculata

Knowledge on the immune system of Pomacea canaliculata is becoming increasingly important, because of this gastropod's role as intermediate host and vector of Angiostrongylus cantonensis, the etiologic agent of eosinophilic meningitis in humans and domestic animals. Immune defenses of this gastropod comprise both humoral and cellular components, but they may also involve organs that act as immune barriers to prevent the spread of alien molecules and organisms. Both the kidney and lung are here shown to serve this function, because of (1) their positions in blood circulation, (2) the intricate architecture of their blood spaces, and (3) the proliferative and nodulation reactions of hemocytes to an immune challenge. However, these organs differ in that only the kidney shows permanent hemocyte aggregations. Microcirculation in the kidney was found to flow through an intricate vascular bed containing the permanent aggregations, which occurred either as hemocyte islets anchored by cytoplasmic projections of the renal epithelium or as perivascular accretions. Within 96 h of the injection of yeast cells, hemocyte nodules were formed both in the kidney and lung. Moreover, cell proliferation in renal hemocyte islets was measured by bromodeoxyuridine (BrdU) incorporation. The proportion of BrdU positive nuclei increased 48 h after injection. Signs of nodule regression (apoptotic bodies, lipofuscin-like deposits) and a decrease in the proportion of BrdU positive nuclei were found at 96 h. In addition, the area of renal hemocyte islets was significantly increased 96 h after injection. Nevertheless, the high complexity of the small vascular chambers that constitute the lung's respiratory lamina would also facilitate hemocyte-antigen contacts, required to elicit cellular aggregation, and hence, nodulation. To our knowledge, this paper includes the first quantitative indication of hemocyte proliferation after an immune challenge among Caenogastropoda.

The opposite roles of PAS-5 and Galectin-1 in immune response during the early infection of Angiostrongylus cantonensis

BACKGROUND

Angiostrongylus cantonensis is a human zoonotic nematode parasite. Our previous studies found that PAS-5 and Galectin-1 (Gal-1) proteins of A. cantonensis could be strongly recognized by sera from mice infected with A. cantonensis. In this study, we further evaluated the potential roles of these two proteins in the induction of immune response in mice.

METHODS

Mice were immunized with recombinant PAS-5 or Gal-1 and then challenged with 30 infective A. cantonensis larvae following the last immunization. We then examined the infected mice for changes in serum antibodies and cytokines by ELISA, CD4+ T cells and CD4+CD25+FoxP3+ regulatory T cells (Tregs) by flow cytometry, and tissue damage severity by hematoxylin-eosin (H&E) staining.

RESULTS

Compared with control mice, the PAS-5-immunized mice exhibited increased levels of serum antibodies and cytokines (except for IL-10) at different time points post-infection. PAS-5 immunization promoted significant proliferation of CD4+ T cells, and caused more damage in the brain tissue. Vaccination with Gal-1 inhibited the production of antibodies (except for IgG1) and IFN-γ, but promoted the expression of IL-4 and IL-10. Gal-1 immunization results in significant increases in the levels of CD4+CD25+FoxP3+ Tregs, and mild inflammatory changes.

CONCLUSIONS

Taken together, our findings show that PAS-5 enhances, but Gal-1 inhibits the immune response in the early stage of A. cantonensis infections.

Snail-borne parasitic diseases: an update on global epidemiological distribution, transmission interruption and control methods

Background

Snail-borne parasitic diseases, such as angiostrongyliasis, clonorchiasis, fascioliasis, fasciolopsiasis, opisthorchiasis, paragonimiasis and schistosomiasis, pose risks to human health and cause major socioeconomic problems in many tropical and sub-tropical countries. In this review we summarize the core roles of snails in the life cycles of the parasites they host, their clinical manifestations and disease distributions, as well as snail control methods.

Main body

Snails have four roles in the life cycles of the parasites they host: as an intermediate host infected by the first-stage larvae, as the only intermediate host infected by miracidia, as the first intermediate host that ingests the parasite eggs are ingested, and as the first intermediate host penetrated by miracidia with or without the second intermediate host being an aquatic animal. Snail-borne parasitic diseases target many organs, such as the lungs, liver, biliary tract, intestines, brain and kidneys, leading to overactive immune responses, cancers, organ failure, infertility and even death. Developing countries in Africa, Asia and Latin America have the highest incidences of these diseases, while some endemic parasites have developed into worldwide epidemics through the global spread of snails. Physical, chemical and biological methods have been introduced to control the host snail populations to prevent disease.

Conclusions

In this review, we summarize the roles of snails in the life cycles of the parasites they host, the worldwide distribution of parasite-transmitting snails, the epidemiology and pathogenesis of snail-transmitted parasitic diseases, and the existing snail control measures, which will contribute to further understanding the snail-parasite relationship and new strategies for controlling snail-borne parasitic diseases.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0414-7) contains supplementary material, which is available to authorized users.

Apoptosis and necroptosis of mouse hippocampal and parenchymal astrocytes, microglia and neurons caused by Angiostrongylus cantonensis infection

BACKGROUND

Angiostrongylus cantonensis has been the only parasite among Angiostrongylidae to cause human central nervous system infection characterized by eosinophilic meningitis or meningoencephalitis. The mechanism of the extensive neurological impairments of hosts caused by A. cantonensis larvae remains unclear. The aim of the present study was to investigate apoptosis, necroptosis and autophagy in the brains of mice infected with A. cantonensis, which will be valuable for better understanding the pathogenesis of angiostrongyliasis cantonensis.

METHODS

Functional and histological neurological impairments of brain tissues from mice infected with A. cantonensis were measured by the Morris water maze test and haematoxylin and eosin (H&E) staining, respectively. The transcriptional and translational levels of apoptosis-, necroptosis- and autophagy-related genes were quantified by quantitative real-time polymerase chain reaction (RT-PCR), and assessed by western blot and immunohistochemistry (IHC) analysis. Apoptotic and necroptotic cells and their distributions in infected brain tissues were analysed by flow cytometry and transmission electron microscopy (TEM).

RESULTS

Inflammatory response in the central nervous system deteriorated as A. cantonensis infection evolved, as characterized by abundant inflammatory cell infiltration underneath the meninges, which peaked at 21 days post-infection (dpi). The learning and memory capacities of the mice were significantly decreased at 14 dpi, indicating prominent impairment of their cognitive functions. Compared with those of the control group, the mRNA levels of caspase-3, -4, -6, and RIP3 and the protein levels of caspase-4, cleaved caspase-3, cleaved caspase-6, RIP3, and pRIP3 were obviously elevated. However, no changes in the mRNA or protein levels of FADD, Beclin-1 or LC3B were evident, indicating that apoptosis and necroptosis, but not autophagy, occurred in the brain tissues of mice infected with A. cantonensis. The quantitative RT-PCR, western blot, IHC, flow cytometry and TEM results further revealed the apoptotic and necroptotic microglia, astrocytes and neurons in the parenchymal and hippocampal regions of infected mice.

CONCLUSIONS

To our knowledge, we showed for the first time that A. cantonensis infection causes the apoptosis and necroptosis of microglia and astrocytes in the parenchymal and hippocampal regions of host brain tissues, further demonstrating the pathogenesis of A. cantonensis infection and providing potential therapeutic targets for the management of angiostrongyliasis.

Angiostrongylus cantonensis: An optimized cultivation of this parasitic nematode under laboratory conditions

Angiostrongylus cantonensis (A. cantonensis), a parasitic nematode, is the important neurotropic pathogen which causes human angiostrongyliasis. It has a complex life-cycle and severe parasite-host interaction in contrast to free-living nematode. Establishment of a well-suited life-cycle and in vitro cultivation of A. cantonensis in the laboratory will be one of the key techniques to elucidate the mechanism of parasite-host interaction. However, the low survival and growth rate of worms is still to be the problem. We optimized the known life-cycle of A. cantonensis in the laboratory, showing that small in size, easy to breed, and high compatibility of Biomphalaria straminea precede the common snails as an intermediate host of A. cantonensis. Furthermore, the egg hatching rate in Ham's F-12 medium reached approximately 80% using the eggs of mature female adult worms. We also demonstrated that the survival of larvae could be sustained for more than 30 days by in vitro cultivation of L1 larvae in DMEM with mixed antibiotics (100 units/mL of penicillin G potassium, 50 μg/mL of streptomycin sulfate, and 0.5 μg/mL of amphotericin B) and L3, L4, and L5 larvae in Waymouth's medium with 20% fetal calf serum and mixed antibiotics. Infective L1 and L3 larvae kept high infective rate to the snail and rat after cultivation in these media, respectively. It will provide the basis for studying on genetic manipulations for functional genes, new drug screening, and the mechanism of parasite-host interaction of parasitic nematodes.

Comparative transcriptomic analysis of two important life stages of Angiostrongylus cantonensis: fifth-stage larvae and female adults

The mechanisms involved in the fast growth of Angiostrongylus cantonensis from fifth-stage larvae (L5) to female adults and how L5 breaks through the blood-brain barrier in a permissive host remain unclear. In this work, we compared the transcriptomes of these two life stages to identify the main factors involved in the rapid growth and transition to adulthood. RNA samples from the two stages were sequenced and assembled de novo. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses of 1,346 differentially expressed genes between L5 and female adults was then undertaken. Based on a combination of analytical results and developmental characteristics, we suggest that A. cantonensis synthesizes a large amount of cuticle in L5 to allow body dilatation in the rapid growth period. Products that are degraded via the lysosomal pathway may provide sufficient raw materials for cuticle production. In addition, metallopeptidases may play a key role in parasite penetration of the blood-brain barrier during migration from the brain. Overall, these results indicate that the profiles of each transcriptome are tailored to the need for survival in each developmental stage.

Anti-apoptotic effects of Sonic hedgehog signalling through oxidative stress reduction in astrocytes co-cultured with excretory-secretory products of larval Angiostrongylus cantonensis

Angiostrongylus cantonensis, the rat lungworm, is an important aetiologic agent of eosinophilic meningitis and meningoencephalitis in humans. Co-culturing astrocytes with soluble antigens of A. cantonensis activated the Sonic hedgehog (Shh) signalling pathway and inhibited the apoptosis of astrocytes via the activation of Bcl-2. This study was conducted to determine the roles of the Shh signalling pathway, apoptosis, and oxidative stress in astrocytes after treatment with excretory-secretory products (ESP) from A. cantonensis fifth-stage larvae. Although astrocyte viability was significantly decreased after ESP treatment, the expression of Shh signalling pathway related proteins (Shh, Ptch-1 and Gli-1) was significantly increased. However, apoptosis in astrocytes was significantly decreased after activation of the Shh signalling pathway. Moreover, superoxide and hydrogen superoxide levels in astrocytes were significantly reduced after the activation of Shh pathway signalling due to increasing levels of the antioxidants catalase and superoxide dismutase. These findings indicate that the anti-apoptotic effects of the Shh signalling pathway in the astrocytes of mice infected with A. cantonensis are due to reduced levels of oxidative stress caused by the activation of antioxidants.

Angiostrongylus cantonensis Infection: A Cause of Fever of Unknown Origin in Pediatric Patients

Fever of unknown origin (FUO) in children is frequently caused by infectious diseases. Angiostrongylus cantonensis, while a primary cause of eosinophilic meningitis, is rarely a cause of FUO. We present 2 pediatric cases of FUO caused by Angiostrongylus cantonensis acquired in Houston, Texas, outside its usual geographic distribution.

Angiostrongylus cantonensis: a review of its distribution, molecular biology and clinical significance as a human pathogen

Angiostrongylus cantonensis is a metastrongyloid nematode found widely in the Asia-Pacific region, and the aetiological agent of angiostrongyliasis; a disease characterized by eosinophilic meningitis. Rattus rats are definitive hosts of A. cantonensis, while intermediate hosts include terrestrial and aquatic molluscs. Humans are dead-end hosts that usually become infected upon ingestion of infected molluscs. A presumptive diagnosis is often made based on clinical features, a history of mollusc consumption, eosinophilic pleocytosis in cerebral spinal fluid, and advanced imaging such as computed tomography. Serological tests are available for angiostrongyliasis, though many tests are still under development. While there is no treatment consensus, therapy often includes a combination of anthelmintics and corticosteroids. Angiostrongyliasis is relatively rare, but is often associated with morbidity and sometimes mortality. Recent reports suggest the parasites' range is increasing, leading to fatalities in regions previously considered Angiostrongylus-free, and sometimes, delayed diagnosis in newly invaded regions. Increased awareness of angiostrongyliasis would facilitate rapid diagnosis and improved clinical outcomes. This paper summarizes knowledge on the parasites' life cycle, clinical aspects and epidemiology. The molecular biology of Angiostrongylus spp. is also discussed. Attention is paid to the significance of angiostrongyliasis in Australia, given the recent severe cases reported from the Sydney region.

Optic Neuritis: A Model for the Immuno-pathogenesis of Central Nervous System Inflammatory Demyelinating Diseases

Evidence for the tenuous regulation between the immune system and central nervous system (CNS) can be found with examples of interaction between these organ systems gone awry. Multiple sclerosis (MS) is the prototypical inflammatory disease of the CNS and is characterized by widely distributed inflammatory demyelinating plaques that can involve the brain, spinal cord and/or optic nerves. Optic neuritis (ON), inflammatory injury of the optic nerve that frequently occurs in patients with MS, has been the focus of intense study in part given the readily accessible nature of clinical outcome measures. Exploring the clinical and pathological features of ON in relation to other inflammatory demyelinating conditions of the CNS, namely MS and neuromyelitis optica, provides an opportunity to glean common and distinct mechanisms of disease. Emerging data from clinical studies along with various animal models involving ON implicate innate and adaptive immune responses directed at glial targets, including myelin oligodendrocyte glycoprotein and aquaporin 4. Resolution of inflammation in ON is commonly observed both clinically and experimentally, but persistent nerve injury is also one emerging hallmark of ON. One hypothesis seeking evaluation is that, in comparison to other sites targeted in MS, the optic nerve is a highly specialized target within the CNS predisposing to unique immunologic processes that generate ON. Overall, ON serves as a highly relevant entity for understanding the pathogenesis of other CNS demyelinating conditions, most notably MS.