Angiostrongylus cantonensis Is an Important Cause of Eosinophilic Meningitis in Southern Vietnam

Increased expression of the kynurenine pathway in mice with eosinophilic meningitis caused by Angiostrongylus cantonensis infection

Angiostrongylus cantonensis is the major cause of eosinophilic meningitis worldwide. The imbalance of neurotoxic and neuroprotective metabolites in the kynurenine pathway (KP) have been suggested to contribute to the pathogenesis of central nervous system (CNS) infection. We hypothesized that KP may also be involved in parasitic eosinophilic meningitis. BALB/c mice were orally infected with 40 A. cantonensis L3, intraperitoneal dexamethasone at a dose of 500 µg/kg/day was administered from the seventh day of infection until the end of the study. The Evans blue method was used to analyze blood-brain barrier (BBB) dysfunction, and indoleamine 2,3-dioxygenase (IDO) proteins levels was measured by Western blot, immunohistochemistry (IHC), and immunofluorescence. Tryptophan and kynurenine concentrations were analyzed by IHC and liquid chromatography-tandem mass spectrometry (LC-MS/MS). The concentrations of Evans blue, IDO, tryptophan and kynurenine in the different groups of mice were compared using the nonparametric Kruskal-Wallis test. BBB dysfunction was found in mice with eosinophilic meningitis. The administration of dexamethasone significantly decreased the amount of Evans blue. An increased IDO expression was shown in Western blot, IHC and immunofluorescence following 2-3 weeks infection. Increased tryptophan and kynurenine expressions in the brain and cerebrospinal fluid (CSF) were also found in IHC and LC-MS/MS studies. The administration of dexamethasone significantly decreased the amount of IDO, tryptophan and kynurenine. In conclusion, A. cantonensis infection inducing BBB damage, then increased the influx of tryptophan into CSF. The administration of dexamethasone significantly decreased the amount of IDO, tryptophan and kynurenine.

Screening the Efficacy and Safety of Molluscicides from Three Leaf Extracts of Chimonanthus against the Invasive Apple Snail, Pomacea canaliculata

Pomacea canaliculata, the invasive snail, is a host of the parasitic nematode Angiostrongylus cantonensis, which has adverse effects on the agriculture system and human health. This work evaluated the molluscicidal activity of petroleum ether extracts (PEEs) from three species of Chimonanthus against the snail P. canaliculate. Pcp (PEE of C. praecox) showed the most effective molluscicide activity. Sixty-one compounds were identified by GC-MS and the main components were terpenoids and fatty acids. The half-lethal concentration (LC50) of Pcp at 24 h (0.27 mg/mL) and 48 h (0.19 mg/mL) was used to evaluate the biochemical alterations in snail tissue. These sublethal concentrations caused the levels of alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) activity to increase, while acetylcholinesterase (AChE) activity decreased. Also, under LC50 treatment, several histological changes were observed in the hepatopancreas and foot of the snail compared with the control group. Moreover, the toxic test in rice demonstrated that Pcp has low toxicity. These results suggest that Pcp could be developed as an effective molluscicide for P. canaliculata control.

Environmentally-Friendly Pesticidal Activities of Callicarpa and Karomia Essential Oils from Vietnam and Their Microemulsions

There is an ongoing interest to identify alternative pesticidal agents to avoid the chronic problems associated with synthetic pesticides. Essential oils have shown promise as botanical pest control agents. In the present study, the essential oils of four members of the Lamiaceae (Callicarpa candicans, C. erioclona, C. macrophylla, and Karomia fragrans; Vietnamese names: Nàng nàng, Tu châu lông mem, Tu châu lá to and Cà diện, respectively), obtained from wild populations in Vietnam, have been obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. The essential oils were formulated into microemulsions and the essential oils and their microemulsions were screened for mosquito larvicidal activity against Aedes aegypti, Aedes albopictus, Culex quinquefasciatus, and for molluscicidal activity against Pomacea canaliculata. Atractylone and (E)-caryophyllene dominated the volatiles of C. candicans (CCEO) and C. erioclona (CEEO), while the major component in C. macrophylla (CMEO) and K. fragrans (KFEO) was (E)-caryophyllene. The essential oils and microemulsions of both C. candicans and C. erioclona exhibited excellent larvicidal activity against all three mosquito species (Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus) with LC₅₀ values <10 μg/mL. Additionally, the larvicidal activity of the microemulsions were significantly improved compared with their free essential oils, especially for C. candicans and C. erioclona. All four essential oils and their microemulsions showed excellent molluscicidal activity with LC₅₀ <10 μg/mL. In most cases, the essential oils and microemulsions showed greater pesticidal activity against target organisms than the non-target freshwater fish, Oreochromis niloticus. The in silico studies on physicochemical and ADMET properties of the major components in the studied essential oils were also investigated and most of the compounds possessed a favorable ADMET profile. Computational modeling studies of the studied compounds demonstrated a favorable binding interaction with the mosquito odorant-binding protein target and support atractylone, β-selinene, and caryophyllene oxide as potential inhibitors. Based on the observed pesticidal activities of the essential oils and their microemulsions, the Callicarpa species and K. fragrans should be considered for potential cultivation and further exploration as botanical pesticidal agents.

Molluscicidal Activity of Compounds From the Roots of Aralia armata Against the Golden Apple Snail (Pomacea canaliculata)

Background: Aralia armata (Araliaceae) is considered to exhibit effective molluscicidal activity, however, the relationship between the chemical components and molluscicidal activity has not been clearly elucidated. This research attempts to decipher these correlations among the 15 compounds isolated from Vietnam-grown A. armata roots against the freshwater snail, Pomacea canaliculata, a gastropod causing severe damage in agricultural production. Methods: Fifteen saponins were isolated from the methanol root extract of A. armata using chromatographic methods and were identified using spectroscopic techniques. The compounds were screened for molluscicidal activity against P. canaliculata, as well as toxicity against brine shrimp ( Artemia sp.) and phytotoxicity against rice germination and growth. Results: The saponin compounds exhibited extraordinary inhibition of P. canaliculata with LC50 values ranging from 7.90 to 17.50 µg/mL. Notably, the active compounds from A. armata exhibit safety for both nontarget aquatic animals, specifically Artemia sp. with LC50 values between 148.55 and 193.22 µg/mL, and the growth and development of Oryza sativa L. plants showed very little difference compared with the negative control . A molecular docking analysis indicated P. canaliculata acetylcholinesterase (PcAChE) and the actin-binding protein villin (PcVillin) to be potential biomolecular targets of the A. armata saponins. Conclusion: The present experimental and in silico data illustrate the potential of A. armata in agricultural applications.

Calycosin attenuates Angiostrongylus cantonensis-induced parasitic meningitis through modulation of HO-1 and NF-κB activation

Angiostrongylus cantonensis causes a form of parasitic meningitis in humans. Albendazole (ABZ) kills nematode larvae in the brain. However, dead larvae can trigger a severe inflammatory response, resulting in brain damage. Accumulating evidence suggests that calycosin represents a potential anti-inflammatory therapeutic candidate. In this study, we investigated the combined effects of ABZ and calycosin in angiostrongyliasis caused by A. cantonensis in BALB/c mice. Inflammatory mediators (such as phospho-nuclear factor-κB, cyclooxygenase-2, matrix metalloproteinase-9, tumour necrosis factor-α and interleukin-1β) are associated with the development of meningitis and immune inflammatory reactions. We found that A. cantonensis significantly induces inflammatory mediator production and increases the blood–brain barrier (BBB) permeability. However, co-administration of both ABZ and calycosin markedly suppressed meningitis and inflammatory mediator production and decreased the BBB permeability compared to treatment with a single drug. Furthermore, calycosin and ABZ plus calycosin treatment facilitated production of the antioxidant haem oxygenase-1 (HO-1). Moreover, co-therapy with ABZ and calycosin failed to mitigate angiostrongyliasis in the presence of tin-protoporphyrin IX, an HO-1-specific inhibitor. This finding suggests that the beneficial effects of ABZ plus calycosin treatment on the regulation of inflammation are mediated by the modulation of HO-1 activation. The present results provide new insights into the treatment of human angiostrongyliasis using co-therapy with ABZ and calycosin.

Clinical Efficacy and Safety of Albendazole and Other Benzimidazole Anthelmintics for Rat Lungworm Disease (Neuroangiostrongyliasis): A Systematic Analysis of Clinical Reports and Animal Studies

The safety and efficacy of benzimidazole anthelmintics for the treatment of rat lungworm disease (neuroangiostrongyliasis) have been questioned regardless of numerous experimental animal studies and clinical reports. In this review, 40 of these experimental animal studies and 104 clinical reports are compiled with a focus on albendazole. Among the 144 articles involving an estimated 1034 patients and 2561 animals, 4.1% were inconclusive or vague regarding the use of benzimidazoles. Of the remaining 138 articles, 90.5% found benzimidazoles to be safe and effective (885 patients, 2530 animals), 4.3% as safe but ineffective (73 patients, 3 animals), and 5.0% caused adverse reactions (7 patients, 28 animals). Among those clinical reports that described a confirmed diagnosis of neuroangiostrongyliasis in which albendazole monotherapy was used, 100% reported high efficacy (743 patients, 479 animals). In those where albendazole-corticosteroid co-therapy was used, 97.87% reported it to be effective (323 patients, 130 animals).

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.

Proteogenomics Reveals Orthologous Alternatively Spliced Proteoforms in the Same Human and Mouse Brain Regions with Differential Abundance in an Alzheimer's Disease Mouse Model

Alternative splicing (AS) may increase the number of proteoforms produced by a gene. Alzheimer's disease (AD) is a neurodegenerative disease with well-characterized AS proteoforms. In this study, we used a proteogenomics strategy to build a customized protein sequence database and identify orthologous AS proteoforms between humans and mice on publicly available shotgun proteomics (MS/MS) data of the corpus callosum (CC) and olfactory bulb (OB). Identical proteotypic peptides of six orthologous AS proteoforms were found in both species: PKM1 (gene PKM/Pkm), STXBP1a (gene STXBP1/Stxbp1), Isoform 3 (gene HNRNPK/Hnrnpk), LCRMP-1 (gene CRMP1/Crmp1), SP3 (gene CADM1/Cadm1), and PKCβII (gene PRKCB/Prkcb). These AS variants were also detected at the transcript level by publicly available RNA-Seq data and experimentally validated by RT-qPCR. Additionally, PKM1 and STXBP1a were detected at higher abundances in a publicly available MS/MS dataset of the AD mouse model APP/PS1 than its wild type. These data corroborate other reports, which suggest that PKM1 and STXBP1a AS proteoforms might play a role in amyloid-like aggregate formation. To the best of our knowledge, this report is the first to describe PKM1 and STXBP1a overexpression in the OB of an AD mouse model. We hope that our strategy may be of use in future human neurodegenerative studies using mouse models.

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.

Il4ra-independent vaginal eosinophil accumulation following helminth infection exacerbates epithelial ulcerative pathology of HSV-2 infection

How helminths influence the pathogenesis of sexually transmitted viral infections is not comprehensively understood. Here, we show that an acute helminth infection (Nippostrongylus brasiliensis [Nb]) induced a type 2 immune profile in the female genital tract (FGT). This leads to heightened epithelial ulceration and pathology in subsequent herpes simplex virus (HSV)-2 infection. This was IL-5-dependent but IL-4 receptor alpha (Il4ra) independent, associated with increased FGT eosinophils, raised vaginal IL-33, and enhanced epithelial necrosis. Vaginal eosinophil accumulation was promoted by IL-33 induction following targeted vaginal epithelium damage from a papain challenge. Inhibition of IL-33 protected against Nb-exacerbated HSV-2 pathology. Eosinophil depletion reduced IL-33 release and HSV-2 ulceration in Nb-infected mice. These findings demonstrate that Nb-initiated FGT eosinophil recruitment promotes an eosinophil, IL-33, and IL-5 inflammatory circuit that enhances vaginal epithelial necrosis and pathology following HSV-2 infection. These findings identify a mechanistic framework as to how helminth infections can exacerbate viral-induced vaginal pathology.

Lantana camara Essential Oils from Vietnam: Chemical Composition, Molluscicidal, and Mosquito Larvicidal Activity

Lantana camara is a troublesome invasive plant introduced to many tropical regions, including Southeast Asia. However, the plant does hold promise as a source of essential oils that may be explored for potential use. Fresh water snails such as Pomacea canaliculata, Gyraulus convexiusculus, and Tarebia granifera can be problematic agricultural pests as well as hosts for parasitic worms. Aedes and Culex mosquitoes are notorious vectors of numerous viral pathogens. Control of these vectors is of utmost importance. In this work, the essential oil compositions, molluscicidal, and mosquito larvicidal activities of four collections of L. camara from north-central Vietnam have been investigated. The sesquiterpene-rich L. camara essential oils showed wide variation in their compositions, not only compared to essential oils from other geographical locations (at least six possible chemotypes), but also between the four samples from Vietnam. L. camara essential oils showed molluscicidal activities comparable to the positive control, tea saponin, as well as other botanical agents. The median lethal concentrations (LC₅₀ ) against the snails were 23.6-40.2 μg/mL (P. canaliculata), 7.9-29.6 μg/mL (G. convexiusculus), and 15.0-29.6 μg/mL (T. granifera). The essential oils showed good mosquito larvicidal activities with 24-h LC₅₀ values of 15.1-29.0 μg/mL, 26.4-53.8 μg/mL, and 20.8-59.3 μg/mL against Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus, respectively. The essential oils were more toxic to snails and mosquito larvae than they were to the non-target water bug, Diplonychus rusticus (24-h LC₅₀ =103.7-162.5 μg/mL). Sesquiterpene components of the essential oils may be acting as acetylcholinesterase (AChE) inhibitors. These results suggest that the invasive plant, L. camara, may be a renewable botanical pesticidal agent.

Meningitis patients with Angiostrongylus cantonensis may present without eosinophilia in the cerebrospinal fluid in northern Vietnam

Background

Eosinophilic meningitis (EM) is a rare clinical syndrome caused by both infectious and noninfectious diseases. In tropical pacific countries, Angiostrongylus cantonensis is the most common cause. However, the EM definition varies in the literature, and its relation to parasitic meningitis (PM) remains unclear.

Methodology/Principal findings

Adult and adolescent patients of 13 years old or above with suspected central nervous system (CNS) infections with abnormal CSF findings were prospectively enrolled at a tertiary referral hospital in Hanoi, Vietnam from June 2012 to May 2014. Patients with EM or suspected PM (EM/PM) were defined by the presence of either ≥10% eosinophils or an absolute eosinophil cell counts of ≥10/mm³ in the CSF or blood eosinophilia (>16% of WBCs) without CSF eosinophils. In total 679 patients were enrolled: 7 (1.03%) had ≥10% CSF eosinophilia, 20 (2.95%) had ≥10/mm³ CSF eosinophilia, and 7 (1.03%) had >16% blood eosinophilia. The patients with ≥10% CSF eosinophilia were significantly younger (p = 0.017), had a lower body temperature (p = 0.036) than patients with ≥10/mm³ CSF eosinophilia among whom bacterial pathogens were detected in 72.2% (13/18) of those who were tested by culture and/or PCR. In contrast, the characteristics of the patients with >16% blood eosinophilia resembled those of patients with ≥10% CSF eosinophilia. We further conducted serological tests and real-time PCR to identify A. cantonensis. Serology or real-time PCR was positive in 3 (42.8%) patients with ≥10% CSF eosinophilia and 6 (85.7%) patients with >16% blood eosinophilia without CSF eosinophils but none of patients with ≥10/mm³ CSF eosinophilia.

Conclusions

The etiology of PM in northern Vietnam is A. cantonensis. The eosinophil percentage is a more reliable predictor of parasitic EM than absolute eosinophil count in the CSF. Patients with PM may present with a high percentage of eosinophils in the peripheral blood but not in the CSF.

Eosinophilic meningitis (EM) is a rare meningitis accompanied by eosinophils in the CSF and caused by multiple etiologies. Angiostrongylus cantonensis, which is a rat lungworm parasite, is the most common cause in tropical Asia. Previous papers have defined EM as CSF eosinophils ≥10% or CSF eosinophils ≥10/mm³. However, the relationship of EM to parasitic meningitis (PM) remains unclear. This prospective study enrolled 679 patients with suspected CNS infection who were admitted to a tertiary referral hospital in Hanoi, Vietnam from June 2012 to May 2014. The characteristics of patients with ≥10% CSF eosinophilia resembled those of patients with >16% blood eosinophilia without CSF eosinophils, whereas those of patients with ≥10/mm³ CSF eosinophilia were comparable with those of patients with typical bacterial meningitis. Serology or real-time PCR for A. cantonensis was positive in 3 out of 7 patients with ≥10% CSF eosinophilia and 6 out of 7 patients with > 16% blood eosinophilia without CSF eosinophils but none of patients with ≥10/mm³ CSF eosinophilia. The percentage, in contrast to the absolute eosinophil count in CSF, is reliable for predicting parasitic EM. Patients with PM may present with eosinophilia in the peripheral blood but not in the CSF.

Negative impacts of invasive predators used as biological control agents against the pest snail Lissachatina fulica: the snail Euglandina ‘rosea’ and the flatworm Platydemus manokwari

Since 1955 snails of the Euglandina rosea species complex and Platydemus manokwari flatworms were widely introduced in attempted biological control of giant African snails (Lissachatina fulica) but have been implicated in the mass extinction of Pacific island snails. We review the histories of the 60 introductions and their impacts on L. fulica and native snails. Since 1993 there have been unofficial releases of Euglandina within island groups. Only three official P. manokwari releases took place, but new populations are being recorded at an increasing rate, probably because of accidental introduction. Claims that these predators controlled L. fulica cannot be substantiated; in some cases pest snail declines coincided with predator arrival but concomitant declines occurred elsewhere in the absence of the predator and the declines in some cases were only temporary. In the Hawaiian Islands, although there had been some earlier declines of native snails, the Euglandina impacts on native snails are clear with rapid decline of many endemic Hawaiian Achatinellinae following predator arrival. In the Society Islands, Partulidae tree snail populations remained stable until Euglandina introduction, when declines were extremely rapid with an exact correspondence between predator arrival and tree snail decline. Platydemus manokwari invasion coincides with native snail declines on some islands, notably the Ogasawara Islands of Japan, and its invasion of Florida has led to mass mortality of Liguus spp. tree snails. We conclude that Euglandina and P. manokwari are not effective biocontrol agents, but do have major negative effects on native snail faunas. These predatory snails and flatworms are generalist predators and as such are not suitable for biological control.

Seroprevalence of Tissue and Luminal Helminths among Patients in Hanoi Medical University Hospital, Vietnam, 2018

A serological survey was performed using ELISA to estimate the prevalence of tissue and luminal helminthic infections among hospital patients in Hanoi region, Vietnam. An overall seroprevalence of tissue and luminal helminthiases was 64.0% (95% CI 61.2–66.8) among 1,120 patients who visited Hanoi Medical University Hospital, Vietnam in 2018. The highest seroprevalence was observed against Toxocara spp. (59.0%), followed by Strongyloides stercoralis (46.3%), Gnathostoma spp. (25.5%), cysticercus (12.8%), Angiostrongylus cantonensis (10.5%), Fasciola spp. (11.1%), and Clonorchis sinensis (8.7%). Mono-infection by one species (11.1%) was lower than multiple infections (53.0%) (P<0.05). The seroprevalence in males (59.3%) was lower than in females (66.2%) but not statistically significant (P>0.05). Children (<15 years) revealed lower seroprevalence (34.0%) than adults (68.4%), and the age group 51–70 years revealed the highest seroprevalence (76.0%). Among the seropositive patients, eosinophilia (≥8.0%) was noted in 80.2%. The present results suggested active transmission of various tissue and luminal helminths among people in Hanoi, Vietnam.

Internal parasitic burdens in brown rats (Rattus norvegicus) from Grenada, West Indies

This study identified the endoparasites in Brown rat (Rattus norvegicus) during May to July 2017 in Grenada, West Indies. A total of 162 rats, 76 females and 86 males were trapped from St. George and St. David parishes in Grenada. The collected fecal samples were examined for parasitic eggs and/or oocysts using simple fecal flotation technique. Adult parasites found in the intestinal tract were examined for identification. The overall prevalence of intestinal parasites among rats was 79 %.

Ten helminth species were recovered, several of which were reported for the first time in rodents in Grenada. The internal parasites consist of seven nematodes (Angiostrongylus spp., Nippostrongylus braziliensis, Heterakis spumosa, Strongyloides ratti, Aspiculuris tetraptera, Syphacia spp. and Protospirura spp.), one cestode (Hymenolepsis diminuta), one acanthocephalan (Moniliformis moniliformis) and one protozoa species (Eimeria spp.). The most prevalent zoonotic species were Angiostrongylus spp. (35.2%), Hymenolepsis diminuta (7.4%) and Moniliformis moniliformis (3.1%). Several nonzoonotic endoparasites; which included Nippostrongylus braziliensis (50.6%), Heterakis spumosa (15.4%), Strongyloides ratti (43.2%), Aspiculuris tetraptera (2.5%), Syphacia spp. (1.9%), Protospirura spp. (1.2%) and Eimeria spp. (4.7%) were also identified. The most prevalent parasites were Nippostrongylus brasiliensis (50.6%), Strongyloides ratti (43.2%) and Angiostrongylus spp. (35.2%). Co-infections occurred with up to six species per rat showing different combinations of parasitic infections.

Invasive Pomacea snails as important intermediate hosts of Angiostrongylus cantonensis in Laos, Cambodia and Vietnam: Implications for outbreaks of eosinophilic meningitis

The rat lungworm Angiostrongylus cantonensis causes human eosinophilic meningitis and it is endemic in Southeast Asia, but little is known about its distribution in Laos, Cambodia and Vietnam. We conducted a multi-country survey for A. cantonensis in these countries to estimate its prevalence in snails along the Mekong River and the east coast of Vietnam. We identified Angiostrongylus species by morphological and molecular analysis. We found A. cantonensis in the invasive snail, Pomacea spp. The wide accessibility of Pomacea snails, along with their infection by A. cantonensis, indicates that this snail species could be used in surveillance for preventing outbreaks of eosinophilic meningitis.

Molluscicidal activity of Solidago canadensis L. extracts on the snail Pomacea canaliculata Lam

Extracts from the aerial parts of Solidago canadensis L. were evaluated for molluscicidal activity against Pomacea canaliculata Lam. using an immersion bioassay method. The petroleum ether fraction of the ethanolic extract (PEEE) from S. canadensis exhibited strong molluscicidal activity. The PEEE mode of action in the hepatopancreas tissue of P. canaliculata was tested at several concentrations. Biochemical parameters, namely, soluble sugar content, protein, malondialdehyde (MDA), acetylcholinesterase (AChE) activity, alanine aminotransferase (ALT), and aspartate transaminase (AST) were significantly decreased or increased after exposure to PEEE for 48 h (p<0.05). Histological assessment results showed that hepatopancreas tissue structure was destroyed by exposure to PEEE. Gas chromatography-mass spectrometry analysis (GC-MS) was used to identify 15 compounds that could contribute to the molluscicidal efficacy of the PEEE. Molluscicidal assay, biochemical tests and histological assessments suggest that the PEEE from S. canadensis has potential utility as a molluscicide.

Angiostrongylus cantonensis DNA in Cerebrospinal Fluid of Persons with Eosinophilic Meningitis, Laos

Definitive identification of Angiostrongylus cantonensis parasites from clinical specimens is difficult. As a result, regional epidemiology and burden are poorly characterized. To ascertain presence of this parasite in patients in Laos with eosinophilic meningitis, we performed quantitative PCRs on 36 cerebrospinal fluid samples; 4 positive samples confirmed the parasite’s presence.

Chi3l3: a potential key orchestrator of eosinophil recruitment in meningitis induced by Angiostrongylus cantonensis

BACKGROUND

Angiostrongylus cantonensis, an important foodborne parasite, can induce serious eosinophilic meningitis in non-permissive hosts, such as mouse and human. However, the characteristics and mechanisms of the infection are still poorly understood. This study sought to determine the key molecules and its underlying mechanism in inducing brain eosinophilic infiltration caused by Angiostrongylus cantonensis.

METHODS

Mathematical models were established for prediction of significantly changing genes and the functional associated protein with RNA-seq data in Angiostrongylus cantonensis infection. The expression level of Chi3l3, the predicted key molecule, was verified using Western blotting and real-time quantitative PCR. Critical cell source of Chi3l3 and its relationship with eosinophils were identified with flow cytometry, immunohistochemistry, and further verified by macrophage depletion using liposomal clodronate. The role of soluble antigens of Angiostrongylus cantonensis in eosinophilic response was identified with mice airway allergy model by intranasal administration of Alternaria alternate. The relationship between Chi3l3 and IL-13 was identified with flow cytometry, Western blotting, and Seahorse Bioscience extracellular flux analyzer.

RESULTS

We analyzed the skewed cytokine pattern in brains of Angiostrongylus cantonensis-infected mice and found Chi3l3 to be an important molecule, which increased sharply during the infection. The percentage of inflammatory macrophages, the main source of Chi3l3, also increased, in line with eosinophils percentage in the brain. Network analysis and mathematical modeling predirect a functional association between Chi3l3 and IL-13. Further experiments verified that the soluble antigen of Angiostrongylus cantonensis induce brain eosinophilic meningitis via aggravating a positive feedback loop between IL-13 and Chi3l3.

CONCLUSIONS

We present evidences in favor of a key role for macrophave-derived Chi3l3 molecule in the infection of Angiostrongylus cantonensis, which aggravates eosinophilic meningitis induced by Angiostrongylus cantonensis via a IL-13-mediated positive feedback loop. These reported results constitute a starting point for future research of angiostrongyliasis pathogenesis and imply that targeting chitinases and chitinase-like-proteins may be clinically beneficial in Angiostrongylus cantonensis-induced eosinophilic meningitis.

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.

Study on the tolerance and adaptation of rats to Angiostrongylus cantonensis infection

Angiostrongylus cantonensis (A. cantonensis) is the most common infectious agent causing eosinophilic meningitis. As an important food-borne parasitic disease, angiostrongyliasis cantonensis is an emerging infectious disease which brings severe harm to central nerve system of human. Rat, one of the few permissive hosts of A. cantonensis known to date, plays an indispensable role in the worm's life cycle. However, the tolerance and adaptation of rat to A. cantonensis infection is rarely understood. In this study, we infected rats with different numbers the third stage larvae (L3) of A. cantonensis and explored their tolerance through analysis on survival curve, neurological function score, and detection of pathological damages in organs including the brain, lung, and heart of the animals. Results indicated that rats' survival condition worsens, and body weight dropped more significantly as more worms were used for infection. Death appeared in groups infected with 80 and more A. cantonesnsis per rat. Morris water maze revealed that the neurological function of rats damaged gradually with increasing infection number of A. cantonensis larvae. When the number of infected parasite exceeded 240 per animal, rats showed significant neurological impairments. Collection of A. cantonensis from rat lung after 35 days of infection implied an upper limit for worm entry, and the average length of worm was inversely proportional to the infection amount, while the ratio between female and male worms was positively related to the infection number. The degree of pulmonary and cardiac inflammation was proportional to the infection number of A. cantonensis. Meanwhile, there existed considerable amount of adult worms in rat's right atrium and right ventricle, leading to a right heart myocardial inflammation. The present study firstly reports the tolerance and adaptation of rat, a permissive host of A. cantonensis to its infection, which will not only provide accurate technical parameters for maintaining A. cantonensis life cycle under laboratory conditions but also help unveil the underlying mechanism of the distinct pathological outcomes in the permissive and non-permissive hosts with A. cantonensis infection.