Angiostrongylus cantonensis Meningitis and Myelitis, Texas, USA

Immunodiagnostic Detection of Angiostrongylus cantonensis Exposure on Hawaii Island Using Isogeographic 31-kDa Antigen

Angiostrongylus cantonensis is the leading cause of neuroangiostrongyliasis worldwide, and east Hawaii Island is a hotspot for the disease in the United States. A combination of glycoproteins with molecular weight of 31 kDa has been used as antigen to evaluate antibody response in human serum samples in Thailand with high specificity and sensitivity. In a previous pilot study, the Thailand-isolated 31-kDa proteins showed efficacy in dot-blot tests using serum samples from 435 human volunteers on Hawaii Island. However, we hypothesized that native antigen isolated from Hawaii A. cantonensis may exhibit higher specificity than the Thailand-isolated 31-kDa antigen due to potential minor variation in epitopes between isolates. In this study, 31-kDa glycoproteins were isolated by sodium dodecyl-sulfate polyacrylamide gel electrophoresis from adult A. cantonensis nematodes collected from rats captured on east Hawaii Island. The resultant proteins were purified by electroelution, pooled, bioanalyzed, and quantified. A subset of 148 samples from human participants of the original cohort of 435 was consented for this study, including 12 of the original 15 clinically diagnosed participants. Results of ELISA using the Hawaii-isolated 31-kDa antigen were compared with results of the same serum samples previously tested with both crude Hawaii antigen ELISA and Thailand 31-kDa antigen dot blot. This study shows a seroprevalence in the general population of East Hawaii Island of 25.0%, similar to previous findings of 23.8% seroprevalence in this cohort using crude antigen from Hawaii A. cantonensis and 26.5% using Thailand 31-kDa antigen.

Epidemiological, clinical and laboratory aspects of Angiostrongylus cantonensis infection: an integrative review

This integrative literature review study analyzes the findings of the last 5 years of the parasite Angiostrongylus cantonensis. It is known that this nematode is found in the pulmonary arteries of rats, where it remains as a definitive host. From mice, the cycle spreads to animals, such as snails, which in contact with humans can trigger the disease. In humans, the parasite causes several neurological, abdominal manifestations and mainly meningitis. Based on the review of studies, its epidemiology shows worldwide distribution, although there are endemic cases for this parasite, such as asian countries. Laboratory findings generally showed altered CSF with turbidity, increased protein and eosinophilia, which generated meningeal signs in the patient, moreover MRI exams showed multiple alterations. Rare findings of the nematode in the eyeball, lung and signs of peritoneal inflammation were reported, which requires further studies to understand the whole pathophysiology. Finally, conservative treatment based on anthelmintics and anti-inflammatories brought good responses, although there are reports of deaths, which demonstrates the importance in the prevention and therapy of this disease.

Angiostrongylus cantonensis in a Red Ruffed Lemur at a Zoo, Louisiana, USA

A red ruffed lemur (Varecia rubra) from a zoo in Louisiana, USA, was euthanized for worsening paresis. Brain and spinal cord histology identified eosinophilic meningoencephalomyelitis with intralesional adult Angiostrongylus sp. nematodes. PCR and sequencing confirmed A. cantonensis infection, indicating this parasite constitutes an emerging zoonosis in the southeastern United States.

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).

Corticosteroid treatment reduces headache in eosinophilic meningitis: a systematic review

Background:

Eosinophilic meningitis (EOM) is an emerging parasitic disease that can be found worldwide, of which acute severe headache is a presenting symptom. Although such headaches may persist for up to 2 months, studies have found corticosteroid to be effective in reducing this symptom. As the most recent systematic review was published in 2015, the aim of this study was to provide a more up-to-date examination of the role of corticosteroids in EOM.

Methods:

We included randomized controlled trials of corticosteroid treatment for EOM regardless of comparators. Research articles published in five databases were searched and evaluated. The primary outcome was headache, which was compared among various treatment regimens.

Results:

We found a total of 257 articles after duplication removal. Of those, two met the study criteria. According to these studies, oral prednisolone alone or in a combination of albendazole resulted in fewer patients with headache after a 2-week course of treatment compared with placebo (maximum of 9.1% vs. 45.5%). The duration of headache was also shorter in the prednisolone arm vs. placebo (maximum of 5 vs. 13 days). There were no serious side effects reported.

Conclusion:

A 2-week course of treatment with oral corticosteroid with or without albendazole reduced headaches in patients with EOM.

Angiostrongylus cantonensis (rat lungworm) in Florida, USA: current status

Angiostrongylus cantonensis has been found in Florida, USA, from the panhandle in the north to Miami and surrounding areas in the southern parts of the state, in both definitive and intermediate hosts in a limited studies completed in 2015. Additional studies have identified this parasite in a variety of intermediate hosts, both native and non-native gastropod species, with new host species recorded. Many areas in Florida with higher A. cantonensis prevalence were those with a high human population density, which suggests it is a matter of time before human infections occur in Florida. Case reports in the state currently involve non-human primates and include a gibbon and orangutan in Miami. Here, we report the current status of A. cantonensis in the state, as well as the infection in a capuchin monkey and presumptive infection in a red ruffed lemur in Gainesville, Florida.

In vitro efficacy of anthelmintics on Angiostrongylus cantonensis L3 larvae

Angiostrongylus cantonensis is the leading cause of eosinophilic meningitis worldwide, with life-threatening complications if not managed correctly. Previous in vitro studies have utilized change in motility patterns of adult female worms to assess the efficacy of anthelmintics qualitatively. However, it is the third stage larvae (L3) that are infectious to humans. With differential staining using propidium iodide penetration as the indicator of death, we can distinguish between dead and live larvae. This assay has enabled us to quantify the in vitro efficacy of nine clinically established anthelmintics on A. cantonensis L3. All drugs were tested at a 1 mm concentration. Piperazine and niclosamide were ineffective in inducing larval death; however, albendazole sulfoxide, pyrantel pamoate, diethylcarbamazine, levamisole and praziquantel were effective as compared to unexposed controls (P < 0.05). Ivermectin and moxidectin did not induce significant levels of mortality, but they considerably reduced larval motility almost immediately. This study indicates the need for further in vivo studies to determine the optimal dose and time frame for post-infection treatment with anthelmintics that demonstrated efficacy.

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.

Review of Cases of Angiostrongyliasis in Hawaii, 2007-2017

Angiostrongyliasis, caused by the Angiostrongylus cantonensis roundworm, became reportable in the state of Hawaii in 2007. We confirmed 82 reported cases between 2007 and 2017. There was a median of seven cases per year, and the majority (57%) of cases occurred between January and April. Most (83%) cases were found on the island of Hawaii, with geographic information system (GIS) analysis identifying hot spots on the east side of the island. However, cases were identified on the other major islands as well, suggesting the risk of exposure is present statewide. Comparisons of cases from 2007 to 2017 with cases from previous assessments found no statistical differences in cerebrospinal fluid results, peripheral blood results, or ages of cases. However, differences in geographic distribution of the cases were statistically significant. Improved testing and increasing awareness of the disease have contributed to our efforts to better understand the general risk factors and modes of transmission present in Hawaii and also helped improve our prevention efforts, although we still do not fully understand the specific causes of cases being concentrated in certain parts of the state over others. Continued outreach efforts, including public forums and publication of preliminary clinical guidelines, aim to inform and improve our public health response and efforts to prevent angiostrongyliasis.

The genetic basis of adaptive evolution in parasitic environment from the Angiostrongylus cantonensis genome

Angiostrongylus cantonensis (rat lungworm) is the etiological agent of angiostrongyliasis, mainly causing eosinophilic meningitis or meningoencephalitis in human. Although the biology of A. cantonensis is relatively well known, little is understood about the mechanisms of the parasite’s development and survival in definitive hosts, or its adaptation to a broad range of snail intermediate hosts. Here, we generate a high-quality assembly of a well-defined laboratory strain of A. cantonensis from Guangzhou, China, by using Illumina and PacBio sequencing technologies. We undertake comparative analyses with representative helminth genomes and explore transcriptomic data throughout key developmental life-cycles of the parasite. We find that part of retrotransposons and gene families undergo multiple waves of expansions. These include extracellular superoxide dismutase (EC-SOD) and astacin-like proteases which are considered to be associated with invasion and survival of the parasite. Furthermore, these paralogs from different sub-clades based on phylogeny, have different expression patterns in the molluscan and rodent stages, suggesting divergent functions under the different parasitic environment. We also find five candidate convergent signatures in the EC-SOD proteins from flukes and one sub-clade of A. cantonensis. Additionally, genes encoding proteolytic enzymes, involved in host hemoglobin digestion, exhibit expansion in A. cantonensis as well as two other blood-feeding nematodes. Overall, we find several potential adaptive evolutionary signatures in A. cantonensis, and also in some other helminths with similar traits. The genome and transcriptomes provide a useful resource for detailed studies of A. cantonensis-host adaptation and an in-depth understanding of the global-spread of angiostrongyliasis.

Angiostrongylus cantonensis, rat lungworm, is a common pathogen that causes human eosinophilic meningitis via eating contaminated food. Human angiostrongyliasis has been reported globally. This worm has a complex life-cycle, which includes an especially wide range of snails as intermediate hosts, making it more difficult to eradicate. In this study, we sequenced the genome and transcriptome, and performed comparative analyses to study the potential genetics of its biology using short-read and long-read sequencing technologies. We revealed some potential adaptive evolution in the genome, such as the expansion of retrotransposons and gene families encoding antioxidant enzymes, invasion, migration and digestion related proteases. Specifically, we found a potential clue suggesting convergent evolution of EC-SODs in Angiostrongylus and flukes, all of which require snails as intermediate hosts. These results provide an abundant data resource to study the biology and evolution of A. cantonensis and showed some potential targets against A. cantonensis and helminths with similar traits.

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.

Infectious Myelopathies

Infectious diseases are an important cause of spinal cord dysfunction. Infectious myelopathies are of growing concern given increasing global travel and migration and expanding prevention and treatment with vaccinations, antibiotics, and antiretrovirals. Clinicians must recognize these pathologies because outcomes can dramatically improve with prompt diagnosis and management. We provide a complete review of the most frequent infectious agents that can affect the spinal cord. For each pathogen we describe epidemiology, pathophysiology, anatomic location, characteristic clinical syndromes, diagnostic approach, treatment, and prognosis. The review includes spinal imaging from selected cases.

Infectious Myelopathies

PURPOSE OF REVIEW

This article reviews bacterial, viral, fungal, and parasitic pathogens associated with myelopathy. Infectious myelopathies may be due to direct infection or parainfectious autoimmune-mediated mechanisms; this article focuses primarily on the former.

RECENT FINDINGS

Some microorganisms exhibit neurotropism for the spinal cord (eg, enteroviruses such as poliovirus and flaviviruses such as West Nile virus), while others are more protean in neurologic manifestations (eg, herpesviruses such as varicella-zoster virus), and others are only rarely reported to cause myelopathy (eg, certain fungal and parasitic infections). Individuals who are immunocompromised are at increased risk of disseminated infection to the central nervous system. Within the last few years, an enterovirus D68 outbreak has been associated with cases of acute flaccid paralysis in children, and emerging Zika virus infection has been concurrent with cases of acute flaccid paralysis due to Guillain-Barré syndrome, although cases of myelitis have also been reported. Associated pathogens differ by geographic distribution, with myelopathies related to Borrelia burgdorferi (Lyme disease) and West Nile virus more commonly seen in the United States and parasitic infections encountered more often in Latin America, Southeast Asia, and Africa. Characteristic CSF and MRI patterns have been identified with many of these infections.

SUMMARY

A myriad of pathogens are associated with infectious myelopathies. Host factors, geographic distribution, clinical features, CSF profiles, and MRI findings can assist in formulating the differential diagnosis and ultimately guide management.

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.

Validation of a death assay for Angiostrongylus cantonensis larvae (L3) using propidium iodide in a rat model (Rattus norvegicus)

Angiostrongylus cantonensis is a pathogenic nematode and the cause of neuroangiostrongyliasis, an eosinophilic meningitis more commonly known as rat lungworm disease. Transmission is thought to be primarily due to ingestion of infective third stage larvae (L3) in gastropods, on produce, or in contaminated water. The gold standard to determine the effects of physical and chemical treatments on the infectivity of A. cantonensis L3 larvae is to infect rodents with treated L3 larvae and monitor for infection, but animal studies are laborious and expensive and also raise ethical concerns. This study demonstrates propidium iodide (PI) to be a reliable marker of parasite death and loss of infective potential without adversely affecting the development and future reproduction of live A. cantonensis larvae. PI staining allows evaluation of the efficacy of test substances in vitro, an improvement upon the use of lack of motility as an indicator of death. Some potential applications of this assay include determining the effectiveness of various anthelmintics, vegetable washes, electromagnetic radiation and other treatments intended to kill larvae in the prevention and treatment of neuroangiostrongyliasis.

Angiostrongylus (Parastrongylus) cantonensis on intermediate and definitive hosts in Ecuador, 2014-2017

Introduction: Angiostrongylus cantonensis is a serious public health problem and is widely distributed in the country. When the parasite infects the snails, it becomes deeply embedded in their interior and accidentally, it can infect people and other mammals. Objective: To establish the geographical distribution of A. cantonensis intermediate hosts (Achatina fulica) and definitive hosts (Rattus spp.) in Ecuador from 2014 to 2017. Materials and methods: We collected 2,908 A. fulica specimens in 16 provinces using the capture method per unit of effort for 30 minutes. We captured 211 hosts of which 20 were Rattus rattus and 191 R. norvegicus. The specimens were transported to the Instituto Nacional de Salud Pública e Investigación in Guayaquil where the larvae L3 were identified and counted in the tissues of the snail, which were then inoculated in laboratory rats to reproduce the life cycle. In the rodents, the brains, hearts, lung arteries and lungs were dissected, and the parasites were identified by taxonomic morphology. Results: Of the snails harvested, 441 were positive for A. cantonensis (15.2%) and a total of 6,166 L3 larvae were found; 77 (36.5%) specimens of Rattus spp., were infected with A. cantonensis and a total of 220 parasites (L4-L5 larvae and adult worms) were collected. Conclusions: We confirmed the presence of A. cantonensis in several provinces, which ratifies the endemic nature of this zoonosis in the national territory. Rattus spp. specimens constitute the definitive hosts of the parasite, which together with the presence of intermediate hosts, indicates the zoonotic potential of this parasitic infection.

Rat Lungworm Infection in Rodents across Post-Katrina New Orleans, Louisiana, USA

Rat lungworm (Angiostrongylus cantonensis), a parasitic nematode that can cause eosinophilic meningitis in humans, was first detected in New Orleans, Louisiana, USA, in the mid-1980s and now appears to be widespread in the southeastern United States. We assessed the distribution, prevalence, and intensity of A. cantonensis infection in New Orleans by examining lung biopsy samples of rodents trapped at 96 sites in 9 areas in Orleans Parish and 1 area in neighboring St. Bernard Parish during May 2015 through February 2017. These areas were selected to capture contrasting levels of income, flooding, and pos-disaster landscape management after Hurricane Katrina in 2005. We detected A. cantonensis in all areas and in 3 of the 4 rat species trapped. Overall prevalence was ≈38% but varied by area, host species, and host species co-occurrence. Infection intensity also varied by host species. These findings suggest that socioecological analysis of heterogeneity in definitive and intermediate host infection could improve understanding of health risks across the city.

Water transmission potential of Angiostrongylus cantonensis: Larval viability and effectiveness of rainwater catchment sediment filters

Neuroangiostrongyliasis, caused by Angiostrongylus cantonensis, has been reported in Hawaiʻi since the 1950's. An increase in cases is being reported primarily from East Hawaiʻi Island, correlated with the introduction of the semi-slug Parmarion martensi. Households in areas lacking infrastructure for water must use rainwater catchment as their primary domestic water supply, for which there is no federal, state, or county regulation. Despite evidence that slugs and snails can contaminate water and cause infection, regulatory bodies have not addressed this potential transmission route. This study evaluates: 1) the emergence of live, infective-stage A. cantonensis larvae from drowned, non-native, pestiforous gastropods; 2) larvae location in an undisturbed water column; 3) longevity of free-living larvae in water; and 4) effectiveness of rainwater catchment filters in blocking infective-stage larvae. Larvae were shed from minced and whole gastropods drowned in either municipal water or rainwater with ~94% of larvae recovered from the bottom of the water column 72–96 hours post drowning. Infective-stage larvae were active for 21 days in municipal water. Histological sectioning of P. martensi showed proximity of nematode larvae to the body wall of the gastropod, consistent with the potential for shedding of larvae in slime. Gastropod tissue squashes showed effectivity as a quick screening method. Live, infective-stage larvae were able to traverse rainwater catchment polypropylene sediment filters of 20 μm, 10 μm, 5 μm, and 1 μm filtration ratings, but not a 5 μm carbon block filter. These results demonstrate that live, infective-stage A. cantonensis larvae emerge from drowned snails and slugs, survive for extended periods of time in water, and may be able to enter a catchment user's household water supply. This study illustrates the need to better investigate and understand the potential role of contaminated water as a transmission route for neuroangiostrongyliasis.

Angiostrongylus cantonensis Infection of Central Nervous System, Guiana Shield

We report a case of eosinophilic meningitis complicated by transverse myelitis caused by Angiostrongylus cantonensis in a 10-year-old boy from Brazil who had traveled to Suriname. We confirmed diagnosis by serology and real-time PCR in the cerebrospinal fluid. The medical community should be aware of angiostrongyliasis in the Guiana Shield.

Severe CNS angiostrongyliasis in a young marine: a case report and literature review

Angiostrongylus cantonensis is the most common cause of eosinophilic meningitis worldwide. Infection typically occurs through ingestion of undercooked molluscs or vegetables contaminated by infective larvae. Endemic regions were previously limited to southeast Asia and the Pacific basin; however, this parasite is seeing an alarming increase in global distribution with reported cases in more than 30 countries, including several states in the USA. Although infection typically results in meningitis, a broad spectrum of CNS involvement and severity is emerging as diagnostic methods (such as real-time PCR) continue to improve diagnosis. In this Grand Round, we report a case of a 20-year-old active duty US marine serving in Okinawa, Japan, afflicted with severe CNS angiostrongyliasis marked by radiculomyelitis with quadriparesis, hyperaesthesia, and urinary retention. We present this case to highlight that no clear guidelines exist for the treatment of severe CNS angiostrongyliasis and provide our consensus recommendation that treatment algorithms include use of dual corticosteroids plus anthelmintics when radicular symptoms are present. In this Grand Round we review the clinical features, epidemiology, advances to diagnostic techniques, and available data on current treatment options for CNS angiostrongyliasis. This diagnosis should be highly considered in the differential diagnosis of a patient presenting with meningeal symptoms, paraesthesia or hyperaesthesia, and CSF eosinophilia so that treatment can be started early, which is particularly important in children, because of their increased risk of severe disease and mortality. We recommend combined therapy with albendazole and prednisolone, with consideration for increased steroid dosing in severe cases.

Angiostrongylus cantonensis Eosinophilic Meningitis in an Infant, Tennessee, USA

Angiostrongylus cantonensis, the rat lungworm, is the most common infectious cause of eosinophilic meningoencephalitis worldwide. This parasite is endemic to Southeast Asia and the Pacific Islands, and its global distribution is increasing. We report A. cantonensis meningoencephalitis in a 12-month-old boy in Tennessee, USA, who had not traveled outside of southwestern Tennessee or northwestern Mississippi.

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.

Angiostrongylus cantonensis: Agent of a Sometimes Fatal Globally Emerging Infectious Disease (Rat Lungworm Disease)

Angiostrongylus cantonensis, the rat lungworm, is a dangerous invasive species that is the agent of a potentially fatal globally emerging infectious disease. Humans are infected most commonly by ingestion, deliberately or inadvertently, of the parasite larvae in their intermediate snail hosts. The larvae make their way to the brain where they can cause severe neurological damage before eventually dying. Symptoms of the disease are diverse, making it difficult to diagnose. Treatment is primarily with corticosteroids to reduce inflammation, while treatment with anthelmintics to kill the worms remains controversial. There have been almost 3000 cases globally, the majority in southern China, but the parasite is spreading and now occurs much more widely. In the USA, almost all cases have been in Hawaii, but the parasite is also present in southeastern states. As the climate warms, this tropical/subtropical parasite is likely to spread further.