Rat Lungworm Infection Associated with Central Nervous System Disease - Eight U.S. States, January 2011-January 2017

Angiostrongylus cantonensis Infection in Brown Rats (Rattus norvegicus), Atlanta, Georgia, USA, 2019-2022

Rat lungworm (Angiostrongylus cantonensis), a zoonotic parasite invasive to the United States, causes eosinophilic meningoencephalitis. A. cantonensis harbors in rat reservoir hosts and is transmitted through gastropods and other paratenic hosts. We discuss the public health relevance of autochthonous A. cantonensis cases in brown rats (Rattus norvegicus) in Atlanta, Georgia, 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.

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.

Comparison of Antibody Isotype Response to Angiostrongylus cantonensis in Experimentally Infected Rats (Rattus norvegicus) Using Hawai'i 31 kDa Antigen in an Indirect ELISA

Neuroangiostrongyliasis (NAS) is an emerging tropical disease in humans and some animals which is caused by infection with the parasitic nematode Angiostrongylus cantonensis. It is the leading cause of eosinophilic meningitis worldwide. Diagnoses in humans and susceptible animals are generally presumptive and easily confused with other central nervous system disorders. The 31 kDa antigen is currently the only NAS immunodiagnostic assay that has achieved 100% sensitivity. However, little is known about the humoral immune response against the 31 kDa antigen in NAS infections, which would be critical for widespread adoption of this assay. We used the Hawai'i 31 kDa isolate in an indirect ELISA assay to confirm the presence of immunoglobulin IgG, IgM, IgA, and IgE isotypes in six-week post-infection plasma from lab-reared rats infected with 50 live, third-stage, A. cantonensis larvae isolated from a wild Parmarion martensi semi-slug. Our results confirmed the presence of all four isotypes against the Hawaii 31 kDa isolate, with sensitivity ranging from 22-100%. The IgG isotype showed 100% sensitivity in detecting A. cantonensis infection, which validates the use of IgG indirect ELISA with 31 kDa antigen as an effective immunodiagnostic assay for rats six weeks post-infection. Given each isotype may be present at different times during NAS infections, our data provides preliminary information on the humoral immune response to A. cantonensis infection in lab-reared rats and serves as a baseline for future studies.

Management of Rat Lungworm Disease (Neuroangiostrongyliasis) Using Anthelmintics: Recent Updates and Recommendations

While there have been legitimate concerns in the past regarding the use of anthelmintics for the management of neuroangiostrongyliasis (rat lungworm disease), recent studies demonstrate that they can be considered safe and efficacious, particularly albendazole, which is regarded as the choice anthelmintic for its management. However, physician hesitancy to prescribe, as well as problems of availability persist, at least in Hawaii, which is considered the epicenter of this disease in the US. As a result, many patients suffer a diminished quality of life or even death. Here, we discuss recent studies that provide insights into new treatments and preventative interventions, which can be more rigorously used for the management of neuroangiostrongyliasis. In summary, results from recent studies suggest that albendazole and avermectins are beneficial for post-exposure management, pyrantel pamoate is beneficial as a post-exposure prophylactic, and levamisole is deserving of further study for the treatment of neuroangiostrongyliasis.

Neuroangiostrongyliasis: Global Spread of an Emerging Tropical Disease

Neuroangiostrongyliasis (NAS) is an emerging parasitic disease caused by the neurotropic nematode Angiostrongylus cantonensis. Since it was first discovered, in rats in southern China in the 1930s, this tropical to subtropical parasite has spread to much of Southeast Asia, the Pacific Islands (including Hawaii), Australia, Japan, South America, the southeastern United States, the Caribbean, Africa, the Canary Islands, and the Balearic Islands. The parasite completes its natural life cycle in snails and slugs (intermediate hosts), and rats (definitive hosts). Humans become accidental hosts after ingesting infective third-stage larvae contained within uncooked or undercooked intermediate or paratenic hosts, an event that sometimes results in NAS, also known as rat lungworm disease. Although A. cantonensis larvae cannot complete their life cycle in humans, their migration into the brain and spinal cord combined with a powerful inflammatory reaction often leads to eosinophilic meningitis and can, in rare instances, lead to coma, paralysis, and death or, in other cases, chronic, disabling neurologic sequelae. Symptoms of NAS are diverse, which often makes it difficult to diagnose. Treatment may include administration of analgesics, corticosteroids, anthelminthics, and repeat lumbar punctures to reduce intracranial pressure. Unfortunately, few medical providers, even in endemic areas, are familiar with A. cantonensis or its epidemiology, diagnosis, and treatment. As the parasite continues to spread and NAS affects more people, medical practitioners, as well as the general public, must become more aware of this emerging zoonosis and the potentially devastating harm it can cause.

Where Have All the Diagnostic Morphological Parasitologists Gone?

Advances in laboratory techniques have revolutionized parasitology diagnostics over the past several decades. Widespread implementation of rapid antigen detection tests has greatly expanded access to tests for global parasitic threats such as malaria, while next-generation amplification and sequencing methods allow for sensitive and specific detection of human and animal parasites in complex specimen matrices.

A Rare Etiology for Ascending Paralysis in an Infant

An 11-month-old male infant with ascending paralysis had an unremarkable initial cerebrospinal fluid (CSF) analysis and imaging. Progressive neurological symptoms resulted in repeated CSF sampling, microscopy, and plasma microbial cell-free DNA next-generation sequencing analysis, that in combination with epidemiology, confirmed the diagnosis.

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.

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.

Development of a recombinase polymerase amplification (RPA-EXO) and lateral flow assay (RPA-LFA) based on the ITS1 gene for the detection of Angiostrongylus cantonensis in gastropod intermediate hosts

Angiostrongylus cantonensis is a parasitic nematode known to infect humans through the ingestion of third stage larvae which can cause inflammation and damage to the central nervous system. Currently, polymerase chain reaction (PCR) is one of the most reliable diagnostic methods for detecting A. cantonensis in humans as well as in gastropod hosts, but requires expensive and specialized equipment. Here, we compare the sensitivity and accuracy of a recombinase polymerase amplification Exo (RPA-EXO) assay, and a recombinase polymerase amplification lateral flow assay (RPA-LFA) with a traditional quantitative PCR (qPCR) assay currently available. The three assays were used to test 35 slugs from Hawai'i for the presence of A. cantonensis DNA. Consistent results among the three tests were shown in 23/35 samples (65.7%), while 7/35 (20%) were discordant in low infection level samples (<0.01 larvae per mg tissue), and 5/35 (14.3%) were equivocal. To evaluate sensitivity, a partial ITS1 gene was cloned, and serial plasmid dilutions were created ranging from 100 copies μL-1 to ~1 copy μL-1. All three assays consistently detected 50-100 copies μL-1 in triplicate and qPCR was able to detect ~13 copies μL-1 in triplicate. RPA-EXO was able to detect 25 copies μL-1 in triplicate and RPA-LFA was not able to amplify consistently below 50 copies μL-1. Thus, our RPA-EXO and RPA-LFA assays do not appear as sensitive as the current qPCR assay at low DNA concentrations; however, these tests have numerous advantages that may make them useful alternatives to qPCR.

Angiostrongylus spp. (Nematoda; Metastrongyloidea) of global public health importance

Human angiostrongyliasis is an important foodborne zoonosis, caused by the infection with Angiostrongylus costaricensis and Angiostrongylus cantonensis. These two species have a significant public health impact in different areas of the world. Angiostrongyliasis is re-emerging and expanding to urban settings rising significant concerns regarding the control of these infections. This review focuses on aspects such as life cycle, epidemiology, clinical manifestations, diagnostics, food safety and control of illness caused especially by A. cantonensis.

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 Occurrence of Physaloptera hispida and a Mastophorus Sp. in Pulmonary Vessels of Hispid Cotton Rats (Sigmodon hispidus) from Georgia, U.S.A

During 2017-2018, a survey for the rat lungworm, Angiostrongylus cantonensis (Nematoda: Metastrongyloidea), in rodents from Piedmont and Lower Coastal Plains physiographic regions of Georgia was conducted. On 4 occasions, a single worm was recovered from the pulmonary vessels of a single cotton rat (Sigmodon hispidis). One of these worms was identified as a Physaloptera sp. and the remaining 3 as a Mastophorus sp. by morphology. No A. cantonensis were found. Physaloptera (Nematoda: Physalopteroidea) and Mastophorus species (Nematoda: Spiruroidea) are stomach parasites of many wild and domestic animals. This is the first report of these species in the pulmonary vessels of a definitive host. To better characterize these parasites, representative specimens were collected from cotton rat stomachs and identified morphologically and molecularly. Based on partial cytochrome c oxidase subunit 1 (COI) gene sequences, Physaloptera hispida from stomachs were identical to the Physaloptera sp. from the pulmonary vessels. The COI sequences from the Mastophorus sp. from the stomach exhibited a higher degree of variability but confirmed that the pulmonary worms were the same Mastophorus species. Furthermore, sequences of Mastophorus from a coastal site clustered separately from a clade of Mastophorus sequences from cotton rats from a Piedmont site. Our data show that adult worms recovered from pulmonary vessels of cotton rats could be either Physaloptera or Mastophorus sp., indicating that these parasitic worms are not always restricted to the stomach and that worms from pulmonary vessels must be carefully examined to obtain a definitive diagnosis of A. cantonensis infection.

Severe Eosinophilic Meningoencephalitis Secondary to Suspected Neuroangiostrongyliasis with a Good Clinical Outcome

Angiostrongylus cantonensis has caused sporadic cases of eosinophilic meningoencephalitis in Sydney, Australia. We describe a 36-year-old man who presented subacutely with fevers, reduced level of consciousness, confusion, ophthalmoplegia, and urinary incontinence. He was diagnosed with severe eosinophilic meningoencephalitis secondary to suspected Angiostrongylus cantonensis based on clinical, serological, and radiological findings. The patient was treated with albendazole and prednisolone with full neurological recovery. Management of neuroangiostrongyliasis with anthelminthic is controversial as it is thought to cause worsened outcomes through inciting an inflammatory response as a result of parasite killing. We managed to successfully treat our patient using albendazole and prednisolone and achieved a good outcome.