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

Eosinophilic Meningitis: Eleven-Year Experience at Texas Children's Hospital

Eosinophilic meningitis can be caused by various etiologies and is reported mostly in tropical climates. The diagnosis is rare in the continental US, presenting challenges for management. Following a case of pediatric eosinophilic meningitis, we reviewed our 11-year experience with this diagnosis at a large US children's hospital.

In vivo efficacy of pyrantel pamoate as a post-exposure prophylactic for rat lungworm (Angiostrongylus cantonensis)

Rat lungworm (Angiostrongylus cantonensis) is a neurotropic nematode, and the leading cause of eosinophilic meningitis worldwide. The parasite is usually contracted through ingestion of infected gastropods, often hidden in raw or partially cooked produce. Pharmaceutical grade pyrantel pamoate was evaluated as a post-exposure prophylactic against A. cantonensis. Pyrantel pamoate is readily available over-the-counter in most pharmacies in the USA and possesses anthelmintic activity exclusive to the gastrointestinal tract (GIT). Administering pyrantel pamoate immediately after exposure should theoretically paralyze the larvae in the GIT, causing the larvae to be expelled via peristalsis without entering the systemic circulation. In this study, pyrantel pamoate (11 mg/kg) was orally administered to experimentally infected rats at 0, 2-, 4-, 6-, or 8-h post-infection. The rats were euthanized six weeks post-infection, and worm burden was evaluated from the heart-lung complex. This is the first in vivo study to evaluate its efficacy against A. cantonensis. This study demonstrates that pyrantel pamoate can significantly reduce worm burden by 53–72% (P = 0.004), and thus likely reduce the severity of infection that is known to be associated with worm burden. This paralyzing effect of pyrantel pamoate on the parasite may also be beneficial for delaying the establishment of infection until a more suitable anthelmintic such as albendazole is made available to the patient.

•

Pyrantel pamoate (PP) shows significant in vivo efficacy against A. cantonensis.

•

Efficacy of PP was evaluated for the first time in an experimental animal model.

•

Administering PP between 4 and 8 h post-exposure significantly reduces worm burden.

•

PP is a new post-exposure prophylactic for rat lungworm disease.

Canine and Feline Parasitology: Analogies, Differences, and Relevance for Human Health

Cats and dogs are treated as family members by most pet owners. Therefore, a high quality of veterinary care and preventive medicine is imperative for animal health and welfare and for the protection of humans from zoonotic pathogens. There is a general perception of cats being treated as "small dogs," especially in the field of clinical parasitology. As a result, several important differences between the two animal species are not taken into proper consideration and are often overlooked. Dogs and cats are profoundly different under evolutionary, biological, ethological, behavioral, and immunological standpoints. These differences impact clinical features, diagnosis, and control of canine and feline parasites and transmission risk for humans. This review outlines the most common parasitoses and vector-borne diseases of dogs and cats, with a focus on major convergences and divergences, and discusses parasites that have (i) evolved based on different preys for dogs and cats, (ii) adapted due to different immunological or behavioral animal profiles, and (iii) developed more similarities than differences in canine and feline infections and associated diseases. Differences, similarities, and peculiarities of canine and feline parasitology are herein reviewed in three macrosections: (i) carnivorism, vegetarianism, anatomy, genetics, and parasites, (ii) evolutionary adaptation of nematodes, including veterinary reconsideration and zoonotic importance, and (iii) behavior and immune system driving ectoparasites and transmitted diseases. Emphasis is given to provide further steps toward a more accurate evaluation of canine and feline parasitology in a changing world in terms of public health relevance and One Health approach.

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.

Eosinophilic Meningitis due to Angiostrongylus cantonensis in Children

Meningoencephalitis is not a rare disease in children. However, eosinophilic meningitis due to Angiostrongylus cantonensis is unusual in the pediatric population. We describe the case of a 12-year-old girl from the central area of Vietnam with eosinophilic meningitis due to A. cantonensis. The patient lived in a rural area, where farming is widespread, and presented with fever and headache. Laboratory results showed peripheral eosinophilia, a cerebrospinal fluid white blood cell count of 730/mm³ with 65% eosinophils. Cerebrospinal fluid ELISA was positive for A. cantonensis, and blood ELISA was positive for A. cantonensis. The presentation was consistent with a diagnosis of A. cantonensis eosinophilic meningitis. The patient recovered fully after administration of albendazole (200 mg/day for 2 weeks), as well as intravenous dexamethasone (0.6 mg/kg/day every 8 h) and mannitol (1.5 g/kg/day every 8 h) for the first 3 days, followed by 5 days of oral prednisolone (2 mg/kg/day).

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.

AcanR3990 qPCR: a novel, highly sensitive, bioinformatically-informed assay to detect Angiostrongylus cantonensis infections

BACKGROUND

Angiostrongylus cantonensis (Ac), or the rat lungworm, is a major cause of eosinophilic meningitis. Humans are infected by ingesting the 3 rd stage larvae from primary hosts, snails and slugs, or paratenic hosts. The currently used molecular test is a qPCR assay targeting the ITS1 rDNA region (ITS1) of Ac.

METHODS

In silico design of a more sensitive qPCR assay was performed based on tandem repeats predicted to be the most abundant by the RepeatExplorer algorithm. Genomic DNA (gDNA) of Ac were used to determine the analytical sensitivity and specificity of the best primer/probe combination. This assay was then applied to clinical and environmental samples.

RESULTS

The limit of detection of the best performing assay, AcanR3990, was 1 fg (the DNA equivalent of 1/100,000 dilution of a single 3 rd stage larvae). Out of 127 CDC archived CSF samples from varied geographic locations, the AcanR3990 qPCR detected the presence of Ac in 49/49 ITS1 confirmed angiostrongyliasis patients along with 15/73 samples previously negative by ITS1 qPCR despite strong clinical suspicion for angiostrongyliasis. Intermediate hosts (gastropods) and an accidental host, a symptomatic horse, were also tested with similar improvement in detection observed. AcanR3990 qPCR did not cross-react in five CSF from patients with proven neurocysticercosis, toxocariasis, gnathostomiasis and baylisascariasis. AcanR3990 qPCR failed to amplify genomic DNA from the other related Angiostrongylus species tested except for A. mackerrasae (Am), a neurotropic species limited to Australia that would be expected to present with a clinical syndrome indistinguishable from Ac.

CONCLUSION

These results suggest AcanR3990 qPCR assay is highly sensitive and specific with potential wide applicability as a One Health detection method for Ac and Am.

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.

Angiostrongylus cantonensis central nervous system infection in captive callitrichids in Texas

Angiostrongylus cantonensis is a tropical lungworm of rats known for central nervous system migration in aberrant primate hosts. Here, we describe A. cantonensis infection in three captive callitrichids from a Texas zoo. The affected animals included a Goeldi's monkey (Callimico goeldii), a cotton-top tamarin (Saguinus oedipus), and a pied tamarin (Saguinus bicolor) that ranged from 8 to 18 years old. Clinical signs included lethargy, ataxia, and seizures. Histologically, these animals had an eosinophilic meningoencephalitis to myelitis and some areas had abundant macrophages and parasite migration tracts. All cases had intralesional metastrongyle parasites, and nematodes were extracted from the formalin-fixed brain specimen in one case. This extracted parasite was identified as Angiostrongylus cantonensis based on morphologic features and diagnosis was confirmed with PCR. These cases represent the first report of this parasite in non-human primates in Texas, highlighting the western spread of A. cantonensis in the continental United States.

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.

Next-generation sequencing specifies Angiostrongylus eosinophilic meningoencephalitis in infants: Two case reports

RATIONALE

Angiostrongylus cantonensis-induced eosinophilic meningoencephalitis (AEM) in infants is a very rare but fatal disease. Utilization of genetic assay to detect the cerebral parasite plays an important role for the treatment of the infection.

PATIENT CONCERNS

Two infants (<2 years) presented with cough, intermittent fever, mental fatigue, and poor diet.

DIAGNOSIS

The patients were under clinical examination and laboratory test including cardiac ultrasound, chest X-ray, blood or cerebrospinal fluid (CSF) cell counting, serum enzyme-linked immunosorbent assay (ELISA), head magnetic resonance imaging (MRI) and next-generation sequencing (NGS) on DNA from CSF. Due to hypereosinophils in patients' peripheral blood and CSF, and abundant DNA sequences from A cantonensis in CSF, the patients were diagnosed with Angiostrongylus eosinophilic meningoencephalitis.

INTERVENTIONS

The patients were treated with albendazole to deworm, and methylprednisolone to reduce inflammation.

OUTCOME

The patients were completely recovered from AEM without relapse after 10-day treatment.

LESSONS

ELISA and MRI are not sufficiently accurate for the diagnosis of AEM in infants. NGS can specify the infection by the cerebral parasite and offers a new effective approach for the early and precise diagnosis of AEM in infants.

Frequency of Occurrence of the Rat Lungworm Parasite in the Invasive Island Apple Snail in South Carolina, USA

The rat lungworm Angiostrongylus cantonensis is a nematode parasite that can cause potentially fatal eosinophilic meningitis in humans. The life cycle of A. cantonensis involves multiple hosts, with the most common terminal hosts being rodents and intermediate hosts comprising gastropods. One such gastropod is the invasive island apple snail Pomacea maculata, which is native to South America but is currently established in several states in the USA, including South Carolina. It has been identified as an intermediate host for A. cantonensis in several locations in Louisiana. The ability of the island apple snail to serve as an intermediate host for A. cantonensis poses significant potential threats to human health, yet no studies to date have determined the prevalence of this parasite in island apple snails in South Carolina. The objective of this study was to investigate the frequency of occurrence of A. cantonensis in South Carolina island apple snails by using a real-time PCR assay. One-hundred individuals from each of three distinct stormwater retention ponds were tested, and no positive detections were found. Determining the prevalence of A. cantonensis in island apple snails is critical in accurately informing the public as to the risks involved in handling and/or consuming island apple snails.

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 Meningitis and Myelitis, Texas, USA

Infection with Angiostrongylus cantonensis roundworms is endemic in Southeast Asia and the Pacific Basin. A. cantonensis meningitis and myelitis occurred in summer 2013 in a child with no history of travel outside of Texas, USA. Angiostrongyliasis is an emerging neurotropic helminthic disease in Texas and warrants increased awareness among healthcare providers.

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

We utilized polymerase chain reaction (PCR) to demonstrate that Angiostrongylus cantonensis was responsible for 67.3% of 55 cases of eosinophilic meningitis from a cohort of 1,690 adult patients with CNS infection at a tertiary hospital in southern Vietnam. Longer duration of illness, depressed consciousness, and peripheral blood eosinophilia were associated with PCR positivity.

Geographic distribution of Angiostrongylus cantonensis in wild rats (Rattus rattus) and terrestrial snails in Florida, USA

The parasitic nematode Angiostrongylus cantonensis is a major cause of eosinophilic meningitis in humans, and has been documented in other incidental hosts such as birds, horses, dogs and non-human primates. It is endemic in Hawaii, and there have been sporadic reports in the southern continental United States. This parasite uses rats as definitive hosts and snails as intermediate hosts. In this study, we collected potential definitive and intermediate hosts throughout Florida to ascertain the geographic distribution in the state: Rats, environmental rat fecal samples, and snails were collected from 18 counties throughout the state. Classical diagnostics and morphological identification, along with molecular techniques were used to identify nematode species and confirm the presence of A. cantonensis.

Of the 171 Rattus rattus collected, 39 (22.8%) were positive for A. cantonensis, and 6 of the 37 (16.2%) environmental rat fecal samples collected in three of the surveyed counties were also positive for this parasite by real time PCR. We examined 1,437 gastropods, which represented 32 species; 27 (1.9%) were positive for A. cantonensis from multiple sites across Florida. Three non-native gastropod species, Bradybaena similaris, Zachrysia provisoria, and Paropeas achatinaceum, and three native gastropod species, Succinea floridana, Ventridens demissus, and Zonitoides arboreus, which are newly recorded intermediate hosts for the parasite, were positive for A. cantonensis. This study indicates that A. cantonensis is established in Florida through the finding of adult and larval stages in definitive and intermediate hosts, respectively, throughout the state. The ability for this historically subtropical nematode to thrive in a more temperate climate is alarming, however as the climate changes and average temperatures rise, gastropod distributions will probably expand, leading to the spread of this parasite in more temperate areas. Through greater awareness of host species and prevalence of A. cantonensis in the United States, potential accidental infections may be avoided.