Brain Magnetic Resonance Imaging Abnormalities in Eosinophilic Meningitis Caused byAngiostrongylus cantonensisInfection

The returned traveler with neurologic manifestations: could my patient have a parasite?

PURPOSE OF REVIEW

The present review focuses on parasitic infections of the central nervous system (CNS) that can affect the international traveler.

RECENT FINDINGS

The epidemiology of imported parasitic infections is changing and clinicians are treating increasing numbers of returned travelers with parasitic infections in the CNS with which they are not familiar.

SUMMARY

The epidemiology, life cycle, clinical manifestations, diagnosis, and treatment of parasites that affect the CNS will be discussed.

Genetic Characterization and Detection of Angiostrongylus cantonensis by Molecular Approaches

Angiostrongylus cantonensis constitutes a major etiologic agent of eosinophilic meningoencephalitis. The detection methods for angiostrongyliasis mainly depend on morphology or immunology. A firmer diagnosis could be reached by directly detecting the parasite in the cerebrospinal fluid or through laboratory assays that are specific for Angiostrongylus-induced antibodies or the parasite's DNA. A. cantonensis detection could be carried out by larva release from the tissue upon pepsin digestion. However, the procedure requires live mollusks, which might complicate the analysis of large amounts of samples. Since morphological assays are limited, multiple molecular techniques have been put forward for detecting A. cantonensis, including PCR amplification of targets followed by fragment length or DNA sequence analysis. This allows rapid and accurate identification of A. cantonensis for efficient infection management and epidemiological purposes. In this study, we reviewed the current methods, concepts, and applications of molecular approaches to better understand the genetic characterization, molecular detection methods, and practical application of molecular detection in A. cantonensis.

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).

Magnetic resonance imaging in dogs with neuroangiostrongyliasis (rat lungworm disease)

The magnetic resonance imaging (MRI) appearance of the brain and spinal cord in humans with neuroangiostrongyliasis (NA) due to Angiostrongylus cantonensis infection has been well reported. Equivalent studies in animals are lacking. This case series describes clinical and MRI findings in 11 dogs with presumptively or definitively diagnosed NA. MRI of the brain and/or spinal cord was performed using high-field (1.5 T) or low-field (0.25 T) scanners using various combinations of transverse, sagittal, dorsal and three-dimensional (3D) T1-weighted (T1W), transverse, sagittal and dorsal T2-weighted (T2W), T2W fluid-attenuated inversion recovery (FLAIR) and T2*-weighted (T2*W) gradient echo (GRE), dorsal T2W short tau inversion recovery (STIR) and post-gadolinium transverse, sagittal, dorsal and 3D T1W and transverse T2W FLAIR sequences. In 4/6 cases where the brain was imaged, changes consistent with diffuse meningoencephalitis were observed. Evidence of meningeal involvement was evident even when not clinically apparent. The spinal cord was imaged in 9 dogs, with evidence of meningitis and myelitis detected in regions consistent with the observed neuroanatomical localization. Pathognomonic changes of neural larva migrans, as described in some human patients with NA, were not detected. NA should be considered in the differential diagnosis of dogs with MRI evidence of focal or diffuse meningitis, myelitis and/or encephalitis, especially in areas where A. cantonensis is endemic. If not precluded by imaging findings suggestive of brain herniation, cerebrospinal fluid (CSF) collection for cytology, fluid analysis, real-time polymerase chain reaction (qPCR) and enzyme-linked immunosorbent assay (ELISA) testing should be considered mandatory in such cases after the MRI studies.

MicroRNA miR-155-5p knockdown attenuates Angiostrongylus cantonensis-induced eosinophilic meningitis by downregulating MMP9 and TSLP proteins

Angiostrongylus cantonensis infection is a major cause of eosinophilic meningitis (EM). Severe cases or cases that involve infants and children present poor prognoses. MicroRNAs (miRNAs), which are important regulators of gene expression in many biological processes, were recently found to be regulators of the host response to infection by parasites; however, their roles in brain inflammation caused by A. cantonensis are still unclear. The current study confirmed that miR-155-5p peaked at 21 days after A. cantonensis infection, and its expression was positively correlated with the concentration of excretory and secretory products (ESPs). We found that miR-155-5p knockdown lentivirus successfully ameliorated brain injury and downregulated the expression of major basic protein (MBP) in vivo, and the number of eosinophils in CSF (and the percentage of eosinophils in peripheral blood were also decreased in the miR-155-5p knockdown group. Moreover, the expression of several eosinophilic inflammation cytokines such as CCL6/C10, ICAM-1, and MMP9, declined after the miR-155-5p knockdown. SOCS1 protein, which is an important negative regulator of inflammation activation, was identified as a direct miR-155-5p target. We further detected the effect of miR-155-5p knockdown on phosphorylated-STAT3 and phosphorylated-p65 proteins, which were found to be negatively regulated by SOCS1 and play an important role in regulating the inflammatory response. We found that miR-155-5p knockdown decreased the activity of p-STAT3 and p-p65, thereby leading to lower expression of MMP9 and TSLP proteins, which were closely related to the chemotaxis and infiltration of eosinophils. Interestingly, the inhibition of p-STAT3 or p-p65 was found to induce the downregulation of miR-155-5p in an opposite manner. These observations suggest that a positive feedback loop was formed between miR-155-5p, STAT3, and NF-κB in A. cantonensis infection and that miR-155-5p inhibition might provide a novel strategy to attenuate eosinophilic meningitis.

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.

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.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

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

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

Characterizing longitudinal changes in rabbit brains infected with Angiostrongylus Cantonensis based on diffusion anisotropy

Angiostrongylus cantonensis has become a global source of infection in recent years, and the differential diagnosis and timely follow-up are crucial in the management of the infection. Magnetic resonance imaging (MRI) has been suggested as a non-invasive technique in characterizing and localizing lesions during the parasitic infections in the brain. Non-invasive diffusion tensor imaging (DTI) can be used to distinguish microscopic cerebral structures but cannot resolve the more complicated neural structure. Several methods have been proposed to overcome this limitation. One such method, generalized q-sampling imaging (GQI), can be applied to a variety of datasets, including the single shell, multi-shell or grid sampling schemes, which are believed to resolve complicated crossing fibers. This study aimed to characterize angiostrongyliasis in the rabbit brain over a 6-week period using anatomical and diffusion MRI, including DTI and GQI. Our anatomical T2WI and R2 mapping results showed that the ventricle size of the rabbit brain increased after A. cantonensis larvae infection, and the DTI and GQI indices both showed pathological changes in the corpus callosum, hippocampus and cortex over a 6-week infection period. These results were consistent with our histopathological findings. Our results demonstrated that the diagnosis of larvae infection using anatomical and diffusion MRI is possible and that follow-up characterization is informative in revealing the effects of angiostrongyliasis in various brain areas. These support the use of anatomical and diffusion MRI was helpful for diagnosis of eosinophilic meningitis caused by A. cantonensis infection. This non-invasive MRI platform could be used to improve the management of eosinophilic meningitis or eosinophilic meningoencephalitis in humans.

An 8-week brain MRI follow-up analysis of rat eosinophilic meningitis caused by Angiostrongylus cantonensis infection

Early differential diagnosis and timely follow-up are advantageous in the management of Angiostrongylus cantonensis infection. This study aimed to characterize angiostrongyliasis in the rat brain for an 8-week period using magnetic resonance imaging (MRI) with contrast-enhanced T1-weighted images (T1WI), T2-weighted imaging (T2WI), fluid attenuation inversion recovery (FLAIR) and R2 mapping sequences. The data were analysed with Mathematica and Matlab software programs for weekly changes in each brain following the infection of 20, 50, 100 and 300 third-stage larvae (L3), respectively. The results showed that the average subarachnoid space detected by T2WI technique was peaked up to 10% increase of original size on day 35 after 100 or 300 larvae infection, while those infected with 20 or 50 larvae showed less than 4% increase during the entire course of observation. This increase was relevant to the mortality of the infected rats, because those with 100 or 300 larvae infections showed a sharp decrease in survival rate before day 40. After day 40, the average subarachnoid space was decreased, but the average ventricle size was persistently increased, with the highest increase observed in the group infected with 300 larvae on day 56. Furthermore, the R2 mapping mean and R2 mapping size were significantly different between the brains with severe infection (100 and 300 larvae groups together) and those with mild infection (20 and 50 larvae groups together) on day 49, but not on day 35. Our results showed that diagnosis for different quantity of larvae infection using MRI is possible and follow-up characterization is informative in revealing the effects of angiostrongyliasis on different brain areas. In conclusion, our results support the use of MRI as a non-invasive diagnostic technique for eosinophilic meningitis caused by A. cantonensis infection.

Severe hemorrhagic meningoencephalitis due to Angiostrongylus cantonensis among young children in Sydney, Australia

Angiostrongylus cantonensis is the most common cause of eosinophilic meningitis worldwide. We describe 2 cases among young children from Sydney, Australia, where locally acquired infection of children has not been reported previously. Both cases manifested as severe hemorrhagic meningoencephalitis, one resulting in death. Angiostrongyliasis must be considered in acute neurological presentations occurring among individuals who live in endemic areas.

Ym1, an eosinophilic chemotactic factor, participates in the brain inflammation induced by Angiostrongylus cantonensis in mice

Angiostrongylus cantonensis is an emerging zoonotic pathogen that has caused hundreds of cases of human angiostrongyliasis worldwide. The larva in nonpermissive hosts cannot develop into an adult worm and can cause eosinophilic meningitis and ocular angiostrongyliasis. The mechanism of brain inflammation caused by the worm remains poorly defined. According to previous data of GeneChip, Ym1 in the brain of mice 21 days after infection with A. cantonensis was highly upregulated to over 7,300 times than the untreated mice. Ym1 is an eosinophilic chemotactic factor with the alternative names of chitinase-3-like protein 3, eosinophil chemotactic cytokine, and ECF-L. Ym1 displays chemotactic activity for T lymphocytes, bone marrow cells, and eosinophils and may favor inflammatory responses induced by parasitic infections and allergy. It has been reported that Ym1 is synthesized and secreted by activated macrophages during parasitic infection (Chang et al., J Biol Chem 276(20):17497-17506, 2001). In the brain, microglia are alternatively activated macrophage-derived cells which are the key immune cells in central nervous system inflammation. To explore the role of Ym1 in inflammation caused by A. cantonensis-infected mice, we examined the levels of Ym1 in the sera and cerebrospinal fluid (CSF) of the infected animals, followed by detection of the mRNA expression level of Ym1 in various organs including the brain, lung, liver, spleen, and kidney and of the cytokines IL-5 and IL-13 in the brain of the infected mice with or without intraperitoneal injection of minocycline (an inhibitor of microglial activation) by real-time reserve transcription PCR. Furthermore, immunolocalization of Ym1 in the brains of the infected mice was observed by using a fluorescence microscope. Our results showed that Ym1 was most highly expressed in the brains and CSF of the infected mice along with the process of inflammation. The antibody localized Ym1 to the microglia in the brain of the mice in both infection and minocycline + infection groups. And as in the brain, the mRNA level of Ym1 changed more obviously than IL-5 and IL-13. The study implies that Ym1 might serve as an alternative potential pathological marker which is detected not only in the sera and CSF but also in the brains of the infected mice and Ym1 secreted by microglia might be involved in eosinophilic meningitis and meningoencephalitis caused by A. cantonensis infection.