Epidemiologic studies of eosinophilic meningitis in southern Taiwan

Comparative biology of parasitic nematodes in the genus Angiostrongylus and related genera

The rise to prominence of some Angiostrongylus species through associated emerging disease in humans and dogs has stimulated calls for a renewed focus on the biology of this genus and three related genera. Although significant research efforts have been made in recent years these have tended to focus on individual species and specific aspects such as diagnosis and treatment of disease or new records of occurrence and hosts. This comprehensive review takes a comparative approach, seeking commonalities and differences among species and asking such questions as: Which species belong to this and to closely related genera and how are they related? Why do only some species appear to be spreading geographically and what factors might underlie range expansion? Which animal species are involved in the life cycles as definitive, intermediate, paratenic and accidental hosts? How do parasite larvae find, infect and develop within these hosts? What are the consequences of infection for host health? How will climate change affect future spread and global health? Appreciating how species resemble and differ from each other shines a spotlight on knowledge gaps and provides provisional guidance on key species characteristics warranting detailed study. Similarities exist among species, including the basic life cycle and transmission processes, but important details such as host range, climatic requirements, migration patterns within hosts and disease mechanisms differ, with much more information available for A. cantonensis and A. vasorum than for other species. Nonetheless, comparison across Angiostrongylus reveals some common patterns. Historically narrow definitive host ranges are expanding with new knowledge, combining with very broad ranges of intermediate gastropod hosts and vertebrate and invertebrate paratenic and accidental hosts to provide the backdrop to complex interactions among climate, ecology and transmission that remain only partly understood, even for the species of dominant concern. Key outstanding questions concern larval dynamics and the potential for transmission outside trophic relations, relations between infection and disease severity in different hosts, and how global change is altering transmission beyond immediate impacts on development rate in gastropods. The concept of encounter and compatibility filters could help to explain differences in the relative importance of different gastropod species as intermediate hosts and determine the importance of host community composition and related environmental factors to transmission and range. Across the group, it remains unclear what, physiologically, immunologically or taxonomically, delimits definitive, accidental and paratenic hosts. Impacts of infection on definitive host fitness and consequences for population dynamics and transmission remain mostly unexplored across the genus. Continual updating and cross-referencing across species of Angiostrongylus and related genera is important to synthesise rapid advances in understanding of key traits and behaviours, especially in important Angiostrongylus species that are emerging causative agents of disease in humans and other animals.

Proteomic Analysis of Differentially Expressed Proteins in Intracranial Angiostrongylus cantonensis Larvae in Permissive and Non-Permissive Hosts

Angiostrongylus cantonensis infection can lead to severe neuropathological damage caused by the development of these nematodes in the central nervous system after penetrating the blood-brain barrier. They commonly cause eosinophilic meningitis or meningoencephalitis in non-permissive hosts (e.g., mice). It has been shown that differences exist in the brains of permissive and non-permissive hosts during the larval development of A. cantonensis; however, the mechanism underlying the difference is not completely understood. This study analyzed and characterized the differentially expressed proteins in the intracranial A. cantonensis larvae in rat (ILR) and mouse (ILM) brains by using proteomics. We found that 29 proteins were differentially expressed: 12 of these proteins were highly expressed in ILR, whereas the remaining 17 proteins were highly expressed in ILM. Three protein spots were homologous to the actin-2, actin-1, and disorganized muscle protein 1 (dim-1) of Caenorhabditis elegans. In addition, proteomic analyses revealed that act-1 and act-2 were up-regulated in ILM compared to ILR, whereas dim-1 was down-regulated in ILM. Annotation using gene ontology revealed that act-1, act-2, and dim-1 were mainly associated with adenosine triphosphate (ATP) catabolic processes and ATP binding. Quantitative real-time polymerase chain reaction analyses of act-1 and dim-1 using the first internal transcribed spacers of A. cantonensis 18S ribosomal RNA (rRNA) was consistent with 2-dimensional gel electrophoresis (2-DE) and the sizes of these parasites; ILR was longer and wider than ILM. These results indicate that the differentially expressed proteins dim-1 and act-1 could be related to the development and pathogenicity of A. cantonensis in different hosts.

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.

Eosinophil chemotactic chemokine profilings of the brain from permissive and non-permissive hosts infected with Angiostrongylus cantonenis

Angiostrongylus cantonensis invasion primarily cause heavy or negligible eosinophic meningitis and meningoencephalitis in the brain of non-permissive and permissive hosts, respectively. Chemokines are effective leukocyte chemoattractants and may play an essential role in mediating eosinophil recruitment in angiostrongyliasis. In the present study, we comparatively analyzed changes in peripheral and CSF eosinophil counts, and expression profilings of eosinophil chemotactic chemokines in A. cantonensis-infected mice (CCL 2, CCL 3, CCL 5, CCL7, CCL 8, CCL 11, CCL 12, CCL 24 and CCL 28) and rats (CCL 2, CCL 3, CCL 5, CCL 11 and CCL 12) were explored at 1, 2, 5, 7, 14, and 21 days post-infection (dpi), and found significantly elevated numbers of eosinophils in blood and CSF of infected mice after 5 dpi, while significant increases of eosinophils in blood and CSF of infected rats were detected after 5 and 14 dpi, respectively. The kinetics of CSF eosinophilia is basically correlated with eosinophil chemotactic chemokine levels in brains of infected animals at each time point. Interestingly, less CSF eosinophils and infiltration of eosinophils in the brain were noted in rats than in mice, though extremely high levels of chemokines were also maintained in the brains of infected rats at 21 dpi. We further described CCL 11 (eotaxin), a previously reported eosinophil chemotactic factor in angiostrongyliasis, was mainly released from activated microglia in mice and rats infected with A. cantonensis. Our results reveal that different complicated chemokine networks mediate recruitment of eosinophils between permissive and non-permissive hosts during A. cantonensis infection, and provide promising targets for clinical treatment of angiostrongyliasis.

Differences of larval development and pathological changes in permissive and nonpermissive rodent hosts for Angiostrongylus cantonensis infection

Angiostrongylus cantonensis is a neurotrophic and pulmonary parasite which causes severe neuropathological damages by invading and developing in the central nervous system (CNS). Nonpermissive host with A. cantonensis infection appeared to have more serious neurologic symptoms, and there is still not much knowledge about the host-parasite interrelationship in different hosts. We investigated and compared the larval size, recovery rate, distribution, and the severity of pathologic injuries in the CNS of both permissive host (e.g., rats) and nonpermissive hosts (e.g., mice). In present study, mice infected with A. cantonensis showed higher worm recovery rate in late-stage infection and smaller size of intracranial larvae as compared to the infected rats. Intracranial larvae mainly aggregated on cerebral surface of infected rats but on surface of cerebellum and brainstem in mice. Hemorrhage and tissue edema on brain surface caused by worm migration appeared earlier and severer in infected mice than in rats. Neuropathological examination revealed that injuries induced by A. cantonensis in brain parenchyma included hemorrhage, vascular dilatation, focal necrosis with neuronal loss, and infiltration of inflammatory cells. In the comparison of these pathological changes in rats and mice, infected mice suffered more serious injuries and provoked more intense inflammatory response as compared to infected rats. All these morphological evidences indicate that larval development was retardant in the CNS of nonpermissive host, and nonpermissive host experienced more serious pathological injuries than permissive host. It implies that the difference in innate immune response to parasite infection attribute to host specificity.

Clinical manifestations of eosinophilic meningitis caused by Angiostrongylus cantonensis: 18 years' experience in a medical center in southern Taiwan

BACKGROUND

With the improvement of public health, eosinophilic meningitis associated with Angiostrongylus cantonensis infection is now seldom reported in Taiwan. Eosinophilic meningitis typically occurred sporadically in children. This study aims to analyze the clinical manifestations and change in the contemporary epidemiology of eosinophilic meningitis in Taiwan.

METHODS

This is a retrospective study of patients diagnosed with eosinophilic meningitis at Kaohsiung Veterans General Hospital, from December 1991 to September 2009. The demographic characteristics, clinical presentations, laboratory data, radiographic imaging, and treatment and clinical outcome were analyzed. A PubMed search with the keywords of eosinophilic meningitis, A cantonensis, and Taiwan was performed to retrieve cases of eosinophilic meningitis caused by A cantonensis since 1960.

RESULTS

Thirty-seven patients were diagnosed to have eosinophilic meningitis during a period of 18 years. The median age was 32 years (range, 2-80 years). Ninety five percent (35/37) of the patients were adults. The median incubation period was 10.5 days (range, 3-80 days). Most of the patients presented with headache (29, 78%), fever (25, 68%), and 11(30%) had hyperesthesia. Patients with hyperesthesia had longer incubation period (55 vs. 7 days, p=0.004), lower serum immunoglobulin E levels (127.5 vs. 1295 IU/mL, p<0.001), and longer duration between symptom onset and spinal taps (14 vs. 5 days, p=0.011). Three patients presented initially with lymphocytic meningitis, and eosinophilia only appeared on a second lumbar puncture. Magnetic resonance imaging of the brain disclosed leptomeningeal enhancement (17/26, 65%) and increased signal intensity (10/26, 38%) on T2-weighted and fluid-attenuated inversion recovery images. There were eight relapses and two patients died. No sequela was noted except in one 2-year-old toddler, who had weakness of both lower limbs.

CONCLUSIONS

The epidemiology of eosinophilic meningitis has changed during the past two decades in Taiwan and occurs mainly in adults in the setting of outbreaks. Hyperesthesia; repeated lumbar puncture in cases with lymphocytic meningitis of uncertain cause; and a detailed history, including food consumption, are important to establish an accurate diagnosis.

Helminth infections of the central nervous system occurring in Southeast Asia and the Far East

Although helminth infections of the central nervous system (CNS) are rare, their public health implications must not be neglected. Indeed, several helminth species can cause cerebrospinal infections, especially if humans serve as intermediate or non-permissive host. The diagnosis of cerebrospinal helminthiases is difficult, and the detection of parasites in cerebrospinal fluid is rarely successful. Cerebrospinal helminth infections therefore often remain undetected, and hence prognosis is poor. Increases in tourism and population movements are risk factors for cerebrospinal helminthiases and infections pose particular challenges to clinicians in non-endemic areas. In this review, we focus primarily on food-borne helminthiases that are endemic and often emerging in Southeast Asia and the Far East, namely angiostrongyliasis, gnathostomiasis, sparganosis, paragonimiasis and cysticercosis. Additionally, we discuss neuroschistosomiasis, a disease that is transmitted through human-water contact. For each disease, we describe the pathogen, its transmission route and possible mechanisms for entering the CNS. We also summarise common signs and symptoms, challenges and opportunities for diagnosis, treatment, clinical management, geographical distribution and epidemiology. The adoption of a comprehensive set of diagnostic criteria for different cerebrospinal helminthiases is proposed, including epidemiological history, typical signs and symptoms, neuroimaging and laboratory findings. Finally, risk factors, and research needs for enhanced patient management and population-based control measures are discussed.

Oxidative stress in mice infected with Angiostrongylus cantonensis coincides with enhanced glutathione-dependent enzymes activity

This study aimed to estimate reactive oxygen species (ROS) production, antioxidants activity, and biomarkers level of oxidative damage to protein and DNA in the cerebrospinal fluid (CSF) of C57BL/6 mice infected with Angiostrongylus cantonensis. The mean ROS concentration in the CSF of infected mice increased gradually, and the increase in ROS in CSF became statistical significance at days 12-30 post-infection compared to that before infection (P<0.001), and then ROS returned to normal level at day 45 after infection. In parallel with the increase in ROS in the CSF, infected mice showed similar of changes in reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx), and glutathione S-transferase (GST) as that in ROS in the CSF. GSH, GR, GPx, and GST in the CSF of infected mice were all significantly higher than they were before infection during days 12-30 post-infection. However, protein carbonyl content and 8-hydroxy-2'-deoxyguanosine, biomarkers of oxidative damage to protein and DNA, respectively, were also significantly higher in the CSF of infected mice during this period. These results suggest that oxidative stress occur in the cells of central nervous system of mice infected with A. cantonensis during days 12-30 after infection due to ROS overproduction in CSF despite the increase in antioxidants during this period.

Human angiostrongyliasis outbreak in Dali, China

Background

Several angiostrongyliasis outbreaks have been reported in recent years but the disease continues to be neglected in public health circles. We describe an outbreak in Dali, southwest China in order to highlight some key problems for the control of this helminth infection.

Methodology/Principal Findings

All available medical records of suspected angiostrongyliasis patients visiting hospitals in Dali in the period 1 October 2007–31 March 2008 were reviewed, and tentative diagnoses of varying strengths were reached according to given sets of criteria. Snails collected from local markets, restaurants and natural habitats were also screened for the presence of Angiostrongylus cantonensis. A total of 33 patients met criteria for infection, and 11 among them were classified as clinically confirmed. An additional eight patients were identified through a surveillance system put in operation in response to the outbreak. The epidemic lasted for 8 months with its peak in February 2008. Of the 33 patients, 97.0% complained of severe headache. 84.8% patients had high eosinophil cell counts either in the peripheral blood or in cerebrospinal fluid (CSF). Three-quarters of the patients were treated with a combination of albendazole and corticosteroids, resulting in significantly improved overall conditions. Twenty-two patients reported the consumption of raw or undercooked snails prior to the onset of the symptoms, and approximately 1.0% of the Pomacea canaliculata snails on sale were found to be infected with A. cantonensis. The snails were also found in certain habitats around Dali but no parasites were detected in these populations.

Conclusions/Significance

The import and sale of infected P. canaliculata is the likely trigger for this angiostrongyliasis outbreak. Awareness of angiostrongyliasis must be raised, and standardized diagnosis and treatment are needed in order to provide clinicians with a guide to address this disease. Health education campaigns could limit the risk, and a hospital-based surveillance system should be established in order to detect future outbreaks.

Angiostrongyliasis, caused by the rat lungworm Angiostrongylus cantonensis, is a potentially fatal food-borne disease. It is endemic in parts of Southeast Asia, the Pacific Islands, Australia, and the Caribbean. Outbreaks have become increasingly common in China due to the spread of efficient intermediate host snails, most notably Pomacea canaliculata. However, infections are difficult to detect since the disease has a rather long incubation period and few diagnostic clinical symptoms. Reliable diagnostic tests are not widely available. The described angiostrongyliasis epidemic in Dali, China lasted for eight months. Only 11 of a total of 33 suspected patients were clinically confirmed based on a set of diagnostic criteria. Our results demonstrate that the rapid and correct diagnosis of the index patient is crucial to adequately respond to an epidemic, and a set of standardized diagnostic procedures is needed to guide clinicians. Integrated control and management measures including health education, clinical guidelines and a hospital-based surveillance system, should be implemented in areas where snails are a popular food item.

Distribution of eosinophilic meningitis cases attributable to Angiostrongylus cantonensis, Hawaii

During November 2004-January 2005, 5 cases of eosinophilic meningitis (EM) attributable to Angiostrongylus cantonensis infection were reported in Hawaii. To determine if this temporal clustering reflected an increased incidence, we ascertained EM and A. cantonensis cases by systematic review of statewide laboratory and medical records for January 2001-February 2005 and generalized the data to population estimates. We identified 83 EM cases; 24 (29%) were attributed to A. cantonensis infection, which was included in the discharge diagnoses for only 2 cases. Comparison of A. cantonensis infection incidence rates (per 100,000 person-years) for the baseline (January 2001-October 2004) and cluster (November 2004-February 2005) periods showed statistically significant increases for the state as a whole (0.3 vs. 2.1), the Big Island of Hawaii (1.1 vs. 7.4), and Maui County (0.4 vs. 4.3). These findings underscore the need to consider the diagnosis of A. cantonensis infection, especially in the state of Hawaii.

Cerebrospinal fluid cytokine responses in human eosinophilic meningitis associated with angiostrongyliasis

The levels of interleukin 5 (IL5), IL10, and IL13 in the cerebrospinal fluid (CSF) were markedly higher in 30 patients with eosinophilic meningitis associated with angiostrongyliasis (EOMA) than in the controls (P<0.001). IL2, IL4, interferon gamma (IFNgamma), and tumor necrosis factor alpha (TNFalpha) levels were not significantly different (P>0.05). IL5, IL10, and TNFalpha levels correlated with eosinophil levels (P=0.023, P=0.018, and P=0.005, respectively) while IL2, IL4, IL13, and IFNgamma did not (P>0.05). Our data suggest that local T-helper-2 (TH2) cytokine responses are predominant in the CSF of patients with EOMA. Data on T lymphocyte-parasite interactions are important for the design of effective vaccines and immunotherapies. The measurement of T-helper-1 (TH1)/TH2 cytokines in the CSF may also have some potential for the diagnosis of parasite associated meningitis.

Eosinophilic Meningitis

Eosinophilic meningitis (EM) is a distinct clinical entity that may have infectious and noninfectious causes. Worldwide, infection with the helminthic parasite, Angiostrongylus cantonensis, is the most common infectious etiology. Historically, this infection has been acquired through ingestion of competent intermediate and paratenic (carrier) hosts or contaminated food in Southeast Asia and the Pacific Islands. A recent outbreak of A. cantonensis-associated EM among US travelers to Jamaica and subsequent parasitologic surveys of local snails and rats confirm earlier case reports and engender a wider appreciation of the Caribbean islands as a new region for endemic A. cantonensis infections. Clinically, eosinophilia is not always present in the cerebrospinal fluid or in the peripheral blood during the initial manifestions of A. cantonensis-associated EM, which include headache and cutaneous sensory alterations. Effective management of patients involves careful attention to the control of intracranial pressure. Steroid therapy without specific anthelmintic treatment is safe and effective in control of headache of adult patients with A. cantonensis-associated EM.

An outbreak of eosinophilic meningitis caused by Angiostrongylus cantonensis in travelers returning from the Caribbean

BACKGROUND

Outbreaks of eosinophilic meningitis caused by the roundworm Angiostrongylus cantonensis are rarely reported, even in regions of endemic infection such as Southeast Asia and the Pacific Basin. We report an outbreak of A. cantonensis meningitis among travelers returning from the Caribbean.

METHODS

We conducted a retrospective cohort study among 23 young adults who had traveled to Jamaica. We used a clinical definition of eosinophilic meningitis that included headache that began within 35 days after the trip plus at least one of the following: neck pain, nuchal rigidity, altered cutaneous sensations, photophobia, or visual disturbances.

RESULTS

Twelve travelers met the case definition for eosinophilic meningitis. The symptoms began a median of 11 days (range, 6 to 31) after their return to the United States. Eosinophilia was eventually documented in all nine patients who were hospitalized, although on initial evaluation, it was present in the peripheral blood of only four of the nine (44 percent) and in the cerebrospinal fluid of five (56 percent). Repeated lumbar punctures and corticosteroid therapy led to improvement in symptoms in two of three patients with severe headache, and intracranial pressure decreased during corticosteroid therapy in all three. Consumption of one meal (P=0.001) and of a Caesar salad at that meal (P=0.007) were strongly associated with eosinophilic meningitis. Antibodies against an A. cantonensis--specific 31-kD antigen were detected in convalescent-phase serum samples from 11 patients.

CONCLUSIONS

Among travelers at risk, the presence of headache, elevated intracranial pressure, and pleocytosis, with or without eosinophilia, particularly in association with paresthesias or hyperesthesias, should alert clinicians to the possibility of A. cantonensis infection.

Neuro-angiostrongyliasis: unresolved issues

Angiostrongylus cantonensis, the rat lungworm, probably evolved with its hosts, members of the genus Rattus and closely related species, in south-east Asia. Since its first discovery in rats in China and in a case of human infection in Taiwan, the parasite has been found to infect humans and other mammals across a wide and ever-increasing territory, which now encompasses much of south-east Asia, Melanesia, Polynesia and eastern Australia. It has also established a foothold in Africa, India, the Caribbean and south-eastern USA. This dispersal has been a direct result of human activity, and in some cases has been linked with the spread of the African giant land snail, Achatina fulica. However, this snail is not critical to the extension of the parasite's range, as numerous other indigenous molluscan species serve as adequate intermediate hosts; the importance of Achatina to the life cycle may have been over-emphasized. In Australia, the parasite is established along parts of the east coast, and the presence of an indigenous close relative, Angiostrongylus mackerrasae, suggests a long association of the parasite with its local rat hosts, a situation analogous to that of Angiostrongylus malaysiensis in south-east Asia. These three Angiostrongylus species share virtually the same life cycle, but only A. cantonensis has been confirmed to be a human pathogen.

Studies on cryopreservation of third-stage larvae of Parastrongylus cantonensis

Attempts have been made to increase the survival rate of third-stage larvae of Parastrongylus cantonensis during cryopreservation. Parasites were obtained from experimentally infected snails, Biomphalaria glabrata. The maximum non-toxic concentrations of cryoprotectants dimethyl sulphoxide (DMSO) and glycerol were determined as 10% v/v in NCTC 109 medium. Different pre-cooling times and serum additives were assayed to determine their effects on the viability of larvae. Larvae pre-cooled at -20 degrees C for 15-20 minutes before transfer to -70 degrees C had the optimum survival rate. The presence of serum was essential for further cooling to -196 degrees C. There were no differences between native and heat-inactivated sera on the larval viability. The survival of larvae recovered after storage at -196 degrees C was higher in sera collected from the rat, man, or fetal calf than in sera collected from the mouse, dog, or horse. Viability assessed by mouse-infections showed that thawed larvae retained infectivity for susceptible hosts, but it was significantly lower than that of unfrozen control worms.

Recovery of Angiostrongylus cantonensis from cerebrospinal fluid of a child with eosinophilic meningitis

Viable Angiostrongylus cantonensis was recovered from the cerebrospinal fluid of a 17-month-old boy with eosinophilic meningitis. Neurological findings were minimal, and the child had an uneventful recovery.