PCR for the diagnosis of abdominal angiostrongyliasis in formalin-fixed paraffin-embedded human tissue

Real-time qPCR coupled with high-resolution melting curve analysis for the detection of the internal transcribed spacer 1 of Angiostrongylus costaricensis

Abdominal angiostrongyliasis (AA) is a zoonotic and severe parasitic infection caused by Angiostrongylus costaricensis. AA is currently diagnosed by the observation of A. costaricensis-compatible structures in biopsies or the detection of antibodies in serological tests. However, molecular methods targeting homologous sequences of A. costaricensis have not been designed before, and therefore, an HRM-coupled qPCR was developed to detect the internal transcribed spacer 1 (ITS1) of the parasite. The present assay successfully amplified DNA of A. costaricensis obtained from different hosts and identified slight sequence differences through the HRM analysis. The detection limit of the HRM-qPCR was 0.00036 ng/µL, 1.0 ng/µL, and 0.1 ng/µL when A. costaricensis DNA was diluted in nuclease-free water, whole blood, and sera, respectively, which highlights its potential use for cell-free DNA detection. Moreover, the reaction did not cross-amplify DNA of Angiostrongylus cantonensis, Strongyloides stercoralis, and other nematodes, thus emphasizing its specificity. Additionally, the assay tested positive in formalin-fixed paraffin embedded biopsies with visible A. costaricensis adults or eggs, but not in samples without evident parasites or a low number of larvae, which suggests that the reaction is useful for confirming the presence of the nematode in clinical samples. Finally, DNA of sera from patients with AA was evaluated with the HRM-qPCR but none tested positive, possibly due to long storage periods of the samples which could have led to cfDNA degradation. These results indicate that this assay may be useful in the confirmation of AA and its prospection for cell-free DNA detection protocols.

Insights into the genetic diversity of Angiostrongylus spp. causing human angiostrongyliasis and implications for molecular identification and diagnosis

Angiostrongylus cantonensis and Angiostrongylus costaricensis are known human pathogens responsible for eosinophilic angiostrongyliasis and abdominal angiostrongyliasis, respectively. Humans are accidental hosts, where infection occurs through the consumption of the infective larva stage 3 in intermediate or paratenic hosts. The proven method for abdominal angiostrongyliasis diagnosis is the histological examination through tissue biopsy, while the diagnosis of eosinophilic angiostrongyliasis is the detection of larva in the cerebrospinal fluid. As there is molecular evidence of cryptic species within A. cantonensis and A. costaricensis lineages, along with morphological similarities within both lineages, accurate species identification and disease diagnosis may be challenging. Moreover, species within the lineages share similar intermediate and definitive hosts and geographic distribution. For example, both A. cantonensis and Angiostrongylus malaysiensis (a closely related species in A. cantonensis lineage) overlap in their geographic distribution in Southeast Asia. Additionally, variations in the molecular makeup of A. costaricensis and A. cantonensis lineages may impact the pathogenicity, infectivity, and disease severity of angiostrongyliasis. Understanding of the genetic diversity of both lineages is a cornerstone for improved diagnosis and disease intervention, especially in a changing global environment. To shed light and provide insights into the genetic diversity of the Angiostrongylus lineages causing human angiostrongyliasis, we aim to present an up-to-date review of the studies conducted and genetic markers used for A. costaricensis and A. cantonensis lineages. The implications for accurate molecular identification and diagnosis of human angiostrongyliasis are also discussed.

Diagnostic criteria and case definitions for abdominal angiostrongyliasis: a systematic review from the Brazilian experience

Although rare, Angiostrongylus costaricensis infection may be a more prevalent etiology of inflammatory bowel disease than ulcerative colitis and Chron's disease in endemic areas in Central and South America. The present study reviewed the occurrence of A. costaricensis in Brazil, its clinical presentation and pathology; and proposed diagnostic criteria and case definitions for abdominal angiostrongyliasis (AA). Southern and southeastern Brazilian regions are the main endemic areas, and AA affects both genders and all age groups. A review of all 23 published reports of 51 Brazilian patients highlighted the following features that were subsequently classified as minor diagnostic criteria: abdominal pain, palpable mass in the right lower abdominal quadrant, history of exposure, ileocecal tumor, and intestinal perforation with wall thickening. Proposed major criteria include right lower quadrant abdominal pain, blood eosinophilia, positive serology (antibody detection), intense eosinophilic infiltration that involves all strata of the intestinal wall, eosinophilic granulomatous reaction, and eosinophilic vasculitis. In addition to the definitions of suspected and possible cases according to increasing strength of evidence of this infection, demonstration of worms/eggs/larvae in tissues or Angiostrongylus DNA in tissues or serum are required for a confirmed diagnosis. The application of the proposed criteria and definitions may improve patient management, epidemiologic surveillance, and identification of new endemic areas.

A practical guide for the diagnosis of abdominal angiostrongyliasis caused by the nematode Angiostrongylus costaricensis

Abdominal angiostrongyliasis (AA) is a severe parasitic infection caused by the nematode Angiostrongylus costaricensis. This disease is characterized by abdominal pain, a strong inflammatory eosinophilic response in the blood and tissues, and eventually intestinal perforation. Diagnosis of AA is challenging since there are no commercially available serological kits for A. costaricensis, and thus, histopathological analysis remains the gold standard. Herein we provide a decision flowchart for clinicians to improve the diagnosis of AA based on a patient's clinical manifestations, laboratory findings, macroscopic observations of the gut lesions, as well as characteristic microscopic alterations in biopsies. A brief discussion of the available polymerase chain reaction and in-house serological methods is also presented. The aim of this mini-review is to improve the diagnosis of AA, which should lead to prompt detection of cases and better estimates of the epidemiology and geographical distribution of A. costaricensis.

Detection of Enterobius vermicularis in archived formalin-fixed paraffin-embedded (FFPE) appendectomy blocks: It's potential to compare genetic variations based on mitochondrial DNA (cox1) gene

Acute appendicitis represents one of the most common causes of emergency abdominal surgery worldwide. Meanwhile, Enterobius vermicularis has been suggested as one of the probable causes of appendicitis. In this study, the morphological characteristics of the remnant pinworms and pathologic changes were explored in old-archived FFPE tissues of appendectomies. Moreover, we provide the first molecular identification, genetic, and haplotype variation of this nematode from the old-archived FFPE tissue section of appendectomy using the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene. Seventeen FFPE appendectomies with E. vermicularis infection, stored over 12-22 years, were collected from two different geographical areas of Iran. In the histopathological examination, tissue changes were observed in thirteen cases (76.4%) and inflammation in four blocks (23.5%). After DNA extraction, the cox1 gene was amplified in twelve (70.6%) cases using the nested polymerase chain reaction (PCR). Phylogenetic analysis and a median-joining network of 78 available cox1 sequences of E. vermicularis revealed 59 haplotypes. We identified five haplotypes that fell into type B. All Haplotypes are novel except for two haplotypes, Hap32 and Hap37, identical to E. vermicularis sequences from Iran, Greece, and Germany. The ranges of diversity distance and haplotype diversity within the isolates were 0-1.9% and HD:0.643-0.667, subsequently. Overall, the absence of inflammation or even tissue changes in some sections can suggest the possible non-inflammatory role of E. vermicularis in appendicitis. Although FFPE material suffers from PCR inhibition, we could successfully use nested PCR to characterize E. vermicularis in old-archived appendectomy blocks and suggest this method as a complementary diagnosis technique in pathology. While the predominant type was B in the Middle East and Europe, further studies on a larger sample size from different geographical regions could probably confirm the results obtained in the present study.

Molecular diagnosis of abdominal angiostrongyliasis by PCR using serum samples

Abdominal angiostrongyliasis (AA) is a zoonotic disease caused by the nematode Angiostrongylus costaricensis, which is endemic in southern Brazil. Humans become infected by ingesting third-stage (L3) larvae and are considered accidental hosts since neither eggs nor first-stage (L1) larvae are found in feces. The definitive diagnosis can be made by histopathologic examination of surgical specimens or intestinal biopsies. The present study assessed the use of PCR to carry out the molecular detection of AA from serum samples. A total of 62 human serum samples were divided into three groups: (i) 28 serum samples from human patients with presumptive histopathological diagnosis of AA; (ii) 23 serum samples from individuals with unknown serology for AA; (iii) 11 serum samples from patients that suffered from different parasitosis were included. The serum samples were initially tested by in-house indirect ELISA and then by PCR. A total of 14 samples were positive by ELISA, and 6 were positive by PCR. Six samples that were negative by ELISA were positive by PCR. Amplicons were sequenced, and Angiostrongylus DNA was confirmed. We conclude that PCR amplification can be used to confirm Angiostrongylus DNA in serum, which is especially important in cases where antibody levels are too low to be detected. It may also serve as a useful target for survey studies.

Abdominal angiostrongyliasis in the Americas: fifty years since the discovery of a new metastrongylid species, Angiostrongylus costaricensis

Angiostrongylus costaricensis is a zoonotic parasitic nematode described for the first time in 1971 by Pedro Morera and Rodolfo Céspedes in Costa Rica. This parasite causes an infection known as abdominal angiostrongyliasis, affecting mainly school-aged children and young adults. Infection with A. costaricensis has been associated with a myriad of rodent and mollusk species in the Americas and the Caribbean, as its natural hosts and reservoirs. In this commemorative review, we highlight the extensive research collected through a 50-year journey, which includes ecological, pathological, and molecular studies on A. costaricensis and its implicated disease. We also identify major knowledge gaps in its evolutionary history, the ecological role of imported and invasive mollusk species, and immune response. We propose that the advent of -omics analyses will allow us to gather novel information regarding A. costaricensis biology and infection dynamics, as well as to promote the design of much-needed sensitive and specific diagnostic tools.

Mitochondrial ribosomal genes as novel genetic markers for discrimination of closely related species in the Angiostrongylus cantonensis lineage

The Angiostrongylus cantonensis lineage (Nematoda: Metastrongyloidea) consists of the closely related species A. cantonensis, Angiostrongylus malaysiensis, and Angiostrongylus mackerrasae. Various genetic markers have been used for species discrimination in molecular phylogenetic studies of this lineage. However, despite showing potential in other organisms, mitochondrial 12S and 16S ribosomal RNA (rRNA) genes have not been used for Angiostrongylus species discrimination. Therefore, this study assessed these genes' suitability for inter- and intraspecies discrimination in the A. cantonensis lineage. The ultimate aim was to provide a novel genetic marker to support existing phylogenies. Sixty adult Angiostrongylus spp. worms from four geographic locations in Thailand were identified morphologically before molecular identification with 12S and 16S rRNA genes. Neighbor-joining and maximum likelihood algorithms were used for phylogenetic analyzes, and sequence variation was calculated to determine whether the genes could be used to discriminate among species. Furthermore, sequence variation was compared among previously used genetic markers to evaluate the robustness of the 12S and 16S rRNA genes as markers. Using both markers, the A. cantonensis lineage formed a monophyletic clade with a clear separation between A. cantonensis, A. malaysiensis, and A. mackerrasae. From our representative A. cantonensis and A. malaysiensis specimens, the genetic distance between the two clades was 6.8% -7.9% and 7.9% -10.0% for 12S and 16S rRNA genes, respectively, which is sufficient interspecific genetic variation for species discrimination. Higher levels of genetic variation were observed for the 16S rRNA gene, with 12 haplotypes and an intraspecific variation ≤2.2%. Thus, as a genetic marker, the 16S rRNA gene is comparable to mitochondrial protein-coding genes, which are commonly used in intra-level Angiostrongylus spp. studies. In conclusion, mitochondrial 12S and 16S rRNA genes can discriminate among closely related species in the A. cantonensis lineage, and they represent novel genetic markers for supporting existing phylogenies and verifying the phylogenetic position of A. mackerrasae.

Abdominal angiostrongyliasis: pathologic findings in Swiss mice infected with different doses of Angiostrongylus costaricensis

Abdominal angiostrongyliasis is caused by Angiostrongylus costaricensis, the definitive and intermediate hosts of which are wild rodents and terrestrial molluscs, respectively. Humans are accidental hosts and can be infected by ingesting the third-stage (infective) larvae (L3). It remains unclear whether the number of L3 inoculated is related to lesion severity. Our aim was to analyse histopathological alterations in Swiss mice infected with different doses of A. costaricensis. Thirty-two mice were randomly divided into four groups (n = 8/group): uninfected, control mice; mice infected with a low dose (five L3); mice infected with an intermediate dose (15 L3); and mice infected with a high dose (30 L3). The frequency of intestinal thrombi, splenitis, eggs/larvae, hepatic infarction and acute pancreatitis differed among the groups, the last being considered a significant finding. We conclude that different infective doses alter the histopathological aspects of the infection in Swiss mice, those aspects being more pronounced at medium and high doses, with no effect on the development of the disease. This experimental model shows that the parasite life cycle can be maintained in Swiss mice through the inoculation of a low dose (five L3).

First case report of nematode parasitic myelopathy in a wild feline in Brazil

Parasitic myelopathy caused by Gurltia paralysans in domestic cats is a disease commonly reported in several South American countries. The adult parasite is lodged in the meningeal veins and spinal cord, often causing clinical manifestations of vascular proliferation, thrombophlebitis, and medullary compression. Wild felines are believed to be the definitive hosts of this parasite. The infection occurs through the ingestion of paratenic hosts, but the life cycle of G. paralysans is not yet clearly understood. In this paper, we discuss a case of parasitic myelopathy in a margay (Leopardus wiedii) that died during post-surgical care. Necropsy revealed focal hemorrhages in the thoracolumbar spinal cord. A microscopic examination revealed adult nematodes and eggs inside the veins of subarachnoid space in spinal cord, suggesting G. paralysans infection. This is first description of parasitic myelopathy in a margay in Brazil.

Angiostrongylus costaricensis infection in Martinique, Lesser Antilles, from 2000 to 2017

Human abdominal angiostrongyliasis (HAA) is a parasitic disease caused by the accidental ingestion of the nematode Angiostrongylus costaricensis in its larval form. Human infection can lead to severe ischemic and inflammatory intestinal lesions, sometimes complicated by life-threatening ileal perforations. Only one case had been reported in Martinique, an Island in the French Antilles, in 1988. We retrospectively reviewed the medical charts of patients diagnosed with abdominal angiostrongyliasis at the University Hospital of Martinique between 2000 and 2017. The objectives of this study were to evaluate the incidence and perform a descriptive analysis of the clinical, biological, radiological, and histopathological features of HAA in Martinique. Two confirmed cases and two probable cases were identified in patients aged from 1 to 21 years during the 18-year period, with an estimated incidence of 0.2 cases per year (0.003 case/year/100.000 inhabitants (IC95% = 0.00-0.05)). All patients presented with abdominal pain associated with high blood eosinophilia (median: 7.24 G/L [min 4.25; max 52.28 G/L]). Two developed ileal perforation and were managed by surgery, with diagnostic confirmation based on histopathological findings on surgical specimens. The other two cases were probable, with serum specimens reactive to Angiostrongylus sp. antigen in the absence of surgery. All cases improved without sequelae. The description of this case series highlights the need to increase awareness of this life-threatening disease in the medical community and to facilitate access to specific diagnostic tools in Martinique. Environmental and epidemiological studies are needed to broaden our knowledge of the burden of this disease.

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.

Central nervous system manifestations of Angiostrongylus cantonensis infection

Over 20 species of Angiostrongylus have been described from around the world, but only Angiostrongylus cantonensis has been confirmed to cause central nervous system disease in humans. A neurotropic parasite that matures in the pulmonary arteries of rats, A. cantonensis is the most common cause of eosinophilic meningitis in southern Asia and the Pacific and Caribbean islands. The parasite can also cause encephalitis/encephalomyelitis and rarely ocular angiostrongyliasis. The present paper reviews the life cycle, epidemiology, pathogenesis, clinical features, diagnosis, treatment, prevention and prognosis of A. cantonesis infection. Emphasis is given on the spectrum of central nervous system manifestations and disease pathogenesis.