Complete mitochondrial genome of Gnathostoma binucleatum.

This report describes the mitochondrial genome of the parasite Gnathostoma binucleatum (G. binucleatum), which was obtained from naturally infected freshwater fish in Sinaloa, Mexico (22°46'00.1″N 105°40'21.8″W). G. binucleatum is responsible for human gnathostomiasis and is endemic to Mexico. It belongs to the Spirurida order of the Secernentea class of Nematoda.

Gnathostoma infection after ingestion of raw fish is a probable cause of eosinophilic meningitis in the Brazilian Amazon

ABSTRACT We report a case of eosinophilic meningitis associated with the ingestion of raw fish (Cichla sp.) from the Brazilian Amazon, likely caused by Gnathostoma. A 36-year-old male visited Juruena river on a fishing trip. After 50 days, the patient presented with an intense frontal headache. A cerebrospinal fluid examination revealed 63% eosinophilia. Another individual who ingested raw fish developed linear dermatitis on the abdominal wall. Anti-Gnathostoma serum antibodies were detected, and the patient made a full recovery after treatment with corticosteroids and albendazole. To date, autochthonous Gnathostoma spp. infections in Latin American countries have only caused linear panniculitis. This report raises awareness of gnathostomiasis-causing meningitis.

Regulation of immune response against third-stage Gnathostoma spinigerum larvae by human genes.

Background: Gnathostomiasis is an important zoonosis in tropical areas that is mainly caused by third-stage Gnathostoma spinigerum larvae (G. spinigerum L3). Objectives: This study aimed to prove whether G. spinigerum L3 produces extracellular vesicles (EVs) and investigate human gene profiles related to the immune response against the larvae. Methods: We created an immune cell model using normal human peripheral blood mononuclear cells (PBMCs) co-cultured with the larvae for 1 and 3 days, respectively. The PBMCs were harvested for transcriptome sequencing analysis. The EV ultrastructure was examined in the larvae and the cultured medium. Results: Extracellular vesicle-like particles were observed under the larval teguments and in the pellets in the medium. RNA-seq analysis revealed that 2,847 and 3,118 genes were significantly expressed on days 1 and 3 after culture, respectively. The downregulated genes on day 1 after culture were involved in pro-inflammatory cytokines, the complement system and apoptosis, whereas those on day 3 were involved in T cell-dependent B cell activation and wound healing. Significantly upregulated genes related to cell proliferation, activation and development, as well as cytotoxicity, were observed on day 1, and genes regulating T cell maturation, granulocyte function, nuclear factor-κB and toll-like receptor pathways were predominantly observed on day 3 after culture. Conclusion: G. spinigerum L3 produces EV-like particles and releases them into the excretory-secretory products. Overall, genotypic findings during our 3-day observation revealed that most significant gene expressions were related to T and B cell signalling, driving T helper 2 cells related to chronic infection, immune evasion of the larvae, and the pathogenesis of gnathostomiasis. Further in-depth studies are necessary to clarify gene functions in the pathogenesis and immune evasion mechanisms of the infective larvae.

Intracameral Gnathostomiasis: A Case Report and Literature Review.

PURPOSE: The purpose of this article is to report a case of ocular gnathostomiasis presenting with acute anterior uveitis and uveitis glaucoma. METHODS: observational case report and literature review. RESULTS: A 56-year-old Thai male was referred to a tertiary eye center with acute anterior uveitis and uveitis glaucoma in the right eye. A nematode was found in the right anterior chamber. Surgical removal of the nematode was successfully performed. Gnathostoma spinigerum was the nematode identified on pathological examination. CONCLUSIONS: Early detection of the parasite and timely surgical removal is the key to the management of ocular gnathostomiasis.

A Rare Case of Eosinophilic Myelitis Due to Gnathostomiasis.

Eosinophilic myelitis is an important cause of transverse myelopathy and has to be considered in an appropriate clinical setting. Eosinophilic myelitis due to parasitic infection should be suspected in cases with cerebrospinal fluid (CSF) eosinophilia along with migratory serpiginous skin lesions and recent travel to endemic areas. We report a case with a 1-month history of fever followed by truncal paresthesias, erythematous creeping skin eruptions, and paraparesis with blood and CSF eosinophilia on a background history of consuming undercooked fish. Magnetic resonance imaging (MRI) spine showed long segment T2 hyperintensities with contrast enhancement. He was tested positive for 24kDa antigenic component of Gnathostoma spinigerum in CSF and serum by immunoblot testing. The patient showed significant improvement with parenteral steroids.

Ocular Gnathostomiasis Presenting as Branch Retinal Artery Occlusion.

PURPOSE: To report a case of ocular Gnathostomiasis presenting as branch retinal artery occlusion. METHOD: Observational case report. RESULT: A 22-year-old Asian woman presented to her ophthalmologist with redness, tearing, and decreased vision in her left eye. Examination revealed anterior uveitis and branch retinal artery occlusion associated with both intra-retinal and vitreous hemorrhage. The patient was treated with topical corticosteroids and cycloplegics. After 3 weeks, she presented in our emergency, with further decrease in vision and worsening pain in the left eye. Slit lamp examination revealed a brown colored live worm on the posterior corneal surface, anterior uveitis, multiple iris holes, and vitreous cells. Indirect ophthalmoscopy showed focal retinal hemorrhages, subretinal tracts, and vitreous hemorrhage. Surgical removal of the worm from anterior chamber was done immediately. CONCLUSION: Branched retinal artery occlusion with intraretinal and vitreous hemorrhage, panuveitis, and multiple iris holes may suggest the presence of an intraocular parasite.

Human gnathostomiasis in Sri Lanka: an underreported disease?

A healthy young man from Sri Lanka, currently living in Switzerland, consulted at the University Hospital of Geneva with a history of painful erythema and swelling of the left forearm. Laboratory tests showed a slight eosinophilia. Western blot serology for Gnathostoma spp, inconclusive at presentation, became positive 2 weeks later.

Detection of Gnathostoma spinigerum Advanced 3rd-Stage Larvae in the Chinese Edible Frog, Hoplobatrachus rugulosus, from Local Markets in Phnom Penh, Cambodia.

The Chinese edible frogs, Hoplobatrachus rugulosus (n=20), and the striped snakehead fish, Channa striata (n=34), were purchased from local markets in 3 administrative regions of Cambodia (Phnom Penh, Pursat, and Takeo Provinces) from May 2017 to April 2019, and their infection status with Gnathostoma sp. larvae was investigated. The frogs and fish were transported to the laboratory with ice and examined using the artificial digestion method. Advanced 3rd-stage larvae (AdL3) of Gnathostoma spinigerum, 24 in total number (1-6 larvae/frog), were detected from 6 (60.0%) out of 10 frogs purchased from Phnom Penh. No gnathostome larvae were detected in 10 frogs purchased from Takeo Province and 34 snakeheads from Phnom Penh, Pursat, and Takeo Provinces. AdL3 isolated from the frogs were 2.55- 3.90 mm long and 0.31-0.36 mm wide. They had a characteristic head bulb (0.081×0.191 mm in average size) with 4 rows of hooklets, a muscular long esophagus (0.950-1.230 mm long), and 2 pairs of cervical sacs (0.530-0.890 mm long). The average number of hooklets in the 1st, 2nd, 3rd, and 4th rows was 41, 45, 48, and 51, respectively. These features were consistent with G. spinigerum AdL3. By the present study, it has been first confirmed that the Chinese edible frog, H. rugulosus, from Phnom Penh serves as a second intermediate host for G. spinigerum, although their intensity of infection was not so high compared to other previously reported localities.

Proteomics of Gnathostomiasis: A Way Forward for Diagnosis and Treatment Development.

Gnathostoma spinigerum is the most common cause of gnathostomiasis in humans. It has a complex life cycle, which requires two intermediate hosts and a definitive host, and poses a high risk for zoonosis. Definitive prognosis of gnathostomiasis relies mainly on the isolation of advanced-stage larvae (aL3), which is very challenging especially if the aL3 is sequestered in difficult-to-reach organs. There is also a lack of a confirmatory diagnostic test for gnathostomiasis. With the ongoing advancement of proteomics, a potential diagnostic approach is underway using immunoproteomics and immunodiagnostics. In addition to this, the employment of mass spectrometry could further elucidate not only understanding the biology of the parasite but also determining potential targets of prospective drugs and vaccines. This article reports the past, present, and future application of proteomics in the study of gnathostomiasis.

Morphological and Phylogenetic Analysis of Eustrongylides sp. and Gnathostoma spinigerum Parasitizing the Asian Swamp Eel Monopterusalbus in China.

Nematode infections transmitted to humans by the consumption of wild or cultured eels are increasingly being reported. In the present study, 120 Asian swamp eel, Monopterus albus (Zuiew), individuals collected from China were examined for parasite infections, and 78 larval nematodes were isolated. Morphological and molecular characteristics, including sequence and phylogenetic analysis of the internal transcribed spacer (ITS) and cytochrome c oxidase subunit I (COI) gene regions, were employed to identify these nematodes at the lowest taxonomic level possible. Asian swamp eel was infected with two zoonotic parasite taxa: Gnathostoma spinigerum advanced third-stage larvae, with 6.67% prevalence and mean intensity = 1.25, and Eustrongylides sp. fourth-stage larvae, with 26.67% prevalence and mean intensity = 2.13. These findings evidence the need to enhance public hygiene and food safety awareness toward eel consumption.

Human gnathostomiasis: a neglected food-borne zoonosis.

BACKGROUND: Human gnathostomiasis is a food-borne zoonosis. Its etiological agents are the third-stage larvae of Gnathostoma spp. Human gnathostomiasis is often reported in developing countries, but it is also an emerging disease in developed countries in non-endemic areas. The recent surge in cases of human gnathostomiasis is mainly due to the increasing consumption of raw freshwater fish, amphibians, and reptiles. METHODS: This article reviews the literature on Gnathostoma spp. and the disease that these parasites cause in humans. We review the literature on the life cycle and pathogenesis of these parasites, the clinical features, epidemiology, diagnosis, treatment, control, and new molecular findings on human gnathostomiasis, and social-ecological factors related to the transmission of this disease. CONCLUSIONS: The information presented provides an impetus for studying the parasite biology and host immunity. It is urgently needed to develop a quick and sensitive diagnosis and to develop an effective regimen for the management and control of human gnathostomiasis.

Seroprevalence of Tissue and Luminal Helminths among Patients in Hanoi Medical University Hospital, Vietnam, 2018.

A serological survey was performed using ELISA to estimate the prevalence of tissue and luminal helminthic infections among hospital patients in Hanoi region, Vietnam. An overall seroprevalence of tissue and luminal helminthiases was 64.0% (95% CI 61.2-66.8) among 1,120 patients who visited Hanoi Medical University Hospital, Vietnam in 2018. The highest seroprevalence was observed against Toxocara spp. (59.0%), followed by Strongyloides stercoralis (46.3%), Gnathostoma spp. (25.5%), cysticercus (12.8%), Angiostrongylus cantonensis (10.5%), Fasciola spp. (11.1%), and Clonorchis sinensis (8.7%). Mono-infection by one species (11.1%) was lower than multiple infections (53.0%) (P<0.05). The seroprevalence in males (59.3%) was lower than in females (66.2%) but not statistically significant (P>0.05). Children (<15 years) revealed lower seroprevalence (34.0%) than adults (68.4%), and the age group 51-70 years revealed the highest seroprevalence (76.0%). Among the seropositive patients, eosinophilia (≥8.0%) was noted in 80.2%. The present results suggested active transmission of various tissue and luminal helminths among people in Hanoi, Vietnam.

Larval Gnathostomes and Spargana in Chinese Edible Frogs, Hoplobatrachus rugulosus, from Myanmar: Potential Risk of Human Infection.

Chinese edible frogs, Hoplobatrachus rugulosus, were examined to estimate the potential risks of human gnathostomiasis and sparganosis in Myanmar. A total of 20 frogs were purchased in a local market of Yangon and examined with naked eyes and the artificial digestion method after skin peeling in June 2018 and June 2019. Larvae of gnathostomes and Spirometra (=spargana) were detected in 15 (75.0%) and 15 (75.0%) frogs with average intensities of 10.5 and 6.3 larvae per infected frog, respectively. Gnathostome larvae were 2.75-3.80 (av. 3.30) mm long and 0.29-0.36 (0.33) mm wide. They had a characteristic head bulb with 4 rows of hooklets, a muscular long esophagus, and 2 pairs of cervical sac. The mean number of hooklets were 41, 44, 47, and 50 on the 1st, 2nd, 3rd, and 4th row, respectively. Collected spargana were actively moving, particularly with the scolex part, and have ivory-white color and variable in size. Conclusively, it has been first confirmed that Chinese edible frogs, H. rugulosus, are highly infected with larval gnathostomes and spargana in this study. Consuming these frogs is considered a potential risk of human gnathostomiasis and sparganosis in Myanmar.

Autochthonous Gnathostomiasis in Madagascar.

We used molecular tools to identify an autochthonous case of gnathostomiasis in Madagascar. This severe ocular infection, caused by Gnathostoma spinigerum nematodes, led to vision loss in the patient's left eye. Clinicians should be aware of this parasitosis in Madagascar and other countries in Africa.

Gnathostomiasis Acquired by Visitors to the Okavango Delta, Botswana.

Gnathostomiasis is a zoonotic nematode parasite disease, most commonly acquired by eating raw or undercooked fish. Although the disease is well known in parts of Asia and Central and South America, relatively few cases have been reported from Africa. Raw fish consumed in the Okavango River delta area of Botswana, and in nearby western Zambia, has previously produced laboratory-proven gnathostomiasis in tourists. The purpose of this communication is to record additional cases of the infection acquired in the Okavango delta, and to alert visitors to the inadvisability of eating raw freshwater fish in the southern African region.

Effects of Gnathostoma spinigerum infective stage larva excretory-secretory products on NK cells in peripheral blood mononuclear cell culture: focused on expressions of IFN-γ and killer cell lectin-like receptors.

Human gnathostomiasis is mainly caused by third-stage larvae of Gnathostoma spinigerum (G. spinigerum L3). Excretory-secretory products (ES) released from infective helminthic larvae are associated with larval migration and host immunity modulation. Natural killer (NK) cells have important immune functions against helminth infection. Currently, the effects of ES from G. spinigerum L3 (G. spinigerum ES) on NK cell activity are unclear. This study investigated whether G. spinigerum ES affected human NK cells. Human normal peripheral blood mononuclear cell (PBMC) cultures were used to mimic immune cells within the circulation. PBMC were co-cultured with G. spinigerum ES (0.01-0.05 µg/ml) for 5 or 7 days. Levels of IFN-γ in cultured supernatants were measured by enzyme-linked immunosorbent assay. The expressions of mRNA encoding NK cell receptors, especially the C type killer cell lectin-like family (KLR; NKG2A, NKG2C, and NKG2D) and IFN-γ in ES induced PBMC were determined by quantitative reverse transcription-polymerase chain reaction (RT-qPCR). ES induced PBMC markedly decreased the levels of IFN-γ and increased the expressions of NKG2A and NKG2D on NK cells. In conclusion, low amounts of G. spinigerum ES modulated NK cells by downregulating the transcription of IFN-γ and upregulating the expressions of KLR (NKG2A and NKG2D receptors) during the 7-day observation period. These findings indicate more in-depth studies of NK cell function are required to better understand the mechanism involved in immune evasive strategies of human gnathostomiasis.

Molecular Identification of the Etiological Agent of Human Gnathostomiasis in an Endemic Area of Mexico.

Human gnathostomiasis, which is endemic in Mexico, is a worldwide health concern. It is mainly caused by the consumption of raw or insufficiently cooked fish containing the advanced third-stage larvae (AL3A) of Gnathostoma species. The diagnosis of gnathostomiasis is based on epidemiological surveys and immunological diagnostic tests. When a larva is recovered, the species can be identified by molecular techniques. Polymerase chain reaction (PCR) amplification of the second internal transcription spacer (ITS-2) is useful to identify nematode species, including Gnathostoma species. This study aims to develop a duplex-PCR amplification method of the ITS-2 region to differentiate between the Gnathostoma binucleatum and G. turgidum parasites that coexist in the same endemic area, as well as to identify the Gnathostoma larvae recovered from the biopsies of two gnathostomiasis patients from Sinaloa, Mexico. The duplex PCR established based on the ITS-2 sequence showed that the length of the amplicons was 321 bp for G. binucleatum and 226 bp for G. turgidum. The amplicons from the AL3A of both patients were 321 bp. Furthermore, the length and composition of these amplicons were identical to those deposited in GenBank as G. binucleatum (accession No. JF919679), corroborating our previous morphological finding that G. binucleatum is the etiological agent for human gnathostomiasis in the endemic area of Sinaloa, Mexico.

Infection Status of Gnathostoma spinigerum Larvae in Asian Swamp Eels, Monopterus albus, Purchased from Local Markets in Cambodia.

Present study was performed to know the infection status of Gnathostoma sp. larvae in swamp eels from Cambodia. We purchased total 30 Asian swamp eels, Monopterus albus, from local markets in Pursat and Takeo Provinces and Phnom Penh on May and November 2017 and May 2018. All collected eels were transferred to our laboratory with ice and each of them was examined by artificial digestion method. A total of 15 larval gnathostomes (1-5 larvae) were detected from 55.6% (5/9) swamp eels in Pursat Province. No larval gnathostomes were found in 21 swamp eels in Takeo Province and Phnom Penh. The advanced third-stage larvae (AdL3) detected were 2.575-3.825 (3.250) mm in length and 0.375-0.425 (0.386) mm in width. They had the characteristic head bulb (av. 0.104×0.218 mm) with 4 rows of hooklets, long muscular esophagus (1.048 mm), and 2 pairs of cervical sacs (0.615 mm). The number of hooklets in 4 rows on the head bulb was 41, 44, 47, and 50. In scanning electron microscopy, characteristic features were 4 rows of hooklets on the head bulb, cervical papillae, tegumental spines regularly arranged in transverse striations, and anus. The larval gnathostomes were identified as AdL3 of Gnathostoma spinigerum based on the morphological characters. By the present study, it has been confirmed that G. spinigerum larvae are infected in Asian swamp eels, M. albus, in Pursat Province, Cambodia.