Genetic diversity of infective larvae of Gnathostoma spinigerum (Nematoda: Gnathostomatidae) in freshwater swamp eels from Thailand.

Human gnathostomiasis is a food-borne zoonosis caused by a tissue nematode of the genus Gnathostoma. The disease is highly endemic in Asia, including Thailand. The freshwater swamp eel (Monopterus albus), the second intermediate host of the gnathostome nematode, has an important role in transmitting the infection in Thailand. Surveys on the infective larvae of Gnathostoma spinigerum based on morphological features in freshwater swamp eels have been performed continuously and reported in Thailand. However, there is still limited molecular data on intra-species variations of the parasite. In this study, a total of 19 third-stage larvae of morphologically identified G. spinigerum were collected from 437 liver samples of freshwater swamp eels purchased from a large wholesale market in Bangkok, Thailand. Molecular characterization based on mitochondrial cytochrome c oxidase subunit I (COI) sequences was performed to elucidate their genetic variations and phylogenetic relationship. Among the 19 infective larvae recovered from these eels, 16 were sequenced successfully. Phylogenetic analyses inferred from the partial COI gene showed the presence of three distinct COI haplotypes. Our findings confirm the presence of G. spinigerum as the main species in Thailand.

Genetic variation of NADH dehydrogenase subunit 1 (nad1) mitochondrial gene sequence in adult Necator americanus hookworms recovered from a female patient in Thailand.

Two female and one male adult hookworms were recovered from a female patient in Thailand. Based on gross and microscopic morphology, the three hookworms are members of Necator americanus. Phylogenetic reconstruction based on partial NADH dehydrogenase subunit 1 (nad1) mitochondrial gene sequences shows that these hookworms belong to the same genetic lineage as N. americanus adult worm from Zhejiang, China. The male and female hookworms were genetically distinct, belonging to two different nad1-haplotypes. This is the first report targeting the nad1 gene on the identification and genetic characterization of the human hookworms originated from infected patient. The nad1 gene marker is useful for species and higher taxa differentiation of hookworms.

Genetic differentiation of Anisakis species (Nematoda: Anisakidae) in marine fish Priacanthus tayenus from Gulf of Thailand.

Members of the genus Anisakis are parasitic nematodes of the family Anisakidae. They are potential zoonotic parasites, causing anisakiasis in humans who consume raw or undercooked seafood (fish or squid) infected with the larvae of this nematode. In the present study, anisakid nematodes collected from the marine fish Priacanthus tayenus (Purplespotted big-eye) caught from the Gulf of Thailand were examined morphologically and characterized genetically by DNA sequence analysis. Sequence data from the mitochondrial cytochrome c oxidase subunit II (mtDNA cox2) gene were used to identify these nematodes to species level and to evaluate the phylogenetic relationship among various taxa. All the 15 third-stage larvae of Anisakis nematodes investigated in this study belonged to the same genetic lineage as the A. typica species complex (named here as A. typica sp. T - T for Thailand). Eight mtDNA cox2 haplotypes were revealed in the 15 isolates of this Anisakis from Thailand. The mtDNA cox2 haplotypes of A. typica sp. T from Thailand were genetically distinct from those of the A. typica sensu stricto. Taxonomic description of this A. typica sp. T as a distinct species however awaits the availability of adult specimens.

Molecular identification of Gnathostoma spinigerum (Nematoda: Gnathostomatidae) as causative agent of human gnathostomiasis in Thailand.

A 43-year-old male residing in Prachin Buri Province, Thailand, was admitted to the Siriraj University Hospital of Mahidol University, Thailand, in July 2014 with right eyelid swelling and serpiginous lesion for three weeks. A nematode specimen was accidentally recovered from his upper right eyelid area. The body of the worm was cylindrical and measured 11.0 × 1.4 mm. The head bulb had eight circles of transverse spines. Anterior half of the body was covered with rows of comb-like pointed spines. The tail part was rounded dorsally and flattened ventrally and no copulatory spicule was observed at the posterior end. It was morphologically identified as an immature female worm of gnathostome species. Sequence analysis for partial cytochrome c oxidase subunit I (COI) gene revealed this recovered nematode as Gnathostoma spinigerum.

Genetic variation of NADH dehydrogenase subunit 1 (nad1) mitochondrial gene sequence in adult Necator americanus hookworms recovered from a female patient in Thailand

@#Two female and one male adult hookworms were recovered from a female patient in Thailand. Based on gross and microscopic morphology, the three hookworms are members of Necator americanus. Phylogenetic reconstruction based on partial NADH dehydrogenase subunit 1 (nad1) mitochondrial gene sequences shows that these hookworms belong to the same genetic lineage as N. americanus adult worm from Zhejiang, China. The male and female hookworms were genetically distinct, belonging to two different nad1-haplotypes. This is the first report targeting the nad1 gene on the identification and genetic characterization of the human hookworms originated from infected patient. The nad1 gene marker is useful for species and higher taxa differentiation of hookworms.

Immunobiological diagnosis of tropical ocular diseases: Toxocara, Pythium insidiosum, Pseudomonas (Burkholderia) pseudomallei, Mycobacterium chelonei and Toxoplasma gondii.

Of the sera obtained from 18 patients with ocular diseases comprising ocular larva migrans (OLM), Toxoplasma gondii, Mycobacterium chelonei, Pythium insidiosum bacteria and tumour, 3 sera were positive for Toxocara antibody at the titre over 1/1600 ELISA. All 3 of these sera came from males with unilateral grayish fundi. We demonstrated the value of the direct immunofluorescent assay (DIFA) on vitreous specimens from 7 cases of Toxoplasma retinitis. One vitreous specimen under electronmicroscopic examination revealed bradyzoites of T. gondii. In addition, a few cases of keratoconjunctivitis/ corneal ulcer with endophthalmitis, due to P. insidiosum, Ps. pseudomallei and Mycobacterium chelonei, were also diagnosed.

Genetic differentiation of Anisakis species (Nematoda: Anisakidae) in marine fish Priacanthus tayenus from Gulf of Thailand

@#Members of the genus Anisakis are parasitic nematodes of the family Anisakidae. They are potential zoonotic parasites, causing anisakiasis in humans who consume raw or undercooked seafood (fish or squid) infected with the larvae of this nematode. In the present study, anisakid nematodes collected from the marine fish Priacanthus tayenus (Purplespotted big-eye) caught from the Gulf of Thailand were examined morphologically and characterized genetically by DNA sequence analysis. Sequence data from the mitochondrial cytochrome c oxidase subunit II (mtDNA cox2) gene were used to identify these nematodes to species level and to evaluate the phylogenetic relationship among various taxa. All the 15 third-stage larvae of Anisakis nematodes investigated in this study belonged to the same genetic lineage as the A. typica species complex (named here as A. typica sp. T – T for Thailand). Eight mtDNA cox2 haplotypes were revealed in the 15 isolates of this Anisakis from Thailand. The mtDNA cox2 haplotypes of A. typica sp. T from Thailand were genetically distinct from those of the A. typica sensu stricto. Taxonomic description of this A. typica sp. T as a distinct species however awaits the availability of adult specimens.