Angiostrongylus cantonensis is a zoonotic nematode parasite causing human eosinophilic meningitis (or meningoencephalitis) worldwide. A closely related species, Angiostrongylus malaysiensis, might also be a human pathogen. Larvae were obtained from land snails in Lao PDR, Cambodia, Myanmar and Thailand. We sequenced two nuclear gene regions (nuclear ribosomal ITS2 and SSU rRNA) and a portion of one mitochondrial gene (COI) from these larvae. Angiostrongylus cantonensis and A. malaysiensis were identified. This is the first report of the molecular identification of the two Angiostrongylus species in Lao PDR, Cambodia and Myanmar. The regional distributions of the two species broadly overlap. Phylogenetic relationships were inferred including data from Angiostrongylus species deposited in public databases. All the gene regions we sequenced have potential value in distinguishing between species of Angiostrongylus. The COI gene exhibited the greatest intraspecific variation in the study region (five haplotypes in A. cantonensis and four in A. malaysiensis) and might be suitable for more detailed phylogeographic studies.

Despite the existence of effective anthelmintics, parasitic infections remain a major public health problem in Southeast Asia, including Thailand. In rural communities, continuing infection is often reinforced by dietary habits that have a strong cultural basis and by poor personal hygiene and sanitation. This study presents a survey of the prevalence of intestinal parasitic infections among the people in rural Thailand. The community-based cross-sectional study was conducted in villages in Khon Kaen Province, northeastern Thailand, from March to August 2013. A total of 253 stool samples from 102 males and 140 females, aged 2-80 years, were prepared using formalin-ethyl acetate concentration methods and examined using light microscopy. Ninety-four individuals (37.2%) were infected with 1 or more parasite species. Presence of parasitic infection was significantly correlated with gender (P=0.001); nearly half of males in this survey (49.0%) were infected. Older people had a higher prevalence than younger members of the population. The most common parasite found was Opisthorchis viverrini (26.9%), followed by Strongyloides stercoralis (9.5%), Taenia spp. (1.6%), echinostomes (0.4%), and hookworms (0.4%). The prevalence of intestinal protozoa was Blastocystis hominis 1.6%, Entamoeba histolytica 0.8%, Entamoeba coli 0.8%, Balantidium coli 0.4%, Iodamoeba bütschlii 0.4%, and Sarcocystis hominis 0.4%. Co-infections of various helminths and protozoa were present in 15.9% of the people. The present results show that the prevalence of parasitic infections in this region is still high. Proactive education about dietary habits, personal hygiene, and sanitation should be provided to the people in this community to reduce the prevalence of intestinal parasite infections. Moreover, development of policies and programs to control parasites is needed.

The immunoglobulin G class (total IgG) and subclass (IgG1, IgG2, IgG3, and IgG4) antibody responses to the spirurid worm Gnathostoma spinigerum were analyzed by immunoblotting technique for the antibodies' potential use in the serodiagnosis of human gnathostomiasis. Serum samples from patients with proven gnathostomiasis and from clinically suspected cases of gnathostomiasis with migratory swelling were tested. Sera from patients with other parasitic illnesses and from healthy volunteers were also analyzed. The total IgG antibody to an antigenic band of approximately 24 kDa from a somatic extract of G. spinigerum advanced third-stage larvae (GS24) gave the highest sensitivity (91.6%) and 87.8% specificity. Individual IgG subclass detection had a lower sensitivity than the detection of specific total IgG antibody, but IgG4 had a slightly higher specificity (93.9%). However, for cost effectiveness, we suggest that anti GS24 total IgG is sufficient for the routine serodiagnosis of human gnathostomiasis as well as for seroepidemiological studies in developing countries.

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The 2 principal species of hookworms infecting humans are Necator americanus and Ancylostoma duodenale. Case studies on zoonotic hookworm infections with Ancylostoma ceylanicum and/or Ancylostoma caninum are known mainly from Asian countries. Of these 2 zoonotic species, only A. ceylanicum can develop to adulthood in humans. In the present study, we report a molecular-based survey of human hookworm infections present in southern and northeastern Thailand. Thirty larval hookworm samples were obtained from fecal agar plate cultures of 10 patients in northeastren Thailand and 20 in southern Thailand. Partial ITS1, 5.8S, and ITS2 regions of the ribosomal DNA genes were amplified using PCR. The amplicons were sequenced, aligned, and compared with other hookworm sequences in GenBank database. The results showed that, in Thailand, N. americanus is more prevalent than Ancylostoma spp. and is found in both study areas. Sporadic cases of A. ceylanicum and A. duodenale infection were seen in northeastern Thailand.