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Hookworm infections remain a significant public health concern in tropical and subtropical regions, including Thailand. This study investigated the species and genetic diversity of hookworm infections in domestic dogs from northeastern Thailand. The molecular analysis focused on amplifying and sequencing specific regions of ribosomal RNA genes (ITS1-5.8S-ITS2 region) and the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene in hookworm larvae recovered from 21 domestic dog stool samples. Among 21 larvae (one larva per infected dog) analyzed, 14 had sequences identical to Ancylostoma caninum, and 7 showed sequences almost identical to Ancylostoma ceylanicum. Phylogenetic analysis of cox1 sequences placed A. caninum and A. ceylanicum in separate clades. The median-joining network of A. caninum cox1 sequences from Thailand showed high haplotype diversity and belonged to the same cluster as sequences from Australia while forming separate clusters from those of A. caninum samples from the USA. The available published A. ceylanicum cox1 sequences (n = 33), in combination with seven sequences in the present study, represented 15 haplotypes distributed among three clusters. Interestingly, A. ceylanicum sequences from dogs and humans shared the same haplotypes. These findings are crucial for recognizing the potential for zoonotic transmission, highlighting the necessity for targeted control measures, and increasing awareness among pet owners and healthcare professionals to mitigate the risk of hookworm transmission to humans., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Chronic infections of humans with Opisthorchis viverrini and Clonorchis sinensis spanning decades may lead to life-threatening pathology prior to cholangiocarcinoma (CCA), which usually has a poor prognosis. Serological tools can support the parasitological examination in clinical diagnosis and support screening for risk of CCA. We developed novel immunochromatographic test kits using a soluble, somatic tissue extract of adult O. viverrini worms as an antigen and colloidal gold-labeled conjugates of IgG and IgG4 antibodies, and evaluated the diagnostic values of both the OvSO-IgG and OvSO-IgG4 kits. For diagnosis of human opisthorchiasis individually, the diagnostic sensitivity, specificity, and positive and negative predictive values with 95% confidence intervals in the OvSO-IgG kit were 86.6% (78.9-92.3), 89.5% (84.2-93.5), 82.9% (74.8-89.2), and 91.9% (87.0-95.4), respectively, while the 75% (65.9-82.7), 98.4% (95.5-99.7), 96.6% (90.3-99.3), and 87% (81.7-91.2), respectively, for the OvSO-IgG4 kit at the prevalence of infection of 37.1%. Twenty-three (76.7%) and 14 (46.7%) of 30 clonorchiasis sera showed positive reactivity with the OvSO-IgG and OvSO-IgG4 kits, respectively. There was 84.1% (κ-value = 0.649) concordance between the two kits, which was statistically significant (p < 0.001). Both ICT kits can be employed as quick and easy point-of-care diagnostic tools, and hence, the OvSO-IgG and OvSO-IgG4 kits can support expanded capacity for clinical diagnosis of human opisthorchiasis and clonorchiasis. These kits may find utility in large-scale surveys in endemic areas where there are limited sophisticated medical facilities or capacity., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Cattle and buffaloes, popular protein sources worldwide, are intermediate hosts for several Sarcocystis species. These coccidian protozoans cause sarcocystosis resulting in subclinical and chronic infections in striated muscles by forming macrocysts or microcysts. In Thailand, Lao People's Democratic Republic, and Cambodia, Sarcocystis species have been reported, but molecular identification has been lacking. This study investigates the prevalence of infection, histo-morphology, and molecular identification of Sarcocystis species in hearts of cattle and buffalo sold in local markets. A phylogenetic tree inferred from a portion of the 18S ribosomal (r) RNA gene was used to identify the genus and species of Sarcocystis. The mitochondrial cytochrome c oxidase subunit 1 (cox-1 gene) was sequenced to confirm the species of host tissue. In Thailand, Sarcocystis was detected in 66.7% (14/21) of samples. In Lao People's Democratic Republic, 90% (9/10) of samples were infected and in Cambodia 100% (8/8). For the first time from these countries, we report Sarcocystis cruzi, Sarcocystis heydorni, and Sarcocystis levinei found in taurine cattle (Bos taurus) and water buffalo (Bubalus bubalis). Zoonotic protozoan transmission needs to be controlled by inspection activities by local health inspectors, and appropriate action is required at all points in the food chain by competent authorities to protect consumer health and prevent sarcocystosis in cattle and water buffaloes., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Fascioliasis, a food- and water-borne trematodiasis, has been identified as a public health threat by the World Health Organization, with millions of people estimated to be infected or at risk of infection worldwide. We developed an immunochromatographic test (ICT) as a point-of-care (POC) tool for the rapid serodiagnosis of human fascioliasis caused by Fasciola gigantica and evaluated their diagnostic ability. Two tests were developed using antigens from adult F. gigantica excretory-secretory (ES) product and recombinant F. gigantica cathepsin L (rFgCL). Sera from 12 patients with parasitologically proven fascioliasis caused by F. gigantica, 18 with clinically suspected fascioliasis, 65 with other parasitic infections, and 30 healthy controls were used. Using a cutoff of > 0.5 for antibody detection, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the ES-based ICT method were 100%, 98.9% 96.8%, 100%, and 99.2%, respectively, and those of the rFgCL-based ICT method were 86.7%, 93.7%, 81.3%, 95.7%, and 92.0%, respectively. The concordance between the two methods was 91.2%. Tests using F. gigantica ES and rFgCL antigens can be employed quickly and easily as POC diagnostic tools. They can be used to support the clinical diagnosis of human fascioliasis gigantica and in large-scale surveys in endemic areas throughout tropical regions without necessitating additional facilities or ancillary supplies.

Gnathostomiasis, an emerging food-borne parasitic zoonosis in Asia, is mainly caused by Gnathostoma spinigerum (Nematoda: Gnathostomatidae). Consumption of raw meat or freshwater fishes in endemic areas is the major risk factor. Throughout Southeast Asia, including Thailand, Lao PDR, Cambodia, and Myanmar, freshwater fish are often consumed raw or undercooked. The risk of this practice for gnathostomiasis infection in Lao PDR, Cambodia, and Myanmar has never been evaluated. Here, we identified larvae of Gnathostoma species contaminating freshwater fishes sold at local markets in these three countries. Public health authorities should advise people living in, or travelling to, these areas to avoid eating raw or undercooked freshwater fishes. Identification of larvae was done using molecular methods: DNA was sequenced from Gnathostoma advanced third-stage larvae recovered from snakehead fishes (Channa striata) and freshwater swamp eels (Monopterus albus). Phylogenetic analysis of a portion of the mitochondrial cytochrome c oxidase subunit I gene showed that the G. spinigerum sequences recovered from southern Lao PDR, Cambodia, and Myanmar samples had high similarity to those of G. spinigerum from China. Sequences of the nuclear ribosomal DNA internal transcribed spacer 2 region closely resembled sequences of G. spinigerum from Thailand, Indonesia, the USA, and central Lao PDR. This is the first molecular evidence of G. spinigerum from freshwater fishes in southern Lao PDR, Cambodia, and Myanmar.

Ascaris lumbricoides is the largest roundworm known from the human intestine while Ascaris suum is an internal parasite of pigs. Ascariasis, caused by Ascaris lumbricoides, has a worldwide distribution. Here, we have provided the first molecular identification of Ascaris eggs and adults recovered from humans and pigs in Thailand, Lao PDR, and Myanmar. We amplified and sequenced nuclear ribosomal DNA (ITS1 and ITS2 regions) and mitochondrial DNA (cox1 gene). Sequence chromatograms of PCR-amplified ITS1 region revealed a probable hybrid genotype from two human ascariasis cases from Chiang Mai Province, northern Thailand. All complete ITS2 sequences were identical and did not differ between the species. Phylogenetic trees and haplotype analysis of cox1 sequences showed three clusters with 99 haplotypes. Forty-seven samples from the present study represented 14 haplotypes, including 7 new haplotypes. To our knowledge, this is the first molecular confirmation of Ascaris species in Thailand, Lao PDR, and Myanmar. Zoonotic cross-transmission of Ascaris roundworm between pigs and humans probably occurs in these countries.

The present study explored potentially immunogenic proteins of the encapsulated (Trichinella spiralis) and non-encapsulated (T. pseudospiralis, T. papuae) species within the genus Trichinella. The somatic muscle larval extracts of each species were subjected to immunoblotting analysis using human T. spiralis-infected serum samples. Fifteen reactive bands of all three species were selected for further protein identification by liquid chromatography-tandem mass spectrometry, and their possible functions were ascertained using the gene ontology. Our findings showed immunogenic protein patterns with molecular mass in the range of 33-67 kDa. Proteomic and bioinformatic analysis revealed a wide variety of functions of 17 identified proteins, which are associated with catalytic, binding, and structural activities. Most proteins were involved in cellular and metabolic processes that contribute in the invasion of host tissues and the larval molting processes. The parasite proteins were identified as actin-5C, serine protease, deoxyribonuclease-2, and intermediate filament protein ifa-1. This information may lead to alternative tools for selection of potential diagnostic protein markers or aid in the design of vaccine candidates for prevention and control of Trichinella infection.

Intestinal capillariasis, a fish-borne nematodiasis, is an important emerging zoonotic disease. Patients present clinical symptoms of borborygmus chronic diarrhea, intermittent abdominal pain, weight loss, and several degrees of painless lower-leg edema. Death may occur in cases of misdiagnosis and improper treatment. Diagnosis is difficult because of the atypical clinical symptoms and diagnostic confusion with diarrhea caused by gastrointestinal cancer, opportunistic infections in human immunodeficiency virus patients, and hyperthyroidism. In addition, parasite eggs are not always found in stool examination. Serology can provide a supportive diagnostic tool. We have produced a rapid and simple immunochromatographic test (ICT) kit for diagnosis of intestinal capillariasis by detection of diagnostic antibodies in human sera. Serum samples from healthy volunteers and patients with proven intestinal capillariasis and other parasitic diseases were evaluated with the Trichinella spiralis larval extract antigen absorbed ICT strips. The diagnostic sensitivity, specificity, and positive and negative predictive values were 100, 96.6, 90.2, and 100%, respectively. The ICT kit is simple and rapid to use and can supplement stool examination in clinical diagnosis of intestinal capillariasis. The test can be completed in 15 min without a need for any sophisticated instruments or reagents.

Lymphatic filariasis, a mosquito-borne disease, is still a major public health problem in tropical and sub-tropical countries. Effective diagnostic tools are required for identification of infected individuals, for epidemiological assessment, and for monitoring of control programs. A duplex droplet digital polymerase chain reaction (ddPCR) was conducted to differentiate and quantify Wuchereria bancrofti DNA by targeting the long DNA repeat (LDR) element and Brugia malayi DNA by targeting the HhaI element in blood samples and mosquito vectors. The analytical sensitivity and specificity were evaluated. Our results indicated that the duplex ddPCR assay could differentiate and quantify W. bancrofti and B. malayi DNA from blood samples and mosquitoes. DNA from a single larva in 50 μl of a blood sample, or in one mosquito vector, could be detected. The analytical sensitivity and specificity for W. bancrofti are both 100 %. Corresponding values for B. malayi are 100 and 98.3 %, respectively. Therefore, duplex ddPCR is a potential tool for simultaneous diagnosis and monitoring of bancroftian and brugian filariasis in endemic areas.

Strongyloidiasis is a major soil-transmitted helminth (STH) disease that affects people worldwide. We present updated data on prevalence in the Lao People's Democratic Republic (Lao PDR) in 2015, arising from a community cross-sectional helminthiasis survey. Fecal samples were collected from 327 individuals across three provinces in Lao PDR (Luang Prabang in the north, Khammouane in the center, and Champasack in the south). Agar plate culture and Kato-Katz methods were used to examine duplicate stool samples from each participant to detect Strongyloides stercoralis and co-infecting helminths. Overall prevalences of S. strercoralis human hookworm, Taenia spp., Trichuris trichiura, Ascaris lumbricoides, and Enterobius vermicularis were 41.0, 28.1, 4.9, 4.0, 1.5, and 0.9 %, respectively. The prevalence of miscellaneous trematodiases (including opisthorchiasis) was 37.9 % and of Schistosoma mekongi infection was 0.3 %. Strongyloidiasis is a current major STH disease in Lao PDR. We also report the molecular-phylogenetic identification of S. stercoralis adult males collected from 40 representative human strongyliodiasis fecal samples. DNA was extracted, amplified, and sequenced from a portion of the mitochondrial cox1 gene and the nuclear 18S ribosomal DNA. Phylogenetic analyses indicated that all specimens sequenced belonged to S. stercoralis (Bavay, 1876) Stiles and Hassall, 1902. The cox1 sequences exhibited great diversity (24 haplotypes) in Lao PDR. This is the first molecular identification and report of genetic diversity of S. stercoralis in humans from Lao PDR. An effective parasite control program is needed to reduce the serious health impacts.