Rapid resurgence of syphilis in Japan after the COVID-19 pandemic: A descriptive study.

Some countries have reported a post-pandemic resurgence in syphilis prevalence, but trend data in the World Health Organization Western Pacific Region (WHO-WPRO), including Japan, are severely lacking. Thus, the present study compares the number of syphilis cases before and after the COVID-19 pandemic in some WHO-WPRO countries. In addition, temporal trends in the number of syphilis cases in Japan pre- and post-pandemic are described. Annual numbers of syphilis cases during the study periods from China, New Zealand, Australia and Japan were compared. Annual trends of the numbers of syphilis cases during the same study periods were examined in Japan. In 2020, the number of syphilis-positive cases decreased in all four countries. In 2021, though, China, Australia and Japan all showed an increase in the numbers of syphilis cases. However, the rate of increase in China (+2.8%) and Australia (+4.8%) was low compared to Japan (+36.0%). The number of syphilis cases in New Zealand in 2021 was 12.6% lower than in 2020. In 2022, the number of cases of syphilis in China was 7.4% lower than in 2021. The increase of syphilis-positive cases was approximately 6.3-fold higher in Japan compared to Australia (+66.2% vs. +10.5%) in 2022. In conclusion, post-pandemic resurgence of syphilis occurred in Australia and Japan, but not in China and New Zealand. The reason for the substantial increase in syphilis-positive cases in Japan remains unclear. Post-pandemic, prevention and control of sexually transmitted infections still require attention.

Web-Based Search Volume for HIV Tests and HIV-Testing Preferences During the COVID-19 Pandemic in Japan: Infodemiology Study.

BACKGROUND: Research has found a COVID-19 pandemic-related impact on HIV medical services, including clinic visits, testing, and antiviral therapy initiation in countries including Japan. However, the change in trend for HIV/AIDS testing during the COVID-19 pandemic has not been explored extensively in the Japanese population. OBJECTIVE: This infodemiology study examines the web-based search interest for two types of HIV tests, self-test kits and facility-based tests, before and during the COVID-19 pandemic in Japan. METHODS: The monthly search volume of queried search terms was obtained from Yahoo! JAPAN. Search volumes for the following terms were collected from November 2017 to October 2018: "HIV test," "HIV test kit," and "HIV test health center." The search term "Corona PCR" and the number of new COVID-19 cases by month were used as a control for the search trends. The number of new HIV cases in the corresponding study period was obtained from the AIDS Trend Committee Quarterly Report from the AIDS Prevention Foundation. RESULTS: Compared to the search volume of "corona-PCR," which roughly fluctuated corresponding to the number of new COVID-19 cases in Japan, the search volume of "HIV test" was relatively stable from 2019 to 2022. When we further stratified by the type of HIV test, the respective web-based search interest in HIV self-testing and facility-based testing showed distinct patterns from 2018 to 2022. While the search volume of "HIV test kit" remained stable, that of "HIV test health center" displayed a decreasing trend starting in 2018 and has remained low since the beginning of the COVID-19 pandemic. Around 66%-71% of the search volume of "HIV test kits" was attributable to searches made by male internet users from 2018 to 2022, and the top three contributing age groups were those aged 30-39 (27%-32%), 20-29 (19%-32%), and 40-49 (19%-25%) years. On the other hand, the search volume of "HIV test health centers" by male users decreased from more than 500 from 2018 to 2019 to fewer than 300 from 2020 to 2022. CONCLUSIONS: Our study found a notable decrease in the search volume of "HIV test health center" during the pandemic, while the search volume for HIV self-testing kits remained stable before and during the COVID-19 crisis in Japan. This suggests that the previously reported COVID-19-related decrease in the number of HIV tests mostly likely referred to facility-based testing. This sheds light on the change in HIV-testing preferences in Japan, calling for a more comprehensive application and regulatory acceptance of HIV self-instructed tests.

Effects of Serum Antibody Test Reagent Discontinuation on Diagnosis of Amebiasis in Japan: Interrupted Time-Series Analysis.

Amebiasis is a notifiable infectious disease in Japan, and the number of reported cases had been on the rise, but since the discontinuation of insurance-covered serum antibody testing reagent in 2017, concerns have arisen regarding the decrease in reported cases. This study aimed to investigate changes occurring after discontinuation of the serum antibody test reagent production. We retrospectively analyzed amebiasis cases from January 2014 to December 2019 using the National Center for Epidemiology of Infectious Diseases system. Interrupted time-series regression analysis was used to evaluate trends in weekly amebiasis cases before and after the discontinuation period. The study period was divided into prediscontinuation (2014-2017) and discontinuation (2018-2019) periods. A total of 6,179 amebiasis cases were reported. The average numbers of weekly cases were 21.5 during 2014-2017 and 16.3 during 2018-2019. The frequency of diagnoses decreased in the discontinuation period (prevalence rate ratio = 0.78; 95% CI, 0.67-0.89; P < 0.01). Subgroup analysis showed lower diagnostic rates, particularly for extraintestinal amebiasis (prevalence rate ratio = 0.37; 95% CI, 0.22-0.55; P < 0.01). We observed a significant decrease in the number of reported amebiasis cases per week after discontinuation of the serum antibody test reagent in Japan. Our findings hold significance for both public health policy and practice in Japan, underscoring the requirement for enhanced amebiasis diagnostic tools and strategies. To ensure accurate diagnosis, availability of antibody reagents for serum testing, covered by insurance, should be encouraged.

High body temperature increases gut microbiota-dependent host resistance to influenza A virus and SARS-CoV-2 infection.

Fever is a common symptom of influenza and coronavirus disease 2019 (COVID-19), yet its physiological role in host resistance to viral infection remains less clear. Here, we demonstrate that exposure of mice to the high ambient temperature of 36 °C increases host resistance to viral pathogens including influenza virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). High heat-exposed mice increase basal body temperature over 38 °C to enable more bile acids production in a gut microbiota-dependent manner. The gut microbiota-derived deoxycholic acid (DCA) and its plasma membrane-bound receptor Takeda G-protein-coupled receptor 5 (TGR5) signaling increase host resistance to influenza virus infection by suppressing virus replication and neutrophil-dependent tissue damage. Furthermore, the DCA and its nuclear farnesoid X receptor (FXR) agonist protect Syrian hamsters from lethal SARS-CoV-2 infection. Moreover, we demonstrate that certain bile acids are reduced in the plasma of COVID-19 patients who develop moderate I/II disease compared with the minor severity of illness group. These findings implicate a mechanism by which virus-induced high fever increases host resistance to influenza virus and SARS-CoV-2 in a gut microbiota-dependent manner.

Longitudinal Analyses after COVID-19 Recovery or Prolonged Infection Reveal Unique Immunological Signatures after Repeated Vaccinations.

To develop preventive and therapeutic measures against coronavirus disease 2019, the complete characterization of immune response and sustained immune activation following viral infection and vaccination are critical. However, the mechanisms controlling intrapersonal variation in antibody titers against SARS-CoV-2 antigens remain unclear. To gain further insights, we performed a robust molecular and cellular investigation of immune responses in infected, recovered, and vaccinated individuals. We evaluated the serum levels of 29 cytokines and their correlation with neutralizing antibody titer. We investigated memory B-cell response in patients infected with the original SARS-CoV-2 strain or other variants, and in vaccinated individuals. Longitudinal correlation analyses revealed that post-vaccination neutralizing potential was more strongly associated with various serum cytokine levels in recovered patients than in naïve individuals. We found that IL-10, CCL2, CXCL10, and IL-12p40 are candidate biomarkers of serum-neutralizing antibody titer after the vaccination of recovered individuals. We found a similar distribution of virus-specific antibody gene families in triple-vaccinated individuals and a patient with COVID-19 pneumonia for 1 year. Thus, distinct immune responses occur depending on the viral strain and clinical history, suggesting that therapeutic options should be selected on a case-by-case basis. Candidate biomarkers that correlate with repeated vaccination may support the efficacy and safety evaluation systems of mRNA vaccines and lead to the development of novel vaccine strategies.

COVID-19 Severity and Thrombo-Inflammatory Response Linked to Ethnicity.

Although there is strong evidence that SARS-CoV-2 infection is associated with adverse outcomes in certain ethnic groups, the association of disease severity and risk factors such as comorbidities and biomarkers with racial disparities remains undefined. This retrospective study between March 2020 and February 2021 explores COVID-19 risk factors as predictors for patients' disease progression through country comparison. Disease severity predictors in Germany and Japan were cardiovascular-associated comorbidities, dementia, and age. We adjusted age, sex, body mass index, and history of cardiovascular disease comorbidity in the country cohorts using a propensity score matching (PSM) technique to reduce the influence of differences in sample size and the surprisingly young, lean Japanese cohort. Analysis of the 170 PSM pairs confirmed that 65.29% of German and 85.29% of Japanese patients were in the uncomplicated phase. More German than Japanese patients were admitted in the complicated and critical phase. Ethnic differences were identified in patients without cardiovascular comorbidities. Japanese patients in the uncomplicated phase presented a suppressed inflammatory response and coagulopathy with hypocoagulation. In contrast, German patients exhibited a hyperactive inflammatory response and coagulopathy with hypercoagulation. These differences were less pronounced in patients in the complicated phase or with cardiovascular diseases. Coagulation/fibrinolysis-associated biomarkers rather than inflammatory-related biomarkers predicted disease severity in patients with cardiovascular comorbidities: platelet counts were associated with severe illness in German patients. In contrast, high D-dimer and fibrinogen levels predicted disease severity in Japanese patients. Our comparative study indicates that ethnicity influences COVID-19-associated biomarker expression linked to the inflammatory and coagulation (thrombo-inflammatory) response. Future studies will be necessary to determine whether these differences contributed to the less severe disease progression observed in Japanese COVID-19 patients compared with those in Germany.

The impact of the COVID-19 pandemic on other infections differs by their route of transmission: A retrospective, observational study in Japan.

INTRODUCTION: The Coronavirus disease 2019 (COVID-19) pandemic and people's subsequent behavioral changes have decreased the cases of respiratory infection worldwide. However, research on infectious diseases with other transmission modes is insufficient. The aim was to assess the impact of the COVID-19 pandemic on non-respiratory infectious diseases: infectious enterocolitis, sexually transmitted diseases such as human immunodeficiency virus (HIV) infection and syphilis, and tick-borne diseases. METHODS: This retrospective, cohort study used comprehensive surveillance data from the National Institute of Infectious Diseases in Japan from January 1, 2018, to December 31, 2021. The number of cases of infectious diseases before the COVID-19 pandemic (2018-2019) was compared with that during the COVID-19 pandemic (2020-2021). Reduction rates were calculated as the number of disease cases during the COVID-19 pandemic in 2020 and 2021, respectively, divided by the mean number of disease cases in 2018 and 2019. RESULTS: The total numbers of cases of infectious enterocolitis, sexually transmitted diseases, and tick-borne diseases during the study period were 2,507,304 cases, 24,972 cases, and 3012 cases, respectively. The number of cases decreased for infectious enterocolitis and sexually transmitted diseases during the COVID-19 pandemic compared with before the COVID-19 pandemic, with an approximately 40-50% decrease in enterocolitis and 30-55% decreases in sexually transmitted diseases. However, cases of tick-borne diseases changed little, with a 0.2% increase in 2020 and a 6% increase in 2021. CONCLUSION: The COVID-19 pandemic had a different impact on the number of cases of infectious diseases depending on their mode of transmission.

Molecular characterization of SARS-CoV-2 detected in Tokyo, Japan during five waves: Identification of the amino acid substitutions associated with transmissibility and severity.

Many variants of SARS-CoV-2 have emerged around the world. It is therefore important to understand its global viral evolution and the corresponding mutations associated with transmissibility and severity. In this study, we analyzed 112 whole genome sequences of SARS-CoV-2 collected from patients at Juntendo University Hospital in Tokyo and the genome data from entire Japan deposited in Global Initiative on Sharing Avian Influenza Data (GISAID) to examine the relationship of amino acid changes with the transmissibility and the severity of each strain/lineage. We identified 12 lineages, including B.1.1.284, B.1.1.214, R.1, AY.29, and AY.29.1, which were prevalent specifically in Japan. B.1.1.284 was most frequently detected in the second wave, but B.1.1.214 became the predominant lineage in the third wave, indicating that B.1.1.214 has a higher transmissibility than B.1.1.284. The most prevalent lineage during the fourth and fifth wave was B.1.1.7 and AY.29, respectively. In regard to the severity of identified lineages, B.1.1.214 was significantly lower than the reference lineage, B.1.1.284. Analysis of the genome sequence and other traits of each lineage/strain revealed the mutations in S, N, and NSPs that increase the transmissibility and/or severity. These mutations include S: M153T, N: P151L, NSP3: S543P, NSP5: P108S, and NSP12: A423V in B.1.1.284; S: W152L and E484K in R.1; S: H69del, V70del, and N501Y in the Alpha strain; S: L452R, T478K, and P681R in the Delta strain. Furthermore, it is suggested that the transmissibility of B.1.1.214 could be enhanced by the mutations N: M234I, NSP14: P43L, and NSP16: R287I. To address the issue of the virus evolution, it is necessary to continuously monitor the genomes of SARS-CoV-2 and analyze the effects of mutations for developing vaccines and antiviral drugs effective against SARS-CoV-2 variants.

Syphilis in people living with HIV does not account for the syphilis resurgence in Japan.

OBJECTIVES: This study aimed to determine whether the current syphilis resurgence in Japan is attributable to incident syphilis in people living with HIV (PLWH). METHODS: This observational, retrospective, population-based study used data from the Japanese National Database. Data were extracted for PLWH who received antiretroviral treatment between January 2009 and December 2018. Using these data, along with the annual number of PLWH and syphilis diagnoses in the total population of Japan acquired from the National Institute of Infectious Diseases, the fraction of PLWH with syphilis compared to the total number of syphilis patients reported each year was calculated. RESULTS: There was a dramatic increase in syphilis cases during the study period. However, the incidence of syphilis in PLWH was stable during 2010-2018; the fraction of PLWH with newly diagnosed syphilis remaining at approximately 2% of the total PLWH cases in Japan each year. The proportion of newly diagnosed syphilis cases in PLWH decreased during the study period and accounted for <10% of the total syphilis cases in Japan since 2016 (14.9% in 2015 to 9.5% in 2016 and 5.9% in 2018). An increasing trend in the number of newly diagnosed syphilis cases in PLWH aged >50 years was observed (7.4% in 2010 to 10.4% in 2014 and 14.9% in 2018). CONCLUSIONS: The recent dramatic increase in syphilis cases in Japan was not seen in PLWH. Thus, the resurgence of syphilis in Japan cannot be attributed to its transmission in the PLWH population.

Pneumonia, influenza, and dengue cases decreased after the COVID-19 pandemic in Thailand.

The coronavirus disease 2019 (COVID-19) pandemic has affected all healthcare systems worldwide. Effective COVID-19 preventive measures, including wearing a mask, hand washing, avoiding the "Three Cs", and city lockdowns, could decrease other infectious diseases. The case numbers of the major infectious diseases in Thailand were investigated (pneumonia, influenza, and dengue fever) during the COVID-19 pandemic using Thailand government national data sources from 2018 to August 2021. Pneumonia, influenza, and dengue fever cases decreased after the COVID-19 pandemic. In addition to respiratory tract infections, COVID-19 preventive measures could decrease dengue fever cases.

Analysis of antiretroviral therapy switch rate and switching pattern for people living with HIV from a national database in Japan.

To report the status of switch rates and time-to-switch of antiretroviral therapy (ART) regimens by evaluating anchor drug classes and common switching patterns in Japanese people living with human immunodeficiency virus (HIV, PLWH). This cross-sectional cohort study extracted data of 28,089 PLWH from the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB), which contains data representing the entire population of Japan. PLWH with first prescription records of ART administered between January 2011 and March 2019 were identified (n = 16,069). The median time-to-switch and switch rates of anchor drug classes were estimated by Kaplan-Meier analysis. Brookmeyer-Crowley and Greenwood methods were used to estimate 95% confidence intervals for switch rates and median days, respectively. Switch rates were compared between anchor drug classes by year using log-rank tests. A total of 3108 (19.3%) PLWH switched anchor drug classes from first to second regimens. Switch rates increased continuously over 8 years for non-nucleoside reverse transcriptase inhibitors (NNRTIs) (14.9-65.5%) and protease inhibitors (PIs) (13.2-67.7%), with median time-to-switch of 1826 and 1583 days, respectively. Integrase strand transfer inhibitors (INSTIs) maintained a low switch rate (3.0-7.6%), precluding median-days calculation. Overall, the majority of patients treated initially with NNRTIs and PIs switched to INSTIs regardless of switching times (< 1 year: 67.3% and 85.9%, respectively; ≥ 1 year: 95.5% and 93.6%, respectively). The foremost switching strategies for first-to-second ART regimens are from NNRTIs or PIs to INSTIs regimens that maintain low switch rates long term. There was no observable difference in trend between sex, age and status of AIDS disease at first ART regimen. INSTIs HIV agents may be the most durable anchor drug class for PLWH receiving ART.

Delayed diagnosis of human immunodeficiency virus infection in people diagnosed with syphilis: A nationwide cohort study from 2011 to 2018 in Japan.

Early treatment of HIV infection depends on timely diagnosis, but many persons living with HIV/AIDS (PLWHA) are unaware of their infection. Though many patients seeking medical attention for sexually transmitted diseases have HIV, many patients' HIV co-infection is undiagnosed in Japan. This is the first report to analyze the timing of syphilis infection in PLWHA of all ages through the use of the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB), containing clinical data of the largest group of HIV-positive patients available in Japan. Overall, 1521 PLWHA (male 93.2%) newly diagnosed and started on antiretroviral therapy were identified in 2016, and 646 (42.5%) patients had a diagnosis of syphilis between 2011 and 2018. Although 100 patients were diagnosed with syphilis before their HIV diagnosis, only 17 (17.0%) had been tested for HIV. Over 50 patients per year became infected with syphilis even after their HIV diagnosis (2017, n = 65 (4.3%); 2018, n = 58 (3.8%)). Although early diagnosis of HIV infection is important, most syphilis patients in Japan had not been properly tested for HIV infection. Since a certain number of HIV patients developed syphilis after HIV diagnosis, education for newly diagnosed HIV patients is important.

The COVID-19 pandemic increased the demand for pneumococcal vaccination in Japan.

Although routine vaccinations in children decreased during the coronavirus disease 2019 (COVID-19) pandemic, pneumococcal vaccine coverage in older adults has remained unknown. This study was performed to investigate the impact of the COVID-19 pandemic on pneumococcal vaccination in Japan. The numbers of 23-valent pneumococcal polysaccharide vaccines (PPV23) shipped was obtained from an office memorandum released by the Ministry of Health, Labor and Welfare. The results showed that the COVID-19 pandemic increased the need for pneumococcal vaccination, causing shipping restrictions of pneumococcal vaccines. Regular vaccination is still important because there may be a shortage of vaccines during a pandemic.

Molecular identification of Pentatrichomonas hominis in animals in central and western Thailand.

BACKGROUND: Pentatrichomonas hominis inhabits the digestive tracts of several vertebrates, such as humans, monkeys, pigs, dogs, cats and rats. This protozoan was originally considered a commensal of the digestive tract but has subsequently been identified as a potential zoonotic parasite and a causative agent of diarrhoea. Molecular techniques are considered more sensitive and specific to detect P. hominis. This study aimed to determine the presence and genetic diversity of P. hominis in animals in Thailand. A total of 403 faecal samples were collected from 119 cats, 55 dogs, 73 goats, 35 monkeys, 55 cattle and 66 pigs, and the presence of P. hominis was determined using the nested polymerase chain reaction method. Sequence analysis of small-subunit ribosomal RNA genes was used to determine the genotype of the organism. RESULTS: Twenty-six samples (26/403, 6.45%) were positive for P. hominis. The highest prevalence was found in cats (21/119; 17.65%), followed by cattle (3/55; 5.45%) and dogs (2/55; 3.64%). Seven out of 26 nucleotides demonstrated 100% sequence identity with existing sequences; additionally, 16 novel sequence patterns were identified. All nucleotide sequences of P. hominis-positive samples were shown in the same branch with the previously described P. hominis sequences found in humans, dogs and goat. CONCLUSION: This is the first study on P. hominis infections in animals in Thailand. Our findings revealed that the prevalence of P. hominis was significantly higher in cats than in cattle and dogs. Cats were the main reservoir host; however, P. hominis can infect several kinds of animals. Therefore, the proper waste management of animals is necessary to reduce and prevent infection in the community.

"Enterocytozoon bieneusi and Cryptosporidium: a cross-sectional study conducted throughout Thailand".

BACKGROUND: Enterocytozoon bieneusi and Cryptosporidium spp. are prevalent zoonotic parasites associated with a high burden among children. To date only limited molecular epidemiological data on E. bieneusi and Cryptosporidium spp. in humans living in Thailand has been published. METHODS: PCR-based tools were used to detect and characterize E. bieneusi and Cryptosporidium spp. The internal transcribed spacer (ITS) region of the rRNA gene was used to investigate E. bieneusi, and the small subunit (SSU) rRNA gene was used to investigate Cryptosporidium spp., and 697 fecal samples from villagers and school children in rural areas in Thailand were analyzed. RESULTS: The infection rates were 2.15% (15/697) for E. bieneusi and 0.14% (1/697) for Cryptosporidium spp. The prevalence of E. bieneusi was significantly high in Loei province. Sequence analysis indicated that the Cryptosporidium isolate was C. parvum. Nine E. bieneusi genotypes were identified, EbpC, Peru12, TMH6, TMH3, TMH7, H, D, and two novel genotypes TMLH1 and TMLH2. E. bieneusi prevalence was significantly higher in male participants than in female participants, and in children aged 3-15 years than in participants aged > 15 years. CONCLUSIONS: The prevalence, genotypes, and zoonotic potential of E. bieneusi were found to vary significantly high even in one country. Transmission routes and key animal carriers of E. bieneusi may be associated with differences in hygiene, sanitation, and cultural behaviors. Further molecular studies including longitudinal studies will be required to unveil epidemiological characteristics of these opportunistic intestinal protozoa in all over the countries.

Mass spectrometry-based identification and whole-genome characterisation of the first pteropine orthoreovirus isolated from monkey faeces in Thailand.

BACKGROUND: The pteropine orthoreovirus (PRV) was isolated from monkey (Macaca fascicularis) faecal samples collected from human-inhabited areas in Lopburi Province, Thailand. These samples were initially obtained to survey for the presence of hepatitis E virus (HEV). RESULTS: Two virus isolates were retrieved by virus culture of 55 monkey faecal samples. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was successfully used to identify the viruses as the segmented dsRNA orthoreovirus. Phylogenetic analysis of the Lopburi orthoreovirus whole-genomes revealed relationships with the well-characterised PRVs Pulau (segment L1), Cangyuan (segments L2, M3 and S3), Melaka (segments L3 and M2), Kampar (segments M1 and S2) and Sikamat (segments S1 and S4) of Southeast Asia and China with nucleotide sequence identities of 93.5-98.9%. RT-PCR showed that PRV was detected in 10.9% (6/55) and HEV was detected in 25.5% (14/55) of the monkey faecal samples. CONCLUSIONS: PRV was isolated from monkey faeces for the first time in Thailand via viral culture and LC-MS/MS. The genetic diversity of the virus genome segments suggested a re-assortment within the PRV species group. The overall findings emphasise that monkey faeces can be sources of zoonotic viruses, including PRV and HEV, and suggest the need for active virus surveillance in areas of human and monkey co-habitation to prevent and control emerging zoonotic diseases in the future.

Blastocystis subtype 5: Predominant subtype on pig farms, Thailand.

Blastocystis is a unicellular protist most commonly detected in humans and a variety of animals. The predominant mode of its transmission is the fecal-oral route, but its zoonotic potential is not completely understood. The objective of this study was to determine the presence and genetic diversity of Blastocystis on pig farms in Nakhon Pathom Province, Central Thailand. A total of 154 human and 90 pig stool samples were collected and analyzed. Nested PCR detected Blastocystis in 35.55% of the pig samples and 6.49% of the human samples. Subtyping based on regions of the small-subunit ribosomal RNA (SSU rRNA) gene identified three Blastocystis subtypes in pigs and humans: ST1, ST3, and ST5. Blastocystis ST5 was the predominant subtype, followed by ST1 and then ST3. All the sequences from the Blastocystis-positive samples from both pigs and humans were closely related. This study reveals a possibility of low host specificity of Blastocystis STs (ST1, ST3 and ST5) on pig farms in Thailand. We tentatively suggest that close contact with or exposure to pig stools may be a significant source of Blastocystis detected in pig handlers. Further studies are required to confirm the zoonotic transmission of this organism in Thailand, because pigs may play an important role in the transmission of Blastocystis.

Blastocystis infection and subtype distribution in humans, cattle, goats, and pigs in central and western Thailand.

Blastocystis is a common intestinal pathogen of humans and a variety of animals, with various host-specific subtypes. The aim of this study was to determine the prevalence and subtype distribution of Blastocystis in humans and domestic animals, Thailand. 113 stool samples were collected from pigs, goats, and cattle in Ayutthaya Province (AP; central Thailand) and 218 stool samples were collected from pigs, dogs, cats, chickens, and humans in Kanchanaburi Province (KP; western Thailand). Blastocystis was detected by nested PCR targeting the SSU rRNA gene. Subtypes were identified by DNA sequencing, and phylogenetic analysis was conducted. The overall prevalence of Blastocystis in animals was 76.1% (86/113) and 11.88% (12/101) in AP and KP, respectively, and the prevalence in humans was 12.82% (15/117) in KP. The prevalence of Blastocystis in the AP and KP pigs were 87.88% (29/33) and 20.37% (11/54), respectively. Blastocystis ST5 was the most abundant in pigs in both areas while Blastocystis ST10 and ST12 were most frequently found in cattle and goats. In addition, low percentage of Blastocystis ST1 and Blastocystis ST14 were found in pigs and goats, respectively. In this study, Blastocystis ST3, followed by ST2 and ST1 were predominantly found in humans. In conclusion, pigs may be a natural host of Blastocystis and this ST may be the pig-adapted ST in the studied areas, in this study.