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  1. Molecular investigation on the occurrence of Toxoplasma gondii oocysts in cat feces using TOX-element and ITS-1 region targets
    Chemoh W, Sawangjaroen N, Nissapatorn V, Sermwittayawong N
    Vet J, 2016 Sep;215:118-22.
    PMID: 27325616 DOI: 10.1016/j.tvjl.2016.05.018
    One of the most important routes of transmission for Toxoplasma gondii infection is the ingestion of foods contaminated with cat feces containing sporulated oocysts. The diagnosis of T. gondii infection by fecal microscopy is complicated, as other similar coccidian oocysts are often present in the same fecal specimen. This study aimed to identify T. gondii oocysts in cat feces using a novel PCR technique. Feline fecal specimens (n = 254) were screened for coccidian oocysts by light microscopy using the Sheather's flotation method. PCR analysis performed on the same specimens targeted a 529 bp repeat element and internal transcribed spacer-1 (ITS-1) regions were used to confirm the presence of Toxoplasma oocysts. By light microscopy, 49/254 (19.3%) of specimens contained coccidian oocysts. PCR analysis demonstrated 2/254 (0.8%) and 17/254 (6.7%) positive results using Tox and ITS-1 primers, respectively. However, coccidian oocysts were not identified on microscopic examination of specimens that were PCR-positive by Tox primers. Coccidian oocysts were identified on microscopic examination of 6/17 (35.3%) of the PCR-positive fecal specimens using ITS-1 primers. The BLAST results of 16 ITS-1 sequences were identified as T. gondii (n = 12; 4.7%) and Hammondia hammondi (n = 4; 1.6%). There was slight agreement between the 529 bp and ITS-1 PCR results (κ = 0.148). This is the first report of the detection of Toxoplasma oocysts using PCR analysis on feline fecal specimens from Southern Thailand. The ITS-1 region has potential as an alternative marker to identify T. gondii oocysts in feline fecal specimens.
  2. Fulltext Parasitic infections in HIV infected individuals: diagnostic & therapeutic challenges
    Nissapatorn V, Sawangjaroen N
    Indian J Med Res, 2011 Dec;134(6):878-97.
    PMID: 22310820 DOI: 10.4103/0971-5916.92633
    After 30 years of the human immunodeficiency virus (HIV) epidemic, parasites have been one of the most common opportunistic infections (OIs) and one of the most frequent causes of morbidity and mortality associated with HIV-infected patients. Due to severe immunosuppression, enteric parasitic pathogens in general are emerging and are OIs capable of causing diarrhoeal disease associated with HIV. Of these, Cryptosporidium parvum and Isospora belli are the two most common intestinal protozoan parasites and pose a public health problem in acquired immunodeficiency syndrome (AIDS) patients. These are the only two enteric protozoan parasites that remain in the case definition of AIDS till today. Leishmaniasis, strongyloidiasis and toxoplasmosis are the three main opportunistic causes of systemic involvements reported in HIV-infected patients. Of these, toxoplasmosis is the most important parasitic infection associated with the central nervous system. Due to its complexity in nature, toxoplasmosis is the only parasitic disease capable of not only causing focal but also disseminated forms and it has been included in AIDS-defining illnesses (ADI) ever since. With the introduction of highly active anti-retroviral therapy (HAART), cryptosporidiosis, leishmaniasis, schistosomiasis, strongyloidiasis, and toxoplasmosis are among parasitic diseases reported in association with immune reconstitution inflammatory syndrome (IRIS). This review addresses various aspects of parasitic infections in term of clinical, diagnostic and therapeutic challenges associated with HIV-infection.
  3. Fulltext Characterization of malaria infection at two border areas of Thailand adjoining with Myanmar and Malaysia
    Sermwittayawong N, Nishibuchi M, Sawangjaroen N, Vuddhakul V
    Southeast Asian J. Trop. Med. Public Health, 2015 Jul;46(4):551-7.
    PMID: 26867373
    During 2009 to 2010, a total of 408 blood samples collected from malaria patients in Ranong (149) and Yala (259) Provinces, Thailand were investigated for Plasmodium spp using microscopic examination. There are no statistical differences in the prevalence of P. falciparum and P. vivax in samples collected from Ranong and Yala (46% vs 52%, and 54% vs 45%, respectively). Single nucleotide polymorphism of codon 86 in pfmdr1 (encoding P. falciparum multidrug resistance protein 1) was investigated among 75 samples of P. falciparum and 2 samples of P. knowlesi. A pfmdr1 N86Y mutation was detected in 1 out of 29 samples and 45 out of 46 samples obtained from Ranong and Yala Provinces, respectively. It is interesting that pfmdr1 was detected in two P. knowlesi DNA samples obtained previously from Ranong Province which was 99% homologous to pfmdr1 obtained from falciparum parasites in the same area but the mutation was not observed. The difference in multidrug resistance protein in Plasmodium obtained from those two border areas of Thailand will be of use in monitoring drug resistance in these border regions of the country.
  4. Fulltext Parasites: from source to vector and human
    Nissapatorn V, Sawangjaroen N, Lee R, Chandra Parija S
    Biomed Res Int, 2014;2014:780715.
    PMID: 25587540 DOI: 10.1155/2014/780715
  5. Fulltext Toxoplasmosis-serological evidence and associated risk factors among pregnant women in southern Thailand
    Nissapatorn V, Suwanrath C, Sawangjaroen N, Ling LY, Chandeying V
    Am J Trop Med Hyg, 2011 Aug;85(2):243-7.
    PMID: 21813842 DOI: 10.4269/ajtmh.2011.10-0633
    Toxoplasma gondii is an important parasite in pregnant women. This case-controlled study assessed the seroprevalence of toxoplasmosis in 640 pregnant women in southern Thailand and identified their associated risk factors. The overall seroprevalence of toxoplasmosis was 181 (28.3%). Of this, 138 (21.6%) were positive for only anti-Toxoplasma immunoglobulin G (IgG) antibody, 43 (6.7%) were positive for both IgG and IgM antibodies, and none were positive for IgM antibody. Multivariate analysis revealed that increasing age (adjusted odds ratio [OR] = 1.64, 95% confidence interval [CI] = 1.01-2.67), living outside Songkhla province (adjusted OR = 1.56, 95% CI = 1.08-2.24), parity (adjusted OR = 1.65, 95% CI = 1.01-2.68), contact with cats (adjusted OR = 1.70, 95% CI = 1.20-2.43), and drinking of unclean water (adjusted OR = 1.70, 95% CI = 1.08-2.68) were factors associated with Toxoplasma seroprevalence. On the basis of the results obtained, a health surveillance program should be initiated as a primary preventive measure for congenital toxoplasmosis and focus on educating women of the child-bearing age group to avoid contact with cats and to strictly practice personal hygiene.
  6. Fulltext Molecular Surveillance of Pfkelch13 and Pfmdr1 Mutations in Plasmodium falciparum Isolates from Southern Thailand
    Khammanee T, Sawangjaroen N, Buncherd H, Tun AW, Thanapongpichat S
    Korean J Parasitol, 2019 Aug;57(4):369-377.
    PMID: 31533403 DOI: 10.3347/kjp.2019.57.4.369
    Artemisinin-based combination therapy (ACT) resistance is widespread throughout the Greater Mekong Subregion. This raises concern over the antimalarial treatment in Thailand since it shares borders with Cambodia, Laos, and Myanmar where high ACT failure rates were reported. It is crucial to have information about the spread of ACT resistance for efficient planning and treatment. This study was to identify the molecular markers for antimalarial drug resistance: Pfkelch13 and Pfmdr1 mutations from 5 provinces of southern Thailand, from 2012 to 2017, of which 2 provinces on the Thai- Myanmar border (Chumphon and Ranong), one on Thai-Malaysia border (Yala) and 2 from non-border provinces (Phang Nga and Surat Thani). The results showed that C580Y mutation of Pfkelch13 was found mainly in the province on the Thai-Myanmar border. No mutations in the PfKelch13 gene were found in Surat Thani and Yala. The Pfmdr1 gene isolated from the Thai-Malaysia border was a different pattern from those found in other areas (100% N86Y) whereas wild type strain was present in Phang Nga. Our study indicated that the molecular markers of artemisinin resistance were spread in the provinces bordering along the Thai-Myanmar, and the pattern of Pfmdr1 mutations from the areas along the international border of Thailand differed from those of the non-border provinces. The information of the molecular markers from this study highlighted the recent spread of artemisinin resistant parasites from the endemic area, and the data will be useful for optimizing antimalarial treatment based on regional differences.
  7. Fulltext Toxoplasma gondii - Prevalence and Risk Factors in HIV-infected Patients from Songklanagarind Hospital, Southern Thailand
    Chemoh W, Sawangjaroen N, Siripaitoon P, Andiappan H, Hortiwakul T, Sermwittayawong N, et al.
    Front Microbiol, 2015;6:1304.
    PMID: 26635769 DOI: 10.3389/fmicb.2015.01304
    Toxoplasmosis is one of the most common opportunistic parasitic diseases in patients living with HIV/AIDS. This study aimed to determine the seroprevalence of Toxoplasma infection in HIV-infected patients and to identify associated risk factors in Toxoplasma seropositive patients. This study was conducted at a regional public hospital in Hat Yai, southern Thailand during October 2009 to June 2010. Blood samples were collected from 300 HIV-infected patients. Each subject also answered a socio-demographic and risk factors associated with Toxoplasma infection. The prevalence of anti-Toxoplasma IgG antibodies in HIV-infected patients was 109 (36.3%), of which 83 (76.2%) had past infection and 26 (23.9%) had recently acquired Toxoplasma infection as indicated by their IgG avidity. Multivariate analysis using logistic regression showed that gender difference (adjusted OR = 1.69, 95% CI = 1.05-2.72) was the only factor associated with Toxoplasma infection. From the results obtained, these HIV-infected patients could be at high risk of developing clinical evidence of severe toxoplasmosis. Therefore, it is necessary to introduce primary behavioral practices to prevent Toxoplasma infection among HIV-infected patients.
  8. Fulltext Toxoplasma infection in pregnant women: a current status in Songklanagarind hospital, southern Thailand
    Andiappan H, Nissapatorn V, Sawangjaroen N, Chemoh W, Lau YL, Kumar T, et al.
    Parasit Vectors, 2014;7:239.
    PMID: 24886651 DOI: 10.1186/1756-3305-7-239
    Toxoplasmosis, being one of the TORCH's infections in pregnant women, is caused by Toxoplasma gondii, an obligate intracellular protozoan parasite. This parasitic infection in pregnancy congenitally causes severe outcomes to their fetus and newborn. This study aimed to determine the seroprevalence and stages of Toxoplasma infection in pregnant women and its associated risks exposures.
  9. Fulltext Molecular detection of drug resistant malaria in Southern Thailand
    Noisang C, Prosser C, Meyer W, Chemoh W, Ellis J, Sawangjaroen N, et al.
    Malar J, 2019 Aug 15;18(1):275.
    PMID: 31416468 DOI: 10.1186/s12936-019-2903-y
    BACKGROUND: Drug resistance within the major malaria parasites Plasmodium vivax and Plasmodium falciparum threatens malaria control and elimination in Southeast Asia. Plasmodium vivax first-line treatment drug is chloroquine together with primaquine, and the first-line treatment for P. falciparum malaria is artemisinin in combination with a partner drug. Plasmodium vivax and P. falciparum parasites resistant to their respective first-line therapies are now found within Southeast Asia. The resistance perimeters may include high transmission regions of Southern Thailand which are underrepresented in surveillance efforts.

    METHODS: This study investigated blood samples from malaria centres in Southern Thailand. Genetic loci associated with drug resistance were amplified and sequenced. Drug resistance associated genes Pvmdr1, Pvcrt-o, Pvdhfr, and Pvdhps were characterized for 145 cases of P. vivax malaria, as well as the artemisinin resistance-associated Pfkelch13 gene from 91 cases of P. falciparum malaria.

    RESULTS: Plasmodium vivax samples from Southern Thai provinces showed numerous chloroquine and antifolate resistance-associated mutations, including SNP and Pvcrt-o K10-insertion combinations suggestive of chloroquine resistant P. vivax phenotypes. A high proportion of the C580Y coding mutation (conferring artemisinin resistance) was detected in P. falciparum samples originating from Ranong and Yala (where the mutation was previously unreported).

    CONCLUSIONS: The results demonstrate a risk of chloroquine and antifolate resistant P. vivax phenotypes in Southern Thailand, and artemisinin resistant P. falciparum observed as far south as the Thai-Malaysian border region. Ongoing surveillance of antimalarial drug resistance markers is called for in Southern Thailand to inform case management.

  10. DNA barcoding relates Trichuris species from a human and a man's best friend to non-human primate sources
    Brandon-Mong GJ, Ketzis JK, Choy JS, Boonroumkaew P, Tooba M, Sawangjaroen N, et al.
    Trop Biomed, 2018 Dec 01;35(4):1131-1139.
    PMID: 33601860
    Trichuris trichiura, the whipworm of humans, is one of the most prevalent soiltransmitted helminths (STH) reported worldwide. According to a recent study, out of 289 STH studies in Southeast Asia, only three studies used molecular methods. Hence, the genetic assemblages of Trichuris in Southeast Asia are poorly understood. In this study, we used partial mitochondrial DNA (cytochrome c oxidase subunit 1 or COI) sequences for analysis. Trichuris grouped in a same clade with different hosts indicate the potential of cross infection between hosts. Based on COI, the adult Trichuris isolated from a Malaysian patient was most closely related to Trichuris isolated from Papio anubis (olive baboons) from the USA. The Trichuris isolated from the dog from Malaysia was genetically similar to a Trichuris species isolated from Macaca silenus (lion-tailed macaque) from Czech Republic. Both the human and dog isolated Trichuris grouped in clades with different hosts indicating the potential of cross infection between hosts. Specific PCR primers based on the partial COI of T. trichiura isolated from African green monkey and T. serrata were designed and successfully amplified using multiplex PCR of the pooled DNA samples. Our results suggest a complex parasite-host relationship, and support the theory of cross infection of Trichuris between humans and non-human primates as suggested in previous publications.
  11. Prevalence and risk factors of Toxoplasma infection - an update in Malaysian pregnant women
    Chemoh W, Nur Farhana MN, Noor Azmi MA, Si Lay K, Sawangjaroen N, Tan TC, et al.
    Trop Biomed, 2019 Sep 01;36(3):694-702.
    PMID: 33597491
    Toxoplasma gondii is a protozoan parasite that is capable of causing a zoonotic disease, known as toxoplasmosis. Vertical transmission of T. gondii from the mother to the fetus, during pregnancy may cause severe complications to the developing fetus. This current study aimed to determine the seroprevalence and investigate the associated risk factors of Toxoplasma infection in pregnant women (n=219) visiting the antenatal clinic at UMMC. While the elevated level of anti-Toxoplasma IgG and IgM antibodies indicates the presence of infection, it fails to differentiate between a past and a recent infection. Thus, the study also demonstrates the usefulness of IgG avidity in validating the timing of infection. The serum samples were tested for the presence of anti-Toxoplasma IgG and IgM antibodies by ELISA test, and the seropositive samples for both anti-Toxoplasma IgG and IgM antibodies were further evaluated by IgG avidity. The results showed that the overall prevalence of T. gondii seropositivity was 34.7%. Of these, 30.6% (67/219) were positive for anti-Toxoplasma IgG antibody only, 2.3% (5/219) were positive for anti-Toxoplasma IgM only, and the remaining 1.8% (4/219) was positive for both anti-Toxoplasma IgG and IgM antibodies. All of the pregnant women who were positive for both anti-Toxoplasma IgG and IgM antibody were found to have past infection when evaluated by IgG avidity. In this study, Malay ethnicity and the number of existing previous children were significantly associated with T. gondii seropositivity (p<0.05). Based on these findings, information and education on the transmission and prevention of congenital toxoplasmosis are very crucial as a public health effort towards a healthier society.
  12. Fulltext Comparative study on Toxoplasma infection between Malaysian and Myanmar pregnant women
    Andiappan H, Nissapatorn V, Sawangjaroen N, Nyunt MH, Lau YL, Khaing SL, et al.
    Parasit Vectors, 2014;7:564.
    PMID: 25498432 DOI: 10.1186/s13071-014-0564-9
    Toxoplasma gondii, an obligate intracellular protozoan parasite, causes a disease called toxoplasmosis which can sometimes be acquired congenitally by a newborn from an infected mother. This study aimed to determine the seroprevalence of Toxoplasma infection and its associated risks among 219 and 215 pregnant women from Malaysia and Myanmar, respectively.
  13. Fulltext Knowledge and practice on Toxoplasma infection in pregnant women from Malaysia, Philippines, and Thailand
    Andiappan H, Nissapatorn V, Sawangjaroen N, Khaing SL, Salibay CC, Cheung MM, et al.
    Front Microbiol, 2014;5:291.
    PMID: 24966855 DOI: 10.3389/fmicb.2014.00291
    Toxoplasma gondii, is one of the infectious agents of congenital TORCH infections, causes severe clinical outcomes in fetus and newborns. Nevertheless this life-threatening parasitic disease is preventable by simple preventive measures related to lifestyle during pregnancy. We aim to study on the knowledge about toxoplasmosis and practices that prevents this infection among the pregnant women. Total of 2598 pregnant women from Malaysia, Philippines, and Thailand were randomly surveyed to determine the knowledge and their practices on Toxoplasma infection. The questionnaire covered respondents' general information and knowledge on plausible risks factors, symptoms, timing of infection, prevention knowledge, and preventive behavior regarding Toxoplasma infection. Majority of these pregnant women were in their age group of 20-29 years (50.9%), completed secondary level of education (51.7%), in their second trimester of pregnancies (38.1%), non-parous (36.6%), and had no history of abortion (90.4%). Based on this survey, only 11% of these pregnant women had read, heard, or seen information regarding toxoplasmosis and 3.5% of them were aware of being tested for the infection. A small percentage of these pregnant women knew that T. gondii were shed in the feces of infected cats (19.4%) and sometimes found in the raw or undercooked meat (11.0%). There was 16.1% of responding women knew that toxoplasmosis is caused by an infection. Demographic profiles such as age group, level of education, pregnancy term, and number of children of the pregnant women showed significant association with their responses toward prevention knowledge and preventive behavior related questions (P < 0.05). Thus, it is suggested that health education on toxoplasmosis and primary behavioral practices should be consistently offered to reproductive age women in general and pregnant women in particular. This information could help to reduce vertical transmission of Toxoplasma infection during pregnancy.
  14. Fulltext Comparative study on waterborne parasites between Malaysia and Thailand: A new insight
    Kumar T, Onichandran S, Lim YA, Sawangjaroen N, Ithoi I, Andiappan H, et al.
    Am J Trop Med Hyg, 2014 Apr;90(4):682-9.
    PMID: 24567315 DOI: 10.4269/ajtmh.13-0266
    This study investigated the distribution of parasites as main contaminants in water environments of peninsular Malaysia (October 2011-December 2011) and the southeastern coast of Thailand (June 2012). Sixty-four water samples, 33 from Malaysia and 31 from Thailand, of various water types were examined according to U.S. Environmental Protection Agency guidelines. Drinking or household water types from both countries were free from parasitic contamination. The recreational/environmental (except a swimming pool in Malaysia) and effluent water types from these two countries were contaminated with waterborne parasites: Giardia (0.04-4 cysts/L), Cryptosporidium (0.06-2.33 oocysts/L), hookworm (6.67-350 ova/L), Ascaris (0.33-33.33 ova/L), and Schistosoma (9.25-13.33 ova/L). The most contaminated sites were recreational lake garden 3 in Malaysia and river 2 in Thailand. Higher concentrations of Giardia, Cryptosporidium, and hookworm were found in samples from Malaysia than in samples from Thailand. The presence of Giardia cysts showed a significant association with the presence of Cryptosporidium oocysts (P < 0.005).
  15. Fulltext Waterborne parasites: a current status from the Philippines
    Onichandran S, Kumar T, Salibay CC, Dungca JZ, Tabo HA, Tabo N, et al.
    Parasit Vectors, 2014;7:244.
    PMID: 24885105 DOI: 10.1186/1756-3305-7-244
    Despite the amount of awareness created, waterborne disease still poses threat, especially in developing countries. Due to the scarcity of reported data on waterborne parasites, the consumption of unsafe water prolongs. Thus, the occurrences of waterborne parasites from various samples were investigated from one of the Southeast Asian country, the Philippines.
  16. Waterborne parasites and physico-chemical assessment of selected lakes in Malaysia
    Onichandran S, Kumar T, Lim YA, Sawangjaroen N, Andiappan H, Salibay CC, et al.
    Parasitol Res, 2013 Dec;112(12):4185-91.
    PMID: 24046263 DOI: 10.1007/s00436-013-3610-1
    The objective of this study was to assess the physico-chemical parameters and waterborne parasites in selected recreational lakes from Malaysia. Samples were collected from seven stations of Recreational Lake A (RL-A) and six stations of Recreational Lake B (RL-B). The samples were processed to detect the presence of Giardia spp. and Cryptosporidium spp. using immunomagnetic separation kit, helminth eggs or ova by bright field microscopy and Acanthamoeba spp. by cultivation in non-nutrient agar. Chemical parameters such as ammonia, chlorine, fluoride, nitrate and nitrite and physical parameters such as dissolved oxygen, electrical conductivity, pH, salinity, temperature and total dissolved solid were also measured. Both lakes were freshwater with salinity ranging from 0.05 to 0.09 ppt. Most stations of these lakes were contaminated with Cryptosporidium spp., Giardia spp., Ascaris spp. and hookworm. Schistosoma spp. was found in RL-B only, while Acanthamoeba spp. was found in all stations. Of all sampling sites, station 5 of RL-B is the most contaminated. Linear regression and correlation analysis revealed that Giardia spp. and Schistosoma spp. showed a significant negative correlation with turbidity (p 
  17. Fulltext Acanthamoeba in Southeast Asia - Overview and Challenges
    Bunsuwansakul C, Mahboob T, Hounkong K, Laohaprapanon S, Chitapornpan S, Jawjit S, et al.
    Korean J Parasitol, 2019 Aug;57(4):341-357.
    PMID: 31533401 DOI: 10.3347/kjp.2019.57.4.341
    Acanthamoeba, one of free-living amoebae (FLA), remains a high risk of direct contact with this protozoan parasite which is ubiquitous in nature and man-made environment. This pathogenic FLA can cause sight-threatening amoebic keratitis (AK) and fatal granulomatous amoebic encephalitis (GAE) though these cases may not commonly be reported in our clinical settings. Acanthamoeba has been detected from different environmental sources namely; soil, water, hot-spring, swimming pool, air-conditioner, or contact lens storage cases. The identification of Acanthamoeba is based on morphological appearance and molecular techniques using PCR and DNA sequencing for clinico-epidemiological purposes. Recent treatments have long been ineffective against Acanthamoeba cyst, novel anti-Acanthamoeba agents have therefore been extensively investigated. There are efforts to utilize synthetic chemicals, lead compounds from medicinal plant extracts, and animal products to combat Acanthamoeba infection. Applied nanotechnology, an advanced technology, has shown to enhance the anti-Acanthamoeba activity in the encapsulated nanoparticles leading to new therapeutic options. This review attempts to provide an overview of the available data and studies on the occurrence of pathogenic Acanthamoeba among the Association of Southeast Asian Nations (ASEAN) members with the aim of identifying some potential contributing factors such as distribution, demographic profile of the patients, possible source of the parasite, mode of transmission and treatment. Further, this review attempts to provide future direction for prevention and control of the Acanthamoeba infection.
  18. Fulltext Presence of Cryptosporidium parvum and Giardia lamblia in water samples from Southeast Asia: towards an integrated water detection system
    Kumar T, Abd Majid MA, Onichandran S, Jaturas N, Andiappan H, Salibay CC, et al.
    Infect Dis Poverty, 2016 Jan 13;5:3.
    PMID: 26763230 DOI: 10.1186/s40249-016-0095-z
    Access to clean and safe drinking water that is free from pathogenic protozoan parasites, especially Cryptosporidium parvum and Giardia lamblia that cause gastrointestinal illness in humans, is still an issue in Southeast Asia (SEA). This study is the first attempt to detect the aforementioned protozoan parasites in water samples from countries in SEA, using real-time polymerase chain reaction (qPCR) assays.
  19. Fulltext Pathogenic waterborne free-living amoebae: An update from selected Southeast Asian countries
    Abdul Majid MA, Mahboob T, Mong BG, Jaturas N, Richard RL, Tian-Chye T, et al.
    PLoS One, 2017;12(2):e0169448.
    PMID: 28212409 DOI: 10.1371/journal.pone.0169448
    Data on the distribution of free-living amoebae is still lacking especially in Southeast Asian region. The aquatic environment revealed a high occurrence of free-living amoebae (FLA) due to its suitable condition and availability of food source, which subsequently causes infection to humans. A total of 94 water samples consisted of both treated and untreated from Laos (31), Myanmar (42), and Singapore (21) were investigated for the presence of pathogenic FLA. Each water sample was filtered and cultured onto non-nutrient agar seeded with live suspension of Escherichia coli and incubated at room temperature. Morphological identification was conducted for both trophozoites and cysts via microscopic stains (Giemsa and immunofluorescence). The presence of Naegleria-like structures was the most frequently encountered in both treated and untreated water samples, followed by Acanthamoeba-like and Vermamoeba-like features. To identify the pathogenic isolates, species-specific primer sets were applied for molecular identification of Acanthamoeba, Naegleria, and Vermamoeba. The pathogenic species of Acanthamoeba lenticulata and A. triangularis were detected from untreated water samples, while Vermamoeba vermiformis was found in both treated and untreated water samples. Our results suggested that poor water quality as well as inadequate maintenance and treatment might be the cause of this alarming problem since chlorine disinfection is ineffective in eradicating these amoebas in treated water samples. Regular monitoring and examination of water qualities are necessary in order to control the growth, hence, further preventing the widespread of FLA infections among the public.
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