Rapid Single-Step Immunochromatographic Assay for Angiostrongylus cantonensis Specific Antigen Detection.

Angiostrongylus cantonensis is the major etiological nematode parasite causing eosinophilic meningitis and/or eosinophilic meningoencephalitis in humans. The rapid global spread of Angiostrongylus cantonensis and the emerging occurrence of the infection have exposed the shortcomings of traditional/conventional diagnostics. This has spurred efforts to develop faster, simpler and more scalable platforms that can be decentralized for point-of-need laboratory testing. By far, the point-of-care immunoassays such as the lateral flow assay (LFA) are the best-placed. In this work, a LFA in the form of an immunochromatographic test device (designated AcAgQuickDx), based on the detection of a circulating Angiostrongylus cantonensis-derived antigen, was established using anti-31 kDa Angiostrongylus cantonensis antibody as the capture reagent and anti-Angiostrongylus cantonensis polyclonal antibody as the indicator reagent. The AcAgQuickDx was evaluated for its diagnostic potential with a total of 20 cerebrospinal fluids (CSF) and 105 serum samples from patients with angiostrongyliasis and other clinically related parasitic diseases, as well as serum samples from normal healthy subjects. Three of the ten CSF samples from serologically confirmed angiostrongyliasis cases and two of the five suspected cases with negative anti-Angiostrongylus cantonensis antibodies showed a positive AcAgQuickDx reaction. Likewise, the AcAgQuickDx was able to detect Angiostrongylus cantonensis specific antigens in four serum samples of the 27 serologically confirmed angiostrongyliasis cases. No positive reaction by AcAgQuickDx was observed in any of the CSF (n = 5) and serum (n = 43) samples with other parasitic infections, or the normal healthy controls (n = 35). The AcAgQuickDx enabled the rapid detection of active/acute Angiostrongylus cantonensis infection. It is easy to use, can be transported at room temperature and does not require refrigeration for long-term stability over a wide range of climate. It can supplement existing diagnostic tests for neuroangiostrongyliasis under clinical or field environments, particularly in remote and resource-poor areas.

Genetic diversity and identity of Ascaris worms from human and pig hosts in Thailand.

Ascaris roundworms are of public health and socio-economic importance worldwide. They are conventionally attributed to two taxa - A. lumbricoides infecting principally human and A. suum infecting principally pig. Phylogenomic analysis has revealed that Ascaris worms from both human and pig are represented in Clades A and B. A recent study indicates that the Ascaris worms from human and pig in Thailand belong to Clade A. We examined adult Ascaris worms from human and pig in Thailand by means of the partial sequences of three mitochondrial genes (cox1, cox2 and nad1) and concatenation of these genes. Phylogenomic analysis indicates that two isolates (H1,H2) of A. lumbricoides from human belonged to Clade B; one isolate (H3) belonged to Clade A (based on cox1, cox2 and concatenated sequences) or as an outlier to Clades A and B (based on nad1 sequences). All the eight isolates of A. suum from pig clustered in Clade A. The partial nad1 and the concatenated sequences revealed two lineages of A. suum isolates which were distinct from the two A. lumbricoides isolates of Clade B. It is evident that greater genetic diversity, and a more robust phylogeny, could be uncovered by the application of multiple genes. In sum, the present study reveals the presence in Thailand of A. lumbricoides from human in Clades A and B which necessitates appropriate treatment and control measures; Clades A and B have been reported to contain haplotypes of Ascaris worms from both human and pig in other parts of the world. A country wide study is needed to elucidate the identity, distribution, prevalence, cross transmission, genetic diversity and phylogeny of the Ascaris worms in Thailand.

Quantitative PCR to Discriminate Between Pneumocystis Pneumonia and Colonization in HIV and Non-HIV Immunocompromised Patients.

Pneumocystis pneumonia (PCP) is an opportunistic infection that commonly occurs in immunocompromised individuals. A definite diagnosis of PCP can be made only when the organism is identified in a respiratory specimen. It remains unclear whether qPCR can differentiate patients with PCP from those with Pneumocystis jirovecii colonization. In this study, we retrospectively collected data from HIV and non-HIV patients during 2013-2019. A diagnosis of definite, probable PCP, or PCP excluded was made based on clinical criteria, radiological reports, and three standard laboratory staining methods with blinding to qPCR data. Data from qPCR that was performed to determine the fungal burden (DNA copies/µl) in the BAL specimens of 69 HIV and 286 non-HIV patients were then obtained and reviewed. Receiver Operating Characteristic (ROC) curve analysis was performed to determine the upper and lower cut-off values for PCP diagnosis in HIV and non-HIV groups. In the non-HIV group, the lower cut-off value of 1,480 DNA copies/µl yielded a sensitivity of 100% (95% confidence interval [CI], 91.0-100), specificity of 72.9% (95% CI, 64.0-80.7), a positive predictive value (PPV) of 54.9% (95% CI, 47.6-62.1), and a negative predictive value (NPV) of 100% with Youden index of 0.73 for PCP diagnosis. In this group, the upper cut-off value of 9,655 DNA copies/µl showed the sensitivity of 100% (95% CI, 91.0-100) and specificity of 95.8% (95% CI, 90.4-98.6) with PPV of 88.6% (95% CI, 76.8-94.8) and a NPV of 100% with Youden index of 0.96 for PCP diagnosis. Regarding the HIV group, the lower cut-off value of 1,480 DNA copies/µl showed the sensitivity of 100% (95% CI, 92.5-100%) and specificity of 91.7% (95% CI, 61.5-99.8) with PPV of 97.9% (95% CI, 87.8-99.7) and a NPV of 100% with Youden index of 0.92 for PCP diagnosis. The sensitivity and specificity of the upper cut-off value of 12,718 DNA copies/µl in this group were 97.9% (95%CI, 88.7-100) and 100% (95%CI, 73.5-100), respectively. The values above the upper cut-off point had a PPV of 100% (95% CI, N/A) and a NPV of 92.3% (95% CI, 63.3-98.8) with Youden index of 0.98 for PCP diagnosis in the HIV group.

Sandwich dot-immunogold filtration assay (DIGFA) for specific immunodiagnosis of active neuroangiostrongyliasis.

Serological tests may yield false-negative results for specific antibodies detection before or at the early seroconversion phase. Tests that detect circulating antigens of Angiostrongylus cantonensis would therefore be of value in diagnosis to distinguish current or past infection. Here, a quick, easy to perform, portable and inexpensive diagnostic device for detection of 31-kDa A. cantonensis specific antigens had been developed. This sandwich dot-immunogold filtration assay (AcDIGFAAg), for detecting active angiostrongyliasis was produced using anti-A. cantonensis polyclonal antibody dotted on the nitrocellulose membrane as a capture agent and colloidal gold-labelled anti-31 kDa A. cantonensis antibody as a detection agent. A well-defined pink dot, indicating positivity, was seen readily by naked eye within 10-15 min. The AcDIGFAAg detected A. cantonensis-specific antigens in cerebrospinal fluid samples from 4 out of 10 serologically confirmed angiostrongyliasis cases and 2 out of 5 suspected cases with negative anti-A. cantonensis antibodies. Among the 19 patient sera with A. cantonensis infection, 2 showed positive reaction by AcDIGFAAg. No positive AcDIGFAAg reaction was observed in all the serum samples with other parasitic diseases, and the healthy controls. The present 'AcDIGFAAg' enables rapid qualitative detection of the specific 31-kDa antigens of A. cantonensis in clinical samples with potential for application even under resource-limited settings.

Immunochromatographic test for rapid serological diagnosis of human angiostrongyliasis.

OBJECTIVES: The serological diagnosis of human infection with Angiostrongylus cantonensis remains problematic because there are no commercially available validated tests. Most laboratories use domestically prepared tests such as the enzyme-linked immunosorbent assay (ELISA) or immunoblotting. Since laboratory facilities are not always available in endemic areas, we developed and assessed a rapid lateral flow immunochromatographic assay (AcQuickDx Test) to detect anti-A. cantonensis antibodies in human serum. METHODS: The test device was assembled with purified 31-kDa glycoprotein as diagnostic antigen and with gold-labelled anti-human immunoglublin-G as the detector reagent. A total of 97 serum samples were tested - 19 samples from clinically diagnosed patients with detectable A. cantonensis-specific antibody in immunoblotting; 43 samples from patients with other parasitic diseases, i.e. gnathostomiasis (n=13), toxocariasis (n=2), trichinellosis (n=2), hookworm infection (n=4), filariasis (n=5), cysticercosis (n=9), paragonimiasis (n=2), opisthorchiasis (n=3), and malaria (n=3); and 35 samples from normal healthy subjects. RESULTS: The sensitivity, specificity, positive predictive value and negative predictive value of AcQuickDx Test to detect anti-A. cantonensis specific antibodies in serologically confirmed angiostrongyliasis cases, were 100%, 98.72%, 95% and 100%, respectively. Positive AcQuickDx was observed in 1 of 4 cases with hookworm infections. No positive AcQuickDx was observed in cases with other parasitic diseases, and the individual healthy subjects. CONCLUSIONS: AcQuickDx Test is rapid, highly sensitive and specific, and easy to perform without additional equipment or ancillary supplies. It yields results that are interpreted visually, and possesses a long shelf-life at room temperature. Thus, it can be applied as an additional test for clinical diagnostic support of angiostrongyliasis either in conventional laboratories or for remote areas where laboratory infrastructure is not available.

Rapid Differentiation of Filariae in Unstained and Stained Paraffin-Embedded Sections by a High-Resolution Melting Analysis PCR Assay.

BACKGROUND: Apart from infection with human filariae, zoonotic filariasis also occurs worldwide, and the numbers of cases have been increasing steadily. Diagnosis of intact filariae in tissues or organs depends on histological identification. The morphology of parasites in tissue-embedded sections is poor and shows high levels of homoplasy. Thus, the use of morphological characteristics in taxonomic studies is difficult and may not allow a specific diagnosis. METHODS: Here we report the use of real-time PCR with high-resolution melting analysis (HRM) to detect and identify Brugia malayi, Brugia pahangi, Wuchereria bancrofti, and Dirofilaria immitis in paraffin-embedded sections. Assay specificity was determined using other tissue-dwelling parasites, Angiostrongylus cantonensis, Gnathostoma spinigerum, and Cysticercus cellulosae. We also developed a quick paraffin removal protocol. RESULTS: Both human and animal filariae in formalin-fixed paraffin-embedded sections (FFPES) were diagnosed and identified rapidly, whereas other parasites were negative. There was no difference in the melting temperature of products amplified from filarial DNA obtained from unstained FFPES and Hematoxylin & Eosin-stained sections. Therefore, the DNA extraction protocols developed in this study could be used for real-time PCR with HRM. CONCLUSIONS: We report the successful application of a HRM-PCR assay to differentiate four filarial parasites in FFPES, thus providing the pathologist with an effective alternative diagnostic procedure. Furthermore, the quick paraffin removal protocol developed could shorten the duration and number of steps required for paraffin removal using a standard protocol.

Prevalence and risk factors of acquiring Strongyloides stercoralis infection among patients attending a tertiary hospital in Thailand.

OBJECTIVES: We aimed to determine the prevalence and risk factors for Strongyloides stercoralis infection in adult patients attending Siriraj Hospital, a tertiary hospital in Thailand. METHODS: A case-control study was carried out between July 2008 and April 2010. Case and control were identified from 6022 patients for whom results of faecal examination were available. A case was a patient who had S. stercoralis larva detected from faecal examination. Control was randomly selected from patients without S. stercoralis larvae detected in three consecutive faecal examinations. The proportion of control to case was 2 : 1. Demographic and clinical data for the day of diagnosis and retrospectively up to 15 days preceding the date of faecal examination were reviewed from their medical records. RESULTS: Overall, 149 (2.47%) patients had S. stercoralis larvae positive. There were 105 males (70.5%), with the mean (SD) age of 53.9 (17.2) years. A total of 300 controls were selected. Male gender (odds ratio (OR)  =  2.79, 95% confidence interval (CI) 1.78-4.27)), human immunodeficiency virus (HIV) infection (OR  =  3.23, 95% CI 1.43-7.29), and eosinophilia (OR  =  1.81, 95% CI 1.33-2.47) were found to be independent risk factors associated with S. stercoralis infection in this setting. Corticosteroid or other immunosuppressive treatment, and other concomitant illnesses were not associated with increased risk of S. stercoralis infection. CONCLUSION: In this setting, strongyloidiasis was seen more often in male patients with eosinophilia and with HIV infection. Prevention of fatal complication caused by S. stercoralis by regular faecal examination, or serology for early detection and treatment of undiagnosed S. stercoralis infection, is warranted in these high-risk patients.

Molecular diagnosis of eosinophilic meningitis due to Angiostrongylus cantonensis (Nematoda: Metastrongyloidea) by polymerase chain reaction-DNA sequencing of cerebrospinal fluids of patients.

Cerebrospinal fluid (CSF) samples from clinically diagnosed patients with detectable Angiostrongylus cantonensis-specific antibodies (n = 10), patients with clinically suspected cases that tested negative for A. cantonensis-antibodies (n = 5) and patients with cerebral gnathostomiasis (n = 2) and neurocysticercosis (n = 2) were examined by a single-step polymerase chain reaction (PCR) method using the AC primers for the 66-kDa native protein gene. The PCR method detected A. cantonensis DNA in CSF samples from four of 10 serologically confirmed angiostrongyliasis cases. The PCR results were negative for the remaining CSF samples. The nucleotide sequences of three positive CSF-PCR samples shared 98.8-99.2% similarity with the reference sequence of A. cantonensis. These results indicate the potential application of this PCR assay with clinical CSF samples for additional support in the confirmation of eosinophilic meningitis due to A. cantonensis.

Molecular diagnosis of eosinophilic meningitis due to Angiostrongylus cantonensis (Nematoda: Metastrongyloidea) by polymerase chain reaction-DNA sequencing of cerebrospinal fluids of patients

Cerebrospinal fluid (CSF) samples from clinically diagnosed patients with detectable Angiostrongylus canto-nensis-specific antibodies (n = 10), patients with clinically suspected cases that tested negative for A. cantonensis-an-tibodies (n = 5) and patients with cerebral gnathostomiasis (n = 2) and neurocysticercosis (n = 2) were examined by a single-step polymerase chain reaction (PCR) method using the AC primers for the 66-kDa native protein gene. The PCR method detected A. cantonensis DNA in CSF samples from four of 10 serologically confirmed angiostrongyliasis cases. The PCR results were negative for the remaining CSF samples. The nucleotide sequences of three positive CSF-PCR samples shared 98.8-99.2% similarity with the reference sequence of A. cantonensis. These results indicate the potential application of this PCR assay with clinical CSF samples for additional support in the confirmation of eosinophilic meningitis due to A. cantonensis.

Clinical features of Acanthamoeba keratitis in contact lens wearers and non-wearers.

Clinical presentations of patients with Acanthamoeba keratitis (AK) attending the Faculty of Medicine Siriraj Hospital during 1996-2006 were reviewed. The studied parameters included history of ocular trauma, use of contact lenses, associated eye diseases, systemic diseases, visual acuity, symptoms, signs, treatment, visual outcomes, and sequelae. Data were analyzed by comparing non-contact lens (nCL) and contact lens (CL) wearers with eachother. Twenty-two patients (24 affected eyes) (68.2% female) had AK, 9 (37.5%) were nCL and 15 (62.5%) were CL. Both groups had similar basic characteristics; however the nCL group was significantly older (48.3 +/- 14.5 vs 30.6 +/- 15.3 years old, p=0.006), and tended to have a longer duration of symptoms with more severe clinical findings, but this was not statistically significant. Eleven had severe ciliary injection (nCL 55.5%, CL 40.0%), 3 had satellite lesions (nCL 22.2%, CL 6.7%), 2 had radial keratoneuritis in the CL group (13.3%), 1 ring infillrate in the nCL group (11.1%) and 1 pseudodendrite in the CL group (6.7%). The mean duration of follow-up was 8.2 +/- 7.9 (ranging 0.3-29) months. Therapeutic measures included anti-Acanthamoeba medications (5/9 for nCL, 8/15 for CL), penetrating keratoplasty due to uncontrolled infections (1/9 for nCL, 2/15 for CL) and corneal perforation (1/9 for nCL), and enucleation due to endophthalmitis (1/9 for CL). At the last follow-up visit, the CL [corrected] group had slightly better visual acuity (55.5% vs 66.7%). In conclusion, AK among patients who do not use contact lenses may have a delayed diagnosis, resulted in more severe ocular manifestations and poorer prognosis. Physicians should be aware of Acanthamoeba infection as a cause of keratitis in any patient, not just contact lens wearers. Long periods of follow-up are recommended to observe for recurrent episodes and proper management of AK patients.

Efficacy and safety of single and double doses of ivermectin versus 7-day high dose albendazole for chronic strongyloidiasis.

BACKGROUND: Strongyloidiasis, caused by an intestinal helminth Strongyloides stercoralis, is common throughout the tropics. It remains an important health problem due to autoinfection, which may result in hyperinfection and disseminated infection in immunosuppressed patients, especially patients receiving chemotherapy or corticosteroid treatment. Ivermectin and albendazole are effective against strongyloidiasis. However, the efficacy and the most effective dosing regimen are to be determined. METHODS: A prospective, randomized, open study was conducted in which a 7-day course of oral albendazole 800 mg daily was compared with a single dose (200 microgram/kilogram body weight), or double doses, given 2 weeks apart, of ivermectin in Thai patients with chronic strongyloidiasis. Patients were followed-up with 2 weeks after initiation of treatment, then 1 month, 3 months, 6 months, 9 months, and 1 year after treatment. Combination of direct microscopic examination of fecal smear, formol-ether concentration method, and modified Koga agar plate culture were used to detect strongyloides larvae in two consecutive fecal samples in each follow-up visit. The primary endpoint was clearance of strongyloides larvae from feces after treatment and at one year follow-up. RESULTS: Ninety patients were included in the analysis (30, 31 and 29 patients in albendazole, single dose, and double doses ivermectin group, respectively). All except one patient in this study had at least one concomitant disease. Diabetes mellitus, systemic lupus erythrematosus, nephrotic syndrome, hematologic malignancy, solid tumor and human immunodeficiency virus infection were common concomitant diseases in these patients. The median (range) duration of follow-up were 19 (2-76) weeks in albendazole group, 39 (2-74) weeks in single dose ivermectin group, and 26 (2-74) weeks in double doses ivermectin group. Parasitological cure rate were 63.3%, 96.8% and 93.1% in albendazole, single dose oral ivermectin, and double doses of oral ivermectin respectively (P = 0.006) in modified intention to treat analysis. No serious adverse event associated with treatment was found in any of the groups. CONCLUSION/SIGNIFICANCE: This study confirms that both a single, and a double dose of oral ivermectin taken two weeks apart, is more effective than a 7-day course of high dose albendazole for patients with chronic infection due to S. stercoralis. Double dose of ivermectin, taken two weeks apart, might be more effective than a single dose in patients with concomitant illness. TRIAL REGISTRATION: ClinicalTrials.gov NCT00765024.

Efficacy of contact lens solutions against Thai clinical isolates of Acanthamoeba.

Three clinical isolates of Acanthamoeba (A. castellanii, A. polyphaga, and A. mauritaniensis) were used to evaluate the cysticidal activity of four different contact lens multi-purpose solutions (Complete Protec, ReNu MultiPlus, Solocare Aqua, and Opti-free Aldox). Enumeration of amoebic was carried out with the control and test samples at 0, 2, 4, 6, 8, 10, and 24 hours after being added to the solutions using the most probable number (MPN) technique. A contact lens solution which achieved a 3-log reduction of Acanthamoeba during the manufacturer's minimum recommended disinfection time (MMRDT) was considered an effective solution. The studied contact lens solutions demonstrated decreasing number of amoebic with increasing exposure times, but were not effective against Acanthamoeba cysts during the MMRDT. Solocare Aqua gave the greatest reduction in A. castellanii (0.70-log reduction) and A. mauritaniensis (0.33-log reduction) by 4 hours. Only Solocare Aqua caused a 3-log reduction in A. castellanii (3.02-log reduction) by 24 hours. Opti-free Aldox showed the greatest cysticidal activity against A. polyphaga (0.32-log reduction) by 6 hours, and gave the greatest reduction in A. mauritaniensis by 8, 10, and 24 hours.

Seasonal levels of the major American cockroach allergen per a 9 (arginine kinase) in Bangkok and their relevance for disease severity.

Monitoring the levels of cockroach (CR) allergen in the environment has medical relevance as a clear dose response relationship between CR allergen exposure, sensitization and hospitalization has been reported. In this study, a cross-sectional survey of the levels of a major American cockroach (Periplaneta americana) allergen, i.e. Per a 9 (arginine kinase) in dust samples collected in various seasons throughout the year 2007 from 76 houses of CR allergic Thai patients in the Bangkok metropolitan area were determined. A monoclonal antibody-polyclonal antibody (MAb-PAb) based-sandwich ELISA was used. The MAb was specific to Per a 9 and the PAb was raised in a rabbit against the crude extract of P. americana. The detection limit of the assay was 122 pg of the allergen or 0.024 microg per gram of fine dust powder. The concentrations of Per a 9 were found to be highest during the winter months and lowest in summer. The levels of this CR allergen had a direct correlation with disease exacerbation; i.e. the majority of the CR allergic patients had their most severe clinical manifestations during winter. Moreover, the CR allergen levels were found to be higher in wood based-houses than in concrete houses.

Visceral leishmaniasis caused by Leishmania infantum in Thailand.

Thailand is considered as a non-endemic area for leishmaniasis. We report the first case of visceral leishmaniasis caused by Leishmania infantum in a Thai man living in Bangkok.

Sensitive detection of Pneumocystis jirovecii DNA in gastric wash using nested polymerase chain reaction.

One hundred and five samples of gastric washes were obtained from 52 pediatric patients. Eleven of the 105 samples (10%) gave positive results using immunofluorescence antibody test (IFA) for Pneumocystis jirovecii. Single-step polymerase chain reaction (PCR) produced 13% (14 samples), whereas detection by nested PCR was increased to 65 samples (62%). Moderate agreement (kappa = 0.5) was found between test results of IFA and single-step PCR, but no agreement was found between the results of IFA and nested PCR (kappa = 0.1).

Ganoderma lucidum: a cause of pseudoparasitosis.

We report a pseudoparasitosis case due to Ganoderma lucidum, (lingzhi or reishi mushroom); we believe this to be a first reported case in Thailand. A 49-year-old male patient with non-Hodgkins lymphoma presented with chronic watery diarrhea. He had a history of consumption of powdered lingzhi extract as a dietary supplement and herbal medicine. Stool examination demonstrated many spores of G. lucidum, which must be differentiated from intestinal helminth ova and coccidia. After discontinuation of mushroom spores ingestion, the diarrheal symptoms improved and fecal examination subsequently showed no Ganoderma spores. Many artifacts in the stool may be confused with parasites. Differentiation of parasites from artifacts depends on characterization of the size, shape, structure, and reactivity with common stains.

Determination of fecal occult blood in primary schoolchildren infected with Trichuris trichiura.

A correlation of Trichuris trichiura infection and fecal occult blood detection was conducted in 146 primary schoolchildren in Narathiwat Province, Thailand. The Kato-Katz thick smear method was used for determining egg counts and stated as eggs per gram of feces (epg). The number of T. trichiura eggs was categorized as class I (1-499 epg), class 11 (500-4,999 epg), and class III (> 5,000 epg), according to the relation between infection intensity and reduced hemoglobin concentration. Each fecal sample was processed to detect occult blood using a guaiac-based test (Hema-Screen, USA) and an immunochromatographic-based test (HEXAGON OBTI test, Germany). There were 50 schoolchildren without parasitic infection in the control group. Of 96 cases with T. trichiura infection, 85 and 11 children were classified in the class I and class II groups, respectively, but no subjects were in the class III group. Positive occult blood detection results in the control, class I, and class II groups using the guaiac and the immunochemical tests were 0, 3.5, and 9.1% (p=0.19), and 0, 2.4, and 36.4%, (p<0.0001) respectively. This study suggests that T. trichiura infection with an intensity of 500 epg or greater may be associated with intestinal bleeding.

Intestinal microsporidiosis in HIV-infected children with diarrhea.

Intestinal microsporidiosis is a common opportunistic disease associated with diarrhea in adult AIDS patients in Thailand; the data regarding this infection in children are scarce. The present study was designed to investigate the prevalence and clinical features of intestinal microsporidiosis in hospitalized HIV-infected and uninfected (free of HIV) children with diarrhea. Of the 95 HIV-infected children and 87 uninfected children, 24 (25.3%) and 13 (14.9%) respectively were diagnosed with intestinal microsporidiosis. Species identification of microsporidia spores, by transmission electron microscopy, demonstrated Enterocytozoon bieneusi in 5 cases. Cryptosporidium parvum was a common coinfective parasite; pneumonia was the most frequent concurrent disease found in children with intestinal microsporidiosis. Malnutrition was commoner in the HIV-infected group (79.2% vs 23.1%; p = 0.003). This study indicates that intestinal microsporidiosis is an important disease in both HIV-infected and uninfected Thai children with diarrhea.