Diarrheal diseases are important causes of morbidity and mortality in young children [1]. Diarrhea can be caused by various pathogens, including bacteria, viruses, and protozoans. Among the protozoans, Cryptosporidium species, Giardia lamblia (synonymous with G. duodenalis and G. intestinalis) and Entamoeba histolytica are well known etiologies of the human diarrheal diseases [2]. These protozoans are distributed worldwide and more prevalent in areas with poor sanitation, including southeastern Asia [3,4]. Although a previous study reported the prevalence of intestinal protozoans from the Burmese immigrants working in Thailand, the infection status of Burmese people residing in Myanmar with these protozoans has not been known [5]. In this study, we performed a cross-sectional survey to identify the prevalence of intestinal protozoans among Burmese people near Yangon, Myanmar.
The study participants were schoolchildren and their guardians from 7 primary schools in South Dagon and Hlaing Thar Yar district, Yangon, Myanmar (Fig. 1), and the study was done in 2015. Stool samples were collected from the participants, 1 sample per person, and fixed with sodium acetate-acetic acid-formalin (SAF) solution. The mixture was filtered through gauze and centrifuged at 800 g for 10 min twice. The sediment was finally fixed with a small amount of 10% formalin and moved onto a slide glass. The slides were observed under a microscope after iodine staining. The cysts of intestinal protozoans, such as G. lamblia, E. histolytica, Entamoeba coli, and Endolimax nana were identified according to their typical morphologies.
A total of 821 people consisting of 556 schoolchildren and 265 guardians submitted their stool samples (Table 1). The median age was 6 years (interquartile range, IQR; 5-7) for the schoolchildren and 36 (IQR; 30-41) for the guardians. With regard to gender, 53.1% of the schoolchildren and 14.6% of the guardians were males. The overall positive rate for protozoan cysts was 10.0%; the rate was 10.6% for schoolchildren and 8.7% for guardians (Table 2). Among the schoolchildren, the prevalence of each protozoan species was as follows: 4.3% (24/556) for G. lamblia, 3.1% (17/556) for E. coli, 3.1% (17/556) for E. nana, and 0.9% (5/556) for E. histolytica. In comparison, among the guardians, the prevalence was 4.5% (12/265) for E. coli, 3.0% (8/265) for E. nana, 1.9% (5/265) for E. histolytica, and 1.5% (4/265) for G. lamblia (Table 2). In South Dagon, the schoolchildren in 3 primary schools showed overall prevalences of 7.2-12.7% compared to 6.5-20.0% of schoolchildren in 4 primary schools in Hlaing Thar Yar (Table. 3). G. lamblia was more prevalent in Hlaing Thar Yar than in South Dagon (7.1% vs 2.0%, P=0.003) in schoolchildren. Boys revealed higher prevalences of E. coli (4.1% vs 1.8%, P=0.006) and E. histolytica (1.3% vs 0.5%, P=0.035) when analyzed by the chi-square test.
In this study, we showed that overall 10% of the schoolchildren and their guardians were positive for intestinal protozoans in primary schools near Yangon. Protozoans with human pathogenic potential, such as G. lamblia and E. histolytica, were also prevalent in 3.4% and 1.2%, respectively. So far as we know, this is the first report on the prevalence of intestinal protozoans among schoolchildren in Myanmar.
The prevalences of intestinal protozoans among schoolchildren in this study were similar to those reported from schoolchildren in Cambodia [6,7]. The prevalences of G. lamblia and E. histolytica were 2.9-3.2% and 0.8%, respectively, in Cambodia [6,7]. In Thailand, G. lamblia was positive in 2.2% of some population in rural provinces and 6.5% of schoolchildren in suburban provinces [8]. Collectively, the prevalences of intestinal protozoans in Myanmar were similar to those from neighboring countries. However, it is of note that Myanmar immigrants working in Thailand revealed a higher prevalence (14.1%) of G. lamblia than in this study [5]. This suggests 2 possibilities. One is that intestinal protozoan infections may be more highly prevalent in rural areas of Myanmar (possibly their hometowns), whereas the subjected areas in this study were suburban areas near Yangon. Another possibility is that Myanmar immigrant workers were more frequently exposed to fecal-oral contamination of food or water either in specific localities of Myanmar or Thailand.
It is also interesting to see that whereas the overall prevalence was similar between the 2 surveyed districts in this study, G. lamblia was more highly prevalent in Hlaing Thar Yar than in South Dagon. In general, intestinal protozoans are considered to be prevalent in areas with poor sanitation and low socioeconomic status. Out of the 2 districts included in our study, Sough Dagon is generally known as the one with poorer socioeconomic status than Hlaing Thar Yar. Our previous study on Enterobius vermicularis identified significantly higher prevalence among children in South Dagon than in Hlaing Thar Yar [9]. Since the results of this study does not agree with this general concept, specific cause of fecal-oral contamination of G. lamblia in primary schoolchildren in Hlang Thar Yar district needs to be further elucidated.
Our study has several limitations. First, since cysts of Entamoeba dispar and Entamoeba moshkovskii have indistinguishable morphology from that of E. histolytica, the prevalence of E. histolytica could have been overestimated [10]. Second, we could not differentiate symptomatic infections from asymptomatic carrier states due to lack of clinical information. Despite these limitations, our study adds valuable information on the current status of intestinal protozoan infections among the people in Myanmar. The high prevalence of pathogenic protozoa implies that health interventions, such as hand washing education, improvement of sanitation, and establishment of water purification systems are urgently needed in these areas.
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