Proceeding Example

Prevalence of Soil-Transmitted Helminths in Rural Communities of Khon Kaen Province, Northeast Thailand

Chivorn Leang,1,* Apiporn Thinkhamrop,2 Sasithorn Kaewkes,1,3 Thewarach Laha,1 John F. Smith,1 Banchob Sripa1,3,**

1 Tropical Medicine International Graduate Program, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand

2 Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand

3 Tropical Disease Research Laboratory, Department of Pathology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand

*e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.; **e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract: Soil-transmitted helminth (STH) infections are still a major public health problem in rural Thailand due in part to poor personal hygiene and lack of systematic health education. From November to December 2015 a community-based cross-sectional survey was conducted  on the prevalence of STH infections among  villagers in rural communities in Khon Kaen Province, northeastern Thailand. A total 260 stool samples from participants in 5 villages were examined using agar plate culture and formalin-ethyl acetate concentration (FECT) methods. Results showed that of  4 STH parasitic infections examined for, i.e., Ascaris lumbricoides, Trichuris trichiura, hookworm, and Strongyloides stercoralis, only S. stercoralis infection was detected  (42/260, 16%).  Prevalence in each village ranged from 4.1% to 31.8%. Agar plate culture method detected 41 cases of S. stercoralis while only 12 cases were detected by FECT. Gender and age were significantly associated with the infection; males more likely to be infected than females. Older people (age over 60) had higher prevalence compared to younger age groups. In conclusion, S. stercoralis was found to be the major STH infection in rural communities in Khon Kaen province. More intensive community health education is necessity to promote healthy hygiene practices to prevent STH parasite transmission and infection.

Keywords: Soil-transmitted helminths, Strongyloides stercoralis, prevalence, Khon Kaen, Thailand

Introduction: Neglected tropical diseases (NTDs) are groups of infectious diseases that affect the poor in over 149 countries and are associated with inadequate clean water, poor sanitation and health services access1. Over 80 percent of common NTDs are caused by soil-transmitted helminths (STHs) via humans ingesting parasite eggs, or, through contacting parasite larvae in contaminated soil. STHs are among the most common gastrointestinal worm infection in humans. WHO estimates more than two billion of the world’s population are infected with at least one species of STHs and 4 billion are at infection risk  in both tropical and subtropical countries 2. STH infections are considered a leading cause of sickness, absenteeism and disability adjusted life years (DALYs) lost.

People are infected after ingesting eggs from contaminated soil or food (Ascaris lumbricoides and Trichuris trichiura), or for hookworms and S. stercoralis  through active penetration of the skin by infective larval stages present in contaminated soil3. STH infection is endemic in parts of Thailand  due to a combination of  appropriate warm climate and adequate moisture, a relative lack of personal or environmental hygiene, poor sanitation and knowledge about these parasites 4–6. Some parasites continue as public health problems in certain rural parts of Thailand, although effective antihelmintic drug and prevent and control parasites program are available.  There are only few previous reports describing STH infection in northeastern Thailand7,8. This cross-sectional survey therefore aimed to update STH infection prevalence data among  rural communities in Khon Kaen Province, Thailand.

Methodology: A community-based cross-sectional study was conducted in 5 villages in rural community of Khon Kaen Province, northeastern Thailand including Borke, DonDu, Norng Huachang, Norng ThungMon, and ThaKoi villages. These villages have  high infection prevalence for  Opisthorchis viverrini (O. viverrini) 9. The sample size was calculated according to WHO 10 by using an  estimate of 20% of population proportion, with 95% level of confidence and 5% of expected precision. In total, 260 participants were enrolled in this study. All participants were informed about study proposes and procedures before written inform consent was obtained.  This study was reviewed and approved by the Khon Kaen University Human Ethics Committee (#HE591165).

Figure 1. Map of 5 villages in Khon Kaen Province

Figure 1. Map of 5 villages in Khon Kaen Province

Stool containers were given to participants with instructions on fecal specimen collection. One stool sample was collected from each participant and parasite infection determined using formalin-ethyl acetate concentration (FECT) and agar plate culture (APC). For FECT, two grams of stool specimen were processed by adding 7 milliliter of 10% formalin. Then 3 ml of ethyl acetate was added. The sample was shaken and centrifuged for 5 minutes. The top layer debris plug was discarded. Total number of parasite eggs or larvae in the sediment was counted and calculated as the number of eggs per gram of feces (EPG) or larvae per gram of feces (LPG) 11,12. For APC method, three grams of stool sample was placed at the center of the agar plate media and covered with the lid. The plates were incubated at room temperature (26 to 33°C) for 48 hours before detecting larvae or larvae tracks by microscopy. All microscopically positive agar dishes were washed with a 10% formalin solution to collect worms for specie identification under a light microscope 11,13.

Data was entered in Microsoft Excel 2003 and exported to SPSS version 22. The prevalence was reported by descriptive statistics. Pearson’s Chi-squared test was used to assessed the association between prevalence and gender or age groups.

Results and Discussion:  Te percentages of the 260 participants from each of the five villages, BoreKe, DonDu, Norng Huachang, Norng Thungmon, and ThaKoi,  is shown in Figure 2. Participants’ demographic data is shown in Table 1; ages ranged from 17 to 83 years (mean 50.23 + 9.7) with 160 (61.53%) being  female and 100 (38.64%)  male.

Figure 2. Participant distribution in 5 villages of Khon Kaen Province

Figure 2. Participant distribution in 5 villages of Khon Kaen Province

Table 1. Demographic characteristics of participants in 5 villages























Age (years)


   Mean + SD

49.3 +7

49.8 +6.6

50.2 +10.4

52.5 +13.3

50.6 +11.4

50.2 +9.7









26 - 63

33 - 61

18 - 71

37 - 83

17 - 75

17 - 83

   BK = BoreKe, DD = DobDu, NC = Norng Huachang, NM = Norng Thungmon, TK = ThaKoi

Forty-two participants (16.15%) were infected with S. stercoralis infection, while the three other parasites A. lumbricoides, T. trichiura, and hookworm were not detected. This result is similar to a previous study in rural communities of Khon Kaen that showed 9.5% prevalence of S. stercoralis,  0.4%  for hookworm but no A. lumbricoides and T. trichiura 7.  A recent national survey of helminths in Thailand in 2009  reported similar prevalence of A. lumbricoides, T. trichiura, and S. stercoralis (0%, 0.4%, 2.8%, respectively) in northeastern Thailand 14. There was no hookworm infection detected in our study even through S. stercoralis and hookworm have similar transmission modes.  This is likely due   unfavorable environmental conditions for hookworm such as local climate, soil type and rainfall.  15.

Twelve participants (4.62%) were positive for S. stercoralis by FECT with an average larvae count of  26.58 LPG (range from 7 to 82.5 LPG). However, forty-one participants (15.77%) were positive for S. stercoralis by APC. Due to absence of a true gold standard of diagnosis, a combination of APC and FECT was considered as a true positive in this study. With this criterion, the sensitivity of APC and FECT were 97.61% and 28.57%, respectively. The low detection rate by FECT is likely explained by several factors such as loss of larvae during feces processing. Investigators found that larvae were in the debris plug, floated in the formalin layer, and also got stuck in layer gauze. As the result many larvae were removed from the sample  and only a small number of larvae  settled in sediment contributing to  false negative results and low sensitivity 11,16. Even though, APC had higher detection rates than FECT, one sample was found negative by APC but  positive by FECT.  This negative Strongyloides APC count  was probably due to high temperature, and/or issues with improper sample collection  sample transportation to laboratory 17.

Table 3. Positive sample by APC and FECT





















APC = Agar Plate Culture method, FECT = Formalin-ethyl acetate concentration method


Norng Thungmon village had the highest prevalence of S. stercoralis (31.80%) followed by ThaKoi village (30.30%) with Norng Huachang, Borke, and DonDu villages having  11.80%, 9.10%, and 4.10% prevalencerespectively. Norng Thungmon and ThaKoi villages’ higher prevalence may be related to the lower economic status and the poorer infrastructure in those villages. Most villagers in Norng Thungmon and ThaKoi village had very low incomes and their livelihoods came from working on the land. Both villages had poor physical infrastructure such as small dirt roads and basic rural-style housing.

Participants’ gender was significantly associated with S. stercoralis infection (p< 0.001) with males having 8 times higher prevalence rate than females, similar results to other studies 7,18–20. This gender difference likely reflects behavioral factors such as males greater soil contact through their work.  Age was also a significant risk factor associated with prevalence of S. stercoralis infection (p= 0.003). Those  aged over  60  had much higher risk of the infection than younger people similar to other reports7. This may be explained by the fact that risk factors for parasite infection increase with age and older people have poor hygiene practice and poor health education.

Table4: The prevalence of S. stercoralis infection in gender and age group.





P value






















      >40 – 50





      >50 – 60










 Conclusion: Soil-transmitted helminth infection, particularly S. stercoralis, is still highly prevalent in rural communities of northeastern Thailand. APC  method was again found  more sensitive than FECT  method for detection of S. stercoralis infection 11,16,17. Males had higher infection prevalence than females with older persons (60 years plus) having the highest prevalence of all age groups. Decreasing STH transmission and reinfection are likely to require a mix of health education to encourage healthy behaviors and improved personal hygiene practices as well as physical infrastructure development to reduce soil exposure risk from moving about for work and other daily community activities.

Acknowledgements: This work was partially supported by the Thailand Research Fund (TRF) grant number RTA 5680006 and the National Institute of Allergy and Infectious Diseases (NIAID), NIH, grant number P50AI098639. We thank Tropical Disease Research Laboratory staff for technical assistance. CL received Her Royal Highness Mahachakri Sirindhorn’s Scholarship for Cambodia. BS is a TRF Senior Research Scholar.


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