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High prevalence of soil-transmitted helminth infections in Myanmar schoolchildren

Authors:
  • Northern Sydney Local Health District
  • Parasitology Research Division

Abstract and Figures

Background Achieving the elimination of soil-transmitted helminth (STH) infections requires a sufficient understanding of the current epidemiological status of STH endemicity. We aimed to examine the status of STH in Myanmar – a country with the eighth highest STH prevalence in the world, 10 years after instigation of the national deworming programme. Methods In August 2016 we screened for STH infections using Kato Katz (KK) microscopy and real-time PCR (qPCR) in schoolchildren from the Bago Region township of Phyu, a STH sentinel site in Myanmar. Ten schools were randomly selected, and one stool sample each from a total of 264 students was examined. Prevalence and intensity of infection were calculated for each STH. Results High prevalence of STH was identified in the study area with 78.8% of the schoolchildren infected with at least one STH by qPCR, and 33.3% by KK. The most prevalent STH was Trichuris trichiura , diagnosed by both KK (26.1%) and qPCR (67.1%), followed by Ascaris lumbricoides (15.5% KK; 54.9% qPCR). No hookworm infections were identified by KK; however, the qPCR analysis showed a high prevalence of Ancylostoma sp. infection (29.6%) with few Necator americanus (1.1%) infections. Conclusions Despite bi-annual deworming of schoolchildren in the fourth-grade and below, STH prevalence remains stubbornly high. These results informed the expansion of the Myanmar National STH control programme to include all school-aged children by the Ministry of Health and Sports in 2017, however further expansion to the whole community should be considered along with improving sanitation and hygiene measures. This would be augmented by rigorous monitoring and evaluation, including national prevalence surveys.
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Aungetal. Infectious Diseases of Poverty (2022) 11:28
https://doi.org/10.1186/s40249-022-00952-6
RESEARCH ARTICLE
High prevalence ofsoil-transmitted helminth
infections inMyanmar schoolchildren
Eindra Aung1,2, Kay Thwe Han3, Catherine A. Gordon4 , Nyein Nyein Hlaing5, Moe Moe Aye5, Myo Win Htun3,
Khin Thet Wai3, Su Mon Myat6, Thida Lay Thwe5, Aung Tun7, Kinley Wangdi1, Yuesheng Li4,8, Gail M. Williams9,
Archie C. A. Clements1,10, Susana Vaz Nery1,11, Donald P. McManus4 and Darren J. Gray1*
Abstract
Background: Achieving the elimination of soil-transmitted helminth (STH) infections requires a sufficient under-
standing of the current epidemiological status of STH endemicity. We aimed to examine the status of STH in Myanmar
– a country with the eighth highest STH prevalence in the world, 10 years after instigation of the national deworming
programme.
Methods: In August 2016 we screened for STH infections using Kato Katz (KK) microscopy and real-time PCR (qPCR)
in schoolchildren from the Bago Region township of Phyu, a STH sentinel site in Myanmar. Ten schools were randomly
selected, and one stool sample each from a total of 264 students was examined. Prevalence and intensity of infection
were calculated for each STH.
Results: High prevalence of STH was identified in the study area with 78.8% of the schoolchildren infected with at
least one STH by qPCR, and 33.3% by KK. The most prevalent STH was Trichuris trichiura, diagnosed by both KK (26.1%)
and qPCR (67.1%), followed by Ascaris lumbricoides (15.5% KK; 54.9% qPCR). No hookworm infections were identified
by KK; however, the qPCR analysis showed a high prevalence of Ancylostoma sp. infection (29.6%) with few Necator
americanus (1.1%) infections.
Conclusions: Despite bi-annual deworming of schoolchildren in the fourth-grade and below, STH prevalence
remains stubbornly high. These results informed the expansion of the Myanmar National STH control programme to
include all school-aged children by the Ministry of Health and Sports in 2017, however further expansion to the whole
community should be considered along with improving sanitation and hygiene measures. This would be augmented
by rigorous monitoring and evaluation, including national prevalence surveys.
Keywords: Ascaris lumbricoides, Hookworm, Ancylostoma, Necator americanus, Trichuris trichiura, Soil-transmitted
helminth, Myanmar, Real-time PCR, Kato Katz
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Background
More than 1.5 billion people are currently infected with
soil-transmitted helminths (STH) (Ascaris lumbricoides,
Trichuris trichiura and the hookworms Necator ameri-
canus and Ancylostoma sp.) primarily in Asian, African,
and Latin American countries [1, 2]. e STH are intesti-
nal parasitic nematode worms that are some of the most
common and disabling chronic human pathogens in the
developing world [3]. STH are intimately associated with
Open Access
*Correspondence: darren.gray@anu.edu.au
1 Department of Global Health, Research School of Population Health,
Australian National University, Canberra, ACT , Australia
Full list of author information is available at the end of the article
Page 2 of 12
Aungetal. Infectious Diseases of Poverty (2022) 11:28
rural poverty, inadequate sanitation and poor hygiene,
lack of clean water, and limited access to health care and
preventive measures (e.g. health education)[35]. STH
impact significantly on public health and may cause
severe disability among the world’s poorest communi-
ties [1, 6, 7] – particularly among school-aged children
(SAC), who, if chronically infected, may suffer from pro-
found physical deficits, including anaemia and malnutri-
tion, stunted growth, reduced fitness and cognitive delays
[816].
Myanmar has the eighth highest prevalence of STH of
any country worldwide, with an estimated 40.8 million
people at risk, and requiring preventive chemotherapy,
including nearly 13 million children living in endemic
areas [16]. A Ministry of Health and Sports (MoHS)
parasitological survey in 2002–2003 showed a 70% STH
prevalence in 1,000 schoolchildren across four eco-
logical areas for STH transmission (plains, hills, coast
and delta) [17, 18]. Based on these results the MoHS
introduced a National STH control programme in 2006
[19]. Forming part of the School and Youth Health
Programme (SYHP), the STH control programme fol-
lows World Health Organization (WHO) guidelines,
which are to provide bi-annual albendazole chemo-
therapy (400mg single oral dose), usually in February
and August, via targeted deworming in pre-SAC (aged
2–4years) and SAC (aged 5–9years) [19, 20]. In 2012,
the MoHS repeated their 2002–2003 parasitologi-
cal survey in 1,000 SAC, 7 years after the commence-
ment of the national deworming programme. e
survey results showed that whilst the STH prevalence
had decreased to 21% overall, and 0% in hilly areas,
the prevalence still remained high in the plains (30%),
coastal (38%), and delta areas (15%) [19].
A cross-sectional survey of two Myanmar villages in
2015–2016 showed a high prevalence of 27.81% by Kato-
Katz (KK) for human infection with at least one STH,
peaking at 36% in the 5–14year age group [21]. T. trichi-
ura was the most prevalent STH, possibly due to the low
efficacy of albendazole (ABZ) to treat this species com-
pared with other STH [21, 22].
As STH control continues in Myanmar, ongoing rigor-
ous monitoring and evaluation will be required to inform
the MoHS on programme effectiveness and decision-
making around up-scaling of control activities [23]. To
achieve this, there is a requirement to utilize highly sen-
sitive and specific methods for detecting infected indi-
viduals. e WHO recommends the KK thick smear
technique for assessing both the prevalence and inten-
sity of infection in helminth control programmes, and
was used for all of the aforementioned surveys in Myan-
mar [24]. However, the KK technique lacks sensitivity,
particularly with low-intensity infections, such as those
occurring in areas with ongoing mass deworming pro-
grammes [2528]. Molecular approaches are increasingly
being used in monitoring and surveillance as they have
higher sensitivity and can differentiate species (or gen-
era) of hookworms, unlike KK [26, 2934]. We previously
showed that real-time PCR (qPCR) is considerably more
sensitive than KK for STH detection in the Philippines
[34, 35], a feature supported by a number of other recent
studies in South East Asia [27, 32, 3537].
Here we present the results of a parasitological sur-
vey we conducted among SAC in Phyu Township, Bago
Region – a sentinel site for the Myanmar National STH
control programme. Our aim was to determine the status
of STH infection by both the KK and qPCR after 10years
of targeted deworming.
Methods
Study design
A cross-sectional study was conducted in August, 2016
in Phyu Township, Bago Region, Myanmar (Fig. 1), to
determine the prevalence of STH infections in SAC uti-
lising KK and qPCR procedures.
Ethical approval
Ethical approval was provided by the Protocol and Eth-
ics Review Committee, the Department of Medical
Research, Ministry of Health and Sports, Myanmar,
(Approval Number: Ethics/DMR/2016/099), and the Sci-
ence and Medical Delegated Ethics Review Committee,
e Australian National University, Australia (Protocol:
2016/406).
Study setting andpopulation
e study was undertaken on grade five schoolchildren
(aged 9–11years) across ten randomly selected schools
(5 urban; 5 rural) in Phyu Township – the sentinel site
for the ‘plains’ ecological area in the previous Myan-
mar MoHS surveys [17, 19]. Phyu Township is situated
162kms south of Nay Pyi Taw (the capital of Myanmar)
and 185 kms north of Yangon (the former capital). ere
were 215 schools, enrolling a total of 5,120 fifth graders
in Phyu Township for the 2016–2017 school year (June to
February), with the number of fifth graders ranging from
three to 154 per school.
e selection of the study participants was based
on WHO guidelines [24], which recommends a target
sample size of 50 per school in five randomly-selected
schools in each ecologically homogenous area. Ten
schools were randomly selected in this study as student
numbers in most schools were less than 50. All grade five
schoolchildren in the 10 schools (n = 363) were invited
to participate to ensure enrolment of 250 children. De-
worming was undertaken in primary schoolchildren
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Aungetal. Infectious Diseases of Poverty (2022) 11:28
(from kindergarten to grade four) in January and July in
2016 as part of the national STH control programme. e
fifth graders recruited into this study were last treated in
January 2016 before they completed grade four, and they
were not treated in July 2016.
Field andmicroscopy procedures
In each of the selected schools, the study team conducted
a meeting with parents or guardians of the fifth graders
to explain the study and obtain consent. Participating
students were given a stool container and instructions
on how to collect their stool at home and asked to pro-
vide one stool sample each. A questionnaire was also
administered at the school to collect data on demograph-
ics; knowledge, attitudes and practices around intesti-
nal worms and hygiene; and water and sanitation status.
Samples were processed at the Phyu Township hospital
within 2–3h after collection and read the same day using
triplicate KK thick smears (41.7mg of stool/smear) [38].
For quality control, all of the slides were rechecked by
the leader of the stool processing and examination team
for the study. e team comprised four microbiologists
(including the leader) and two research assistants from
the Department of Medical Research in Myanmar and
the Department of Zoology, the University of Yangon.
Ten percent of the slides were examined by an independ-
ent microbiologist at a government hospital in Yangon
for additional quality control.
Approximately 2–3g of faeces collected from each par-
ticipant was stored in 80% (v/v) ethanol for DNA extrac-
tion and qPCR analysis at the QIMR Berghofer Medical
Research Institute (QIMRB), Brisbane, Australia.
DNA extraction
DNA extraction was performed on all stool samples;
200mg of stool were placed into a 2ml screw cap tube
and washed once with MilliQ water by adding 500µl of
MilliQ to each tube and centrifuging at maximum speed
in a benchtop centrifuge (Eppendorf, Hamburg, Ger-
many) for 3min. en the supernatant was removed and
500µl of ROSE buffer [39] and 1g of 0.5mm silica/zirco-
nia beads (Daintree Scientific Australia, St Helens, Aus-
tralia) were added to each tube [32, 35]. e tubes were
placed into a Precellys Homogeniser (Bertin Instruments,
Paris, France) at 3306 × g for 30s to fully homogenise the
stool samples, a step crucial for rupturing T. trichiura
eggs. e tubes were then placed in a heating block at
95 for 5min, then centrifuged (Eppendorf, Hamburg,
Fig. 1 Map of Myanmar showing the study area in Bago Region (left panel); approximate locations of the ten participating schools in Phyu
Township (right panel). (Source: Myanmar Information Management Unit and Google Maps)
Page 4 of 12
Aungetal. Infectious Diseases of Poverty (2022) 11:28
Germany) at maximum speed to pellet the sample. e
supernatant was then added to the first well of a Maxwell
16 LEV Plant DNA Kit (Promega, Madison, USA) car-
tridge to which 200µl of MilliQ water had already been
added. e cartridge was then placed in a Maxwell 16
robot, along with elution tubes containing 50µl of elu-
tion buffer, and plungers placed in well 8. On the Max-
well 16 robot the program for plant DNA was selected
and automated extraction commenced. Once extraction
was completed the elution tubes were removed. e
Maxwell system uses magnetic beads for DNA extrac-
tion and some carryover of beads to the eluted DNA can
occur. ese can be removed by using a magnetic rack
(ermo Fisher Scientific, Waltham, USA) to attract the
magnets to one side of the tube while the supernatant
containing DNA can be removed and placed into a clean,
labelled tube. DNA quality and quantity were verified
using a Powerwave (BioTek, Winooski, USA).
Multiplex qPCR
A multiplex qPCR was conducted using previously pub-
lished primers and probes for A. lumbricoides, T. trichi-
ura, N. americanus, and Ancylostoma sp. (Table1) [32,
33, 35, 40]. Reactions in a total volume of 15µl contained
8µl of GoTaq (Promega), 3.2µl of MilliQ water, and the
appropriate concentrations of primers and probes for
each species as shown in Table1.
e qPCR was performed using a multiplex CFX384
(Biorad, Hercules, USA) under the following conditions:
2min initialisation at 98 , followed by 40 cycles at 98°C
for 20s, 58°C for 20s, and 72°C for 20s, followed by a
final extension at 72°C for 5min.
Genomic DNAs of A. lumbricoides, T. trichiura, N.
americanus, and Ancylostoma sp., extracted from adult
worms or eggs, were used as positive controls. e con-
trol DNAs were combined to create aliquots comprising
equal DNA quantities of the four species. A 1:10 dilution
series (to 1:105) of the DNA combination was used in
each assay as a positive control and to allow comparisons
of individual multiplex PCR assays. Two no template
controls were also subjected to the multiplex PCR assay.
All samples were analysed in triplicate.
Positive samples were determined using the average
cycle threshold (Ct) for each triplicate sample. Stand-
ard deviation (SD) was calculated for the replicates. To
be considered positive at least two replicates required a
SD of < 1. Samples with positive Ct but > 1 SD between
replicates were repeated. A Ct value < 35 was considered
positive.
Statistical analyses
Statistical analyses were carried out using Microsoft
Excel 2016 (Microsoft, Albuquerque, New Mexico,
USA), SPSS statistical software (IBM® SPSS® Statistics
23.0, Chicago, IL, USA), Venny 2.1 (BioinfoGP, Centro
Nacional de Biotecnología, Spain), and GraphPad Prism
8 (GraphPad Software Inc., SanDiego, California, USA).
A positive case of infection was determined by the pres-
ence of at least 1 egg on one KK slide or a qPCR Ct score
of < 35. Descriptive statistics (frequency, percentages,
means and standard deviations) were used to examine
the main study variables (STH prevalence and intensity),
the t-test was used to detect differences in means, and
the chi-square test determined differences in propor-
tions. Confidence intervals were calculated using a one
sample t-test. Infection intensity was calculated using
both arithmetic mean eggs per gram of faeces (AMEPG)
Table 1 PCR primers and probes used in this study
Organism Target References Name Fluorophore/Quencher Final
concentration
(nmol/L)
Sequence (5’ 3’)
Ascaris lumbricoides ITS1 [33, 40] Asc F FAM/Iowa Black 60 GTA ATA GCA GTC GGC GGT TTCTT
Asc R 60 GCC CAA CAT GCC ACC TAT TC
Asc P 100 TTG GCG GAC AAT TGC ATG CGAT
Ancylostoma sp.ITS2 [33, 40] Anc F Cy5/Iowa Black 200 GAA TGA CAG CAA ACT CGT TGTTG
Anc R 200 ATA CTA GCC ACT GCC GAA ACGT
Anc P 200 ATC GTT TAC CGA CTT TAG
Necator americanus ITS2 [33, 40] Nam F JOE NHS Ester/Iowa Black 200 CTG TTT GTC GAA CGG TAC TTGC
Nam R 200 ATA ACA GCG TGC ACA TGT TGC
Nam P 100 CTG TAC TAC GCA T TG TAT AC
Trichuris trichiura ITS1 [37]Trich F Cy5.5/Iowa black 60 TCC GAA CGG CGG ATCA
Trich R 60 CTC GAG TGT CAC GTC GTC CTT
Trich P 100 TTG GCT CGT AGG TCGTT
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Aungetal. Infectious Diseases of Poverty (2022) 11:28
and geometric mean eggs per gram of faeces (GMEPG)
in infected individuals.
Results
Study participation
Overall participation rate was 76% (274/363) ranging
from 50% to 100% among participating schools, with a
total of 274 grade-five students partaking in the study
and providing one stool sample each. All 274 stool sam-
ples were examined by KK; however, only 264 samples
were examined by qPCR due to insufficient stool quan-
tity in 10 samples. Participants that had both KK and
qPCR (n = 264) results were included in the analyses
presented here. e mean age of the participants was
11.0 ± 1.1years (range: 9–16 years), with 57% (n = 150)
aged 9–10years, and 53% (n = 139) female. Overall, 65.5%
of participants (n = 173) attended urban schools and the
remainder (34.5%; n = 91) were from rural schools.
STH infection prevalence
KK
STH infection determined by KK (n = 264) showed a
prevalence of 33.3% (95% CI: 27.6–39.1) for at least one
STH infection; 15.5% (95% CI: 11.1–19.9) (n = 41) for A.
lumbricoides, and 26.1% (95% CI: 20.8–31.5) for T. trichi-
ura (Table2). No stool samples were positive for hook-
worm by KK.
qPCR
Analysis by qPCR (n = 264) found a prevalence of 78.8%
(95% CI: 73.8–83.8) for at least one STH infection; 54.9%
(95% CI: 48.9–61.0) for A. lumbricoides, 67.1% (95% CI:
61.3–72.8) for T. trichiura, and 30.7% (95% CI: 25.1–36.3)
for hookworm [Ancylostoma sp. 29.6% (95% CI: 24.0–
35.1); N. americanus 1.1% (95% CI: 0–2.4)] (Table2).
qPCR vs KK
Combining the results from the KK and qPCR analysis
indicated a prevalence of 84.1% (95% CI: 79.7–88.5) for
any STH infection; 59.1% (95% CI: 53.1–65.1) for A. lum-
bricoides, and 74.6% (95% CI: 69.3–79.9) for T. trichiura
(Table 2). As indicated above, no hookworm-positive
individuals were identified by KK. When compared with
the KK, the qPCR analysis identified approximately 3.5
times (145/41) the number of A. lumbricoides infec-
tions and 2.5 (177/69) times the number of T. trichiura
infections.
A comparison between the qPCR and KK procedures
showed that 11 samples positive for A. lumbricoides by
the KK method were negative by qPCR, and 20 samples
positive by KK for T. trichiura were negative by qPCR
(Table3 and Fig.2). Conversely, 115 samples negative for
A. lumbricoides by the KK method were found to be posi-
tive by qPCR, and 128 samples found to be negative for T.
trichiura by KK were positive by qPCR.
Table 2 Prevalence and infection intensity of soil transmitted helminths determined by the Kato-Katz procedure, qPCR and the two
methods combined
KK Kato-Katz method, n Number of positive cases, 95% CI 95% condence interval, AMEPG Arithmetic mean of eggs per gram of faeces in infected children, GMEPG
Geometric mean of eggs per gram of faeces in infected children, Any STH Infection with any of the three parasites (A. lumbricoides, T. trichiura, or hookworm), All 3 STH
Infection with all three parasites, Any 2 STH Infection with any two of the three parasites, N/A Not applicable; *The number includes children infected with all three STH
KK qPCR KK and qPCR combined
nPrevalence (95% CI) AMEPG (95% CI) GMEPG (95% CI)nPrevalence (95% CI)nPrevalence (95% CI)
A. lumbricoides 41 15.5% (11.1–19.9) 15,322.3 (7,566.5–
23,078.2) 2,059.1 (892.5–
4,750.1) 145 54.9% (48.9–61.0) 156 59.1% (53.1–65.1)
T. trichiura 69 26.1% (20.8–31.5) 382.5 (207.9–557.1) 123.9 (86.4–177.9) 177 67.1% (61.3–72.8) 197 74.6% (69.3–79.9)
Ancylostoma sp. N/A N/A N/A 78 29.6% (24.0–35.1) N/A
N. americanus N/A N/A N/A 3 1.1% (0–2.4) N/A
Hookworm 0 0% N/A N/A 81 30.7% (25.1–36.3) 81 30.7% (25.1–36.3)
Any STH 88 33.3% (27.6–39.1) N/A N/A 208 78.8% (73.8–83.8) 222 84.1% (79.7–88.5)
All 3 STH 0 0% N/A N/A 63 23.9% (18.7–29.0) 64 24.2% (19.0–29.5)
Any 2 STH 22 8.3% (5.0–11.7) N/A N/A 69 26.1% (20.8–31.5) 84 31.8% (26.2–37.5)
A. lumbricoides
and T. trichiura*22 8.3% (5.0–11.7) N/A N/A 118 44.7% (38.7–50.7) 134 50.8% (44.7–56.8)
A. lumbricoides
and hookworm* 0 0% N/A N/A 65 24.6% (19.4–29.9) 65 24.6% (19.4–29.9)
T. trichiura and
hookworm* 0 0% N/A N/A 75 28.4% (22.9–33.9) 77 29.2% (23.7–34.7)
Page 6 of 12
Aungetal. Infectious Diseases of Poverty (2022) 11:28
Co‑infections
e qPCR analysis indicated that 23.9% (95% CI: 18.7–
29.0) of the schoolchildren were co-infected with all
three STH (A. lumbricoides, T. trichiura and hook-
worm), and 26.1% (95% CI: 20.8–31.5) with any two STH
(Table2). Infections with A. lumbricoides and T. trichiura
were found in 44.7% (95% CI: 38.7–50.7), T. trichiura and
hookworm in 28.4% (95% CI: 22.9–33.9), and A. lumbri-
coides and hookworm in 24.6% (95% CI: 19.4–29.9) of
schoolchildren (Table2). e most common single infec-
tion was T. trichiura (n = 47) followed by A. lumbricoides
(n = 25), while the most common co-infection was triple
infection with T. trichiura, A. lumbricoides, and Ancylos-
toma sp. (n = 63) (Fig.3).
STH prevalence anddemographics
STH prevalence (using the combined KK and qPCR
results) was stratified according to sex, age group and
school location (Table4). Males (34.4%; 95% CI: 27.0–
41.8) had a significantly (P < 0.001) higher prevalence
than females (15.1%; 95% CI: 8.1–22.1) for infections
with all three STH, and a significantly (P = 0.002) higher
prevalence of hookworm; 40.0% (95% CI: 32.0–48.0)
for males compared with 22.3% (95% CI: 14.7–29.9) for
females (Table 4). Children < 11years were more likely
to have any STH infection (88.7%; 95% CI: 82.8–94.5)
compared with individuals 11 years (78.1%; 95% CI:
71.4–84.8) (P = 0.02) (Table4). Rural schoolchildren had
a higher prevalence of any STH infection compared with
urban schoolchildren (93.4%; 95% CI: 86.0–100 vs 79.2%;
95% CI: 73.8–84.6; P = 0.003) (Table4). Children in rural
schools had higher prevalence of hookworm (39.6%; 95%
CI: 30.1–49.0) than children in urban schools (26.0%;
95% CI: 19.1–32.9; P = 0.02) and a higher prevalence of
T. trichiura (86.8%; 95% CI: 78.0–95.6) than children in
urban schools (68.2%; 95% CI: 61.8–74.6; P = 0.001).
ere was no significant difference in A. lumbricoides
prevalence between urban and rural schools (P = 0.47)
(Table4).
Infection intensity
e AMEPG and GMEPG values for A. lumbricoides and
T. trichiura obtained by the KK procedure, stratified by
infection intensity category as defined by the WHO [20]
are shown in Table5. e majority of infected school-
children had low-intensity infections (88.4% with T.
trichiura; 51.2% with A. lumbricoides). Among 88 infec-
tions with any STH (that is either A. lumbricoides or T.
trichiura) by the KK, 23 were moderate-intensity infec-
tions (26.1%) and 4 were high-intensity infections (4.6%).
us, out of all 264 study participants, the proportion of
schoolchildren infected with any STH with moderate-to
heavy-intensity infections was 10.2% (n = 27).
Discussion
is is the first multiplex molecular epidemiological
study to examine the prevalence of four STH species, A.
lumbricoides, T. trichiura, Ancylostoma sp. and N. ameri-
canus, in Myanmar. e results indicate that, despite the
decade-long, bi-annual targeted deworming programme
among pre-SAC (aged 2–4years) and SAC (fourth grade
and below, aged 5–9years) in Myanmar, STH infections
remain highly prevalent among schoolchildren in at least
one sentinel site selected for monitoring of the targeted
school deworming programme [17].
STH infection prevalence andintensity ofinfection
Overall, polyparasitism (determined by qPCR) was also
high with 63.5% of infected individuals having two or
more infections, and 30.3% of infected individuals having
triple infections (Fig.3).
Ascaris lumbricoides andTrichuris trichiura
Results of both KK microscopy and qPCR analysis indi-
cated there was no reduction in infections of A. lum-
bricoides or T. trichiura in schoolchildren and, indeed,
showed a significantly higher prevalence than previously
reported in a MoHS monitoring survey conducted in
the same township (Phyu) in 2012 [19]. e 2012 sur-
vey, which used KK alone, determined prevalences of
5.8%, 18.6%, and 0.3% for A. lumbricoides, T. trichiura,
and hookworm respectively [19], much lower than the
prevalence values reported here (Table 2). is is not
unexpected as qPCR is recognised as being considerably
more sensitive than the KK procedure and would thus
Table 3 Comparison of the Kato-Katz and qPCR methods for diagnosis of A. lumbricoides and T. trichiura
A. lumbricoides T. trichiura
Positive qPCR Negative qPCR Total Positive qPCR Negative qPCR Total
Positive KK 30 11 41 49 20 69
Negative KK 115 108 223 128 67 195
Total 145 119 264 177 87 264
Page 7 of 12
Aungetal. Infectious Diseases of Poverty (2022) 11:28
be expected to identify more infected individuals. How-
ever, analysis by KK alone determined prevalences for A.
lumbricoides and T. trichiura of 15.5% and 26.1%, respec-
tively, and these were significantly higher than reported
in the earlier MoHS survey utilising the same micros-
copy-based procedure [19].
Despite its lower sensitivity compared with the qPCR,
just over 50% of infections determined using the KK
method were light-intensity infections (Table 5). e
remainder were classified as moderate-intensity (39.0% of
samples) or heavy-intensity infections (9.8% of samples)
(Table5). Although the results obtained by qPCR and KK
indicated a very high prevalence overall in schoolchildren
with T. trichiura (74.6%), no heavy-intensity infection
were identified using the KK procedure, and only 11.6%
of infected individuals had moderate-intensity infections.
ese proportions for both A. lumbricoides and T. trichi-
ura are likely to be underestimates as, for example, unfer-
tilised eggs of A. lumbricoides are often missed by the KK
[41]. Nevertheless, the proportion of individuals infected
with either A. lumbricoides or T. trichiura in moder-
ate- to heavy-intensity infections (determined by KK) in
our study was 10.2%, which is comparable to 10.8% pre-
control-programme prevalence of any STH infection
of moderate- to heavy-intensity, reported in 2002 in the
same study area [19]. is pattern of infection intensity
over a period of 14years indicates there is a long road
ahead in order to achieve the WHO-recommended level
for STH elimination as a public health problem; that is
below 1% prevalence for moderate-intensity and heavy-
intensity STH infections [42].
Hookworm
e 2012 MoHS survey recorded a prevalence of 0.4% for
hookworm by the KK procedure [19]. Although we found
no positive samples by KK, the hookworm prevalence
determined by qPCR was 30.7%, with the majority posi-
tive for Ancylostoma sp. (Table2). e low hookworm
prevalence recorded by KK is likely due to the rapid egg
lysis that occurs post-defecation [41, 43]. To minimise
this, stool samples need to be prepared as soon as possi-
ble after defecation and slides read within a few hours of
preparation [41, 43]. Accordingly, the hookworm results
obtained by the KK in this study and from the 2012
national survey [19] are likely underestimated due to egg
lysis. A. ceylanicum, a zoonotic hookworm of dogs, has
recently been identified in Myanmar [44]. e presence
of this hookworm species complicates control efforts and
will require drug treatment of dogs to help control trans-
mission to humans.
e findings presented here based on prevalence alone
underscore the need to up-scale the STH control pro-
gramme in Myanmar, and again highlight the poor sen-
sitivity of the KK method. e KK stool examinations
undertaken in the current study were undertaken with
the existing local capacity and limited resources, reflect-
ing the usual scenario in the monitoring of STH control
programmes in low-income countries, and reflecting
underestimated prevalence/intensity levels in current
national surveillance efforts. Accordingly, in addition to
KK, which is currently the most-commonly used proce-
dure for monitoring purposes in resource-poor settings
[45], more sensitive diagnostic methods, with minimal
interference due to other factors such as egg lysis, should
be integrated into the monitoring of STH control pro-
grammes [44].
qPCR vs KK
Prevalence determined by the KK procedure was much
lower than by the qPCR analysis, a feature of other stud-
ies on STH [34, 35, 46, 47]. is reinforces the inad-
equacy of monitoring STH control programmes using
KK alone, particularly in areas with low intensity infec-
tions—such as in locations where STH chemotherapy is
Fig. 2 Prevalence of soil transmitted helminths determined by qPCR
and Kato-Katz (KK) microscopy (n = 264)
Fig. 3 Venn diagram showing soil transmitted helminths
co-infections in schoolchildren determined by qPCR (Total positive
cases = 208)
Page 8 of 12
Aungetal. Infectious Diseases of Poverty (2022) 11:28
Table 4 Prevalence of soil transmitted helminths by gender, age and urban/rural location
n: Number of positive cases, 95% CI 95% condence interval, Any STH Infection with any of the three parasites (A. lumbricoides, T. trichiura, or hookworm), All 3 STH Infection with all of the three parasites, KK Kato-Katz
method; Chi-square statistics; signicance: *P < 0.05; **P < 0.01; ***P < 0.001
A. lumbricoides T. trichiura Hookworm Any STH All 3 STH
nPrevalence (95% CI)nPrevalence (95% CI)nPrevalence (95% CI)nPrevalence (95% CI)nPrevalence (95% CI)
KK and qPCR combined
Total infections 156 59.1% (53.1–65.1) 197 74.6% (69.3–79.9) 81 30.7% (25.1–36.3) 222 84.1% (79.7–88.5) 64 24.2% (19.0–29.5)
Gender
Male 78 62.4% (53.7–71.1) 95 76.0% (68.3–83.7) 50 40.0% (32.0–48.0)** 104 83.2% (76.7–89.7) 43 34.4% (27.0–41.8)***
Female 78 56.1% (47.9–64.3) 102 73.4% (66.1–80.7) 31 22.3% (14.7–29.9) 118 84.9% (78.8–91.0) 21 15.1% (8.1–22.1)
Age in years
Under 11 94 62.7% (54.8–70.6) 117 78.0% (71.0–85.0) 46 30.7% (23.2–38.1) 133 88.7% (82.8–94.5)* 36 24.0% (17.1–30.9)
11 or older 62 54.4% (45.3–63.5) 80 70.2% (62.2–78.2) 35 30.7% (22.2–39.2) 89 78.1% (71.4–84.8) 28 24.6% (16.6–32.5)
School location
Urban 105 60.7% (53.3–68.1) 118 68.2% (61.8–74.6) ** 45 26.0% (19.1–32.9)* 137 79.2% (73.8–84.6)** 38 22.0% (15.5–28.4)
Rural 51 56.0% (45.9–66.2) 79 86.8% (78.0–95.6) 36 39.6% (30.1–49.0) 85 93.4% (86.0–100) 26 28.6% (19.7–37.4)
qPCR
Total infections 145 53.4% (47.4–59.5) 177 67.1% (61.3–72.8) 81 30.7% (25.1–36.3) 208 78.8% (73.8–83.8) 63 23.9% (18.7–29.0)
Gender
Male 72 57.6% (48.8–66.4) 85 68.0% (59.7–76.3) 50 40.0% (32.0–48.0)** 97 77.6% (70.4–84.8) 42 33.6% (26.2–41.0)***
Female 73 52.5% (44.2–60.8) 92 66.2% (58.3–74.1) 31 22.3% (14.7–29.9) 111 79.9% (73.0–86.7) 21 15.1% (8.1–22.1)
Age in years
Under 11 86 57.3% (49.3–65.4) 100 66.7% (59.1–74.3) 46 30.7% (23.2–38.1) 123 82.0% (75.4–88.6) 35 23.3% (16.5–30.2)
11 or older 59 51.8% (42.6–61.0) 77 67.5% (58.8–76.2) 35 30.7% (22.2–39.2) 85 74.6% (67.0–82.1) 28 24.6% (16.7–32.5)
School location
Urban 100 57.8% (50.4–65.3) 106 61.3% (54.3–68.2) ** 45 26.0% (19.1–32.9)* 130 75.1% (69.0–81.2)* 37 21.4% (15.0–27.8)
Rural 45 49.5% (39.2–59.7) 71 78.0% (68.4–87.6) 36 39.6% (30.1–49.0) 78 85.7% (77.3–94.1) 26 28.6% (19.8–37.4)
KK only
Total infections 41 15.5% (11.1–19.9) 69 26.1% (20.8–31.5) 0 0% 88 33.3% (27.6–39.1) 0 0%
Gender 35 46
Male 19 15.2% (8.8–21.6) 34 28.0% (20.2–35.8) 42 36.8% (28.5–45.1)
Female 22 15.8% (9.8–21.9) 69 24.5% (17.1–31.8) 88 30.2% (22.3–38.1)
Age in years
Under 11 26 17.3% (11.5–23.2) 44 29.3% (22.3–36.4) 53 35.3% (27.7–42.9)
11 or older 15 13.2% (6.5–19.9) 25 21.9% (13.8–30.0) 35 30.7% (22.0–39.4)
School location
Urban 22 12.7% (7.3–18.1) 46 26.6% (20.0–33.2) 54 31.2% (24.1–38.3)
Rural 19 20.9% (13.4–28.3) 23 25.3% (16.2–34.4) 34 37.4% (27.6–47.1)
Page 9 of 12
Aungetal. Infectious Diseases of Poverty (2022) 11:28
undertaken. Only 11 stool samples found positive by KK
for A. lumbricoides were qPCR-negative, whereas 115
samples found positive by qPCR were KK-negative. Simi-
larly, for T. trichiura 20 KK-positives were qPCR-nega-
tive with 128 KK-negatives positive by qPCR; in regards
to hookworm, 81 KK-negatives were shown positive by
qPCR, possibly due to egg lysis having occurred before
KK slides were prepared and read.
Missed infections by qPCR may be due to lack of eggs
in the 200mg stool samples used for DNA extraction or
inefficiencies in the DNA extraction procedure – par-
ticularly for T. trichiura which requires lysis of eggs for
release of DNA and subsequent successful amplification
by qPCR. e presence of inhibitors in stool is also a
factor to consider and will vary from individual to indi-
vidual. For this reason extracted DNA was diluted 1:5 in
water before being added to the PCR reaction as this also
reduces the effect of any potential inhibitors and allows
the reaction to take place optimally.
e high costs of DNA isolation and qPCR should be
taken into consideration in large-scale surveys in low-
income countries, where the majority of STH infections
occur. We recommend qPCR be used to supplement less
expensive approaches (such as faecal floatation, which
is more sensitive than the KK procedure [48]) in initial
mapping surveys to inform STH control programmes,
and in subsequent monitoring when the STH prevalence
determined by the KK is shown to be very low.
In addition to PCR methods there are isothermal
reaction-based tests that occur at a single temperature
which could also be used in resource poor countries as
they do not require a thermocycler. Loop mediated iso-
thermal amplification occurs at 65 and thus requires
a heat block [49] while recombinase polymorphism
amplification occurs at 37 or room temperature [50].
DNA extraction is often the most expensive component
of molecular diagnostics assays, and is often a limiting
factor precluding their use under field conditions. Nev-
ertheless, there have been several recent advances in the
area of crude DNA extraction; these may reduce costs
and simplify the procedure for future field work, thereby
allowing molecular diagnostics to be more accessible in
remote areas where STH are endemic [51, 52].
The Myanmar National STH control programme, MDA
andreinfection
National MDA coverage for 2015 was 95.5% in pre-
SAC and 99.2% in SAC [18], a feature which makes the
persisting infections after a decade of applying tar-
geted deworming in this Myanmar school setting even
more perplexing. At the time of our study, the School
and Youth Health Programme in Myanmar targeted
only pre-SAC and younger SAC (in the fourth grade
and lower) for deworming. Our findings informed the
Myanmar National STH control programme in expand-
ing the deworming coverage. As a result, the targeted
deworming programme was extended to the entire SAC
population (including the fifth grade and above) during
the 2017–2018 academic year. Further scale up of the
deworming programme should be extended to the entire
Myanmar community including adults in endemic areas
as adults can still contribute to environmental contami-
nation with helminth eggs and larvae, leading to contin-
ued transmission. Similarly, while MDA is effective in
treating infected individuals, it cannot prevent re-infec-
tion. Re-infection can be prevented by increasing health
infrastructure, such as the provision of toilets, access to
clean water, and health education, which can increase
knowledge and change practice leading to reduced re-
infection rates [53, 54].
e finding of the presence of the zoonotic hook-
worm, A. ceylanicum, in another study [44], adds another
dimension to the control scenario as dogs can also con-
tribute to ongoing transmission and re-infection. In
Table 5 Soil transmitted helminths infection intensity determined by the Kato-Katz method
n Number of positive cases, 95% CI 95% condence interval, AMEPG Arithmetic mean of eggs per gram of faeces in infected children, GMEPG Geometric mean of eggs
per gram of faeces in infected children, N/A Not applicable
A. lumbricoides T. trichiura
n% in each
category (95%
CI)
AMEPG (95% CI) GMEPG (95% CI)n% in each
category (95%
CI)
AMEPG (95% CI) GMEPG (95% CI)
Light intensity
infections 21 51.2 (35.3–67.2) 881.9 (0–2,582.0) 235.5 (129.7–427.6) 61 88.4 (80.7–96.2) 151.7 (107.9–195.6) 86.3 (64.7–115.1)
Moderate intensity
infections 16 39.0 (23.4–54.6) 18,703.5 (16,755.8–
20,651.2) 14,421.2 (7,294.6–
28,575.9) 8 11.6 (3.9–19.3) 2142.0 (2020.9–
2263.1) 1958.8 (885.1–
4335.1)
Heavy intensity
infections 4 9.8 (0.3–19.2) 77,610.0 (73,714.6–
81,505.4) 75,335.6 (19,186.7–
295,120.9) 0 N/A N/A N/A
Total positive 41 69
Page 10 of 12
Aungetal. Infectious Diseases of Poverty (2022) 11:28
addition to A. ceylanicum there are zoonotic species of
Trichuris and Ascaris (T. vulpix, T. suis, and A. suum) [55]
in canines and pigs which may also contribute to human
infection, although these have not been investigated or
reported in Myanmar to date.
Case nding andmonitoring
Apart from the 2002 and 2012 MOHS monitoring sur-
veys, which only occurred in one township in each of
the four ecological areas [19], no other country-wide
assessments to determine the areas endemic for STH in
Myanmar have been reported. Given that there are 330
townships in the country, surveys covering more exten-
sive geographical areas are needed to estimate the true
extent and distribution of STH infections in Myanmar.
STH prevalence determined by microscopy was likely
underestimated previously in Myanmar, and we recom-
mend that STH mapping of additional sentinel sites
using molecular epidemiological approaches be under-
taken initially. Savings in manpower and overhead costs
could be made if future community monitoring surveys
for STH are conducted in conjunction with transmis-
sion assessment surveys for lymphatic filariasis which is
widely endemic and another major public health prob-
lem in Myanmar [56]. ese survey activities will require
commitment from the government as a key part of health
system strengthening with a strong sense of ownership,
and planning for and provision of sufficient resources to
invest in the health, growth and wellbeing of Myanmar
children, who are the future of the country. e govern-
ment, non-governmental organisations and academic
institutions involved in neglected tropical diseases
research should, rather than working in isolation, col-
laborate and unite to undertake a concerted and effective
STH control and monitoring programme in Myanmar.
Study limitations
In our study, although school selection was randomised,
it was conducted in one township on fifth grade students
only, resulting in a relatively small but, nevertheless,
informative sample size.
e qPCR methodology to determine precise infection
intensity is still evolving, and it is usually estimated from
Ct scores: the lower the Ct score, the higher the infection
intensity [35]. Intensity (eggs per gram of faeces) for A.
lumbricoides and hookworm was estimated in a previous
study using a formula obtained using egg seeding experi-
ments [32] and this study reported that qPCR was more
sensitive than KK in determining infection intensity.
Some assumptions are made when using qPCR to esti-
mate infection intensity in that: 1) seeding negative stool
samples with the correct number of eggs is achieved; 2)
DNA is extracted from all eggs present; and 3) DNA is
amplified with maximum efficiency and that any poten-
tial inhibitors present in human faeces do not affect the
qPCR assay. Although some of these issues can be over-
come, the use of qPCR to determine infection intensity
provides an estimate only. Consequently, the extrapo-
lation of Ct scores into infection intensities should be
interpreted with some caution until further validation
has been undertaken.
Conclusions
e results presented here, particularly those obtained by
qPCR diagnosis, help contribute to an improved under-
standing of the current epidemiological picture of STH
endemicity in Myanmar. Our findings have informed
evaluation of the existing targeted national deworming
programme as well as providing the requisite information
to plan an integrated STH control and monitoring pro-
gramme. We found that 84% of fifth grade students were
infected with at least one STH species. Polyparasitism
was also high with 63.5% harbouring two or more STH
species. is is despite a decade of targeted deworming
and our results, presented to the MOHS, prompted the
expansion of the STH control programme in Myanmar
to include older schoolchildren as of 2017. Ultimately
deworming should be expanded to the whole community.
Currently the national deworming programme is moni-
tored by deworming coverage only [19]. Parasite detec-
tion by the KK procedure has occurred only once (in
2012), in one township only from each of the ecological
areas, on a total of 1,000 SAC. Additional methods of sur-
veillance should be employed in future and the current
programme monitoring may also need to be expanded
into new areas. Nationwide surveys would identify loca-
tions with potential for STH transmission and infection,
which could then be subjected to case finding, control
efforts, and ongoing monitoring. Finally, more sensitive
parasite detection techniques should be employed par-
ticularly in low STH infection intensity areas.
Abbreviations
AMEPG: Arithmetic mean eggs per gram of faeces; EPG: Eggs per gram of fae-
ces; GMEPG: Geometric mean eggs per gram of faeces; KK: Kato-Katz; MoHS:
Ministry of Health and Sports; PCR: Polymerase chain reaction; qPCR: Real time
PCR; QIMRB: QIMR Berghofer Medical Research Institute; STH: Soil transmitted
helminths; SAC: School aged children; WHO: World Health Organization.
Acknowledgements
We extend our sincere thanks to all the schoolchildren who participated in
the study and their teachers and parents. We also appreciate the support we
received from staff of the Ministry of Health and Sports and the Ministry of
Education in Myanmar.
Authors’ contributions
EA and DJG conceptualised and designed the study. EA, DJG, AT, SMM, SVN,
NNH, TLT and KTH prepared the study protocol. EA, KTH, NNH, MMA and
MWT planned and conducted the fieldwork. CAG conducted DNA extrac-
tion and qPCR analysis. EA coordinated data collection and analysed the data
Page 11 of 12
Aungetal. Infectious Diseases of Poverty (2022) 11:28
with GMW. EA, DJG and CAG drafted the manuscript. All authors read and
approved the final manuscript.
Funding
The Australian Government’s Government Partnerships for Development
project GPFD130117R1 through the Myanmar Research Centre and the
Australian National University. The funder had no involvement in study design;
the collection, analysis, and interpretation of data; the writing of the report; or
the decision to submit the paper for publication. EA, KTH, CAG and DJG have
full access to all the data in the study and accept responsibility to submit for
publication.
Availability of data and materials
All required data is included in this manuscript as tables or figures.
Declarations
Ethics approval and consent to participate
Ethical approval was provided by the Protocol and Ethics Review Committee,
The Department of Medical Research, Ministry of Health and Sports, Myanmar,
(Approval Number: Ethics/DMR/2016/099), and the Science and Medical Del-
egated Ethics Review Committee, The Australian National University, Australia
(Protocol: 2016/406).
In each of the selected schools, the study team conducted a meeting with
parents or guardians of the fifth graders to explain the study and obtain
consent.
Consent for publication
Not applicable.
Competing interests
We declare no competing interests.
Author details
1 Department of Global Health, Research School of Population Health, Austral-
ian National University, Canberra, ACT , Australia. 2 St Vincent’s Clinical School,
University of New South Wales, Sydney, NSW, Australia. 3 Parasitology R esearch
Division, Department of Medical Research, Ministry of Health and Sports,
Yangon, Myanmar. 4 Infectious Diseases Program, QIMR Berghofer Medical
Research Institute, Brisbane, QLD, Australia. 5 Department of Zoology, Uni-
versity of Yangon, Yangon, Myanmar. 6 Department of Public Health, Ministry
of Health and Sports, Nay Pyi Taw, Myanmar. 7 Ministry of Health and Sports,
Nay Pyi Taw, Myanmar. 8 Hunan Institute of Parasitic Diseases, World Health
Organization Collaborating Centre for Research and Control On Schistoso-
miasis in Lake Region, Yueyang, China. 9 School of Public Health, University
of Queensland, Brisbane, QLD, Australia. 10 Faculty of Health Sciences, Curtin
University, Perth, WA, Australia. 11 The Kirby Institute, University of New South
Wales, Sydney, NSW, Australia.
Received: 15 November 2021 Accepted: 21 February 2022
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