Prevalence of Strongyloides stercoralis and other intestinal parasitic
infections among mentally retarded residents in central institution of
Azar Shokri, Khojasteh Sharifi Sarasiabi*, Saeed Hosseini Teshnizi, Hamid Mahmoodi
Paramedical School of Bandar Abbas, Hormozgan University of Medical Sciences, Bandar Abbas, Iran
Asian Pacific Journal of Tropical Biomedicine (2012)88-91
Asian Pacific Journal of Tropical Biomedicine
*Corresponding author: Khojasteh Sharifi Sarasiabi, Paramedical School of Bandar
Abbas, Hormozgan University of Medical Sciences, Bandar Abbas, Iran.
Tel: +98 761 6666367
Fax: +98 761 6670724
Foundation Project: This work was financially supported by Research Deputy of Hormozgan
University of Medical Science (grant No. 90/108/1977).
Intestinal parasites infections are major public health
problems worldwide, especially in developing countries[1-3].
The rate of infections varies according to socio-economical
situations and hygienic behaviors[2,4-7]. Contamination of
water and food sources with human wastes and insufficient
hygiene are main causes of fecal-oral transmitted intestinal
Soil-transmitted helminthes (STH) as a major health
problem caused by Ascaris lumbricoides, Trichuris trichiura
and the hookworms are the most prevalent worldwide
and, Strongyloides stercoralis (S. stercoralis) is the most
neglected one among them[9,11,12]. It is estimated that over
1 billion people are infected with STH and 30-100 millions
with S. stercoralis worldwide[7,11-14]. S. stercoralis’s unique
life cycle makes it possible to survive in human host and
causes autoinfection to lead chronic disease which could
have remained for several years[13-15]. Although most of
infections are asymptomatic, disseminated and hyper
infection may occur in immunocompromised and immune
deficient individuals as a fatal disease[16-20].
Strongyloidiasis is endemic in several countries including
Iran with the prevalence of 0.3% in general population[14,21].
Suitable hygiene plays a key role in prevention of intestinal
Mental retardation and consequently poor hygiene
increase the risk of infection with intestinal parasitic
infections[8,23]. Few epidemiological studies carried out in
mentally retarded populations in Iran[24,25] and other parts
of the world have indicated the prevalence of intestinal
parasitic infections among them[26-29]. The present article
evaluates the prevalence of intestinal parasites among
mentally retarded residents in rehabilitation center of
ARTICLE INFO ABSTRACT
Received 25 July 2011
Received in revised form 6 August 2011
Accepted 28 August 2011
Available online 28 February 2012
Objective: To determine the prevalence of intestinal parasitic infections among mentally
retarded residents of rehabilitation center of Bandar Abbas, Hormozgan province, southern
Iran. Methods: A cross-sectional study was carried out in central rehabilitation institute of
Hormozgan province in summer 2010. Fecal samples of all 133 residents (72 males, 61 females)
aged 3-52, were collected in triplicate. Specimens were examined by direct smear, formalin-
ether concentration techniques and stained by permanent Trichrome, Ziehl-Neelsen stains.
Statistical analysis was conducted by SPSS 13.5. Results: Intestinal parasitic infections were seen
in 48.5% (64 out of 133 subjects: 53.4% in males and 46.6% in females). Strongyloides stercoralis with
Giardia lamblia (2.3%), Endolimax nana (2.3%), Hymenolepis nana (0.8%), Oxyuris vermicularis
stercoralis + Giardia lamblia (2.3%), Entamoeba coli + Giardia lamblia (1.5%), Entamoeba coli +
Blastocystis hominis (1.5%), Oxyuris vermicularis + Entamoeba coli (0.8%), Strongyloides stercoralis
+ Entamoeba coli (0.8%), respectively. Conclusions: Our findings reveal that strongyloidiasis is a
common disease among mentally retarded population in southern Iran.
17.3% showed the highest incidence followed by Entamoeba coli (9.8%), Blastocystis hominis (7.5%),
(0.8%), and Chilomasix mesnili (0.8%). Double infections were found to be as: Strongyloides
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Azar Shokri et al./Asian Pacific Journal of Tropical Biomedicine (2012)88-91
Hormozgan province, southern Iran.
2. Materials and methods
A cross-sectional study was conducted in central
institution for mentally retarded population which located
in Bandar Abbas city of Hormozgan province. The province
was located in the South of Iran in tropical region, attached
to Persian Gulf with high humidity (20%-100%) and warm
climate. The institute is the biggest one in province and
affiliated to welfare organization. All mentally retards,
including children and adults from almost every part of the
province were institutionalized there. All studied populations
were residents of the institution and participated to this
study from May to June 2010, aged 3-52 years (22.84暲9.39).
Three stool samples were taken from each participant every
other day and taken to Parasitology Laboratory of Bandar
Abbas Paramedical School. Specimens were examined with
light microscope using normal saline, iodine stain and
formaline-ether concentration techniques. Modified Ziel-
Neelsen and Trichrome stains were also used for more
confirmation as well. Statistical analysis was carried out by
ANOVA and Chi-square test using SPSS software version
13.5, and P value of <0.05 was considered significant.
All of the 133 institutionalized residents in the institute
aged 3-52 participated in the study. Stool examination
showed that 64 (48.5%) of participants were infected with one
or two parasites, among whom 55 cases (41.6%) showed single
infection, 9 (6.9%) double infections, and 69 (51.5%) showed no
intestinal parasitic infections.
S. stercoralis with 23 cases (17.3%) alone and 4 (3.1%) with
double infection (Figure 1) showed the highest prevalence
among others. Entamoeba coli (E. coli) with 13 cases (9.8%)
alone and 6 (4.6%) with double infection, and Blastocystis
hominis (B. hominis) with 10 cases (7.5%) alone and 2 (1.5%)
with double infection consequently were the most common
parasitic infections in our studied population (Table 1). After
that, single infections of Giardia lamblia (G. lamblia) (2.3%),
Endolimax nana (E. nana) (2.3%), Hymenolepis nana (H.
nana) (0.8%), Oxyuris vermicularis (O. vermicularis) (0.8%),
Chilomasix mesnili (C. mesnili) (0.8%) were observed.
The infection rates in males and females were 38 (53.5%) and
26 (41.9%), respectively. Age distribution of intestinal parasitic
infection in studied population was shown in Table 2. No
significant difference was found between age groups and
intestinal parasitic infection (P=0.290) and neither between
Prevalence of intestinal parasitic infection among 133 residents of
central institute of southern Iran [n (%)].
Single S. stercoralis
Double S. stercoralis + G. lamblia
E. coli + G. lamblia
E. coli + B. hominis
E. coli + O. vermicularis
E. coli + S. stercoralis
Age distribution of intestinal parasitic infection in studied population
Age group (years)
(n=133) [n (%)].
Figure 1. S. stercoralis larva in stool smear.
The results of the present study showed that prevalence of
parasitic infections is high among institutionalized mentally
retarded residents in rehabilitation center of Bandar Abbas.
Our study showed that 48.5% of residents in mentioned
center were infected with one or more parasites. Although
eight different parasite species were diagnosed either alone
or in double form of infection, it was determined that the
highest prevalence belonged to S. stercoralis (17.3%), E. coli
(9.8%) and B. hominis (7.5%), respectively.
Azar Shokri et al./Asian Pacific Journal of Tropical Biomedicine (2012)88-91
Also nonpathogenic parasites such as C. mesnili and E.
nana were seen in this group, so these infections relate to
the environment contaminated with feces.
High frequency of S. stercoralis in our studied group
suggests that it must be considered as a health threatening
agent in this institute, despite strongyloidiasis is not
common in general population of Bandar Abbas[30,31].
According to the high prevalence of strongyloidiasis in
the rehabilitation care center, the true prevalence would
be higher if specific diagnostic methods such as Baermann
technique and agar plate culture method were used[11,32,33].
Serological methods can reveal light infections in
asymptomatic individuals and should be used for further
studies among those population[11,15,32] and in order to
achieve real prevalence, screening procedures must be
Previous studies in Iran have indicated that intestinal
protozoan infections are common problems in such
The prevalence of intestinal helminthic infections
in general population varies between 0% to 3.6% in
different parts of Iran and the decrease in prevalence of
helminthic infections is determined by epidemiological
Protozoan infections are still more frequent in most
parts and the rate of infections varies from 1% to 23%. G.
lamblia was frequently found in most parts of Iran and S.
stercoralis as a soil-transmitted helminth was considered
endemic in some parts with the frequency of about 0.3%.
A recent study among geriatric and disabled people in
Kashan revealed that 87.6% of population were infected with
pathogenic and nonpathogenic intestinal protozoan and
the frequency of intestinal parasitic infection in mentally
retarded students in Tehran was 56.8% showing no evidence
of infection with S. stercoralis.
Other study carried out in Isfahan among mentally
retarded students showed the frequency of infection with O.
vermicularis (20.7%) and H. nana (1.3%), respectively, but
they didn’t find S. sterocralis among them.
Apart from O. vermicularis and H. nana infections in our
studied population, other pathogenic and nonpathogenic
parasites frequently alone or double were also observed
The results from the study in an institution for mentally
retarded adults showed only two cases of strongyloidiasis
while our study revealed 23 cases.
Results from other study among mentally disabled
population in Japan showed frequency of intestinal
amoebiasis, but we didn’t find any case of Entamoeba
histolytica in our population.
Study among mentally retarded people in the Philippines
showed high frequency of Entamoeba histolytica in the
population. The same results were found among mentally
retarded residents of Italian institution, but no infection with
S. stercoralis was observed.
Among all parasitic infections in this center, S. stercoralis
is the more frequent and the most important to care about.
Our country is endemic for S. stercoralis, especially the
north of Iran with temperate and the south with warm
and humid climate. Our studied people included severely
mentally retarded individuals with unusual behaviors such
as geophagia and coprophagia and strongyloidiasis was
found to be high among them as we expected.
Unexpectedly, our findings contrasted with the results
from northern Iran, as they didn’t find S. stercoralis infection
in mentally retarded inhabitants in spite of high humidity
like southern Iran.
The origin of parasitic infections in densely populated
places deemed to be person to person transmission[8,9].
Crowdedness, mental retardation, pica, geophagia,
coprophagia, contact with human waste and poor hygiene
are important risk factors making residents of mental retards
institutes more susceptible to infection with S. stercoralis.
Moreover, asymptomatic infection can remain for decades
due to the occurrence of several auto infection cycles[15,17].
Improvement of hygienic condition and prevention of
person to person transmission along with better nutrition
can limit the transmission of disease among this mentally
retarded population. Although all infected individuals were
treated with proper prescribed medicine, permanent care
and screening are needed to eradicate infection in this
Conflict of interest statement
We declare that we have no conflict of interest.
We thank all staff of mentally retarded rehabilitation
affiliated to social welfare organization of Hormozgan
province, Bandar Abbas city for their collaboration in this
study. We thank Abroshan H for his assistance in collecting
samples. This work was financially supported by Research
Deputy of Hormozgan University of Medical Sciences, Iran
with grant number 90/108/1977.
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