Schistosoma mansoni Transmission In Mekele City ,Northern Ethiopia

1. 331
Zelalem Mekonnen, Haftay Haileselassie, Girmay Medhin, Berhanu Erko, Nega Berhe. 2012. Ethiop Med J,
Vo1.50,No.4
BRIEF COMMUNICATION
SCHISTOSOMIASIS MANSONI FOCUS IN MEKELE CITY,
NORTHERN ETHIOPIA
Zelalem Mekonneri', Haftay Haileselassie/, Girmay Medhin 3, Berhanu Erk03, Nega Berhe3
*
ABSTRACT
Background: Intestinal schistosomiasis due to Schistosoma mansoni is prevalent and widely distributed in Ethio-
pia. The disease continues to spread to previously non-endemic areas mainly in connection with water resource
development and population movement.
Objectives: To assess the transmission and magnitude of Schistosoma mansoni infection among school children in
Addisalem and Lachi Primary Schools in Mekele City, northern Ethiopia.
Methods: A cross-sectional study was carried out in two primary schools in Mekele City in March 2011. Stool
specimens were collected and processed for quantitative microscopic examination using Kato-Katz technique and
ova were quantified. Search for intermediate snail hosts was carried out in Elala stream and collected snails were
examinedfor trematode infection by shedding after they were individually exposed to electric light for about one to
two hours.
Result: The overall prevalence of S. mansoni infection was 26.3% and for those infected with S. mansoni the mean
intensity of infection was 50 egg per gram ofstool (epg). About 1.9%,20.8% and 77.4% of the positive childrenfor
S. mansoni had heavy, moderate and light infection, respectively. All collected snails were identified to be Biom-
phalaria pfeifferi, intermediate host for S. mansoni, and 2 of them shed cercariae, accounting for 2.5% (2/80) in-
fection rate of the snails.
Conclusion: The present study showed that transmission of intestinal schistosomiasis is taking place in Ellala
stream. The finding of infected children with S. mansoni, the presence of infected snails in the stream as well as the
prevalence of S. mansoni being above 5% all confirm the endemicity of the area for S. mansoni infection. Preven-
tive and control measures should be instituted to reduce on-going transmission and morbidity of the disease in the
area.
INTRODUCTION
Schistosomiasis is a chronic water- related parasitic
disease caused by blood flukes of the genus Schisto-
soma (I). About 200 million people in 74 countries
across the world have. schistosomiasis of which
nearly 85% live in sub-Saharan Africa where S. man-
soni, S. haematobium and S.intercalatum are en-
demic (2).Schistosomia~iitls an important disease in
terms of its public health and socioeconomic impact
next to malaria and is still a major helminth infection
at the beginning of the 21st century in many develop-
ing countries of the tropics and responsible for about
200,000 deaths annually in the world (1,3,4).
Both S. mansoni and S. haematobium infections are
endemic in Ethiopia. S .mansoni is widely distributed
in the country while S. haematobium is restricted to
three low land areas of the country, including the
Awash and Wabe Shebelle valleys and an intermit-
tently flowing stream in Kurmuk at the Ethio-Sudan
border (5, 6). Increased incidence and spread of S.
mansoni in Ethiopia, as in other developing tropical
regions, has been observed because of water based
development projects, resettlement programs and
population migration associated with absence of safe
water supply, lack of sanitary facilities and aware-
ness of the community about schistosomiasis. For
instance, the establishment of the endemicity of S.
mansoni infection in areas previously non-endemic
*Author for correspondence
'Feleghiwot Regional Referral Hospital, Bahir Oar
2Wollo University, P.O. Box 1145, Dessie, Ethiopia
3Aklilu Lemma Institute of Pathobiology, Addis Ababa University, POBox 1176, Addis Ababa, Ethiopia

2. has been reported from Methara, Wonji, and Finchaa
Sugar plantation areas following introduction of wa-
ter based and water related activities (6,7). Though
there are previous reports of schistosomiasis infec-
tion in Makele City, its transmission was not yet con-
firmed. This present survey was, therefore, under-
taken with the objective of assessing the transmission
of intestinal schistosomiasis in Mekele City.
MATERIALS AND METHODS
The study was conducted in Addisalem and Lachi
Primary Schools in Mekele City, Tigray National
Regional State, in March 2011. Mekele City is lo-
cated some 780 kilometers north of Addis Ababa and
has an elevation of 2084 meters above sea level and
the City covers an area of 109.36 square kilometers.
Mekele City has a mean annual temperature of 19
degree Celsius and a mean annual rainfall ranging
from 50-250mm (8,9).
According to the 2007 Ethiopian Census, the city's
population was 215,546 with 110,788 females and
104,758 males (10). In Mekele district, there are 34
elementary schools, 6 secondary schools and 1 pre-
paratory school. Approximately half of the public
primary schools (16 out of 33) in Mekele lack la-
trines. Regarding government elementary schools,
where the total enrolment is 42,054 and the total
number of toilets is 96, the ratio of students per toilet
is 438:1 which is an alarming number (11). Accord-
ing to the health bureau report of 2009 there are 8-
Health centres, 3- General Hospitals and l-Referall
Hospital in the city (12).
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Ellala stream is located North of Mekele City and is
used by farmers for irrigation purposes. The stream is
near the study schools and students have frequent
contact with the water. The source population was all
children attending grade one to eight in two primary
schools in Mekele City and the study participants
were all children who were randomly selected from
these two schools and consented to take part in the
study. Sample size was determined using
n = (Za/2/d)2 *p(1- p)
where, n= the required minimum sample size,
Za/2 = 1.96
from the standard normal distribution
assuming 95% confidence level in our estimate,p =
expected prevalence of S. mansoni in the total popu-
lation of school children which was taken as 50% in
this study, d=expected margin of error in our esti-
mate of S. mansoni prevalence which was assumed to
be 5% in this study. To account for contingencies for
non-response and recording error the sample size was
increased by 10% resulting in 422 students. During
the recruitment of study participants 403 school chil-
dren agreed to participate and 19 refused to take part
in the study.
Stool samples were processed for quantitative micro-
scopic examination using Kato-Katz technique im-
mediately after collection (13). Microscopic exami-
nation and ova quantification were performed by
same laboratory technicians employed by the project
on morbidity studies of schistosomiasis in Ethiopia.
Eggs were counted and converted into number of
eggs per gram of stool (EPG). The intensity of infec-
tion was classified as heavy, moderate and light ac-
cording to the WHO guideline for the evaluation of
soil transmitted helminthiasis and schistosomiasis
(14).
Figurel. Partial sketch map of Mekele City showing the survey area
Main streets
~ Streams
'~
W Schools
•
•

3. Intermediate snail hosts were searched and collected
by using scoop from Elala stream, located north of
Mekele City. The collected snails were put individu-
ally in Petri-dish with some water collected from the
stream and exposed to sun light for 1-2 hours. Each
snail in Petri-dish was_then examined under dissect-
ing microscope for cercaria! shedding. After comple-
tion of the field work, snails were transported to
Akililu Lemma Institute of Pathiobiology, Medical
Parasitology Research Unit, and identified by mala-
cologist of Aklilu Lemma Institute of Pathobiology
based on their shell morphology (15).The snails were
also examined for trematode infection in the Aklilu
Lemma Institute of Pathobiology by shedding after
they were individually exposed to electric light for
about one to two hours. The emerging cercariae were
identified to the genus level using tail morphology
(16).
Data were computerized using Microsoft Excel
spread sheet and exported to STAT A version I I for
analysis. Pearson Chi-square test was used to test the
association of prevalence of infection with age and
sex. Similarly, t-test and one-way analysis of vari-
ance were used to compare intensity of S. mansoni
infection between males and females, and across age
categories, respectively.
The study obtained ethical clearance from Institu-
tional Review Board of Aklilu Lemma Institute of
Pathobiology. With this approval formal letter of
collaboration was written from Akililu Lemma Insti-
tute of Pathobiology to Addisalern and Lachi Primary
Schools in Mekele City of Tigray National Regional
State.
333
The objectives of the study were explained to school
administrative officers, teachers and study partici-
pants and then informed consent (assent in case of
children younger than 18 years) was obtained. Only
children who volunteered were included in the study.
Codes rather than names were used in the documen-
tation of the data to keep confidentiality. Those chil-
dren who tested positive for S. mansoni and/or other
intestinal helminthiases were treated with appropriate
drugs at each school by medical doctors (Nega
Berhe & Zelalem Mekonnen) free of charge using
appropriate drugs immediately on the completion of
laboratory investigation.
RESULT
Overall 403 school children whose age ranges be-
tween 4 and 19 years (54.1 % males and 45.9% fe-
males, mean age of 11.8 yrs) were enrolled in the
current study from two primary schools in Mekele
City. Eighty eight of the study participants (21.84%)
were between the ages of 4 and 9 years, 257(63.8%)
were between the ages of 10 and !4 years and 58
(14.4%) were between theages of 15 and 19 years
(Table-I). Source of drinking water was pump for
251 (62.3%) and spring for 151 (37.7%). Seventy six
percent of the study participants had history of river
or stream water contact.
Table 1: Prevalence and intensity of schistosomiasis mansoni by age and gender among primary school
children in Mekele City, northern Ethiopia, 2011
Number Examined Number (%) Positive EPG ( Geometric Mean)
Age group
Male Female Total Male Female Total Male Female Total
4-9 38 50 88 10 (26.3) 9( 18.0) 19(21.6) 50 42 46
145 112 257 38 (26.2) 33 (29.5) 71(27.6) 55 49 52 •
10-14
15-19 35 23 58 9 (25.7) 7(30.4) 16(27.5) 35 59 44 •
Total 218 185 403 57 (26.2) 49(26.5) 106(26.3) 50.1 49 50
EPG= egg per gram of stool

4. The overall prevalence of S. mansoni was 26.3%
(106/403) and there was no significant difference
between male and females (p-value =0.938) and
across different age groups (p-value = 0.525).Among
the study participants infected with S. mansoni, the
mean intensity of infection was 50 epg. There was no
significant difference in mean S. mansoni epg be-
tween males and females (p-value p=0.89) and across
different age categories (F-value=0.33,P-
value=0.720).
In the present study, 1.9%, 20.8% and 77.4% of the S.
mansoni positive children had heavy, moderate and
light infection, respectively. Intestinal helminths
other than S. mansoni that were observed during
stool examination included H. nana (2.98%), Ascaris
lumbricoides (2.23%), Enterobius vermicularis
(0.99%), and Taenia species (0.5%). All snails that
were collected from human water contact points
(n=80) were checked by the rnalacologistof the Ak-
lilu lemma Institute of Pathobiology. Based on shell
morphology all snails were identified to be Biom-
phalaria pfeifferi which is an intermediate host for S.
mansoni. Out of the total 80 snails only 2 shed cer-
cariae, accounting for the infection prevalence of 2.5
%.
DISCUSSION
In the present study the finding of Biomphalaria
pfeifferi, intermediate host of Schistosoma mansoni,
in Ellala stream, the shedding of schistosome cer-
cariae by some of the snails collected in the stream
and the observation of young children passing Schis-
tosoma mansoni ova all indicated that there is active
transmission of schistosomiasis mansoni in Ellala
stream. Population movements from schistosomiasis
endemic to non-endemic foci that are ecologically
and malacologically receptive areas may lead to the
establishment of new schistosomiasis focus (17). The
present focus is probably a newly established one
and raise great concern since schistosomiasis might
have spread to a number of new foci previously free
as was recently reported from others area in Ethiopia
(I8, 19).
The present study s,zowed an overall S. mansoni
prevalence of 26.30 % ·and intensity of 50 epg. The
prevalence and mean egg count of S. mansoni infec-
tion in the present study was higher than in a survey
done between 1992-1993 among forty communities
in Tigray region with an overall prevalence of 18.4%
(20).However, this figure is lower than the preva-
lence reported in various parts of the country, like in
Adwa (21), Wondo Genet (22) and Bahir Dar
334
(23).The difference in prevalence and intensity of S.
mansoni infection among different communities
might be associated with difference in environmental
sanitation, water supply, socio-economic status of
household, immunity status, altitude, temperature
and the methods of stool examination.
In the present study, the peak prevalence of S. man-
soni infection was observed in school children of the
age group 10-14years, though there was no signifi-
cant difference in prevalence by age group, which is
different from the observations made by different
researchers in Gorgora town (24), Bahir Dar (23), in
South Wollo (25), and overall in Tigray (20), which
showed significant association. This might be be-
cause of similar exposures of children to infected
water source during swimming, bathing, washing or
playing.
Observation on physical characteristics of Ellaia
stream revealed that habitats are favorable for the
survival and breeding of Biomphalaria pfeifferi. The
stream was little turbid, slow flowing, and had dense
vegetation (emergent and submerged) with aquatic
weeds. It has been described that small streams with
flow rate of 10-30 cm/s, with slight turbidity, abun-
dant vegetation at the edge and muddy bottoms have
been found to be potentially favorable habitats for B.
pfeifferi (26). Moreover, observations on the stream
bank showed human excreta a few meters from the
river bank under bushes. It was also observed that the
local people came into contact with the water via
different activities. Some of the activities including
laundering and drawing water for cultivation of vege-
tables and involved spending long periods of time in
cercariae infested water. Hence, human behavior is
conducive for transmission of schistosomiasis.
In conclusion, the present study showed that trans-
mission of intestinal schistosomiasis is taking place
in Ellala stream. The finding of infected children
with S. mansoni, the presence of infected snails in the
stream as well as the prevalence of S. mansoni being
above 5% all confirmed the endemicity of the area
for S. mansoni infection (27).Human activities such
as defection around the stream, swimming and bath-
ing seem to playa great role in the transmission of
the disease in the area. Therefore, appropriate inter-
vention measures need to be in place to reduce mor-
bidity and transmission of intestinal schistosomiasis
in the area; especially health education of students
about the risk behaviors of schistosomiasis and initia-
tion of regular deworming of all school age children
should be undertaken once every 2 years (28).

5. 335
ACKNOWLEDGEMENTS
We would like to acknowledge Ms Lemlem Legesse,
and Messrs Goitom Meharee, Sisay Dessie, Temes-
gen Mulat and Desta W/Tinsae for their unreserved
support during laboratory examination and data col-
lection in the field. We also extend our thanks to
School administrators of Addisalem, director of La-
chi primary school and students in each school for
their willingness and cooperation to make this study
a reality. Finally, we would like to acknowledge
Akililu Lemma Institute of Pathiobiology, Addis
Ababa University, and morbidity studies of schistos-
miasis in Ethiopia, supported by Ulleval University
Hospital and led by Dr Nega Berhe, for financial
support.
REFERENCES
Chitsulo L.D., Engels A., Montresor and Savioli, L. (2000). The global status of Schistosomiasis and its con-
trol. Acta Tropica 77: 41-51.
WHO (2004 ).Schistosomiasis. Available at http://www. who.int/schistosomiasis/epidemiology/enl. Accessed
on: 2711/2011
WHO (20 12).Schistosomiasis. Available at http://www. who.intlschistosomiasis/epidemiology/en/. Accessed
on: 26112/2012
Kloos H., Tsegaye F, Tedla S.( I998).The possible economic and social impact of schistosomiasis in Ethiopia
In Birrie H.,TedlaS, Jemaneh,L., eds. Schistosomiasis in Ethiopia and Eritrea. Addis Ababa University,pp.87-
99.
Ali A., Erko B.,Woldemicheal T.,KloosH.(2006).Schistosomiasis In: Berhane Y., Hailemariam, D., Kloos H.,
eds. Epidemiology and ecology of health and diseases in Ethiopia. Ethiopia: Shama book, pp.66 I-673
Birrie H., Tedela, So, Tilahun, G., kloss, H., Eshete, H. (1998). Schistosomiasis and its distribution in Ethiopia
and Eritrea In: Birrie H., Tedla, S., Jemaneh, L., eds. Schistosomiasis in Ethiopia and Eritrea Addis Ababa:
Addis Ababa University, pp.29-89.
Birrie H, Tedla S, Erko B, Berhe N, Abebe F. (1993). Schistosomiasis in Finchaa river valley, Wellega re-
gion, West Ethiopia. Ethiop J Health Dev. 7:9-15.
Berhane, G. (2002). Engineering Geological Investigation of Mekele area, Tigray, Northern Ethiopia. M.Sc.
Thesis, Addis Ababa University, Addis Ababa, 163pp (Unpublished Report)
9. Bureau of Finance and Economic Development of Tigray [BOFED] (2009). "Administrative boundary delinea-
tion ofMekelle Town," Prepared by G[S-Cartography Unit of BOFED (Mekelle: BOFED)
CSA. (2007).The 2006 Population and Housing Census of Ethiopia: Results for the Tigray Region, CSA,
Addis Ababa
II. Mournie M. (2009). Education Needs Assessment for Mekele City, Tigray, Northern Ethiopia. Mci social see
tor working paper, Mekele, 10pp
12. Genessa G., Kripa K. (2009).Health needs assessment for Mekele City Tigray, Northern Ethiopia. Mci social
sector working paper, Mekele, 16 pp
13. WHO 1991.Basic laboratory methods in Medical parasitology WHO, Geneva.
14. WHO. (2002). The ,p;~vention and control of Schistosomiasis and Soil transmitted Helminthiasis. WHO, Ge-
neva, Technical Report Series. No. 912.
IS. Brown D.S. (1980). Freshwater Snails of Africa and their Medical Importance. Taylor and Francis Ltd., Lon-
don.
16. Frandsen F., Christensen N.( 1984).An introductory guide to the identification of cercariae from African fresh
water snails with special reference to cercariae of trematodes species of medical and veterinary importance.
Acta Tropica 41 :118-202
17. Erko B., Gebre-Michael T., Balcha F., Gundersen, S.G.(200 I). Implication of Papio anubis in the transmission
1.
2.
..,
J.
4.
5.
6.
7.
8.
10.

6. 336
of intestinal schistosomiasis in three new foci in Kime area, Ethiopia. Parasitology International, 50(4):259-66.
18. Erko8., Gemetchu T., Gemeda N., Dessie H. (1996).Transmission of intestinal schistosomiasis in Addis
Ababa, Ethiopia. East African Medical journal, 73 :732-734.
19. Wondimagegnehu T., Birrie H., Yeneneh H.( I997).Schistosomiasis and intestinal helminthic infection in Delo
Awaraja, Bale administrative region south Ethiopia. Ethiopian Journal of Health Development, I I: 183-88
20. Woldemichael T, and Kebede A. (1996). Newly identified endemic areas of Schistosomiasis mansoni in Ti-
gray, Northern Ethiopia.Ethiop Medical Journal, 34:73-82.
21. Legesse L., Erko B., Hailu A. (20 IO).Current status of intestinal schistosomiasis and Soil-transmitted helmin-
thiasis among primary school children in Adwa Town, Northern Ethiopia. Ethiopian Journal of Health Devel-
opment. 24(3): 191-197.
22. Erko B.,Medhin G., Berhe N., Abebe F.,Micheal,T.,Gundersen,S.G.(2002).Epidemiological Studies on intesti-
nal schistosomiasis in Wondo Genet, South Ethiopia. Ethiopian Medical Journal, 40:29-39
23. Erko 8., Tedla S., Petros B. (1991).Transmission of Intestinal Schistosomiasis in Bahir Oar, Northwest Ethio-
pia. Ethiopian Medical Jounal, 29:200-21 I.
24. Degnew M. Status of S. mansoni infection at Gorgora, Northwest Ethiopia. Ethiopian Journal of Health Dcvo
lopment.1999; 13( I): 15 - 20.
25. Assefa T., Woldemicheal T., Dejene, A. (I 998).lntestinal parasitism among students in three localities in south
wolIo, Ethiopia. Ethiopian Journal of Health Development, 12:231-35.
26. Lo C.T., Redda A. and Gemeda N. (1982). Malacological studies of human schistosomiasis in Ethiopia. In:
Proceedings of Symposium on Human Schistosomiasis in Ethiopia (Ayele, T. and Lo. C. T.). Institute of Patho-
biology, Addis Ababa University
27. Teklemariam A.(l982). The distribution of schistosomiasis in Ethiopia: result of 1978-82 survey. In: Tekle-
mariam A., Lo CT eds. Proceedings of a symposium of human Schistosomiasis in Ethiopia. Addis Ababa Uni-
versity. November 1-4, 1982.
28. WHO(2006). Schistosomiasis and soil transmitted helminth Infections Preliminary estimates of the number
of children treated with Albendazole or Mebendazole .World Health Organization, Geneva.
•