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The IAMURE Internaonal Journal of Ecology and Conservaon aims to publish new dis-
coveries in ecology and conservaon which are contributed by member researchers from
around the world.
The IAMURE Internaonal Journal of Ecology and Conservaon is an internaonal peer
reviewed, online, indexed, cross referenced journal produced by IAMURE Muldisciplinary
Research, an ISO 9001:2008 cered by AJA Registrars, Inc. The journal provides a venue
for scholars to publish their research ndings for advocacy and ulizaon.
Editorial Board
Aim and Scope
Editor in Chief
Edwin R. Tadiosa, Ph. D.
Naonal Museum of the Philippines, Philippines
Associate Editors
Puvadol Doydee, Ph. D.
Kasetsart University, Thailand
Wilson L. Tisera, Ph. D.
ArthaWacana Chrisan University, Indonesia
Roel A. Alli, Ph. D.
West Visayas State University, Philippines
Inocencio E. Buot, Jr., Ph.D
University of the Philippines Los Baños, Laguna, Philippines
Publishing Manager
Jony V. Berjes
Resident Editor
Ismael N. Talili
Managing Editor
Russel B. Obsioma
Webmaster
Lawrence S. Babanto
Print ISSN 2244-1573 • Online ISSN 2244-1581
Internaonal Journal of
Ecology and Conservaon
Vol. 11 July 2014
© 2014 by IAMURE Muldisciplinary Research
All rights reserved.
IAMURE
Table of Contents
Geometric Morphometric Analysis of Individual Variation
in Bumblebee Wings
Ray Vincent E. Araña
doi: http://dx.doi.org/10.7718/ijec.v11i1.804
Vulnerability Assessment of Rice Farming Provinces to Climate
Change in Mekong River Delta in Vietnam
Hoang Ha Anh, Carmelita M. Rebancos, Rico Ancog
& Decibel V. Faustino-Eslava
doi: http://dx.doi.org/10.7718/ijec.v11i1.805
Heavy Metal Concentration in Seawater at Villa Beach,
Iloilo City, Philippines
Brian Gil S. Sarinas, Lorna D. Gellada, Jake Kevin M. Alfonsa,
Kim Domiquel, Leo Rey J. Gumawa, Jay A. Malan
& John Vennard G. Umali
doi: http://dx.doi.org/10.7718/ijec.v11i1.806
Aging Small Scale Coconut Farmers
in Central Philippines-- eir Perspectives on Farming, Succession and
Future Impact on the Local Ecology
Ernesto Go Yap
doi: http://dx.doi.org/10.7718/ijec.v11i1.808
Attenuation of Amoeba in Biochar-amended
Clayey and Sandy Soil
Pearl Aphrodite Bobon-Carnice
doi: http://dx.doi.org/10.7718/ijec.v11i1.807
Distribution of Oncomelania quadrasi (Mollendorf 1895)
and Prevalence of Infected Snails in Schistosomiasis Endemic Villages
of Kapatagan and Lala, Lanao del Norte, Philippines
Requel T. Legaspino, Ephrime B. Metillo & Florencia Claveria
doi: http://dx.doi.org/10.7718/ijec.v11i1.809
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Editorial Policy
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IAMURE Internaonal Journal of Ecology and Conservaon
vi
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Volume 11 · July 2014
vii
Publication Ethics and Publication Malpractice
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IAMURE Internaonal Journal of Ecology and Conservaon
viii
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• Unconditional acceptance
Volume 11 · July 2014
ix
• Acceptance with revision based on the referee’ recommendations
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referees’ and editorial board’s recommendations
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In situations where the referees disagree substantially about the quality of a work,
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Comments
e IAMURE International Journal of Ecology and Conservation welcomes
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English Writing Readability. Readability tests are designed to indicate
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score is as follows:
Score Notes
90.0 – 100.00 Easily understandable by an average 11 year old student
IAMURE Internaonal Journal of Ecology and Conservaon
x
60.0 – 70.0 Easily understandable by 13 to 15 year old students
0.0 – 30.0 Best understood by university graduates
Gunning Fog Index. Developed by Robert Gunning, an American Businessman
in 1952, Gunning Fog Index measures the readability of English writing. e index
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18 years old) or third year college / university in the Philippines.
Plagiarism Detection. Contributors are advised to use software for plagiarism
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orcid number as proof of membership from orcid.org or open researcher contributor
ID.
Volume 11 · July 2014
xi
GUIDE FOR AUTHORS
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IAMURE Internaonal Journal of Ecology and Conservaon
xii
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Volume 11 · July 2014
xiii
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Literature Cited
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only those works cited within the text. Each entry should contain all information
IAMURE Internaonal Journal of Ecology and Conservaon
xiv
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ejournals.ph.
Volume 11 · July 2014
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Vol. 11 · July 2014
Print ISSN 2244-1573 · Online ISSN 2244-1581
Internaonal Peer Reviewed Journal
doi: hp://dx.doi.org/10.7718/ijec.v11i1.809
Journal Metrics: H Index = 1 from Publish or Perish
This journal is included in Thomson Reuters Journal Masterlist
Published by IAMURE Muldisciplinary Research,
an ISO 9001:2008 cered by the AJA Registrars Inc.
Distribution of Oncomelania quadrasi
(Mollendorf 1895) and Prevalence of
Infected Snails in Schistosomiasis Endemic
Villages of Kapatagan and Lala,
Lanao del Norte, Philippines
REQUEL T. LEGASPINO
ORCID No. 0000-0001-8551-2838
msh_drlegaspino@yahoo.com.ph
MSH CARE Mindanao Foundation of Adventist Medical Center-Iligan
Iligan City, Philippines
EPHRIME B. METILLO
ORCID No. 0000-0001-7162-9891
ephrime.metillo@g.msuiit.edu.ph
Department of Science and Mathematics
Mindanao State University of Iligan and Institute of Technology
Iligan City, Philippines
FLORENCIA CLAVERIA
orencia.claveria@dlsu.edu.ph
Department of Biological Science, De La Salle University
Manila, Philippines
IAMURE Internaonal Journal of Ecology and Conservaon
88
ABSTRACT
A survey of Oncomelania quadrasi was conducted from December 2012 to
February 2013 in the Municipalities of Kapatagan and Lala, Province of Lanao
del Norte, Philippines to geo-reference location of snail colony sites, estimate
snail population density and its environmental determinants, and determine
the prevalence S. japonicum-infected snails. Out of 29 total villages surveyed,
25 (86.21%) were positive of infected snails. 104 (58%) of 180 water body sites
(canals, streams, springs, swampy areas and wet grasslands) inspected had O.
quadrasi snail colonies. Population density averages 9.9 ± 8.1SD to 11.7 ± 6.9SD
snails per colony. Multivariate canonical correspondence analysis revealed that a
combination of large habitat size of 1000-3000 sq km (p < 0.002), 0-11 cm water
depth (p < 0.002) and 30.7-32.8 oC water temperature (p < 0.006) signicantly
explained high density of O. quadrasi populations. e mean prevalence of
infected snails was 1.4 ± 0.8SD and 1.1 ± 0.3SD per colony in Kapatagan and
Lala, respectively. e prevalence of S. japonicum infection in O. quadrasi is
low but indicates active transmission. e geographic position of the irrigation
system seems to promote the spread of O. quadrasi in the vast network of water
bodies. Hence, multi-factorial and intensive control measures are necessary to
prevent transmission of schistosoma infection.
KEYWORDS
Environmental health, abundance, colony, endemic, irrigation,
schistosomiasis, villages, Philippines
INTRODUCTION
Schistosoma japonicum infection is one of the major parasitic worm diseases
contributing to the high burden of global helminth infection. An estimated 200
million cases of schistosomiasis occur worldwide (WHO, 2002). ough it has a
relatively low mortality rate, with estimates between 14,000 (King et al., 2005) and
200,000 annual deaths (WHO, 2002), morbidity from schistosomiasis accounts
for the annual loss of an estimated 1.7 to 4.5 million disability adjusted life years
(WHO, 2002). Schistosomiasis continues to be a community health problem in
many parts of the Philippines (Leonardo et al., 2005). Despite regular attempts
to keep the prevalence of S. japonicum infection at a low level, the infection
Volume 11 · July 2014
89
continues to persist in Kapatagan and Lala, Lanao del Norte. Schistosomiasis
is transmitted from the denitive mammalian host to the aquatic environment
through fecal contamination of waterways.
e intermediate host of S. japonicum is a small operculated, amphibious
and dioecious freshwater snails Oncomelania quadrasi (Pesigan et al., 1958).
Very recently, Saijuntha et al. (2014) reported that Philippine O. quadrasi is
genetically distinct from other Oncomelania species in Asia. Females tend to
be larger than males, and eggs are laid singly on solid objects mostly above the
water line (Pesigan et al., 1958). e pristine habitat of O. quadrasi is ood
plains, forests and swamps (Pesigan et al., 1958). Man-made habitats resulting
from agricultural development, such as drainage channels, roadside ditches and
small canals and drainage canals of irrigation works, are thought to be especially
important habitats. Snails are found primarily on the banks but some are also
found in very shallow water. Habitats preferred by O. quadrasi are shaded by
vegetation, where the temperature is relatively constant and cool. Rice elds do
not constitute an optimal habitat for O. quadrasi because they are rather unstable
(Pesigan et al., 1958; Lipayon et al., 2002). e absence of O. quadrasi snails will
result into an absence of S japonicum infection in humans. However, the ecology
of the snail that varies with environmental change, and the socio-economic factor
poverty seem to be strong predictors of the transmission of O. quadrasi into
human beings (Kristensen & Brown, 1999).
FRAMEWORK
e transmission process of S. japonicum at the village-level is greatly
inuenced by local ecology in the Philippines (Tarafder et al., 2006; Carabin et
al., 2006). Barangays (villages) often have dierent infection proles (Fernandez
et al., 2007). e presence of an obligate free-swimming stage in the life cycle of
S. japonicum suggests that the precise location of ecological features such as snail
colonies, water courses, and rice irrigation canals can have a substantial impact
on the eciency of transmission. Furthermore, the behavior of local humans and
reservoir species, especially in relation to their water-contact and sanitary habits,
is also important. Here, we use an information-theoretic approach (Burnham
& Anderson, 2001) to generate information on the distribution and infection
prevalence of S. japonicum host snail, O. quadrasi, in two Municipalities in the
Province of Lanao del Norte, Mindanao Island, Philippines.
IAMURE Internaonal Journal of Ecology and Conservaon
90
OBJECTIVES OF THE STUDY
e objectives of this study were to: (1) determine geo-reference locations of
O. quadrasi snail colonies, (2) estimate snail population density, (3) determine
the inuence of selected ecological conditions on snail density using multivariate
analysis and; (4) determine the prevalence and intensity of S. japonicum infection
in O. quadrasi from water body habitats in the municipalities of Kapatagan and
Lala, Province of Lanao del Norte, Philippines.
MATERIALS AND METHODS
Study area
A total of 30 villages, 25 with some man-made irrigation and ve with
mostly rain-fed rice-farming systems, in Kapatagan and Lala, Lanao del Norte,
Philippines (Figure 1) were selected on the basis of accessibility, location, and
presence or absence of irrigation infrastructure. Villages were mapped before
snail surveys were made. Water bodies such as streams, springs, irrigation canals
of various types, drainage canals, ponds and swamps were traced by walking and
regularly taking Geographic Positioning System (GPS) records of entire perimeter
and areas. All GPS records were entered into a Geographic Information System
(GIS) database. Irrigation system that supplies water to rice farms was included
in this study.
Figure 1. Map showing the Kapatagan Valley comprising the Municipalities
of Kapatagan and Lala, Lanao del Norte
Volume 11 · July 2014
91
Snail sampling
A team of two or three persons walked the whole perimeter of a major watery
habitat and all sites were inspected for the presence of O. quadrasi snails. In every
snail site identied, a 15.5 cm diameter ring (circlat) was placed over a colony and
all snails were gathered and placed in a pre-labeled plastic container. In extensive
habitats, such as swampy areas or grass lands, a 50-m stretch was selected and
three circlat samples 1m apart (across transect line) was taken. For more extensive
swamps, however, sampling was done along the periphery because it was not easy
to access the interior part. A note indicating which plants provided shading was
taken at the location of each ring sample. Location and number habitat sites with
snails were recorded.
Measurement of environmental factors
Several environmental factors were measured at each site where a quantitative
snail survey was conducted. e irrigation system in the study areas was analyzed.
Shade was noted as the presence of tree cover, grass, badiang and other vegetation
at the site of each ring. Habitats were categorized into stream or spring, canals,
swamp, and seepage. Physical factors recorded were surface temperature, water
temperature, and sediment temperature, dissolved oxygen of surface water,
dissolved oxygen of interstitial water in sediments, and pH of surface water and
soil. In the laboratory, snails were carefully assessed for infection following the
crushing method of Frandsen and Christensen (1984); each snail was crushed
between two microscope slides and tissues checked under a microscope for
cercariae or sporocysts of S. japonicum.
Statistical analysis
Statistical analysis was conducted to explore the relationship between infected
sites and environmental factors using the multivariate Canonical Correspondence
Analysis available in the software CANOCO (Ter Braak & Smilauer, 2002).
RESULTS
Distribution and prevalence of infection
A total of 29 rice farm villages in Kapatagan and Lala, del Norte were
surveyed, and 25 villages (86.21%) were found to have infected snails. A total of
180 water body sites were inspected for possible O. quadrasi colony, and 104, 53
from Kapatagan and 51 from Lala, were recorded to have snail colonies.
IAMURE Internaonal Journal of Ecology and Conservaon
92
Many of the snail colonies were of rather limited spatial extent having
35.57% (n = 37) with only less than 250 square meters, 53.84% (n = 56) of the
sites identied with O. quadrasi covered areas of more from 250 to 600 square
meters, and 10.57% (n = 11) from 1000 to 3000 square meters. Only 11.53%
(n = 12) villages were classied as rain-fed while 86.21% (n = 25) villages whose
agricultural farms were supplied with water from irrigation.
e quantitative survey was conducted in 104 colony sites distributed
in dierent villages of Kapatagan and Lala. e reason for not conducting a
quantitative survey in areas (5 sites) with big water bodies is that the area was too
dicult or dangerous to access.
Figure 2: A-D Photographs of O. quadrasi (A) Ventral
and dorsal view of individuals (B) Total body length of O. quadrasi in
centimeters (C) O. quadrasi attached to a wooden stick from a canal
(D) O. quadrasi individuals compared to grains of rice.
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Table 1. Villages in Kapatagan, Lanao del Norte with colony sites
Kapatagan
Villages
No. of
Colonies
No. of Snails from
three ring samples
No. of Snails
Infected
Percentage of
Infection
Butadon 3154 31.95
Sta. Cruz 2153 0 0
Donggoan 4272 10.37
Taguit ic 4501 81.6
Margos 3 205 5 2.44
Lapinig 4192 31.56
San Vicente 3155 21.29
Cathedral Falls 3197 10.69
Waterfalls 394 44.26
De Asis 5 172 31.74
Maranding Annex 4 172 21.17
St o. To mas 577 11.3
Curvada 5151 21.32
Bagong Silang 5173 10.58
Tiacongan 3156 10.64
Table 1 shows the number of colonies and the total number of snails from
three ring samples of each colony in every endemic village of Kapatagan, Lanao
del Norte, Philippines. A total of 53 colony sites were inspected of which 19 of
them (35.85%) were noted to be negative of infected snails. A total of 2,912
snails were collected of which 37 only (1.27%) revealed to be infected. A total
of 296 of sporocysts and cercariae were identied from the 37 infected snails
examined. e highest number of snails infected (n = 8) was found in the village
of Taguitic followed by Margos village (n = 5) and Waterfalls village (n = 4). e
highest number of cercariae and sporocysts were noted in the village of Taguitic
with 72 counts (24.32 %) of cercariae and sporocysts followed by the village of
Margos with 14.52% comprising 43 counts of cercariae and sporocysts. In Santa
Cruz village, 6.66 percent (n = 1) showed negative infection while 93.33 percent
(n=14) of the endemic villages mentioned showed positive snail infection.
IAMURE Internaonal Journal of Ecology and Conservaon
94
Table 2. Villages in Lala, Lanao del Norte with colony sites
Lala Villages No. of
Colonies
No. of Snails from
three ring samples
No. of Snails
Infected
Percentage of
Infection
Abaga 3212 62.83
Pinuyak 3298 10.34
Maranding 4110 0 0
Ten a zas 5280 41.43
Simpak 296 44.17
Cabasagan 266 11.52
Lanipao 4149 32.01
Santa Cruz Lower 5 167 0 0
Darumawang Ilaya 2113 10.88
Rebe 9334 51.5
San Manuel 5251 31.2
Lala Proper 4154 53.25
Tuna a n 258 0 0
San Isidro Lower 276 11.32
Table 2 shows the number of colonies and the total number of snails collected
from every endemic village in Lala, Lanao del Norte. A total of 50 colony sites
were inspected of which 38% (n = 19) were noted to be negative of infected snails.
A total of 2,322 snails were collected of which 34 of the snails (1.52%) revealed
to be infected. A total of 284 of sporocysts and cercariae were identied from the
34 infected snails examined. e highest number of infected snails (n = 6) was
found in the village of Abaga followed by Rebe village (n=5), Tinazas and Simpak
villages (n = 4). e highest number of cercariae and sporocysts were noted in
the village of Rebe with 18.31 % comprising a total of 52 followed by the village
of Abaga with 14.43% comprising 41 counts of cercariae and sporocysts. ree
villages like Tunaan, Maranding, and Santa Cruz Lower revealed to have negative
infection of the snails.
e distribution of snail colony sites in the two sampling areas is presented in
Figures 3 and 4. e green colored villages (Figure 4) represent schistosomiasis
endemic villages but without a single snail colony. ese villages are Bansarvil,
Suso, Buenavista, El Salvador, Pindulonan, Magpatao, Gumagamot, Raw-an
Point, Dawis, Raw-an, Matampay Bucana, Pacita and Matampay Ilaya.
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95
Figure 3. Geographic Information System (GIS)-generated map showing
the distribution of Oncomelania quadrasi colonies in endemic villages with colony
sites in Kapatagan and Lala, Lanao del Norte
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96
Figure 4. Elevation map showing the endemic villages with colony
sites in Kapatagan, Lala, Baroy, Lanao del Norte using Map Window Geographic
Information System (GIS) version 4.8.6.
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97
Figure 5. Mean prevalence of infected O. quadrasi in comparison to the
mean population of the snails in every colony. Error bar = standard deviation.
Legend: Population of snails
Infected snails
e average prevalence of infected snails reached to an average of 1.38 + 0.775)
and 1.1 + 0.33) per colony in kapatagan and Lala, respectively as compared with
the average snail population with 9.85 + 8.1 and 11.64 + 6.96 in Kapatagan and
Lala, respectively (Figure 5).
Physico-chemical properties of colony sites
Villages like Abaga and Pinuyak in Lala, and Margos, Lapinig and San Vicente
of Kapatagan, Lanao del Norte contained colonies whose areas ranges from 1,000
to 3,000 square kilometers. ese large areas also contain large densities of O.
quadrasi populations. e depth of water where snails were collected ranges from
0 cm (surface water) to 11 cm and 0.0 cm to 6 cm in Kapatagan and Lala colony
sites, respectively. Temperature ranges 31.0 to 32.5 oC in Kapatagan colony sites
for atmospheric temperature, while 30.7 to 32.8 oC in Lala colony sites. e
highest atmospheric temperature was taken in the village of San Manuel, and
lowest in Lala with 30.7 oC. Surface water temperature ranges 27.1 to 29.7 oC
MEAN PREVALENCE
IAMURE Internaonal Journal of Ecology and Conservaon
98
and 27.3 to 30.3 oC in Kapatagan and Lala colony sites respectively. Sediment
temperature ranges 25.3 to 28.3 degree Celsius and 25.3 to 28.3 oC in Kapatagan
and Lala colony sites respectively.
Values of pH in surface water ranged 4.1 to 6.79 and 4.16 to 6.78, and
those of soil ranged 2.34 to 5.98 and 2.52 to 5.98 in Kapatagan and Lala colony
sites, respectively. Dissolved oxygen of surface waters ranges from 2.45 to 8.43
ppm and 2.42 to 8.39 ppm in Kapatagan and Lala colony sites respectively.
Percentage saturation of dissolved oxygen in surface water ranges 3.2% to 96.3%
in Kapatagan colony sites while 31.3% to 87.9% were noted in Lala colony sites.
Dissolved oxygen of soil interstitial water ranges from 0.61 ppm to 5.35 ppm
in Kapatagan colony sites, while 0.56 ppm to 3.64 ppm in Lala colony sites.
Percentage saturation of dissolved oxygen ranges 5.2% to 72.3% in Kapatagan
colony sites, while 2.3% to 56.8% concentration of dissolved oxygen in Lala
colony sites.
e irrigation system in study areas
Maranding River Irrigation System (MARIS) lies in the heart of Kapatagan
Valley (Figure 8). MARIS was constructed in the early part of 1974. It is a run-
o-the river type diversion structure with an average dependable water ow of 13
cu. m. per second capable of irrigating the service area of 4,926 has. farmlands
to benet 4,870 farmers of Kapatagan and Lala. e designed service areas
constitute 6,500 hectares. e proximity of O. quadrasi colonies to a canal of the
irrigation system was from zero to approximately within 50 meters. e main
dam is located in the town of the Municipality of Sapad just a village away from
Bagong Silang which is part of Kapatagan, Lanao del Norte. Bagong Silang is an
endemic village with colonies of O. quadrasi positive of infection by S. japonicum
cercariae. Moreover, snail colonies in Bagong Silang village were located in areas
with an elevation of an average of 97 feet from sea level, which is higher compared
to other areas of snail colonies (Table 3). Next to Bagong Silang village was
Butadon village which is likewise located proximal to the main canal of irrigation
system, just a kilometer from the main dam. San Vicente colonies located lowest
with an average height of 45 feet from sea level as compared to other colonies in
Kapatagan, Lanao del Norte. San Manuel village had the highest level in terms
of elevation from sea level where O. quadrasi colonies located in areas with an
average mean of 109 feet from sea level, followed by the Cabasagan village. Both
belong to a network of water bodies facilitated by the irrigation system of Lala,
Lanao del Norte. Darumawang colonies located very low where O. quadrasi
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99
colonies located just an average height of 11.5 feet from sea level (Table 4).
Figure 9 presents irrigated villages of Kapatagan and Lala, Lanao del Norte.
Only the colonies located in Taguitic, Margos and Lapinig water bodies were not
supported by an irrigation system, while all villages in Lala where colonies were
found were supported by an irrigation system.
Figure 8. GIS-generated (Map Window GIS version 4.8.6) map showing
the endemic villages with colony sites in proximity to the irrigation canal
system in Kapatagan and Lala, Lanao del Norte.
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100
Table 3. Average height (± Standard Deviation (SD)) in feet of colony locations
in endemic villages of Kapatagan, Lanao del Norte
Village Name Height SD
Bagong Silang 97 ± 1.41
Butadon 93 ± 7.0
St o. To mas 93 ± 2.82
Waterfalls 85.3 ± 0.577
Sta. Cruz 84 ± 12.73
Cathedral Falls 76.7 ± 1.15
Curvada 72 ± 1.41
Waterfalls 85.3 ± 0.577
Tiacongan 70 ± 2.0
De Asis 67.5 ± 1.29
Maran-Annex 64.8 ± 11.09
Donggoan 65.5 ± 6.75
Lapinig 49.3 ± 3.94
Margos 49 ± 18.33
San Vicente 45 ± 2.0
Table 4. Average height (± Standard Deviation (SD)) in feet of colony locations
in endemic villages of Lala, Lanao del Norte
Village Name Height SD
San Manuel 109 + 3.86
Cabasagan 54.5 + 14. 85
Rebe 74.78 + 3.27
Maranding 62.75 + 2.21
Abaga 54 + 2.0
Ten a zas 52.2 + 2 .58
Simpak 48.5 + 0.707
San isidro 45 + 5.65
Sta.Cruz Lower 40.2 + 20.14
Pinuyak 40 + 2.0
Lanipao 34 + 1.41
Tuna a n 19 + 4.24
Lala Proper 12 + 2 .16
Darumawang 11.5 + 2.12
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101
Figure 9. GIS-generated (Map Window GIS version 4.8.6)
map showing the endemic villages supported by an irrigation system
in Kapatagan and Lala, Lanao del Norte.
Ordination Analysis
e multivariate Canonical Correspondence Analysis yielded a highly
signicant rst canonical axis (F = 27.707, p = 0.002) and all canonical axes (F
= 3.819 and p = 0.002). is implies that a single variable may explain density
of infected snails but other factors cannot be disregarded. For example, of all
the factors considered in the analysis, three habitat factors (colony size, water
depth and surface water temperature) gave signicant results after Monte Carlo
simulation (Table 5).
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102
Figure 10. Canonical Correspondence Analysis ordination diagram showing
the relationship of abundance of snail populations and their signicant factors
contributory to their favorable existence.
Depth = water depth, Dense = total density of snails,
pHsed = soil pH, pHwat = water pH, DO = dissolved oxygen,
Area = GIS mapped areas with snails, Wtemp = water temperature,
Stemp = soil temperature, SUBS = substrate type,
Dosed = areas treated with mulluscides,
SnPop = number of snails per circlat,
IRRI = irrigated sampling sites,
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Table 5. Factors signicantly correlated with the abundance of snail populations
from Kapatagan and Lala, Lanao del Norte. Water Temp = surface water
temperature
Variables Lambda A p F
Area 0.03 0.002 14.4 6
Depth 0.02 0.002 9.82
Water Temp 0.02 0.006 8.63
DISCUSSION
is study highlights the existence of Schistosoma japonicum intermediate host
snail, Oncomelania quadrasi, populations in Southern Philippines, particularly in
the Province of Lanao del Norte, Municipalities of Kapatagan and Lala. e
researchers inspected 180 potential sites of snails located in 29 villages, and it
is quite alarming that more than half (58%) of these sites harbored O. quadrasi
colonies. is value is more than double the reported 23% infected sites in Samar
(Madsen et al. 2008). Since most of the colonies were found in irrigated villages,
bodies of water like streams and springs may be considered permanent allowing
snail populations to establish and build up over time. Nearly all villages have wet
habitats, including rice elds, irrigation canals, and other water bodies. Although
water movement and availability greatly inuence the distribution of snails in the
dierent villages, snails found in mud attached to farm and domestic animals or
tools used in farming can also contribute to the distribution of snails.
Results of the multivariate analysis in this study suggest that large densities of
O. quadrasi in the sampling areas are related with the availability of large watery
areas (1000-3000 sq. m.) that are shallow (0-11 cm depth) and relatively warm
(30.7-32.8 oC). ese habitat features are known to support the reproduction of
O. quadrasi (Pesigan et al. 1958). We did not nd acidic soil pH values of 2.34-
5.98 to be related with population density, which is in contrast to the report that
a soil pH of 5.6-7.9 and >200 mg CaO/100 g soil is ideal to the reproduction of
Bohol Island O. quadrasi populations (Nihei et al. 1998).
Also, the researchers did not nd a signicant inuence of vegetation and
shading on population density as reported by Madsen et al. (2008) in Samar
colonies. ese dierences in ndings may be related with contrasting local
ecologies at these study areas. It is also possible that distinct genetic sub-
populations exist between Visayas (Bohol and Samar) and Mindanao Islands
as reported among sub-populations of Luzon (Cagayan), Leyte and Mindoro
IAMURE Internaonal Journal of Ecology and Conservaon
104
Islands (Sajuntha et al. 2014).
Although the researchers report a low mean prevalence (1.1-1.4) of infected
snails, the large proportion of sites with snail colonies is indicative of an active
transmission. e study in Samar similarly reported a relatively low prevalence
of 5.7 (Madsen et al., 2008). Since these snail-infested villages are connected
through a vast network of streams and irrigation canals during wet season S.
japonicum transmission could peak as heavy rains maintain owing rivers and
streams, which could facilitate the transport of upstream parasites to downstream
locations. Transmission could happen if cercaria-infected water ows into rice
paddies where farmers and farm animals work (Pesigan et al., 1958).
During the conduct of this study we witnessed human schistosoma infections
in areas without snail colonies. is could be partly explained by limitations in snail
sampling (Vercruysse, 2001). However, we believe that non-farmer residents in
Donggoan village of Kapatagan were contracted with schistosomiasis not because
of occupational risks associated with rice farming, but because of regular ooding
with water that could be infested with cercariae. is underscores the fact that the
present study areas are not hydrologically isolated geographic units (Vercruysse,
2001). Moreover, the uncertainties regarding where and when infected snails will
establish a colony is further compounded by a more wet condition in the study
areas due to global climate change (Martens et al., 1997; Sutherst, 2004), and
the further expansion of water development projects that inuence snail habitats
across huge areas (Zheng et al., 2002; Sow et al., 2002). e World Health
Organization predicts variations in snail and parasite dynamics, but emphasize
the relationship between health and the changes associated with the degradation
of aquatic environments around the world (WHO, 2002).
Schistosomiasis in Kapatagan and Lala is expected to remain a signicant
public health problem and may become more heightened because of the
growing human population and increased levels of fecal contamination, but
few data exist on how much contamination is needed, relative to the freshwater
snail intermediate host population in order to maintain high schistosomiasis
transmission rates in a local population (Vercruysse, 2001). e stability
of snail habitat provided by waters from irrigation canals, reservoirs, and the
concentration of large human populations consequently increase man-water
contacts. Attempts to control snails in the study area through the application of
molluscicidal chemicals derived either from the chemical industry or from local
indigenous plants have been unsuccessful because of strong public resistance. e
evidence that such chemicals have specic eects on target snails is often vague
Volume 11 · July 2014
105
(Oliveira & Paumgartten, 2000; Giovanelli et al., 2002).
It is true that improvement of agricultural productivity in Mindanao and
many parts of the Philippines depends on the abundance of water supply, but
in schistosomiasis areas like in Lanao del Norte, Philippines the establishment
of irrigation systems invariably leads to an increase in the transmission of the S.
japonicum infection. us, the design and development of irrigation systems in
Lanao del Norte, Philippines and elsewhere should consider the multi-factorial
aspects of S. japonicum infection.
CONCLUSIONS
A large proportion of surveyed sites in Kapatagan and Lala, Lanao del Norte
harbor O. quadrasi populations. e prevalence of S. japonicum infection in O.
quadrasi is low but represents active transmission. e geographic position of the
irrigation system seems to promote the spread of O. quadrasi in the vast network
of water bodies in Kapatagan and Lala. e presence of schistosomiasis infection
in O. quadrasi and the dierence in their prevalence is inuenced by the presence
or absence of water reservoirs, irrigation system, area, depth and surface water
temperature of the colony sites, the dierence in height of colony sites from sea
level and the availability of suitable hosts- O. quadrasi.
RECOMMENDATIONS
is study recommends immediate, intensive and practical control
intervention in all colony sites of O. quadrasi such as draining or lling snail
habitats with earth, canal lining, canal relocation with deep burial of snails,
vegetation removal, and improved agricultural practices.
ACKNOWLEDGMENT
is study was funded by the Department of Science and Technology-
Philippine Council for Health Research and Development (DOST-PCHRD).
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The IAMURE Internaonal Journal of Ecology and Conservaon is
published four mes a year by IAMURE Muldisciplinary Research.
Send inquiries to: journal.iamure@gmail.com
Arcles may be research manuscripts and notes on original and
applied research, research reviews and notes on issues, problems
and discoveries of interest to researchers and stakeholders.
All papers undergo double-blind review. The Editorial Board
makes the nal decision on the acceptability of a manuscript aer
reviewing the compliance of the researcher to the instrucons of
the peer reviewers.
The editorial policy is published in this issue and can be accessed
through the journal websites: www.ejournals.ph and www.
iamure.com.
International Journal of Ecology
and Conservation
