4. WHO Expert Committee on Filariasis (Wuchereria and Brugia ln-
7.
fections). Second Report of World Health Organization Technical
Report Series 1967, 359 : 1 - 47.
5. Putali J, Caleb J M. Mass treatment of filarisis in Sidondo, Central
8.
Sulawesi. Bull Pen Kes 1974; 2 (1) : 13 - 16.
6. Partono F, Borahima. Pilot study on the control of Malayan filaria-
sis in South Sulawesi, Indonesia. Bull Pen Kes. 1974; 2 (1) : 17 - 23.
Hawking F. Diethylcarbamazine and new compounds for the treat-
ment of filariasis. Advances in Pharmacology and Chemotherapy,
vol 16. New York London: Academic Press. 1979, pages 130 - 194.
Edeson JFB, Wharton RH.Studies on filariasis in Malaya. Treatment
of Wuchereria malayi carriers with monthly and weekly doses of
diethylcarbamazine (Banocide). Annals Trop Med Parasitol 1958;
52 : 87 - 92.
IV. SCHISTOSOMIASIS
Schistosomiasis in lndonesia, 1980
W Patrick Carney, Moh Sudomo
US Naval Medical Research Unit-2 Jakarta Detachment and
Ecology Division, National Institute for Health Research and
Development
INTRODUCTION
The schistosome fauna of Indonesia is not well documented
as only four species have been reported from this archipelago;
they are Schistosoma japonieum, Schistosoma ineognitum,
Sehistosoma spindale and Trichobilharzia brevis. Of these,
S. japonicum is most important in terms of human health and
its biology in Indonesia is best understood. ln reviewing our
knowledge of schistosomiasis in Indonesia we wish to briefly
mention what is known about S. spindale and T. brevis and
then concentrate the discussion on S. japonicum and S.
incognitum . Further, in our discussion of S. japonieum we wish to
distinguish the classieal form of S. japonicum from S.
japonicum-like schistosomes of lndonesia and their
respective
roles in the etiology of human and animal disease.
Schistosoma spindale
S. spindale was the first schistosome to be reported from
Indonesia. ln 1935 this blood fluke was recovered from water
buffalos in Northeast Sumatera. To our knowledge this is the
only written documentation of S. spindale in lndonesia.
Most likely, however, its distribution is much wider and
probably includes Sumatera, Java and Kalimantan. Besides
Sumatera, S. spindale is known to occur in India, Ceylon and
Thailand. No doubt S. spindale is responsible for cercarial
dermatitis "swimmer s itch
"
in any area of Indonesia where it
is endemic as it is elsewhere in Asia. Fggs have been recovered
from feces of humans on one occasion but this is questionable.
It is definitely a cause of bovine nasal granuloma in areas of
Asia where it oceurs. Larval stages of S. spindale develop in
planorbids mollusks elsewhere in Asia and no doubt planorbids
are responsible for the development of the larval stages of
S. spindale in Indonesia.
This report is based upon studies that have been supported by the
National lnstitute for Health Research and Development, Ministry of
Health, Republic of Indonesia and the U.S. Naval Medical Research
and Development Command for work units MR000010012075
and MF51.524.009003BF61.
The opinions and assertions contained herein are those of the
authors and are not to be construed as the official view of the Ministry
of Health, Republic Indonesia or the U.S. Navy.
Trichobilharzia brevis
T. brevis is an avian blood fluke. In Indonesia it has also
been reported only once in lymnaeid mollusks from the
greaterJakarta area of West Java.
The definitive hosts are usually ducks. T. brevis larval stages
develop in lymnaeid mollusks which are eommon throughout
the Indonesian archipelago, especially in rice growing areas.
T. brevis causes cercarial dermatitis in areas it is endemic.
Most likely its distribution is widespread throughout the
western half of Indonesia as it was originally described from
ducks and lymnaeid mollusks of western Malaysia.
Classical Schistosoma japonicum
Preliminary studies of schistosomiasis in lndonesia were made
in the late 1930 s and the early 1940 s. A focus of Oriental
schistosomiasis was diseovered in the Lindu Valley of Central
Sulawesi (the Celebes).
Humans, dogs, wild deer were found infected and subsequent
microscopic examination of adult worms from these mammals
confirmed them to be S. japonicum. Although
extensive
snail surveys were conducted at that time, the molluscan host
was not found.
In the I970 s there was a resurgence of interest in
the
epidemiology of scistosomiasis in lndonesia.
Oncomelania
hupensis was found in the Lindu Valley, thus confirming that
the disease situation in lndonesia was, in fact, a form of
classical Oriental schistosomiasis similar in its biology and
transmission to that found in the Philippines, Japan and China.
Twenty-two speeies of mammals in the Lindu Lake area
have been examined for S. japonieum and 13 species found
infected. The infection rates in the animals varied considerably
with relatively high rates in civet cats, dogs, rats, shrews, wild
pigs and deer. Water buffalo, cattle and horses were also found
infected in the Lindu Valley but infection rates were compa-
ratively low.
Surveys were conducted in the Lindu Valley to determine
the distribution and infection rates of the parasite in mammals
principally the rat, Rattus exulans. Infections in these rodents
were used to zero in on transmission foci and follow-up snail
surveys. Positive mammals were collected along much of the
perimeter of Lake Lindu. The lack of records along the Sou-
theast shore reflects inpenetrability of the region rather than
the absence of S. japonicum transmission.
The molluscan host of S. japonicum in the Lindu Valley
has been designated a new subspecies, O. h. lindoensis and is
most similar to O. h. quadrasi, the vector host in the Philip-
pines. The subspecific status of the Oncomelania in the Napu
Simposium Masalah Penyakit Parasit
58
Valley has not been determined as yet and is presently referred
to at the Napu geographic strain of O. hupensis.
Oncomelanid snails are widely, but foeally, distributed
throughout the Lindu Valley. Colonies are near cultivated
fields, abandoned farming areas and in the uncultivated virgin
forests surrounding the lake. Over 70 foci have so far been
isolated on the lowlands surrounding the lake. Most of the
colonies isolated have been found on the western and northern
side of the lake. However, the vast, uninhabited lowland marsh
on the eastern side has only been cursorally surveyed due to
its limited accessibility. Oncomelanid colonies probably will be
found in similar niches along the entire perimeter of the valley.
In the Napu Valley, so far 15 colonies of the Napu geogra-
phic strain of Oncomelania hupensis have been delineated.
These colonies are all situated in open, grassy areas adjacent to
the principal north-south and east-west trails that bisect the
valley. Forested areas or along the edge of the forest have not
yet been searched for oncomelanids in the Napu Valley.
Of particular interest is the faet that oncomelanids are not
found at lower elevations in endemie drainage systems where
there appear to be suitable habitats for oncomelanids , else-
where in Sulawesi and throughout the rest of the archipelago.
Reasons for their limited distribution will be discussed later.
Many Oncomelania colonies are found on uncultivated,
yet cleared grassy fields with a rich silty soil adjaeent to
actively worked paddy fields and native cane breaks. These
foci are frequently flooded after rains and during the irrigation
of adjacent paddy fields. Trails used by humans as well as wild
and domestie animals interseet these foci. The grass cover is
sufficiently dense and lush to offer adequate protection, sinee
Oncomelania are usually abundant in this habitat.
Abandoned paddy fields in swampy regions serve as ideal
breeding foei for Oncomelania, whereas fallow paddy fields do
not appear to support the growth and development of Onco-
melania. Apparently the substrate of disturbed areas must be
stabilized and the flora sufficiently dense to provide suitable
habitat for Oncomelania. Oncomelania have not yet been
found in actively worked paddy fields, even though adjacent
grassy fields support high populations of Oncomelania. The
dense vegetation adjacent to irrigation ditches, which form a
network throughout cultivated lowlands, also supports Onco-
melania colonies. It appears that Oncomelania migrate from
these small ditch bank colonies into grassy fields, after they
have been abandoned for a few seasons.
Disturbed areas represent a secondary adaptation for
Oncomelania. In the Lindu Valley Oncomelania thrive in these
habitats along the margins of irrigation ditches, overflow areas
such as abandoned paddy fields and cleared grassy areas
between paddy fields and native eane breaks. Undoubtedly
disturbed areas of today, located on the vast marshland
and moors remaining after the lake receded to its present
level, were natural habitat for Oncomelania before wet rice
cultivation was introduced in the early 1900s.
Natural foci of Oncomelania have been found in a variety
of undisturbed areas, chiefly in an ecotonal zone between the
forest and lowlands.
Natural habitats are well shaded by medium and high tropical
vegetation. In contrast to disturbed areas, the temperatures of
natural foci are more constant and generally cooler. Usually
natural foci are spring fed areas with a silty substrate that
remain moist throughout the entire year. Oncomelania are
found crawling over the silty soil or attached to tanned leaves
or any other flotsam available.
Although the majority of natural foci are found in ecotonal
areas between the forest and lowlands, some foci have been
found in small pockets where the forest vegetation borders
the lake shore. The substrate of these foci is typically sandy
with medium size stones scattered about. Oncomelania are
found
crawling on the rocks, under the surface of tanned
leaves, dead branches or any other flotsam in these spring fed
areas. These foci likewise are well shaded by the medium and
high forest canopy that borders the lake shores. Temperatures
are constant and cooler than in the disturbed area foci.
Natural foci were found on rock slides which bordered
the lake shore. Here again the tall and medium forest vegeta-
tion offered protection from the high temperatures of midday.
Oncomelania were actively crawling about the rocks, tanned
leaves and other debris scattered about the focus. These foci
were moist year around since spring were present.
The Owo area of the Lindu Valley was used as a pasture for
cows, water buffalo and horses. As far as we know it was
never used for rice cultivation. The area became the center of
a controversy a few years ago when the local government
tried to transmigrate 70 families into this land. Unfortunately,
the transmigration project was not stopped as a very large
Oncomelania focus was located there. Within six months, 60%
of the transmigrants, approximately 500 individuals, were
infected with S. japonicum.
Three methods were used to estimate the population
densities of O. h. lindoensis in the Lindu Valley. They were
(I) an exhaustive technique using a brass or iron tube I3,5 cm
in diameter, (2) a fractional technique using a metal ring
also I3,5 cm in diameter and (3) another fractional technique
counting the number of snails per unit of time (man-minute).
The simplest method was the ring sample, but in our hands
this method has not been practical because it cannot be used
where vegetation was thick or where the habitat was under
water. Both conditions occurred frequently in the Lindu
Valley.
The core type sampler which is exhaustive, e.g. m ost of the
snails in a given area are recovered, is the best method but it is
also the most time consuming. The plug sampler yields 97% of
the juvenile and adult snails in a given area. In order to obtain
100% of the snails the sediment must be placed in plastic
buckets and held for up to 48 hours. In view of the time and
logistics involved in gaining the increased accuracy it was not
deemed worthwhile.
As a primary method we adopted the man-minute approach
even though we were aware of its limitations (I) the data
obtained is not comparable with work done elsewhere by
other technicians and (2) for accuraey it depends on the
reliability of the collector. However, this method was able to
be used in all habitats of oncomelanids throughout the valley
and measures of population densities obtained should be
sufficient to evaluate local attempts at control.
At one focus, Luo, all three methods were used to estimate
the density of oncomelanids, ring samples average I8% of total
snail population with a range of 7 to 30%.
When the ring and man-minute methods were compared
5 9
Cermin Dunia Kedokteran, Nomor Khusus 1980
with the plug method it was noted that correlation coefficient
for the man-minute and the plug sampler was higher than
that of the ring method and the plug sampler. In our trials,
then, the man-minute method was actually a better estimate
of the total population than was the ring method.
Man-minute estimates were made at seven foci for at least
16 months. Average values obtained ranged from 0.5 to 2.65
per man-minute. There were no significant differences between
collectors who had participated in 10 or more collections.
When compared to the plug sampling method 1 snail/man
minute =± 500 snails/sq. meter, 2 snails/man minute
= ± 1000 snails/sq. meter and 3 snails/man minute =±
1500 snails/sq. meter.
The exhaustive technique utilized at Luo revealed that
there were. over 1339 snails per square meter. This abandoned
rice field area covers 750 sq. meters. Thus, the oncomelanid
population at this focus alone is estimated at over 10,000,000.
Since the valley floor, minus that under Lake Lindu, is appro-
ximately 50 KM sq., a conservative estimate of 500 snails per
sq. meter over one tenth of the marsh lands (5 KM sq.) would
indicate that the population of oncomelanid in the valley is
astronomical (± 25 billion).
Infection rates of S. japonicum in O. h. lindoensis varied
considerably hetween foci and between sampling periods.
Within a particular colony the distribution of infected snails
was not uniform. The overall average infection rate in the
Lindu Valley was 2.39%.
Usually, average infection rates were less than 3% in large
disturbed area foci. Higher rates (as high as 7%) were frequen-
tly found in small natural foci bordering the lake shore or in
the virgin lowland forests.
There did not appear to be any seasonal correlation of
infection rates in one focus when compared with another.
There were sharp variations in the seasonal infection rates
both in disturbed and in undisturbed areas.
Infection rates were higher in female (2.70%) than in male
snails (1.95%). By age (length) snail infection rates were quite
consistent in snails two months of age or older.
Sentinel animal experiments using mice and monthly
samplings of wild rodents throughout known foci of trans-
mission indicated that transmission took place throughout the
year and that the diurnal peak of cercarial release was between
1600 and 2000 hours.
The distribution of schistosomiasis throughout the
Indone-sianarchipelago was studied extensively in the 1970 s, espe-
cially on the island of Sulawesi. Although more than 50,000
stool specimens were examined and extensive snail surveys
conducted Schistosoma japonicum and O. hupensis appear
limited in their respective distribution to two contiguous
drainage systems of Central Sulawesi the Lindu Valley, 1,000
meters in elevation at the headwaters of the Gumbasa River
drninage system and the Napu Valley, more than 1,000 meters
in etevation at the headwaters of the Lariang River drainage
system.
According to a 1971 census 6,500 Indonesians from a total
population of 120 million lived in confirmed schistosomiasis
transmission areas. However, at least 500 more individuals
have moved into the Lindu Valley. Thus, at least 7,000 indi-
viduals are continuously exposed to schistosomiasis in con-
firmed endemic areas.
Using a very conservative infection rate (35%), 2,500
persons in Indonesia are afflicted with this disease. Most likely,
however, 50 - 60% of the exposed population are infected.
At the latter rate approximately 4,000 individuals are afflicted
with schistosomiasis in Central Sulawesi at any given time.
However, it is important to emphasize that these numbers and
percentages refer to persons passing schistosome eggs in their
stools; a much smaller number and percentage of persons are
really clinically compromised by this infection.
The current status of our knowledge of classical schistoso-
miasis in Indonesia just described really was the situation in
1975 shortly after the Ministry of Health and associated
colleagues from the University of Indonesia and the U.S.
Naval Medical Research Unit completed their base line studies
of the epidemiology of schistosomiasis in Central Sulawesi.
Since 1975 there have been a number of developments
that have changed the epidemiological picture - some for the
better and some, regrettably, for the worse :
a) A pilot control project was initiated by the National
Institute of Health Research and Development in conjunction
with the World Health Organization. This pilot project which
focused on the Paku-Anca area was a multidimensional ap-
proach to control similar in design to the current control
program in the Philippines. It involved selective mass treat-
ment, agro-engineering, mollusciciding, improved sanitation
and health education. The results were good as the prevalence
of schistosomiasis was reduced from 75% to 25% in the
intervention area over a two year period. Regrettably, how-
ever, the control effort has not been maintained and one
indicator of increased transmission, the prevalence of infection
in rodents, suggests that the disease will return to its previous
level of endemicity in a short period.
b) Other schistosomiasis control projects were conducted
throughout the Lindu Valley during the same time frame and
subsequent to the NIHRD -- WHO pilot control project
.
The non-intervention area of one study was accidentally
"controlled" by another project obviously compromising the
results of both studies. In addition, during the past five years
the 4 or 5 villages in the Lindu Valley have been treated by
a number of agencies on more than one occasion using more
than one antischistosomal compound making it difficult to
determine who has been treated, with what, by whom or
when ?
c) Local transmigration programs have relocated people
from other areas of Sulawesi in two areas of the Lindu Valley
that were already known to be schistosomiasis transmission
areas and were declared off limits to human habitation by the
Ministry of Health personnel involved in the basic epidemiolo-
gical studies of schistosomiasis. In the Owo area, approxima-
tely 70 families,± 500 individuals, were exposed to schis-
tosomiasis. In less than one year 50% were infected. In Bamba,
transmigrants were encouraged to farm confirmed transmission
areas; they became ill as expected and left the area. Some of
these farmers returned to a more primitive type of slash and
burn farming on the mountains surrounding Lake Lindu and
this resulted in a series of clashes with governmental officials
interested in preserving the primary forests of that region.
d) In one case a Javanese Bachelor of Sciense volunteer
was sent to Central Sulawesi and assigned the task of helping
the farmers of Owo improve their agricultural production.
Simposium Masalah Penyakit Parasit
6 0
No one in the government warned him about the schistosomia-
sis problem and he needlessly became infected.
e) A logging road has been constructed from the Palolo
Valley close to Bamba which is a confirmed schistosomiasis
transmission area on the northern shore of Lake Lindu.
The only reason schistosomiasis is not a major health problem
in Indonesia today is because of its very focal and limited
distribution. It has the potential to be a much more serious
health problem. Increased contact with the outside world - as
by a commercial road to the valley - would be the most sure
way of spreading schistosomiasis to other areas of Central
Sulawesi. The present isolation of the Lindu and Napu Valleys
is the single most important reason for its limited distribution
and its relative low importance as a national health problem.
The events since 1975 emphasize that if the control of
schistosomiasis is to be successful it will require coordinated
efforts of the local government, the Department of Health, the
Department of Public Workers, the Department of Irrigation
and the Department of the Agriculture . After 30 years of
attempting to control of schistosomiasis in the Philippines,
that government finally created a"Schistosomiasis Control
Council"
which has authority over all departments of the
government in confirmed schistosomiasis areas. Now, in the
Philippines, all agencies of the government must coordinate
their developmental efforts so that the schistosomiasis pro-
blem is managed properly.
When and how schistosomiasis became established on
the island of Sulawesi remain unanswered but the subject of
interesting conjecture. The genus Oncomelania and most
likely Schistosoma japonicum had their origin in China or in
Namma Valley of Burma near the head waters of Yang Tze
River and Irawady where fossil Oncomelania (approximately
1 million years old) have been found. Oncomelanids spread to
Taiwan before it was separated from the continent. Some
think that Oncomelania was introduced to Japan, the Philip-
pines and to Sulawesi, Indonesia at a later time from the
mainland of China or from Taiwan by activities of man - e.g.
by the introduction of rice culture. If oriental schistosomiasis
and its malluscan host were introduced by man to Sulawesi
from the sothern Philippine island of Mindanao where both
the molluscan host O. hupensis and S. japonicum are abun-
dant, why has it not been found at seaports and low lying rice
growing regions (<500 meters) ? Why has it only been found
at or above 950 meters in isolated pockets of the island ? In
the Philippines, Oncomelania habitats are usually found near
sea level but they do occur at elevations up to 900 meters in
one province of Mindanao. Likewise, it is important to note
that wet-rice culture, when practiced in a very primitive
fashion, creates habitats very suitable to the maintenance of
oncomelanids. In the Lindu Valley of Sulawesi however,
wet-rice culture was not introduced until the turn of the
century (1900).
Recent studies in the Lindu Valley have conclusively
demonstrated that the disease and its molluscan host are well
established in undisturbed lowland forests. The presence of
the disease and large populations of the snail in disturbed and
cultivated areas appear to be secondary adaptations.
The concept that schistosomiasis was introduced to Sulawe-
si by man in recent time is difficult to believe. A more credible
answer may be found in geological history of this area. Sula-
wesi is still active, geologically speaking. Schistosomiasis and
its molluscan host, O.
hupensis
,
possibly were widespread
throughout the island of Sulawesi and high mountain valleys
where it is found today may have been much closer to sea
leveL
A land bridge with the Philippines seems indicated by an
analysis of the vertebrate fauna and it is not surprising that
the Lindu strain of
Oncomelania
most closely resembles
O . h. quadrasi in the Philippines. The area of Indonesia east of
the straits of Makassar is geologically unstable, uplifts and
subsidences in the order of 1000 - 2000 meters during the
past 1 to 2 million years were quite possible. A possible land
bridge between Sulawesi and Mindanao via the Minahasa
Peninsula and the Sangir-Kawio chain of islands seems to be
a more reasonable explanation for the extension of the distri-
bution of oncomelanids and schistosmiasis into the Indonesian
Archipelago.
Schistosoma japonicum-like trematodes.
There have been at least 10 reports of Schistosoma japo-
nicum-like infections in man from Java. These have usually
been considered nonautochthonous cases. Eight of the reports
occurred in Indonesian residents of Chinese heritage who had
previously migrated from, or made trips to, Mainland China-
supposedly to an endemic area along the Yang Tze River
system. To our knowledge none of them ever visited the
confirmed schistosomiasis areas in Sulawesi. One case, however,
reportedly made numerous trips to Central Kalimantan (
Bor-neo),staying there for 3- 4 month periods. However, this
indivual, also of Chinese heritage, denied ever having been in
endemic areas of Sulawesi or having traveled outside of Indo-
nesia. Another case that has recently been reported involved
a man of Chinese heritage who denied ever leaving the island
of Java. All of the above 10 cases occurred in middle to older
age males between 34 and 68 years of age and each case was
diagnosed following histological examination of tissue samples
which were recovered for surgical reasons or at autopsy.
Essentially then, these occult cases were due to S.
japonicum
orS. japonicum-like trematodes.
There are at least three possible explanations for the
etiology of these cases :
1).Cases were due to classical S. japonicum and individuals
were exposed an a confirmed endemic area either in Sulawesi
or outside of Indonesia-most likely China since all cases
occurred in individuals of Chinese heritage.
2). Cases were due to classical S.
japonicum
and individuals
were exposed in a currently unknown area of Oriental schisto-
somiasis transmission in Indonesia. This area most likely would
be on the island of Java as nine of the ten cases occurred in
individuals where Indonesian exposure was limited to Java.
3).Cases were due to a S. japonicum-like trematode that is
endemic to Java and/or Kalimantan.
In the cases involving individuals who had migrated from
China or who had visited that country, the most probable
explanation is that these individuals were exposed to a classical
strain of S. japonicum in China. However, the two cases who
never visited known endemic areas either in or out of Indone-
sia, are more difficult to explain. All three of the above
options must be considered :
1).They may have come in contact with a classical strain of
6 1
Cermin Dunia Kedokteran, Nomor Khusus 1980
S. japonicum
in a transmission area of Indonesia that has yet
to be identified.
2).They may have visited an endemic area of classical
S. japonicum,
such as China, but choose not to admit the fact.
3).They may have been exposed to an unknown
S. japo-
nicum-like trematode that is endemic to Java and/or Kali-
mantan.
In light of recent studies in Malaysia where
S.
japonicum-
likeeggs
have also been reported from liver tissue of ten
aborigines; where adult worms indistinguishable from
S. japo-
nicum
were reported in monkeys
(Macaca
fascicularis) in
Ranau atea of Sabah; and where recently they have found
a mammalian schistosome in a triculinid mollusk and rodents
in the same area where infections of
S.
japonicum-like tre-
matode eggs have been found in man, the possibility of a
similar etiology for cases in Indonesia, particulary in Java
and Kalimantan, takes on a new credibility.
The molluscan fauna of Java and Sumatra was studied ex-
tensively by Van Bentham Junting. Habitats similar to those
occupied by amphibious O.
hupensis
elsewhere in Asia were
surveyed throughout both islands yet oncomelanids were not
found. Thus, it is very unlikely that a classical form of
S. japo-
nicum,
transmitted through O.
hupensis,
exists in lndonesia
west of the Wallace s Line. However, habitats occupied by
small aquatic, triculinid mollusks may not have been examined
or they were examined in a very cursory sort of manner.
In Malaysia, triculinid mollusks have been found at the head-
waters of river systems -- in the quartenary branches -- far
removed from concentrations of human populations. Many
such areas exist in Sumatera today and many probably did
exist on the island of Java in the not too distant past.
Likewise, it is unlikely that either of the two cases who
denied having left lndonesia, in fact did. A journey to China
especially if it was done clandestinely, would be very expensive
and neither individual s family was in a financial position
to afford such a luxury.
Thus, the most reasonable explanation of those given
for the cases involving individuals who never left Indonesia or
who never visited endemic areas in Sulawesi is that they came
in contact with another mammalian schistosome with
S. japo-
nicum-like
eggs-possibly one more related to
S. mekongi
than to
S. japonicum. S. mekongi
is endemic to the mainland
of Southeast Asia, where it occurs naturally in dogs and
humans along the Mekong River in Cambodia and Vietnam.
lt is transmitted by a triculinid mollusk,
Tricula aperta,
which is a tiny freshwater mollusk, distantly related to O.
hu-
pensis.
Until recently schistosomes recovered from humans
and dogs in Cambodia and Vietnam were simply called the
Mekong strain of
S. japonicum.The
morphological features of
the adult and larval stages are very similar but there are dis-
tinct biological differences including their respective fasti-
diousness for particular mollusks :
T. aperta
for
S. mekongi
and O.
Hupensis
for
S. japonicum.
As the picture of the co-evolution of schistosomes and their
molluscan hosts in Asia comes into focus though it appears
that there are two distinct branches in the evolution and
distribution of Asian schistosomiasis. One branch involving
ancestors of
Oncomelania
and
S. japonicum
that
make
way from China to Japan, Taiwan, the Philippines and Sula-
wesi, Indonesia during glacial periods and the other branch
involving ancestor of triculinid mollusks and
S. mekongi
that make their way south from the mainland of Southeast
Asia via the
Malaysian peninsula and possibly to Borneo
(Kalimantan), Sumatera and Java.
Schistosoma incognitum
S. incognitum
was described from human
fecal speci-
mens collected in India in 1926. Since then, Indian parasito-
logists have found it is a variety of domestic mammals and,
experimentally, they have established patent infections in a
wide range of laboratory and domestic mammals.
S. incogni-
tum
was found in Thailand during the 1960 s ; there rodents
served as natural host. During the 1970 s it was found on two
islands in the Indonesian archipelago, namely Java and Sula-
wesi. Although a variety of rodents and wild deer have been
found naturally infected in Indonesia, human infections have
not been diagnosed by stool examinations in areas of Indone-
sia where it is enzootic.
S. incognitum
is considered a potential health hazard in
Asia for the following reasons :
1). It lacks definitive host specificity as it can develop in
at least six orders of mammals.
2),It is a common parasite of domestic mammals in India
and of commensal rodents in areas of Southeast Asia where
it has been discovered.
3).Although
patent infections have not been reported
in experimentally exposed primates development to recogni-
zable adult stage has been documented.
4).Humans are constantly being exposed to the cercarial
stage (the infective stage) of
S. incognitum
in rice fields of
Asia where lymnaeid snails and commensal rodents maintain
this sylvatic cycle of this blood fluke. Thus, with any favorable
changes in its gene pool,
S. incognitum
may be able to exploit
the second most common mammal in Asia-man.
Evolutionary pressure is always present and man s cultivation
of rice in habitats that are ideal for the continuation of
S. in-
cognitum
presents a continual opportunity for
S. incognitum
to expand its host range to the readily availble human popu-
lation.
In Sulawesi,
S. incognitum
and
S. japonicum
are sympatric
both in geography and definitive hosts. Their overlapping
distribution obviously raises the question of their potential
hybridization as these two Asian schistosomes have much in
common :
1). Both lack definitive host specificity; both develop in
a wide range of mammalian species from insectivores to
primates.
2).Both utilize amphibious molluscan hosts : a pomatiopsid
O.
hupensis,
in the case of
S. japonicum
and a lymnaeid,
Radix rubiginosa,
in the case of
S. incognitum.
3).Both occur in Southeast Asia.
However, there are also important differences between
S. in-
cognitum
and
S. japonicum :
1).Most strains of
S. japonicum
readily develop to maturity
in humans and other primates whereas
S. incognitum
has not
been shown to develop to patency in any primate in spite of
its purported origin as a parasite of humans in India. Indian
Simposium Masalah Penyakit Parasit
6 2
parasitologists now consider that the source of the original
specimens of S. incognitum was really of porcine origin.
2).The distribution of classical S. japonicum is li mited to
the distribution of O. hupensis and this species is very fasti-
dious in its ecological requirements. On the othcr hand,
S. incognitum which is adapted to ubiquitous lymnaeid snails
potentially has a much larger distribution in Asia and else-
where than classical S. japnnicum because of the latter snail s
dependece on O. hupensis for transmission.
lf these sympathic schistosomes which share the same
definitive hosts in the same geographic region of Indonesia
hybridize successfully, the result could be offspring capable
of infecting humans yet also capable of utilizing mollusks
such as lymnaeids. ln that event human schistosomiasis could
become a problem throughout all of Asia.
S. japonicum and S. incognitum share the same geographic
area and hosts in two areas of Central Sulawesi - the Lindu and
Napu Valleys. There, Rattus exulans have been found infected
with both schistosomes. ln two cases both schistosomes
species were concurrently found in the same rodent and in
one of these cases a heterologous pair- a S. incognitum male
and a S. japonicum female were found in copula. Subsequen-
tly, this same phenomenon was observed in experimental
animals. Laboratory mice were exposed to 50 S. incognitum
cercariae from West Java and challenged with 50 S. japonicum
cercariae from Central Sulawesi 40 days later. When perfused
48 days after challenge female S. incognitum were found in
the gynecophoral canal of S. japonicum males and vice versa.
Heterologously paired females of both species contained eggs
which, as would be expected, were of maternal origin. The
viability of these eggs regrettably was not determined. Thus,
even though these two mammalian schistosomes have been
isolated through a high level of intermediate host specificity,
their sympatric distribution, both geographically and in
regards at least some definitive hosts, presents a natural
opportunity for recombination of genes that may favorably
affect the hybrid s ability to infect a wider range of interme-
diate or definite host. As far human health is concerned the
most dangerous hybrid would be a schistosome capable of
infecting man that was transmitted through lymnaeid snails.
Schistosomes, like all forms of life, continually adapt to
changes in their environment to survive. It is not unreasonable
to assume that their ability to cycle through humans in
addition to other mammals would enhance their chance of
perpetuating themselves in rice growing areas of Asia.
SUMMARY
As we can see from today s discussion schistosomiasis
in lndonesia is not as simple as one might suppose. There
are most likely a number of unidentified schistosomes in the
lndonesian archipelago. In regard to human health the primary
concern is classical Oriental schistosomiasis which is presently
limited to two remote mountain valleys of Central Sulawesi.
It is of utmost importance that a rational control or eradica-
tion program be developed in the near future before economic
exploitation of Sulawesi spreads this disease to other areas.
The second public health concern involves schistosomes of
mammals other than man which may adapt themselves such
that they exploit or utilize the human population in areas
where they are now enzootic for their own survival. Obviously
thc evolutionary stage is set for them to do so. lf this occurs
schistosomiasis in lndonesia could become a major public
health problem. However, with determined efforts classical
schistosomiasis can be controlled and possibly eradicated
from lndonesia. Indonesia, in this case, would be the first
country in the
world to accomplish such an objective, and
of any country
where schistosomiasis is currently endemic,
Indonesia has the
best opportunities of eradicating this
disease. Further, continued monitoring of animal schistoso-
mes throughout the archipelago can provide a sufficient
early warning system in the event zoophilic schistosomes
take a liking to man and become anthropophilic.
V.
CACING USUS
Pengobatan Massal lnfeksi Cacing Usus
dengan Pyrantel Pamoate pada Anak SD
di Yogyakarta
Noerhayati Soeripto , Soegeng Yuwono M , Cholid Baid-
lowi , Prayitno , Soetrisno Eram , Soelarno .
Bagian Parasitologi Fakultas Kedokteran UGM, P3M Dinas
Kesehatan Propinsi DIY
PENDAHULUAN
Jalan yang paling cepat untuk menanggulangi dan mem-
berantas parasit adalah memutuskan lingkaran hidupnya.
Pada keadaan infeksi cacing usus yang ditularkan melalui
tanah ("Soil transmitted helminths") termasuk :
Ascaris lumbricoides, Trichuris trichiura, cacing tambang dan
Strongyloides stercoralis,
cara-cara yang dapat diterapkan
untuk memutuskan lingkaran hidup mereka dapat berupa :
1. Pengobatan
masal
berulang-ulang (secara
periodik)
terhadap penduduk yang terkena infeksi untuk meng-
hilangkan cacing dari dalam tubuh mereka.
2. Perlakuan atau pengobatan terhadap kotoran tinja
untuk membunuh telur cacing maupun larva.
3. Tindakan menghilangkan telur cacing atau membuat
agar telur menjadi inaktif dari dalam makanan atau
sayur-sayuran.
Namun di antara hal-hal tersebut di atas, pengobatan masal
berulang-ulang telah diakui sebagai penyangga utama ("The
main pillar") tempat bersandarnya usaha penanggulangan
atau pemberantasan infeksi Ascaris dan cacing tambang (1).
Di dalam masyarakat, terutama di daerah pedesaan, peng-
obatan masal diberikan dengan tujuan untuk mengurangi
jumlah cacing yang dapat menghasilkan telur, sehingga dengan
demikian dapat mengurangi kesempatan terjadinya reinfeksi.
Di Indonesia, meskipun prevalensi cacing yang ditularkan
6 3
Cermin Dunia Kedokteran, Nomor Khusus 1980