MSP TechRep 1991-11 A preliminary survey on ciguatera fish poisoning in Tuvalu

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The University
of the
Soulh Pacific
ISSN 1018-2896
l\\1AIUNE STUDIBS PROGRAlVIME
TECIINJCAL REPORT
A PRELIMINARY SURVEY ON
CI~UATERA FISH POISONING ON
NAURU ISLAND, CENTRAL PACIFIC
I
SERIES
Number
Temakei Tebano
Institute of Marine Resources
University of the South Pacific
SUVA, FIJI.
1991
7
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A PRELIMINARY SURVEY ON
CIGUATERA FISI-I POISONING
ON NAURU ISLAND,
CENTRAL PACIFIC
by
Temakei Tebano
Institute of Marine Resources
The University of the South Pacific
Suva, Fiji
December 1991

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CONTENTS
Introduction
1
Background
2
Methods
3
Results
3
Discussion
4
Summary and Recommendations 5
References
7
Acknowledgement
8
FIGURE 1
9
TABLE 1
10
INTRODUCTION
Ciguatera fish poisoning is the name given to the disease caused by the ingestion
of a wide variety of circumtropically distributed reef fishes (Tebano and McCarthy,
1991). This form of fish poisoning is endemic in the South, Central and Western Pacific.
Symptoms which normally appear within 2 to 32 hours of consumption include a
range of gastrointestinal, cardiovascular, neurological and dermal disorders (Bagnis,
1973; Withers, 1982, Yasumoto et al, 1984). But the most distinctive symptom is the
reversal of temperature (warm things feel cold and vice versa).
The causative organism which was first promulgated by French and Japanese
researchers has been disputed. Gambierdiscus toxicus, a dinoflagellate presumed
responsible for ciguatera fish poisoning, was first isolated from detritus samples on dead
corals in the Gambier Islands, French Polynesia (Yasumoto et al., 1977a and b). It is
believed to produce the two primary toxins responsible for ciguatera fish poisoning; the
water soluble maitotoxin and the lipid soluble ciguatoxin (Yasumoto et al., 1979b; Bagnis
et al., 1980; Shimizu et al., 1982).
Ciguatera fish poisoning was not known on Nauru Island prior to boat channel
blasting in early 1990. It has taken the Nauman people unaware of the danger it poses on
one of their marine food sources, fish. Because the people themselves are new to this
problem, many assumptions have been rumoured as how some reef fish species got
poisonous. Likewise, local cures which might have been passed on from other Pacific
island communities working for the Nauru Phosphate Commssion and who are more
familiar with this disease in their respective countries, are also part of a new era of the
formidable phenomenon.
Ciguatera fish poisoning had not been documented on Nauru since it is new to this
island. A lot of concerns had been shown by the Nauruans and other ethnic groups on the
problems arising from the consumption of toxic fishes. Because the people living in
Nauru rely so much on reef fish for their daily living, it is envisaged that some baseline
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work on this problem needs to be carried out. It is, therefore, the aim of this survey to
collect and collate data available on ciguatera fish poisoning on this island so that future
plans could be formulated in the areas of environmental protection and management,
public and health education. It is also anticipated that more work will be directed toward
the monitoring of the status of this problem.
BACKGROUND
The Republic of Nauru lies 42 km south of the Equator in the Central Pacific. It is
somewhat like an ukelele in shape and is 21.2 km2 in area (Fig. 1). Its approximate
distances from Melbourne and Auckland are 4830 km NE and 3542 km NW, respectively
(History of Nauru).
The mean temperature is 32°C. Two distinct seasons are the Wet and Dry seasons.
The former lasts from November through February/March while the latter occurs during
the other 8 or 9 months. The mean rainfall is about 193 cm but it may vary from year to
year (History of Nauru).
Nauru is believed to be the top of an oceanic mountain that had been blown up
millions of years ago. The coral reef platform which varies in width surrounds the island
with a sharp drop-off beyond the reef crests. At its highest point, the island is just under
90 m above sea level.
The island is divided up into fourteen districts supposedly owned by various tribes.
All the villages occupy the coastal areas except for Buada which is the only district
situated in the centre of the island (Fig. 1).
The Nauruans are Micronesian in origin but there had been intermarriage with
other ethnic groups in the Pacific and elsewhere. The people are known as skilful
fishermen and craftsmen.
Nauru is rich in phosphate or guano (bird droppings) and it is the main export
commodity of the country, which brings in millions of dollars. Although most Nauruans
enjoy a good standard of living, every household would always look at the sea as the
provider of their main source of protein, fish.
Fish is consumed every day, as agricultural products are scarce and most of the
demand is met by imported food items from Autralia, New Zealand and some Pacific
island nations. Pelagic fish landings had been very high during the past years but now fish
are scarce and heavy pressure is now being imposed on reef fish. Inflation is taking its
toll on the island and the price of fish has gone up to about 400 percent. Each household
prefers to fish for their own consumption rather than buy it from unregulated road-side
marketing.
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METHODS
Two methods were used to collect information on ciguatera fish poisoning namely:
Interviews and Examination of Medical Records.
Interviews
Interviews were conducted in various districts throughout the island state. The
main targets were fishermen with known reputation in either handlining, spear-fishing and
other methods. The fishermen were asked to name the species which they think are toxic
and where they caught them from. A list of some Nauruan fishes with local, English and
scientific names is provided in Table 2. Interviews with various people who apeared to
have an in depth knowledge of the problem were also noted.
Examination of medical records
Cases of fish poisoning were examined and determined on the symptoms shown in
the records. Only in a few was the name of the fish consumed mentioned. None of the
records reported showed where the fish that caused the sickness was caught.
RESULTS
The medical records obtained from the Nauru Phosphate Coporation Hospital
showed 18 cases of fish poisoning for 1990 and 21 cases for 1991 ending September.
However, when the cases were confirmed from the patient's history it was clear that only
5 genuine cases for 1990 and 3 for 1991. This indicates how ciguatera fish poisoning is
poorly understood. Fish species implicated are surgeon fish, often referred to as black
fish, Lutjanidae and Serranidae known as red fish, and shark liver. Other fish poisoning
cases have been caused by the consumption of raw tuna or rock cod, other fish species
and a shellfish presumed to be a trochus shell.
The interviews showed that certain surgeon fish species (Acanthurus mata-Deboe,
Ctenochaetus striatus-Iubwiya), honey comb (Epinephelus merra-lwuro, Epinephelus
microdon-Kawudo and Epinephelus melanostigma-Iwuro), rock cod (Cephalopholis argus-
Etom), red snapper (Lutjanus bohar-Irum) and a red emperor were toxic. Other fishes
that the fishermen also named were reef stonefish (Synanceja verrucosa-Ngope) and a
weedy stingfish (Scorpaenopsis cirrhosus-Ngope).
The areas that were identified as having toxic fish are Anibare Bay particularly
around the boat channel-Anibare Channel, Anabar and Anetan reefs (Fig. 1).
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DISCUSSION
These fish species which were identified to have caused ciguatera fish poisoning in
this small but rich island nation have been reported by various researchers (Bagnis;
Yasumoto et al; Tebano and McCarthy; Tebano 1985). It is obvious that the herbivorous
surgeon fish are always involved where there is an initial flare up in ciguatera fish
poisoning. The other fishes implicated to have caused ciguatera poisoning must have
obtained the toxin from these herbivorous grazers via the food chain.
Fish poisoning cases caused by the consumption a shark liver could not be
identified whether they were ciguatera or hypervitaminous as the symptoms were not
clearly stated. However, there is some certainty that some of the cases could have been
ciguatera.
The fishermen interviewed and the general public have fairly different views on
the cause of fish poisoning flare up. Some claimed that sewage was the cause while others
blamed a French warship which was assumed to have done some underwater drilling and
disposing of some poisonous chemicals which were taken by the fish and thus made them
toxic.
One fisherman explained that when a surgeon fish becomes oily, that is the oil
from the flesh sparks when grilled, then this is the time when some of the fish are bound
to be toxic. He also suggested that this fish eats a brain coral which he assumes is toxic.
Other fishermen related the blasting of Anibare Channel with the flare up of
ciguatera fish poisoning. One confident fisherman and keen scuba diver said that in 1990
Anibare Channel was blasted out of the reef platform to allow boats and canoes have a
better access to the open fishing grounds. Several months later, toxic fishes were caught
from around the channel. Later poisonous fish were reported to have been caught from
nearby areas. This view is in line with what previous researchers in the field had
promulgated. They believe that reef disturbance can trigger the onset of ciguatera
poisoning in the sense that loose coral boulders provide new surfaces on which algae and
seaweed will settle and thus provide more favourable habitats for the toxic dinoflagellate,
Gambierdiscus toxicus. In this way the population density of this dinoflagellate may
increase and at the same time help increase the amount of toxin in the herbivorous fishes
to a level a human body cannot resist.
The causes of fish poisoning mentioned earlier have some truth in them. Although
the sewage system has no direct effect on ciguatera poisoning, it may have some indirect
contribution to the problem. The domestic and other wastes pushed out into the ocean
may be useful nutrients required by the algae and seaweeds for healthy growth. The
abundance of nutrients in the water column encourages algal growth. As stated earlier,
more algae means an incease in the number of Gambierdiscus toxicus cells and thus an
increase in toxin production. Drilling acts in the same way as reef blasting in providing
new surfaces for algal colonisation and growth.
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There are reported cases where the disposal of chemicals in the water had caused
fish poisoning (Bhat et al, 1988), however, the cases were not ciguateric in nature. In the
case of chemcial disposal in Nauru water by warships, there is no proof to substantiate
this claim. But if the chemicals were in fact dumped in the water it is quite possible that
they (chemicals) could act as nutrients as described above or if absorbed by the fish the
sickness that may arise is not necessarily ciguatera.
The oily nature of fish that was also mentioned could be interpreted in the light of
food abundance, that is, algae. The more algae that grow, as a result of reef disturbance
or nutrient influx from home refuse, the more food is available and so the fatter or oilier
the fish are going to be.
It is quite evident that reef disturbance has triggered the onset of ciguatera fish
poisoning on Nauru. The Anibare Channel is implicated as where the poisoning began,
subsequently spreading to Anabar and Anetan reefs. It may continue to spread to the
neighbouring reefs.
Interestingly, the moray eels and parrot fishes which are generally very toxic in
most islands where ciguatera poisoning is a severe problem, are found non-toxic here. It
is quite probable these fish populations have been overfished and that their number is so
low they are not a risk to health at the present time.
SUMMARY AND RECOMMENDATIONS
One point that stands out loud and clear is "the reef surrounding this beautiful
island has the potential to become toxic". In other words, ciguatera fish poisoning had
laid dormant since the very existence of Nauru. Until recently, a couple of months ago
the dormancy was interrupted by human interference and innovation. The flare up was
probably triggered by reef disturbance and the enrichment of water with domestic refuse.
Ciguatera fish poisoning is becoming a serious problem in Nauru. The surgeon
fishes, coral trout/cod and snappers have become toxic and other fish species such as
parrot fish, emperor fish and moray eels should be regarded as potentially toxic. Children
are quite vulnerable and should be prevented from eating reef fishes which are known to
be toxic as well as those which are likely to become toxic.
The toxic areas identified are Anibare, Anetan and Anabar reefs. Toxicity may
spread to other areas and the public should be aware of the fact that other reefs around
thb island have the potential to become toxic if they are disturbed or if excess home
refuse is discarded into the water.
There is some evidence to suggest that some fish species may well be overfished.
These include the herbivorous parrot fishes and the carnivorous moray eels. There is a
need to look into a means of managing some of the fish populations such as these, and
this should help enhance the population to an exploitable level.
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There is a need to devise a means of accurate recording of ciguatera incidences
which would help substantiate the actual status of the problem on the island. A monitoring
programme which should take into account of Gambierdiscus toxicus cell counts to be
related to the level of the toxin in various fish species would enable one to forecast the
seriousness and the trend of the problem. A fish testing unit within the Health or
Fisheries divisions would certainly reduce incidences of ciguatera and other forms of fish
poisoning. With a simple testing method such as the "stick or poke test" developed by Dr.
Y. Hokama of the Pathology Department, University of Hawaii, effecient and reliable
results can be obtained within minutes. The mouse test which can be very expensive may
not be suitable in small island nations but the results are as reliable as the poke test.
Reef disturbance and sewage discharge into the sea are two of the factors that can
contribute to the flare up of ciguatera. Such activities should be carefully considered and
probably avoided in future in light of the problems that the people of Nauru are facing.
Public education on the conservation and management of the marine food
resources should be encouraged. The marine food sources of the island are infinite and
therefore require proper management in order to secure sustainable yields for the future
generations of Nauru.
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REFERENCES
1. Uagnis, R., 1973. Fish Poisoning in the South Pacific. South Pacific Commsission
Publications Bureau, 112pp.
2. Bagnis, R., Chanteau, S., Chungue, E., Hurtel, J.M.,
Yasumoto, T.,
1980. Origins of ciguatera fish poisoning: A new dinoflagellate, Gambierdiscus
toxicus. Adachi and Fukuyo, definitively involved as a causal agent. Toxicon
8: 199-208.
3. Bhat, R. V., Gautami, S., Sashidar, R.B., Lakhani, A.G., 1 9 8 8 . A
foodborne disease outbreak in man due to fish consumption possibly containing
phycotoxins in Bombay, India. Proc. Jap. Assoc. Mycotoxicol. 28:37-39.
4. History of Nauru (undated reference). Kyser College, Nauru.
5. Shimizu, Y., Shimizu, H., Scheuer, P.J., Hokama, Y.,
Oyama, M.,
Miyahara, T., 1982. Gambierdiscus toxicus, a ciguatera-causing dinoflagellate
from Hawaii. Bull. Jap. Soc. Sci. Fish. 48(6):811-813.
6. Tebano, T and McCarthy, D., 1984(1991). Ciguatera fish poisoning and the
causative organism in the Gilberts, Kiribati, University of the South Pacific
Marine Studies Programme Technical Report NQ. 9. 120pp.
7. Tebano, T. and Lewis, R., 1991. Ciguatera fish poisoning and reef disturbance.
Observations on ciguatoxin level in reef fishes at Nei Tebaa Channel, Dai Nippon
Causeway, South Tarawa, Kiribati. University of the South Pacific Marine Studies
Programme Technical Report NQ 6., 12pp.
8. Tebano, T., 1985. Population density study on a toxic dinoflagellate resposible for
ciguatera fish poisoning on South Tarawa Atoll, Republic of Kiribati. Atoll
Research and Development Unit, University of the South Pacific Publication, 46
pp.
9. Withers, N.W., 1982. Ciguatera fish poisoning. Ann. Rev. Med. 33:97-111.
10. Yasumoto, T., Raj, U., Bagnis, R., 1984. Seafood poisoning in tropical regions.
Laboratory of Food Hygiene, Faculty of Agriculture, Tohoku University, Japan,
74pp.
11. Yasumoto, T., Bagnis, R., Thevenin, S., Garcon, M.,
1977a. A survey
of comparative toxicity in the food chain of ciguatera. Bull. Jap. Soc. Sci. Fish.
43(8):1015-1019.
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12. Yasumoto, T., Nakajima, I., Ilagnis, R., Adachi, R.,
1977b. Finding a
dinoflagellate as a likely culprit of ciguatera. Bull. Jap. Soc. Sci. Fish.
43(8): 1021-1026.
13. Yasumoto, T., Inoue, A., Ilagnis, R., 1979b. Ecological survey of a toxic
dinoflagellate possibly responsible for the induction of ciguatera. Bull. Jap. Soc.
Sci. Fish. 45(3):395-399.
ACKNOWLEDGEMENT
I sincerely thank the following individuals for their valuable contributions from their
respective fields and professions:
Dr. Ludwig Keke (Secretary for Health and Education)
Mr. Vassal B Gadoengin (Education)
Dr. Daikop Bill
(Nauru Hospital)
Dr. Alolae Cati
(NPC Hospital)
Dr. Querubin
(NPC Hospital)
Mr. Teaaba
(NPC Hospital
Mr. Anton Jimwereiy (Fisheries)
Mr. Peter Jacob
(Fisheries)
Ms. Makerita Va'ai (Director, USP Centre, Nauru)
Ms. Maranoa Eritai (USP Centre, Nauru)
I also owe a big thank you to the fishermen and individuals who have given their time
and assistance in providing valuable information which make up the bulk of this report.
Once again to all involved, thank you very much.
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Figure 1. Map of Nauru
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Table 1. Some common fishes of Nauru Island.
Nauruan name English Name
Species Name
Apwe
Debagommaroa
Deboe
Degoriria
Degomat
Dereba
Dereba
Dorangarang
Doruwa
Eae
Eae
Eaeo
Earata
Eaeokwor
Eaiar
Eanape
Eanape
Earamai
Earata
Ebawo Kumo
Ebawo
Ebo
Egow
Egop
Egarokoa
Ekadawea
Eimar
Ema
Emorr
Emwan
Emwan
Emwan
Eokong
Eokwoy
Erenai
Etaro
Etom
Eweo
Eyongco
Ianen
Ianit
Ibiya
Dusky jack
Caranx sexfasciatus
Long-tail ray
Himantura sp.
surgeon fish
Acanthurus mata
Tawny shark
Ginglymostoma ferrugineum
Blackspotted
Ostracion cubicus
boxfish
Yellowspotted
Acanthurus aliala
surgeonfish
Redspotted
Acanthurus achilles
surgeon fish
Samoan goatfish
Mulloidichthys samoensis
Lowly trevally
Caranx ignobilis
Skipjack
Katsuwonus pelamis
Mackerel tuna
Ethynnus affinis
Gilbert's Cavalla Carangoides gilberti
Scribbled
Aluterus scriptus
leatherjacket
Oilfish
Ruvettus pretiosus
Silvery mullet
Neomyxux chaptalli
orange rockcod
Epinephelus truncatus
Freckled rockcod Cephalopholis sexamaculata
Blue-fronted
Callyodon apicalis
parrotfish
Yellowblue seaperch Lutjanus kasmira
Whitetip shark
Triaenodon obesus
Ashen drummer
Kyphosus cinerascens
Whitetail
Sagocentron caudimaculatum
squirrelfish
Wahoo
Acanthocybium solandri
Hammerhead shark Sphyrna lewini
Silver squirrelfish Sargocentron microstoma
Longbill garfish Rynchorhampus georgi
Blacktipped shark Carcharhinus limbatus
Smooth flutemouse Fistularia petimba
Flying fish
Cypselurus simus
Bigeye squirrelfish Myripristis amaenus
Violet squirrelfish Myripristis violacea
Fleshy squirrelfish Plectrypops lima
Rabbitfaced
Siganus rostratus
spine foot
Rainbow runner
Elogatis bipinnulatis
Lunar-tailed cod Variola louti
Great barracuda
Sphyraena barracuda
Peacock rockcod
Cephalopholis argus
Convict surgeonfish Acanthurus triostegus
Scorpion cod
Pterois antennata
Blacktipped rockcod Epinephelus fasciatus
Rock cod
Epinephelus sp.
Milkfish
Chanos chanos
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Iebo
Ierangue
Ieru
Ikuri
Ikuri
Iniarne Tebo
Iniarne
Ipwo
Irinarne
Irum
Itsibab
Itsibab
Itsibab
Itsibab
Iubur
Iubwiya
Iudud
Iuiuj
Iwiji
Iwuro
Iwuro
Iwuro
Iwuro
Iyubur
Kawudo
Kawuda
Kimago
Kiyoyo
Kurnum
Kwidada
Ngope
Ngope
Yab Ereber
Port Fraslin
Myripristis pralinia
squirrelfish
Blacktipped rockcod Epinephelus fasciatus
Snake mackerel
Gempylus serpens
Mackerel scad
Decapterus macarellus
Round scad
Decapterus macrosoma
Humpback
Lutjanus gibbus
red snapper
Blackspot seaperch Lutjanus fulviflamma
Leatherjacket
Cantherhines dumerilii
Sailfish (pink)
Xiphias gladiusdius
Twospot red snapper Lutjanus bohar
Bigeye tuna
Thunnus obesus
Yellowfin tuna
Thunnus albacares
Dogtooth tuna
Gymnosarda unicolor
Albacore tuna
Thunnus alalunga
Black marlin
Makaira indica
surgeonfish
Ctenochaetus striatus
Hawkfish
cirrhitus pinnulatus
Choram long-tom
Tylosurus crocodilus
Bluelined
Acanthurus lineatus
surgeonfish
Greasy cod
Epinephelus tauvina
Honeycomb rockcod Epinephelus merra
Orange rockcod
Epinephelus hexagonatus
Rockcod
Epinephelus melanostigma
Shortbill spearfish Tetrapturus angustirostis
Marbled rockcod
Epinephelus microdon
Redspotted coralcod Plectropomus leopardus
Bluebanded
Pygoplites diacanthus
angelfish (yellow)
Longhorned
Naso annulatus
unicornfish
Green triggerfish P s e u d o b a 1 i s t e s
flavimarginatus
Bluefin trevally Caranx melampygus
Reef stonefish
synanceia verrucosa
Weedy stingfish
Scorpaenopsis cirrhosus
Spotted surgeonfish Acanthurus guttatus
Dolphinfish
Coryphaena hippurus
Sailfish
Istiophorus platypterus
NB. Toxic fishes in bold letter.
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