;J

PREVALENCEAND INTENSITY OF THIRD STAGE GNATHOSTOMASPINfGERUM LARVAE IN SWAMP EELS SOLD IN THREE LARGE

MARKETS IN BANGKOK, THAILAND

Wilai Saksirisampantl, Surang Nuchprayoon I. Viroj Wiwanitkit~. Kanyarat Kraivichian I and Jal1lsai Suwansaksri~

'Department of Parasitology,Faculty of Medicine:.Chulalongkom University; 2Department of Labor.ltoryMedicine, racullY ot Medicine, Chulalongkom Uniwrsity; 3Department of Clinical Chemistry, Faculty of Allied

. Health Sciences, Chulalongkom University.Bangkok. Thailand

Abstract. Guathostoma spil/iguulII is:. common human tissue parasite in Thail:.nd. The sw:.mp eel is the

major inte:rmediate or parate:nic host for this parasite. The high pre:valence of the infective third stage larvae (L3)

of this parasite in the rainy season ha..~been noted in previous studies. During JUI1<:1999 (rainy sc:ason), we

perf:>rrned :. cross.sectional survey of the prevalence and the intensity of d spilli.r:erum L3s in the livers ofsw:.mp eels that were obt:Jined from three I:.rge Bangkok markets (Klong Toey, Pr,m Nok, :.nd Tevejl. Of:. tot:J1of 785 livers. G. spitligerum L3s were found in 97: an infection rate of 12%. The prevalence: r,ues in Klong

To.:y. Pr..tOjJo:'. a,.d Tevl'.j rnar'.:e's wer-; 13'7:. :Oq, ar,(j 14% respec!i\.~ly. The:re wa~ n;>s;gr.ifoca'1: differc"ce:

in the proportion of infected eels between the m:.rkets (p > 0.051. The intensity of L3 burden in the:,livers r.lOged

from 1-17 larvae. with :.n average of 2.60 :t 0.2~ I:1rvae (me:.n :t SE). In this study a high prevalence of G..'/,ill(r:erwn L3s was found; there was no significant difference in the intensity of larvae: in swamp eels hetwee:n

markets. These: findings empha..size the importance of pu!)lic he:.lth education: people ne:cd to be aware of thed:lOgers of consuming raw or undercooked food.

U'HRODUCTION

Gllathn.,lOma .,pi/ligulIIl/ is known to be the major

causative agent of human gnathostomiasis. a diseasewhich is common in Thailand (Daengsvar.g. 1980:

i986; Kamiya et al. 1987: Radomyos and Daengsvang.1987). The disease has also been reported in Japan.China, Malaysia. Indonesia. Philippines. Israel andother areas where raw and pickled fish are part of thediet (Andoet al. 1988: Akahane et al. 1994:

Rojekittikhun et al. 1989 a, b; Markell et (// 1999).

The most common outcome of human gnathostomiasisis intermiuen! cutaneous migratory swellings(Dacngsvang. 1986). However. the migration of G..V':"il:::r"m throug:' Impcrtar,t organs such a:; the brai;)

and the eyes. can result in intracranial hemorrhage.paralysis and blindness (Miyazaki. 1960: Daengsvang.1986). A fatal case of eosinophilic encephalomyelitiscaused by this nematode has bt.-enreported (Chitanondhand Rosen. 1967).

Dogs and cats are the definitive hosts of G.

~pilligerum. Copepods or cyclops serve as the firstintermediate hosl. The sccond intermediate hosts are

Correspondence: Wilai Saksirisampant, Department

of Parasitology. Faculty of Medicine, ChulalongkomUniversity. Bangkok 10330. Thailand.Tel: ++66 (0) 2256 4387: Fax: ++66 (0) 2252 4963E-mail: fmedwss@md2.md.chula.ac.th

60

mainly freshwater fish. In Thailand, data about theprevalence and concentration of para.~ites in the secondintermedate hosts (mainly freshwater fish) have beenreported; a high prevalence of G. ~pilligerem L3 wasfound during the rainy season (Rojekittikhun et a/,

1998b). A study of the distribution of GllathO.,IO;"lIinfective larvae in second intermedi;ue hosts during

the rainy season was clearly necessary: the infonnationgained through such a study would help in planningcontrol programs and monitoring the disease.

According to previous surveys. of fifty-nine

species of freshwate:r fish available in the markeL~ ofBangkok. nine were infected with GllatllOS((IlIIalarvae.The ~ighest pr-::vaience flf G. ~pi(li!',('rillllL3s was inFlllid alba (swam~ eds) (Rojck;ttikh,m e; ai, 1':J89;1998 a. b). These larvae can be found in every pan ofthe eel's body. including the liver. To assess the burdenof Gllothostoma parasites in the commonest secondintermediate host. we examined the livers of swampeels that were obtained from three of Bangkok's largemarkets. -

MATERIALS AND METHODS

Collection of swamp eels.A total of785 swamp e:ellivers were obtained from

three of Bangkok's large markets: Klong Toey, Tevaraj(Tevej), and Pran Nok ; the samples were collectedduring June 1999. Each of the three selected marketsserves a different area of Bangkok; each has more

than 1,000 customers per day.

Vol 33 (Suppl 3) 2002v

11-iJ)/»-J .2.Cc,~

G. SPfNIGERUM LARVAE IN EELs IN BANGKOK MARKETS

Collection of gnathostome lan.:fe

The livers were separated fr"m the viscera andwashed with lap water. Each Hver was then digestedwith 25ml artificial gastric juice (0.05 % HCI in 1.5 %

pepsin) in a 27ml screw-cap wOe. Digestion wasperformed in a water bath at 31'C for 4 hours withfrequent agitation. The digested liver was washedseveral times in normal saline by a simple

sedimentation technique. GnathoslOme L3s from eachsedinient were identified and counted by a

stereomicroscopy.

Statistical analysisAll data were analyzed by descriptive statistics.

Differences of prevalence and concentration ofgnathostomalatyaebetweenthe samples ~romthe threemarkcts were regarded as statistically significant ifp $;0.05.

RESULTS

Prevalenceof G.spinigerulll .

Of the 785 swamp eel livers. 97 were positive forgnathostome larvae (Table I). All the detected larvaewere identified as G. spinigem/ll larvae. The infectionrate. of G. .~p:niguum Us was 12%. The highestprevalence rate of G. spini8emlll L3s from swamp eellivers was in Pran No!.: (14%). while those of KlongToey and Tevej markets were 13% and 10%.respectively. There was no significant difference inthe proportion of infected eels between these threemarkets. (£I> 0.05; Table I).

Intensity of G. spinigerum

A lOtal of 244 gnathostome larvae were recoveredfrom 97 positive livers. All were morphologicallyconfirmed to be G. spiniguum. The worm burden of

G. sph::,r;erIlJll L?:; ,'..a:: hig:test in !he cel~ purchased

from Pra" !>iok: 2.75 ~ 0 56 12r"ae V"-r inft:C.ted live!.

The intensity of G. spinigem/ll L3s from Klong Toey

market wa.s2.66 :t 0.67. while those from Tevej andPran Nok market were 2.47 :t 0.35 "nd 2.75 :t 0.50

respectively. However, there was no statisticallysignificant din'erence of intensity between markets.(£I> 0.05).

DISCUSSION

Wc collected our samples during the rainy season.during which a high prevalence of G. .~pilligerulll L~infection is expected (Rojekillikhun et ai, 1998b).

In a previous survey of swamp eels in eleven

provinces of centnil Thailand, Nuamtanong et al (1998)found that Nakhon Nayok had the highest prevalenceof G. JfJilligent/ll L3s (68.7%). The infection rates in

some provinces in central Thailand ranged from 10'kto 33.3'k. These different infection rates depend on

the sources of the swamp eels studied. Many freshwatafish. including eels available in the markets, arccaptured in the natural freshwater, while others an.:from the freshwater fish farms of central Thailand.

(Nuamtanong et al. 1998; Rojekinikhun et al. 1989;1998a). The source of the swamp eels in the present

study was, according to the vendors, from the provincesof central Thailand. (n comparison with a neighboringcountry, the prevalence in June in Thailand(Rojckiuikhun et aI, 1998b) and of our studies were

higher than that in June ofYietnam (8.6%) (Xuan ~ndRojekiuikhun. 2000).

The intensity of G. JpinigerulII L3s (per infectedwhole eel) from provinces in central Thailand variedfrom 2.3 :!: 1.9 to 29.7:t 137.0 (Nuamtanong et aI,

1998). These were different from those found in ourstudy which varied from 2.47 :t 0.35 to 2.75 :t 0.56with an average of 2.6O:t 0.24. These differences aredue to t!le rccove:)' of the j:>1rasiles from th~ whoie

body, whereas wc examine.<! t!l: parasites that were inthe liver only.

Table I

The prevalence and the intensity of G. spinigerwlI L3s in swamp eel livers from three markets in Bangkok(June 1999).

Markets No. eel livers

Total Mean:t SE Iinfected livers

Positive Investigated Range

Klong Toe)'TevejPrb.n-Nok

Total

28

30

3997

214

291280785

o/cPositive No. L3s recovered

\3101412

1-121-91-171.17

2.66:t 0.672.47 :t 0.352.75:t 0.562.60 :t 0.24

67

8691

244

Yol 33 (Suppl~) 2002 61

.,o.

SOUTHEAST ASIAN J TROP MED PeBuc HEALTH

--,In this study, a high prevalence of G. spilligerum

L3s was found in three of Bangku'.;'s markets. As~anpcopie. including Thais. believe th:lI the consumptionof grilled eels benefits health. Unfortunately, thechance ohmJ-cf;:ooking (undergrilling) eels is high.Furthermore, the eating of partially cooked oruncooked freshwater fish is also a normal habit of the

people of Thailand and Japan (Daengsvang, 1986).1"'000 colHrol organizations must act to protectconsumers from these risks. Our data emphasizes theimportance of public health education: awareness of

the dangers of the consumption of raw or partiallycooked food must be maximized. Japanese restaurantsin Thailand that serve swamp eels must be made awareof G. spinigeru/ll infection.

REFERENCES

Ando K. Tanaka H, Taniguchi Y. et al. Two humancases of gnathostomiasisand discoveryof a secondintermediate host of Gllatho.wo/lla IIippOlliclIlII illJapan. J Parasito/1988;74:623-7.

Akahane H, Lamothe-Argumedo R. Martinez-Cruz.JM, et al. A morphological observation of theadvanced. third-stage larvae of MexicanGllathosro/lla. Jpll J Purasitol 1994:43: 18-22.

Chitanondh H. Rosen L. Fatal eosinophilicencephalomyelitis caused by the nematode

GIIlIthos(()/IIa spilligalllll. Alii J i,...p Med H\'g1967;16:638-45.

Daengsvang S. A monograph on the genusGlIlItlw.ftO/llll and gnathostomiasis in Thai land.Tokyo: Southeast Asian Medical Inform:tIionCenter (SEAMIC), International MedicalFoundation of Japan, 1980:85.

Daengsvang S. Gllarlw.wOlIIll spilli.!!erll/ll and human!!n"ih0storr.i:isis. Art' ;.:w. In: S...;:harit S. ~j. Tt:e

2S'h Anniversary of the Faculty of TropicalMedicine, Mahidol University. Bangkok: KrungSiam Press, 1986: 124-47.

62

Kamiya H, Kamiya M. Ohbayashi M, er ai.GllarllO.~IO/IIllmlllll}~\iaeMI)dlaki dnd Dunn, 1965from Rattus sur((erin Thaibnd. Sowheast A.\'iallJ

Trap Med PublicH('alth 1°':;7:18:121-6.

Markell EK, Jonh DT. Kwt"s!.., WA. The bloodcandtissue dwell in!! nematodes. In: Medical

parasitology, 8'h ~d. Phil:tdq'hia: WB Saunders1999:351-2.

Miyazaki r. On the genus GlwthlH"IO/IIaand human

gnathostomiasis with special reference to Japan.Exp ParmilOl 1960: 9:33!i- 70.

NuanHanong S, Waikaglll 1. Anantaphruti MT.Gnathostome infection in swamp eels, Fiutll alba,

in central Thailand. Southeast Asiall Trop MedPuhlic Healrh 1998;29:144-'.

Radon1Yos P. Daengsvang S. A brief report onGllatho.~to/lla.\Jlil/igertl/ll specimens obtained from

human cases. Sowhcasr Asian J Trap Med PublicHealrh 1987:18:215-7.

Rojekiuikhun W. Pubampen S, Hir.lnyachanada P, etal. A survcy 011 the infective larvae of

GllatllO.\"tomaspilligerll/ll in freshwater fish soldin the local markets of Bangkok. J Trap MedPamsi1O1 19R9;1~:7-12.

R(ljekinikhun W. Puh:lIl1pcn S. Waibgul J. Swampeels (FiuTa al!>a),the genuine second intermediate

host of Gllar!wstoma in Thailand. J Trop MedParmilOl 1998a:2 1:-14-5.

Rojekiuikhun W. Pubampen S, Waikagul..1..Seasonal,'ariation in the intensity of Gnathostome larvaein swamp eels (FIutll alba) sold in a local marketin Bangkok. South"Qsr Asiall J Trap Med PuhlicHcalth 1995b: 29:145-53.

\:~::.:n LT. Kojekiaik;;ull W. .-\ :,L:rvcy of in:'ec::\'c b.~';i:~

of Gu(l{llO.wol/la in eels sold in Ho Chi Minh City.

Southeast Asiall J Trop Med Puhlic Health 2000;31: 133- 7.

Vol 33 (Supp! 3) 2002