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- 2

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‘Tah. l- lq idemiolagical role of s ils ia the transmision of SçiGhwnres
Natur#l
Esperimental
Infes tation
Infestation
_.
S. h.
Sh. ‘S.C.
Sh. I
Sb.
S.C.
Snails
A..
0” i,
8.
truncatus
CPO
(30)
.
B.
umbilicatus
B.
@0h0sus
-. - - . -
I3.
senegalensis
f
I
i
8.
forslralii
-.A
S.h.-Si;histosonla haematobum : S Ix -

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In the natural Sahel sonditions thc cpidemiological ~y& is short md wcq%hing hnlqens
ivithin 1 to G months with thc regencration and thi; growth of the p~pulntion of* mol1usc.s . its
infestation and the transmission ot‘schistosomiasis
This ecological bchauour of thesc bulinus sp~&s in the North-Soudaniau regim is \\~ry
itnpotiant in the epidtmûolo~ of human and animai trwatodosis and requieres a K~V contwlling
strate= .
Seasonal flwtuations arc obsm.xA regarding snail abundance and inf~station rate .

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- 5
Sunxy are rwessary to :itudy the dynamlr population of snaiis in natural and in mark
made habitats . and thvir distribution and seasonal infection with ~chistosomtis rtnd O~~L’I
trematodes.
In Scnegal we ha\\-: swn fhat snails arc vomxntrcd in the Narth . the South nnd in thc East
M,.here ec;ologiwl wnditions are betler Cor their develrq~ment . T1te.b art: wm nilh a hjvJtC
hydrogrrlphic netwrk density ( river : lah~s marigots I irrigation canais , drains . ponds . water
bodies , etc: ) nnd a relatiwly heav! rainfall .
‘These areas are those where trematodosis rn gencral and particulwly human and animal
sc;histosomiasis are veq d~veloped .
kfajor factors which ittfluerw disqease q~iclcmiology include environrwntaf c h a n g e s
(” natural” and or man- made ) and human hehaciour .
The typica! e,ïamrJk we bave in hzgai is thi; outbreak of‘ intiistinal schislosomiasis in
lWnrd-‘Toi1 in the Senegai river hasin Fvhich occurcd 3 years afier thG IIiama dam (10 ) . ‘l’his
outbreak is thr: combinAon of‘ set’eral factors :
-The dam and the irrig,atiom si;hemes created more favorable habitats for snails particularl~
ni~~i?l~~l?ril‘r~l‘~ pfiif:.
. . . ~v+ dich bcfkc :vat; unknou-n in thv Sorth f prolif‘cratz in thc d&a and Lac.
de Guiers ,
In the Senegal riwr basin . the oprning of Diama and Manantali dams . the inçreasing of’
irrigated systems and thct rainfall led to the dcvelq~mcnt and extçnsic,n of human snd animal
twniatodosis (hight prevalzncc;s ol’ human s&istosomiasis and a n i m a l
lk~iolosis *
I’;a’at”phjstomiasis and sçhistosomiasis are obserwd in I!X- 1994 ) .
Concerniny the ~pidemiologijcal rok ol‘ snails . VWL need tu clu~idat~ tht: rolc: ol‘ 3. ~~x~~~~~uus
partii;ularly in the Scnegal river basin in thc zyidemtolng~ of‘.S. /icrcn;‘tf,.?l,iîiij;r .
E\\u~ time NC need t o updat.c: our kno~vl&v o n the epidkti!o~,~ o f ihw discaw
wnsidering that it is a dynamic interaction bctwen ixntionnement . host : intennediate-host nnd
parasite Repented matacologi~,?1 wr\\p >s: WC neccswy fi)r fhc study r?i‘ epidwni&gi);içal a.01~ of
sn& kbhosc distribution an4 izbuntianw are net stalic .
II;ilacnlogical datas xc firndamental ftir epidcmiological studios of‘ trematodosis partit:ularl>
sc;histosolniasis and their wntrol .

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- 7

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