Prospection of rivers of Borgu area of Nigeria

\Erom: J.B. Davies, Chief Entonological Evaluation M-IlORAi'JDU],I To: Dr. B. Philippon CYrief, YCU Date: 1.5.81 Reference, ONCtIO/rB Subject: TB.CSPtrCTTC}T Oi. l].I\T]NS OF BORGU AREA OF IVIGINIA Following negotiations between OCP and. tJre }trl'/C Lagos, Professor Unaru *rehu, a joint OCF-ITII/IISD/OO1 aerial prospection of the river betr.reen the River Niger and. the frontier of Benin, was carried. out on the 28 and 2! Apri1, 1981. A {-seater Cessna 1BO of Viking Helicopters was provid.ed. by OCP d:o were represented by 1Ir. Davies. 0n the 2$th the \,,liiO Nigeria tea"n was composed of h. Vioukov and. Ilr. N.K.B. I.lagan, and. on the second. d.ay by Dr. i'.. Du-nbar and. J. Aclekola. Dr. Davies participated on both days" Route ttre airplane, Pilot G. GiI1, left Bobo-Dioulasso on the roorn:ing of 2gth Apri], picketL uo Dr. )avies at Or:agadougou then proceed.ed. to l(and-i,(Aenin) where the team from Ni4pria was waiting. After 1r.rnch, Irs. Vioulov, Hagan and Davies overflew the rlogrcrou, Sora, l'Jessa, 01i, Ofa and Nono riiers, ending for the nigfut at Parakou (Benin). On 2!u: Drs. Dunbar, Davies and. Mr. Adekola sr.lrveyed. the Moshi and Teshi rivers, returrring to ltrakou at rnid.d.ay. 'I:e aircraft then retr:rned- with nr. Davies to OuagarJ-ougou, continuing to Bobo-LJioulasso tJ:e next d.ay. Total flight time from Bobo-Dioulasso to Bobo-Dioulasso was about 11.2 hours. Results Ttre fligtrt route is shown on the accomtrFr\ying map, togettrer with the positions of all observed breed.jng sites which had. the potential of supporting S.da,mrosq4. [kre only river w]:ich t,ras obse:rrred. to contain tfowins watffiJIF Moshi rukrich was flowing between the O}<rilaxa and Aiana IiiUs and. the R. Ni-ger. R. Ilogr_rou hospected from the Nigerian frontier close to the R. Niger at I11o. Only one potential breeding site obserrred-, about 20 Km from the frontier. OtLre:ewise the river flows througlr a flat meandering fIood. plaj::, almost d.isappearing in swamps at places. I1:ere was no flowing water althou$e pools were visible at the lower end. ..,f2 1981 2R. S_ora Pr.ospected frorrr near ilee ,R. Niger upstrearir to the frcntier, where it arises close to the source of the R" Jota. At tlie lower epcl it flows ttrrough a flood. pIain. Tkie first breed.ing sites appear at t1ol1tid and thereafter there are numerous potential roc}ry sites rs the rj-ver flqws out of the high Iand.s near the frontier. fhere is a roacl crossing at ll.o}tN which probabiy darrlee a road from Segbana to Baiiciirua (not marked. on map). R. l.lessa Riees as a srrr&Il meand.ering strea.m jgst east of Babana. Iee first potential treeding sites appear at about 1"57'n. ftrom this point there is an almost continuous series of roclqr sites d.own to its confluence with the i{ainj i lake. R. Iemo A sma1l river entering KainJi Lake south of R. "r/essa, Iiairy smal1 breed.ing siteg. R. OIi Peospected. frorrr close to the lhir$i Lake south of New Bussa, alnost to the sorLrce. In the region of Yengba, and Lesu the river is wide, flowing over a very fragmentecl rociry cou.rse, interspersed. with abundant grassest an extremely i:rmortant breed.ing site. Betweeir the Kaiatra-Buma road. brid.ge a,rd. the Kali game canp the river is virtually otre 1or:.g breeoing sitet wid.ening in places to about 200-J00m wid.e. Above Kali the sites are intermittent but still large, continuing almost to the Benin frontier. Its rnai-n northern tributary, the 0fa, carrj-es sirnilar i-mportant si'bes upstream for about JOIfui fro;n its junction with i.. 01i. The OIi was not floniiig at this tine. Hovrever, lir. Ad.ejiola informs me tliat fron June, r..'hen it rormally begins to f1ow, the }ower end. is treated. lrith D.D.t'. on a 10-d.ay cyc1e. Tkre insecticide is applied. at 2 points near lJew Brrssa (ma:i<ed as tri-angles on the map). frris r6gi"re began in 1979. kior to that alnost the whole of the 01i and its nain f,ributaries were treated. with DDT Emulsion at ! points. Since the opening of the 01i Game Park tlae use of DDT has been stopped.. It is u-r1ike1y that this f,reatment has more tl:an a Local effect at New Bussa. R. ]'loshi Itospected. d.or,v=.strea.m from near Okuta al-most to R. Niger. It begins as an extrene\r meand.ering strea;n flowing through ttrick bush so that it is easy to loose its tra.ck, especially as i.rr places it opens iilto swalApy ppasslancl. Tne first recognisable breed.ing site was for:ncl at about 1-Zltg where the river flows over a rock shel-f. fhree snall sites were found at ,o15tt. 'Ihe breed.ing sites rea11y begin about 201'"m upstream of ttre i(isl:i-Ilaiama 4oad. brid-.qe, 'bhereafter the rocky stretches become more frequentqntil about 4ol:l l*ren the river becornes al-most one long breed.ing site rrntil it reaches the plain of R. i,tri.ger. fhis area is almost totally uninl:abited. arrfl 7) lhe river passes between a series of inselbergs and roclqr hills called. the Oirwara and Aiana hill-s. Here it wiciens to alraost half a i:ifometre in wid.th arrd. for a d.istance of about 12Km forms an enormous breecling site flowing sha1lowIy cver a lrid.e rock face libera111' scattered wit-h boul-d.ers ancl,grasses. It is dtfficult to i-u,agine a more id,ea]- breed.in6g site for S.d.annosr:.n. 'ftre river was flolring in this area. tiro tributaries joining from tire south below this point also appeax to have good potential- breeri.ing sites. At tintes of hi,gh water the I'ioshi is treated. with DDT at the lieshi road crossing. ii. Telhi hospected upstream from its jwiction with R. Iloshi of tkre nain northern tributa^:q7. Breed.jrrg sites were f'ou.nd- just the junction, but thereaftel velTr few sites ivere founfl. file treated with DDT at tiles of ir ncl:m;.m floocl at the l(eshi road. which it is upstream of river is crossing. Coimlents flrere j-s no d.oubt that the 01i and i{oshi rivers together have an enorrrous potential for the production of S.danrygsunr s.1. tire reain breecling sites on thcse rivers li.e between 110 and- 2JO I(m south-east of the heavily invaded R. Sota in the OCP area. To d.ate there is no evid,ence to show that flies invade the OCP from the south-east, so the significance of these brced.ing rivers is r:nknown. \.Jhat is certain however, is that if these rivers are predoriiinantly populatecl ty S._d.amnosrun or S.s-jrbqnLqla their potential as a source for flies invad.ing other areas within say a 4OC Im radius nrust be very great. At the present time, the river of greatest interest to OCP is the Sora vrith its breed.ing sites close to the }3enin-I{igeria frontier. It would be worth investigating this river froil the ground. in July or August when it should. be flolring. trbon its natu-re, it is unlikely to be a serious source of Ii.!.annoewl early jn the vret season, because it is unlikely to be flowing at Eil-Fa. Ilor,rever, this shoulcl be checked. during June. It can probably be reached b3, a636 froin Se5'bana. tr\rtr:re Activities Dr. Vioulcov pro:rised. to try to collect material of biting S. d.anir.o sunr from the rivcrs i:rospecte.1, shoul-d- they be able to rnal:e ground. prospections d.rring the coming wet season. He .r1so a(Feed. to try to obtain emerged ad'ults for norphometric exa*mination. It was hoped. that fr:rther ccoperation could be discusserl cluring his forthcomin5; visit to OCP. Df, B. ilaviesJ Dr Dr Dr lTr 1,'lI ibra].im l'1. Sa".rba J. Grunewald. C. Gboho J. Ourldtaogo]).G. Zerbo Chief, Untomo ogical Rraluatiou Dr. Umam Shehu, ilWC, Lagos Dr. )I.l{.8. ilagan, i: ?l l}r. V.II. Vi-oulov}r. i'.. -Dr-:nbar I