Bargi Dam) in Jabalpur (Central India)
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Joumal of the American Mosquito Control Association, 16(4\279-287, 2OOO Copyright O 2000 by the American Mosquito Control Association,Inc. ANOPHELINE ECOLOGY AND MALARIA TRANSMISSION AT A NEW IRRIGATION PROJECT AREA (BARGI DAM) IN JABALPUR (CENTRAL INDIA) NEERU SINGHlNo A. K. MISHRA Malaria Research Centre (Field Station), Medical College Building, Jabalpur 4820O3, India ABSTRACT, Anopheline ecology and malaria transmission were studied in a newly irrigated area of the Bargi Project, District Jabalpur, Madhya Pradesh, Central India. Observations were made for 2 years (1993-95) in 10 villages along the Bargi irrigation canal, which are situated between 44 km (head end of canal) and 78 km (tail end of canal) from the dam site. Anopheles annularis was the predominant species in the head-end villages and its abundance was directly related to the opening of the canal, whereas Anopheles culicifacies was the most abundant species in tail-end villages, where irrigation is limited. Anopheles culicifacies showed 2 typical peaks not related to canal irrigation. Site-related differences in species prevalence were significant in both immatures and adults. Malaria infection was due to Plasmodium vivax and Plasmodiumfalciparum. The annual parasite incidence in children and adults was significantly higher in head-end villages (>4-fold) as compared to that in tail-end villages. However, seasonal trends in the prevalence of P. falciparum and P. vivax were the same in each group, with some fluctuations. In this study, preliminary results of the investigation are presented, demonstrating the trends in anopheline ecology and parasite prevalence in relation to the dynamics of irrigation development. KEY WORDS Malaria, irrigation, Anopheles, Anopheles culicifocies, Plasmodium vivax, Plasmodium falci- DArum INTRODUCTION Tava Project on a tributary of the Narmada in Hos- hangabad, Madhya Pradesh (Chaudhary 1996). Madhya Pradesh, Central India, the largest state This study was undertaken in villages along the in the country (442,841 km'), lies in the geograph- Bargi Canal. A major aspect of the study focused ical heart of India. It is a rural agricultural state on tracking the abundance and seasonality of marked by severe poverty and underdevelopment. anophelines and the incidence of malaria in a study The food grain production, infrastructure develop- area in the newly developed irigation project. This ment, and irrigation expansion in the state are the paper presents evidence of the formation of new lowest in the country (Tewari 1984). Construction disease foci in the hitherto less malarious area, pre- of a series of multipurpose projects for the devel- sumably under pressure of development. This case opment of the state have been proposed. The Nar- study may serve as a mode for rethinking malaria mada Valley Development Project is the largest of control progftlms under changing environmental the river valley projects so far proposed in India and ecological conditions due to developmental (Anonymous 1992). Balgi Dam, also known as projects. Rani Avanti Bai Sagar Dam, a multipurpose irri- gation and hydroelectric project (1974-88) is the MATERIALS AND METHODS lst completed project in Jabalpur. Water has been Study area: The study was carried out for 2 stored to its full capacity (422.26 m full river level) years (1993-95) in 10 villages (5 from Jabalpur and since 1990. The main left bank canal is 137 km 5 from Narshinghpur) along the Bargi main left long and total length of the canal along with dis- bank canal. Irrigation commenced in 1990 and the tributories is about 3,645 km (Anonymous 1984). irrigation system became fully operational in 1991. The total area proposed to be irrigated by the left The region falls within the lowland dry zone of the bank canal is 160,00O ha. Construction of a 194- state (elevation 360-411 m) with a generally flat km-long right bank canal to irrigate another terrain intemrpted by small foothills. Weather con- 250,000 ha of land has been proposed. Ttadition- ditions recorded at the nearest Agricultural Engi- ally, this study area was understood to be only neering College (Jabalpur) for the 3 years from mildly prone to malaria and hence no studies have 1993 to 1995 were, respectively, total annual rain- been done on mosquitoes and malaria in the dis- fall 1,486,2,083, and 1,417 mm; mean maximum tricts through which the left bank canal passes. temperature 31.7,3O.9O, and 31.60"C; mean mini- However, these developments might have resulted mum temperature 18.3, 18.2, and 18.8"C; and mean in ecological changes that can have a major impact relative humidity 59.90, 60.70, and 63.4OVo. on the incidence of mosquito-borne diseases. Such Head-end villages: Five villages, Dabhola, Bi- an effect has been observed during the develop- chua, Nunpur, Chhapara, and Bijori, are referred to mental projects of Sardar Sarovar, a downstream as head-end villages (total population, 2,302) be- project of Narmada in Gujarat (Kalr:a 1992) and the cause they are located between 44 and 50 km (Fig. 279 280 Jounr*nl oF THE AMERTCANMoseurro CoNrRoL AssocrlrroN Vor. 16,No.4 lo D.id x t IlSs $gsskvitlm Scrle I @=5t& Aad od c ,!. Til6d a Mrir a0d B|'elasd MiDd Nrrui.riE 44 bercro Ro.dr Itisrb [email protected] i RdIrry lrc E I {"c To Grd.rrn -d' faryr ed .io' To Itei Itittrtst N.ni4lt{t Fig. l. Map showing Bargi left bank canal and location of study villages. l) from the dam site (the lst 39 km were not under soykans followed by wheat. The villages are under irrigation). Out of the 5,4have direct water supply routine dichlorodiphenyltrichloroethane (DDT) from the main canal tbrough minor canals (minors). spray (1 g*, 2 rounds each year) for malaria con- Only 1 village sharesits water from Chhapra minc. trol in the months of May and August. Dabhola is the only village through which the main MosQuito sampling: Indoor resting mosquitoes canal passes;the other villages are at about O.5-1.0 (per man hour) were collected onc@a month from km distant from the main canal. All the villages are November 1993 to October 1995 from 2 vrTlages, sparsely populated (scheduled caste 45Vo, sehed- I from the head-endvillages (24 collections) and 1 uled tribe SOVo,and general 5Vo). The total pro- from the tail-end villages (24 collections) using posed area under furigation is 649 ha. A very good standard entomological tecbriques (WHO 1975). network of subminors and distributories exists, yet Anopheles resting inside 4 s€lected sites located in at the time of this study, they were not cornpletely different parts of each village (2 human dwellings lined. Only 5OVoaf the lining work was completed and 2 cattle sheds) were sarnpled in the early morn- in patches- The water supply for irrigation is ex- ing (060O hrs) for 15 min each by a team of 2 insect cellent from October to April during each year. The collectors with flashlights and nlouth aspirators. AII averagedischarge flow in the main canal is 10-15 adult mosquitoes collected were identified morpho- m3/sec and in minor canals it is 1-2 m3lsec. The logically in the laboratory using standard keys main crops are ice, maize, and wheat. These vil- (Cbristophers 1933). lages were under regular hexachlorohexane (HCH) Bait collection' Anophelines attracted to hurnan spray (20O rflglm',3 rounds each year) for malaria and animal baits were sampled from dusk to dawn control in the months of May, July, and Septernber. at fixed stations once a month. Although we Use of HCH has been banned in India since 1997. planned to station human baits both indoors and Tail-end villages: Ponia, Kukla, Manakwara, Pi- outdoors, only I human bait was seatcd on stool in paria, and Dabkia were selected as tail-end villages the courtyard or verandah, where people sleep (total population, 3,896) because they are located throughout the year, because of limited number of at a distance of 75--78 km (Fig. l) from the dam staff for this study and unavailability ofvolunteers. site (of the l37-km-long main canal, only 80 km One additional collector caught anophelines attract- are constructed for irrigation). These villages are ed to buffalo baits (1 inside the house and 1 outside irrigated through 2 minors of the Hareri branch ca- the house) for 15 min each hour. nal (water flow 5-1O mTsec). The total proposed Only indoor resting anophelines were dissected area under irrigation is 868 ha, according to avail- for presence of sporozoites in salivary glands. Par- able records. Irrigation facilities and a network of ity determinations were done only in Anopheles irrigation canals exist, although water supply is not culicifocies Giles, because of its availability as good as in head-end villages. The main cro,p is throughout the year in both villages. Although DeceMsen 2000 Mnumn TRANsMIsstoN nt e New IRRtcATIoN PRoJEcr 281 Anopheles fluviatilis James, Anopheles annularis smears found positive for malaria parasites in a Van der Wulp, Anopheles subpictus Grassi, and An. year per 1,000 persons. culicifocies have been identified as species com- plexes and the members of each complex can be RESULTS distinguished by cytogenetic or DNA probe tech- niques, we did not attempt to identify the mosqui- Larval ecology toes further under the primitive field conditions. Larval sampling: Larval surveys were carried In all, 3,929 larvae were collected in 1,530 dips out once a month with standard dippers (250-ml in the head-end village and 3,451 larvae were col- capacity) from 1 village in each group. Larvae were lected in 1,526 dips in the tail-end village. Seven collected from the main canal and associated mi- anopheline species were identified after adult emer- nors and ditches and density per dip was recorded.