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Field Station- Chennai (Tamil Nadu) |
The field station of Malaria Research Centre at Chennai was established in July 1986. The primary objective was to develop an eco-friendly, cost effective and sustainable intervention technology for control of Urban Malaria with Chennai as a role model. Other research objectives included were mainly related to the understanding of transmission dynamics of malaria in an urban environment. The research findings at the Centre were also intended to strengthen the intervention operations of the local health authorities by providing necessary scientific inputs. Therefore, all activities at the field station are carried out in close coordination with the Local Health Authorities (Corporation of Chennai), The Directorate of Public Health and Preventive Medicine, Govt. of Tamil Nadu and Regional Office for Health & Family Welfare, Govt.of India. All Scientific activities undertaken at this Field Station are being periodically reviewed and oriented according to the Scientific Advisory Committee of the Indian Council of Medical Research.
AN OVERVIEW OF THE RESEARCH ACTIVITIES AT THE FIELD STATION.
I. BIO-ENVIRONMENTAL CONTROL OF MALARIA:
Chennai City contributes 46% to 74% of malaria cases to the total cases recorded in the state of Tamil Nadu. The transmission of malaria is perennial with two peaks, one during the months of July-August and the other during the months of October -November. Anopheles stephensi is the malaria vector and is found to breed prolifically in the domestic stored water systems like the Over Head Tank, Under Ground Tanks (Sumps), Cisterns and Wells. The other breeding sources are rainwater collections in rooftops and discarded containers and water collections in construction sites.
A feasibility study on the bioenvironmental control of Malaria was undertaken in six highly malarious Divisions of Chennai Corporation (Division No's: 86,87,88 in C. pet and 53,54,55 in S.Pet) during the period 1987 to 1992. Bio-environmental interventions methods adopted were (1) introduction of larvivorous fishes ( Gambusia affinis) in open Wells and Over Head Tanks with bore well water, (2) introduction of Expanded Polystyrene (EPS) Beads in unused wells and unapproachable Over Head Tanks, (3) mosquito proofing of Over head Tanks that are inaccessible for periodic monitoring, and (4) Incapacitation of defunct OHT's. The malaria cases reported in the area were treated at the Corporation malaria clinics according to the NAMP drug schedule. The results of the study indicated an effective control in mosquito breeding. The habitat positivity for anopheles breeding in OHT's declined from a pre-intervention status of 35.2 % to 2.06 % during the first year of intervention and was maintained below 4.06 % throughout the observation period. In wells, habitat positivity declined from 26.5% to less than 1.0%. Habitat positivity in OHT's and wells in control area was frequently above 20.0% and ranged between 0.5% and 59.3 %. The annual average density of Anopheles stephensi based on cow shed resting collections ranged between 1.17 to 5.41 in experimental area and 7.29 to 18.24 in control area. The MHD in experimental area was 2.8 to 6.6 times higher than the mean density in corresponding months in the control area indicating suppression of breeding. Epidemiological assessment showed a steady decrease in the SFR from 0.35 in 1987 to 0.005 in 1990 in Chintadripet area. However, in Sowcarpet area though there was a reduction from 2.25 in 1987 to 1.07 in 1989, during subsequent years the SFR was slightly higher reaching a maximum of 3.17. SFR recorded in Chintadripet was 0.41 in 1991 and 1992. Though the reduction in SFR may appear marginal, the segregation of cases registered on false addresses which is very high and exclusion of imported cases indicates a good impact on the control of malaria.
II. SEVEN POINT ACTION PLAN FOR MALARIA CONTROL
A seven-point action plan for the control of Malaria in Chennai City was prepared based on the experiences and information obtained from the successful demonstration of bioenvironmental control of malaria in the high incidence areas. The plan was submitted to the Government of Tamil Nadu in 1990. The action plan includes the following.
1. Action by Government.
2. Inter and Intra-sectoral coordination.
3. Legislative measures.
4. Clearance from Health Department.
5. Tropical aggregation of labourers.
6. Implementation mechanism.
7. Constitution of Committees.
III. MALARIOGENIC STRATIFICATION OF DINDIGUL (UMS TOWN), DINDIGUL DISTRICT, TAMIL NADU.
On request from the DPH & PM, a malariogenic stratification of Dindigul town was undertaken to develop an action plan for the control of malaria and to assist local health authorities to prevent transmission of malaria. The number of malaria cases recorded in the year 1994 was 10184. API and SPR were 54.96 and 31.19 respectively. House to house, visits were made in all the 44 wards in Dindigul town and all potential anopheles and other mosquito breeding places enumerated. A total of 3257 open over head tanks, 1622 open Wells, 1522 non mosquito proofed sumps, 1526 Tap pits and 40,680 Cisterns were present in the town. Anopheles stephensi was found to breed prominently in 47.1% of OHT's, 37.6% of Cisterns, 8.0% of UGT's, 4.0% of Tap pits and 3.0% of the wells. An action plan was prepared and submitted to the local health authorities for sustainable control of the malaria vector, Anopheles stephensi. Intensive intervention activity based on MRC guidance resulted in the reduction of malaria cases in Dindigul municipality.
IV. GIS BASED MALARIA SURVEILLANCE SYSTEM FOR DINDIGUL
During malariogenic stratification of Dindigul municipality, varied parameters like no. Of houses, breeding sources in each house with surface area available for breeding, mosquito breeding particulars, species breeding, street wise, ward wise and town wise malaria incidence were collected. Besides, other epidemiological indicators, which include clinic wise and meteorological information's etc., were obtained at the most basic level. All these informations were used to develop a GIS based module for malaria surveillance. The GIS based module was developed at MRC, Delhi in close collaboration with MRC, Chennai and DPH & PM, Tamil Nadu. Their surveillance system was officially launched on the world GIS day (19.11.1999). The technology has been transferred to Government of Tamil Nadu for implementation. The same is also made available on the web" www. Malaria-tn.org "
V. FIELD EVALUATION OF BACILLUS SPHAERICUS AND BACILLUS THURINGIENSIS VAR. ISRAELENSIS IN WATER WAYS IN CHENNAI CITY.
Large scale trials of biolarvicides namely Bacillus sphaericus and Bacillus thuringiensis var. israelensis from Russia was tested against Culex quinquefasciatus in Cooum river and Otteri nullah during 1993 - 1994. Fortnightly application @ 1gm/m2 resulted in significant reduction in both immature and adult densities. The percentage reduction among late immatures, observed on application of B. sphaericus ranged between 74.0% and 98.0% whereas it was from 64.0% to 100.0% in the case of B. thuringiensis. These bio-control agents have been suggested for the use in non-potable water for mosquito control and the Govt. of Tamil Nadu have approved the use of biocides in intervention operations.
VI. RAINWATER HARVESTING AND ITS IMPLICATION ON VECTOR BREEDING IN CHENNAI.
Rainwater harvesting to recharge ground water reserves has been prioritized in Chennai city to augment depleting underground water reserves. Rainwater harvesting open wells, recharge wells, trench, percolation trenches, percolation pits, and junction pits and RWH UGT's were the breeding habitats/sources identified and surveyed. Fortnightly surveys were carried out for mosquito breeding. Mosquito breeding was frequently observed in Rainwater harvesting wells, Trenches, and Junction pits whereas rarely in Percolation trenches.
Rainwater harvesting open wells supported extensive breeding of Anopheles, Culex and Aedes mosquitoes. Comparatively, the breeding of Aedes was rare. In majority of the RWH wells water was present continuously as defunct/unused domestic wells were used for harvesting rainwater. The number of dry wells ranged between 0.0% to 41.0 %. Habitat positivity for Culex, Aedes and Anopheles ranged from 3.6% to 18.8%, 4.0% to 11.0% and 3.6% to 6.3% respectively. Trenches were generally observed to be dry except after rainfall. The percentage of dry trenches ranged between 81.1% to 100.0%. Culex and Aedes mosquitoes were commonly observed breeding and the habitat positivity ranged from 7.7% to 100.0% in both, with a mode of 100.0% indicating breeding in the trenches whenever water was stagnant. No Anopheles breeding was noticed. In Junction pits, intense breeding of mosquitoes were observed. In many buildings, since the overflow water from overhead tanks was also used for recharging, water accumulation was observed continuously in the junction pits resulting in mosquito breeding. The percentage of dry junction pits observed ranged between 66.7% and 100.0%. Habitat positivity for both Anopheles and Aedes breeding ranged from 3.4% to 33.3% whereas it was between 5.6% and 33.3% for Culex. Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti were the mosquito species observed breeding in the RWH structures.
VII. DRUG RESISTANCE STATUS IN PLASMODIUM FALCIPARUM.
In vitro and In vivo studies have been conducted to study the sensitivity of Plasmodium falciparum to Chloroquine. In-vitro studies conducted in six P. falciparum cases by Ghosh et al. showed high resistance to Chloroquine. In vitro and In vivo studies conducted later in 67 P. falciparum cases by Dua et al also indicated the presence of chloroquine resistantance. P. falciparum malaria in Chennai and only 40% cases were non-respondent to Chloroquine treatment and mostly at RI level.
VIII. THERAPEUTIC EFFICACY OF CHLOROQUINE FOR THE TREATMENT OF VIVAX MALARIA.
A study on the therapeutic efficacy of Chloroquine on the treatment of vivax malaria was undertaken in Chennai. A standard WHO protocols was followed in the study. 143 cases were enrolled. Results of the study revealed 88.0 % clearance of parasites by Day 2. The parasitaemia on Day 0 ranged between 352.0/ml and 39,680.00/ml. No recurrence of parasitaemia was observed on any day within the stipulated 28 days after treatment. Good clinical response without any recurrence of fever was observed indicating Adequate Clinical and Parasitological Response to Chloroquine treatment.
IX. EVALUATION OF PARASIGHT - F IN THE DETECTION OF PLASMODIUM FALCIPARUM
Efficacy of Plasmodium falciparum histidine rich protein (HRP-2) based diagnostic test; Parasight-F was evaluated for diagnosis of Plasmodium falciparum malaria in Chennai. 93 febrile patients were screened. The sensitivity and specificity of the test were 100% for the detection of Plasmodium falciparum infection.
X. EVALUATION OF ICT MALARIA PF/PV IMMUNOCHROMATOGRAPHIC TEST IN INDIA
Efficacy of ICT Malaria Pf/Pv immunochromatographic test kit (AMRAD - ICT, Bookvale, Australia) was evaluated at Chennai as a part of a multicentric trial in India. 268 cases were enrolled in the study out of which 10 and 44 were with falciparum and vivax malaria. The sensitivity and specificity for P. vivax were 68.18% and 100.0% and P. falciparum were 100.0% to 89.9% respectively.
XI. EVALUATION OF HILMILIN (AN igr COMPOUND) AGAINST Culex quinquefasciatus in unused domestic wells.
The larvicidal efficacy of the Igr compound, Hilmilin (Diflubenzuron - 25% WP) applied at the rate of 0.04ppm/m2 and 0.1ppm/m2 was evaluated against Cx. quinquefasciatus, in domestic wells. The pre-treatment density per dip recorded in wells used as control, wells treated with 0.04ppm/m2 and 0.1ppm/m2 were 66.8, 66.3 and 71.72 respectively. Maximum reduction of 60.0% and 78.1% were obtained on the 14th and 28th day after treatment in trials with 0.04ppm and 0.1ppm respectively.
XII. EVALUATION OF MOSQUITO REPELLENT ACTION OF NEEM OIL ON TOPICAL APPLICATION.
Studies were carried out to evaluate the repellent action of neem oil against Culex quinquefasciatus. Application of 2.0 % and 5.0 % neem oil @ 5.0ml / person / night gave 50.0 % and 40.9 % protection in indoor collections and 17.4 % and 5.6 % in outdoor collections as compared with untreated control. The protection time ranged between 1.00 to 3.00 hours and 1.00 to 6.00 hours in indoor and outdoor collections. Results of repellent action of Autan, a synthetic mosquito repellent studied concurrently showed higher protection rate from bites of Cx. quinquefasciatus. Field evaluation of neem oil against Anopheles stephensi revealed more than 90% protection indicating neem oil as an effective repellent against urban malaria vector.
XIII. HEALTH EDUCATION
Health education, particularly on the importance of bio-environmental control of malaria and the need for mosquito proofing of OHT's and Wells are being highlighted in all the programmes organized by MRC and in collaboration with other voluntary organizations like YASS, Probus Club, Civic Exnora and other Associations like Mogappair, Ambattur Associations etc. Health Officer trainees and Medical officer trainees of the DPH&PM, Tamil Nadu are also educated and trained. Live exhibits, which include mosquito vectors, larvivoruous fishes, natural predators etc., are displayed along with educational placards and displays. Video shows on various aspects of malaria and the role of community is emphasized. Training on blood smear preparations, staining techniques and identification of malarial parasites is imparted to DMLT students of various colleges like Thakkar Bapa College, Tambaram, Tagore College, Loyola College etc., are usually organized.
XIV. WORKSHOP
Three workshops on the ' Intersectoral coordination for malaria control ' have been organized for Senior Engineers and other administrators of various governmental departments like PWD, Telephones, Highway department, Slum clearance Board, Chennai Metro Water Supply and Drainage Board etc. in Chennai. One workshop was organized at Dindigul, Tamil Nadu. The role of various departments in the creation of mosquitogenic conditions and necessary actions/precautions to be taken to prevent them has been highlighted
For further information about this field station,please contact:
e mail: alexeapen@yahoo.com
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