Lim ES.
SourceVector Borne Disease Control Program, Ministry of Health, Malaysia.
Abstract
The Malaria Eradication Program was started in 1967 in Peninsular Malaysia. Since then and up to 1980, there was a reduction in the number of reported malaria cases from 160,385 in 1966 to 9,110 cases for Peninsular Malaysia. Although the concept of eradication has changed to one of control in the 1980, the anti-malaria activities have remained the same. However, additional supplementary activities such as the use of impregnated bednets, and the Primary Health Care approach, have been introduced in malarious and malaria-prone areas. Focal spraying activity is instituted in localities with outbreaks in both malaria-prone and non-malarious areas. Passive case detection has been maintained in all operational areas. In 1990, 50,500 cases of malaria were reported of which 69.7% (35,190) were from Sabah, 27.8% (14,066) from Peninsular Malaysia and 2.5% (1,244) from Sarawak. Until June 1991 a total of 18,306 cases were reported for the country. Plasmodium falciparum continues to be the predominant species, contributing to 69.6% of the parasites involved. The case fatality rate for 1990 was 0.09%. There were 43 deaths all of which were attributed to cerebral malaria. The problems faced in the prevention and control of malaria include problems associated with the opening of land for agriculture, mobility of the aborigines of Peninsular Malaysia (Orang Asli) and inaccessibility of malaria problem areas. There is need to ensure prompt investigation and complete treatment of cases especially in malarious areas. The promotion of community participation in control activities should be intensified. Primary Health Care should be continued and intensified in the malarious areas.
Malaria is a major public health problem in Malaysia, particularly in peninsular Malaysia and the state of Sabah. An eradication program started in the states of Sabah and Sarawak in 1961 initially was remarkably successful. A similar but staged program was started in peninsular Malaysia in 1967 and was also quite successful. However, a marked upsurge in incidence in Sabah in 1975-1978 showed that malaria is still a major hazard. The disease leads to great economic losses in terms of the productivity of the labor force and the learning capacity of schoolchildren. The topography, the climate, and the migrations of the people due to increased economic activity are similar in peninsular Malaysia, Sabah, and Sarawak. However, the epidemiologic picture differs strikingly from area to area in terms of species of vectors, distribution of parasitic species, and resistance of Plasmodium falciparum to chloroquine. Likewise, the problems faced by the eradication or control programs in the three regions are dissimilar. Because solutions to only some of these problems are possible, the eradication of malaria in Malaysia is not likely in the near future. However, the situation offers an excellent opportunity for further studies of antimalaria measures.
Despite decades of control success and a competent network of country-wide health infrastructure, malaria remains an important health threat in rural Thailand. All 4 known human malaria parasites have been reported present, with Plasmodium falciparum and Plasmodium vivax predominant. The expansion and intensity of multi-drug resistant Plasmodium falciparum is the most serious development to occur the last several decades. Members of 3 anopheline species complexes, Anopheles dirus, Anopheles minimus, and Anopheles manculatus, are considered to be primary malaria vectors in the country. Representatives within all 3 taxa are difficult or impossible to separate morphologically from one another, and insufficient information exists about population genetics between sibling species and vector status. Vector control in Thailand has been the primary means of malaria control, mainly by the use of routine residual insecticide spray inside houses. The use of DDT in vector control has resulted in measurable successes to interrupt malaria transmission in many parts of the country. Since 1949, DDT has been the predominant compound used: however, its public health use has continued to decline as a result of perceived operational difficulties, political issues and environmental concerns. The increased use of pyrethroids to impregnate bednets and for intradomiciliary spraying are generally more accepted by rural populations and are rapidly replacing the use of DDT. Organized malaria control activities have reduced malaria morbidity from 286/1,000 population in 1947 to 1.5/1,000 population by 1996. Despite encouraging trends in dramatically reducing malaria, the rates of disease may be re-emerging in the country as evidence from an increased annual parasite index from 1.78/1,000 in 1997 to 2.21 in 1998. The possible reasons for the apparent increase in incidence are discussed in terms of the technical, operational and social obstacles in malaria control in Thailand.
Mekong malaria. Malaria, multi-drug resistance and economic development in the greater Mekong subregion of Southeast Asia.
This monograph brings together national malaria databases for 1996, 1997 and 1998 from the 6 countries comprising the Greater Mekong Subregion of Southeast Asia: Cambodia, China (southern provinces), Lao People's Democratic Republic, Myanmar, Thailand, Viet Nam. The objective is to create a regional perspective in what is a global epicenter of drug resistant falciparum malaria, so to enhance the information flow required to improve malaria control on a regional basis in the context of economic and social change. Geographical Information Systems technology has been applied to the regional mapping of total reported malaria cases, malaria incidence, confirmed cases, parasite species distribution. There is great diversity in disease patterns in the 6 countries and at subnational administrative unit area level in each country, so that in the region as a whole there is marked asymmetry in disease distribution, with many areas of high endemicity. Focal expansion of maps in the vicinity of international border areas delineates the differential trans-border malaria distribution that presents a challenge for disease control. The malaria pattern is also depicted in environmental context against regional elevation and forest cover profiles, which affect mosquito breeding site distribution and agricultural activity. Data on resistance of falciparum malaria to a range of anti-malarial drugs summarise the historical and recent context of resistance development and spread in terms of geography and time frame. Data on population movement across international borders identify the magnitude of a major factor in the dispersal of malaria, including resistant parasite strains. Malaria control involves consideration of microeconomic capacity and operates in the broader context of macroeconomic policy: economic and social profiles of the region are included to provide this perspective. So too are maps depicting major economic development projects in the region, projects that have and will continue to have profound, dynamic impacts on malaria epidemiology. The geographic collation of regional malaria databases is thus placed in overall geographic, health, environmental and economic perspective. This beginning can form a basis for the development of an effective regional malaria surveillance system in the context of rapidly evolving social and infrastructural change, leading eventually to a multi-disease surveillance network.
Studies on prevalence of anopheline species and community perception of malaria in Jaffna district, Sri Lanka.
Kannathasan S, Antonyrajan A, Srikrishnaraj KA, Karunaratne SH, Karunaweera ND, Surendran SN.
SourceDepartment of Pathology, Faculty of Medicine, University of Jaffna, Jaffna, Sri Lanka. selvamkannathasan@gmail.com
Abstract
BACKGROUND & OBJECTIVES: Over two decades of civil unrest and the conflict situation have had detrimental effects on vector control activities and management of malaria in Jaffna district which is an endemic region for malaria in Sri Lanka. With the background that only a few small-scale studies on malaria and its vectors have been reported from this district, a study was designed to explore the current status of malaria in the Jaffna district in relation to vector and community aspects.
METHODS: Adults and larvae of anopheline mosquitoes were collected monthly from selected endemic localities. Species prevalence of the collected mosquitoes was studied while the collected adults of Anopheles subpictus, a potential vector in the district, was screened for sibling species composition based on morphological characteristics and exposed to common insecticides using WHO bioassay kits. Knowledge, attitude and practices (KAP) of the community were tested using a pre-tested structured questionnaire in high-risk and low-risk localities in the district.
RESULTS: The anopheline mosquito species distribution in the district was--An. culicifacies (0.5%), An. subpictus (46%), An. varuna (4%), An. nigerrimus (44%) and An. pallidus (5.5%). Among the collected larvae the percent prevalence of An. culicifacies was 13% and other species follows as: An. subpictus (71%), An. varuna (4%), An. nigerrimus (10%) and An. pallidus (2%). Sibling species B, C and D of An. subpictus were present in the district with the predominance of B in both coastal and inland areas, while all members showed both indoor and outdoor resting characteristics, they were highly resistant to DDT (4%) and highly susceptible to malathion (5%). KAP study in the district showed a reasonable level of knowledge, positive attitude and practices towards malaria.
CONCLUSION: An. subpictus, the reported major vector of Jaffna and a well-established secondary vector of malaria in the country, continues to be the predominant anopheline species. The distribution of sibling species of An. subpictus complex in the Jaffna district, revealed for the first time, has implications for future studies on its bionomics and malaria transmission pattern in this area and the planning of control strategies for this region. The community perception of disease, which revealed a satisfactory knowledge indicates the potential for better community participation in future malaria control activities in this region. As potential vectors are still present, health authorities need to be vigilant to prevent any future epidemics of malaria.
DDT indoor residual spray, still an effective tool to control Anopheles fluviatilis-transmitted Plasmodium falciparum malaria in India.
Gunasekaran K, Sahu SS, Jambulingam P, Das PK.
SourceVector Control Research Centre, Medical Complex, Indira Nagar, Pondicherry 605 006, India. k_guna@yahoo.com
Abstract
This study from two districts of Orissa State which are endemic for Plasmodium falciparum transmitted by Anopheles fluviatilis and A. culicifacies investigated the impact of dichlorodiphenyl trichloroethane (DDT) indoor residual spraying, in view of the ongoing discussion on phasing out DDT in India. Based on their high annual parasite incidence and logistical considerations, 26 villages in Malkangiri and 28 in Koraput district were selected for DDT spraying. For comparison, six and four unsprayed villages were chosen from the same districts. In each district, the prevalence of malaria infection and incidence of malaria fever, indoor resting density and parous rate of the vectors, and their susceptibility to DDT were monitored in six and three villages selected randomly from the sprayed and unsprayed groups respectively. Anopheles fluviatilis was susceptible to DDT while A. culicifacies was resistant. DDT residual spraying with 1 g/m(2), was carried out in October-November 2001. Spraying 74-86% of human dwellings and 100% of cattle sheds brought down the indoor resting density of A. fluviatilis by 93-95%. This was associated with a significant reduction of incidence of malaria fever as well as prevalence of malaria infection from November to February in both districts. The spraying also seemed to impact on vector longevity, and a residual effect of DDT on the sprayed walls was observed up to 10-12 weeks despite re-plastering. Hence DDT spraying can still be an effective tool for controlling fluviatilis-transmitted malaria. Although this species is exophilic, its nocturnal resting behaviour facilitates its contact with the sprayed surfaces. DDT is still useful for residual spraying in India, particularly in areas where the vectors are endophilic and not resistant.
Follow-up studies after withdrawal of deltamethrin spraying against Anopheles culicifacies and malaria incidence.
Ansari MA, Razdan RK.
SourceMalaria Research Centre (ICMR), 20-Madhuban, Delhi-110 092, India.
Abstract
Follow-up studies were carried out from 1989 to 1998 after withdrawal of deltamethrin indoor spraying to evaluate the recovery rate of a population of Anopheles culicifacies resistant to dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) in selected villages in Uttar Pradesh State, India. The study revealed 82.4-96.5% reduction in adult density of An. culicifacies and 72.7-96% reduction in malaria incidence in the area sprayed with deltamethrin at 20 mg/m2 as compared to a control area sprayed with HCH, for 5 successive years even after withdrawal of deltamethrin spray. The impact was very clear when the annual falciparum incidence was compared with that of the control area. The vector population gradually started recovering after 5 years. However, the slide falciparum rate remained below 4 even after 10 years of withdrawal of spraying. The study revealed that indoor residual spraying of deltamethrin would be cost-effective, at least in areas where malaria is transmitted by An. culicifacies, which is primarily a zoophilic species and associated with malaria epidemics. In view of this, a review of the insecticide policy and strategy of vector control is urgently needed because of the possible risks associated with the presence of nonbiodegradable insecticide in the environment, as well as to minimize the costs of operation and to enhance the useful life of insecticides.
Field evaluation of deltamethrin against resistant Anopheles culicifacies in Distt. Ghaziabad (U.P.) India.
Ansari MA, Sharma VP, Razdan RK, Mittal PK.
SourceMalaria Research Centre, Delhi, India.
Abstract
A field study to evaluate the impact of deltamethrin spraying on DDT and HCH resistant A. culicifacies population was carried out in Razapur primary health centre (PHC), Distt. Ghaziabad (U.P.) India. The PHC comprising of about 0.14 million population was divided into 3 sections of equal size and sprayed with (i) 3 rounds at 12.5 mg/sq m at 6 weeks interval, and (ii) 2 rounds each at 20 mg/sq m and 25 mg/sq m at 8 weeks interval. One section in Dadri PHC located at a distance of about 22 kms was held as control. In this area 3 rounds of HCH were sprayed by the NMEP as was done to control malaria in this district. Deltamethrin spraying was carried out for 3 years. Results revealed that spraying at 12.5, 20 and 25 mg/sq m resulted in drastic reduction of DDT and HCH resistant A. culicifacies population and in the interruption of malaria transmission. In control area high vector densities and malaria transmission was encountered throughout the period of study. Spraying of deltamethrin resulted in build-up of Culex quinquefasciatus population due to resistance.
Impact of residual spraying of bendiocarb against the malaria vector Anopheles culicifacies in selected villages of the Ghaziabad District, Uttar Pradesh, India.
Ansari MA, Razdan RK.
SourceMalaria Research Centre (ICMR), 20, Madhuban, Delhi-110 092, India.
Abstract
A longitudinal study was carried out to evaluate the bioefficacy of indoor residual spraying of bendiocarb 80% wettable powder (WP) at 0.2 and 0.4 g/m2 against Anopheles culicifacies, a principle malaria vector, and the impact of bendiocarb use on malaria incidence in selected villages of the Ghaziabad District, Uttar Pradesh, India. The control village was sprayed with malathion at 1 g/m2 in 2001. Two rounds of bendiocarb spraying were carried out in each year from 1999 to 2001. Bendiocarb applications resulted in significant reduction in densities of adult An. culicifacies and other mosquito species in villages when compared to that of the control village (P < 0.05). Bioassay tests revealed that persistence of insecticide against An. culicifacies at 100% mortality was observed for about 10, 8, and 10 wk on mud, cement, and brick wall surfaces, respectively. Epidemiological evaluation revealed that malaria cases were significantly reduced after 1 year of spraying (P < 0.05) and by 2001, no Plasmodium falciparum was recorded in either of the bendiocarb-sprayed villages. The study revealed that indoor residual spraying of bendiocarb 80% WP at 0.2 g/m2 produced effective control of resistant An. culicifacies, provided that >95% human-dwelling room coverage is achieved in both 1st and 2nd rounds of spraying at an interval of 10 wk in areas where malaria is a seasonal problem
Impact of residual spraying of Reldan against Anopheles culicifacies in selected villages of District Ghaziabad (Uttar pradesh), India.
Ansari MA, Razdan RK.
SourceMalaria Research Centre (ICMR), 20, Madhuban, Delhi, India. ansari@ndf.vsnl.net.in
Abstract
BACKGROUND & OBJECTIVES: Indoor residual spraying of Reldan 40% EC @ 0.5 and 1 g/m2 was done in Tatarpur and Chauna villages, respectively in Dhaulana PHC, Distt. Ghaziabad (U.P.) to evaluate its impact against Anopheles culicifacies and malaria incidence. Results were compared with that of Piyawali village which was taken as control area.
METHODS: Four rounds of spray were done from 1999--2000 in human dwellings and cattlesheds in experimental villages. Entomological parameters--man hour density, parity rate, sporozoite rate, etc. were monitored using standard procedures. Epidemiological indicators such as SPR, SFR, cases/000, Pf/000 were also calculated. Cone bioassays as per WHO method were also carried out to assess the persistence of the insecticide on different surfaces.
RESULTS: Entomological results revealed that spraying of reldan @ 0.5 g/m2 resulted in significant reduction in adult densities of An. culicifacies in sprayed villages over the control village. Spraying also resulted in reduction of percent parous females, reduction in malaria incidence (p < 0.05).
INTERPRETATION & CONCLUSION: Reldan showed high efficacy @ 0.5 g/m2 in controlling the densities of An. culicifacies and malaria incidence. However, double dosage of reldan @ 1 g/m2 can be used for comprehensive vector control provided > 95% spray coverage is achieved.
Anopheline species complexes & malaria control.
Subbarao SK, Sharma VP.
SourceMalaria Research Centre, Delhi.
Abstract
Species complexes comprising morphologically indistinguishable biological species that are reproductively isolated, are of common occurrence among anophelines. A list of anopheline species complexes identified so far in the world has been given. To demonstrate the importance of species complexes in malaria control, we report the Anopheles culicifacies complex as a case study. An. culicifacies is a major vector of malaria in India and neighbouring countries. This complex comprises four sibling species, A, B, C and D. Stratification of U.P. state and district Allahabad has been shown taking into consideration the biological differences among sibling species, viz., sibling species composition and vectorial potential- species B is a non-vector while others are vectors. To achieve cost effective vector control, microlevel stratification at least at the block level has been suggested. Implications of differential responses of sibling species to DDT and malathion in field operations have been discussed. To achieve selective and sustainable control, and to reduce the unnecessary selection pressure of insecticides, an insecticide spray strategy to control An. culicifacies has been provided.
Malaria and Anopheles mosquitos in Malaysia.
Rahman WA, Che'Rus A, Ahmad AH.
SourceSchool of Biological Sciences, Universiti Sains Malaysia Minden, Penang, Malaysia.
Abstract
Until today, malaria is still one of the most important diseases in Malaysia. This is because Malaysia is located within the equatorial zone with high temperatures and humidities, usually important for the transmission of malaria. The number of malaria cases were estimated to be around 300,000 before the launching of the Malaria Eradication Program (MEP). The program was successful in reducing the numbers progressively during the 1967-1982 period. During the period 1980-1991, the highest number of malaria cases recorded for the country was 65,283 in 1989 (16,902 in Peninsular Malaysia, 47,545 in Sabah and 836 in Sarawak) whilst the lowest was 22,218 (10,069 in Peninsular Malaysia, 11,290 in Sabah and 859 in Sarawak) in 1983. In Malaysia, there are 434 species of mosquitos, representing 20 genera. Of these, 75 species are Anopheles that comprise of 2 subgenus, i.e. Anopheles and Cellia. Of the 75 species, only 9 have been reported as vectors: An. maculatus, An balabacensis, An. dirus, An. letifer An. campestris, An. sundaicus, An. donaldi, An. leucophyrus and An. flavirostris. The behavior, seasonal abundance, biting activities and breeding sites of these species are discussed.
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