The Prevention Of Malaria Biology Essay
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We use cell phones, ride metros, and take advantages of the latest gizmos but when it comes to malaria we come back to the old battle of man and mosquito. The story of malaria prevention and control has been a mixed bag of successes and failures with many initiatives receiving flak and others stick in the system. History of malaria prevention and control in our country is given in figure 1. Let's take a roller coaster ride and go through the various milestones in the history of malaria control.
Figure 1: History of Malaria control
Eradication Programme (2)
(Residual Spray+ Active search of cases & Radical Treatment)
Urban Malaria Scheme (3)
(Passive treatment of malaria cases, antilarval measures, minor engineering methods like closing ditches, biological control and awareness camp)
Control Programme (1)
(Residual insecticide spray with DDT)
Rapid unplanned urbanization, inadequate water and solid waste management and increasing developmental activities like construction, river valley and irrigation projects, mega-industry projects, etc. led to increased incidence
Modified Plan of Operation (MPO) (3) (also included P. falciparum containment programme)
(The programme was integrated with primary health care delivery system in rural areas)
Resurgence in 1976
National Malaria Eradication Programme was renamed as National Anti Malaria Programme
Roll Back Malaria (4)
WHO with other partners, Key interventions are
Insecticide Treated Nets (ITN)
Indoor Residual Spray (IRS)
Intermittent Preventive Therapy during pregnancy (IPT)
Prompt and effective case management in particular artimisinin based combination therapy.
Malaria Action Plan
(Classified areas into Tribal areas, Epidemic prone areas, Project areas, Triple insecticide resistant areas - DDT/ BHC/ Malathion)
Millennium Development Goals (MDGs)(5)
(Reduction of malaria morbidity and mortality is important to meet the overall objectives of reducing poverty)
National Vector Borne
Disease Control Programme
XI Five Year Plan
To continue with the existing strategies of malaria control
XII Five Year Plan
To continue with the existing strategies of malaria control
National Health Policy
(Reduction in mortality on account of malaria and other vector borne diseases by 50 % by 2010 and efficient morbidity control)
The National Vector Borne Disease Control Programme (NVBDCP) directorate is the main body responsible for malaria control in India (6, 7). Earlier the vector borne diseases were managed under separate national health programmes, but NVDCP is an umbrella programme for prevention and control of all six Vector borne diseases namely: Malaria, Dengue, Chikungunya, Japanese Encephalitis, Kala-Azar and Filaria (Lymphatic Filariasis)
Malaria control strategies The National strategy on malaria control has undergone a paradigm shift with the introduction of new interventions for case management and vector control, namely
rapid diagnostic tests, artemisinin based combination therapy and long lasting Insecticide impregnated nets. The spectrum of these strategies under NVBDCP are given in figure 2.
Early case Detection and Prompt Treatment (EDPT)
Monitoring and Evaluation of programme
Prevention and control of Malaria
Personal Prophylactic Measures
Environmental Management & Source Reduction Methods
Figure 2: Spectrum of strategies under NVBDCP for Malaria prevention and control
Early case Detection and Prompt Treatment (EDPT)
In 2010, 4.3 million malaria cases were reported in India (8) with over half due to P. falciparum. Malaria is curable if effective treatment is started early. In the past, chloroquine was effective for treating nearly all cases of malaria. In recent studies, chloroquine-resistant P. falciparum malaria has been observed with increasing frequency across the country. A revised National Drug Policy on Malaria has been adopted by the Ministry of Health and Family Welfare in 2010 and these guidelines have been prepared for healthcare personnel including clinicians involved in the treatment of malaria.Advantages of EDPT are given in box1.
Box1: Advantages of EDPT
â€¢ Complete cure
â€¢ Prevention of progression of uncomplicated malaria to severe disease
â€¢ Prevention of deaths
â€¢ Interruption of transmission
â€¢ Minimizing risk of selection and spread of drug resistant parasite
To achieve early case detection all clinically suspected cases of
malaria should be investigated immediately by microscopy and/or
Rapid Diagnostic Test (RDT). Microscopy of stained thick and
thin blood smears remains the gold standard for confirmation
of diagnosis of malaria Rapid Diagnostic Tests are based on the
detection of circulating parasite antigens. RDK is a
immunochromatographic test. It detects plasmodium
falciparum histidine rich protein in blood. Several types of RDTs
are available(9). Some of them can only detect P.falciparum, while others can detect other parasite species also. The latter kits are expensive and temperature sensitive. Presently, NVBDCP supplies RDT kits for detection of P. falciparum at locations where microscopy results are not obtainable within 24 hours of sample collection.
To detect cases early and give them prompt treatment is a phenomenal task. To achieve this Fortnightly Domiciliary visits which is Active Case Detection (ACD) is carried out by Multi Purpose Workers (MPW) (male) under primary health care system. He carries out search for a fever case or who had fever in between the visits of MPW, collects blood smear from such cases, and administers appropriate anti-malarial (s). The rationale behind this is that a large number of secondary cases can be avoided in the community where malaria transmission is seasonal but well established. The blood smear collection is also based on transmission dynamics of malaria. The incubation interval (It denotes the duration of the full cycle of malaria parasite. It is the sum of the time taken for the development of the parasite in the mosquito and that in the human being.) in case of P.vivax is approximately 22 days while for P.falciparum it is 35 days. Thus, fortnightly visits which are f less than one incubation interval will catch most of the secondary cases before the commencement of next cycle. Similarly appropriate antimalarials are administered to pregnant females by multipurpose workers female.
To avoid delay in detection of cases which occur in between visits of MPW, Fever Treatment Depots (FTD) has been established in villages especially in areas which are remote/ inaccessible and have low population density. Theses depots collect blood smears, administer presumptive treatment, carry out impregnation of bed nets and promotion of larvivorous fishes. In some areas Drug Distribution Centre (DDC) have been set up. The functions of DDCs are the same as those of FTDs, except that the DDCs do not take blood slides but administer drugs to fever cases. Over and above these measures Passive Case Detection (PCD) is done by Allopathic, Ayurvedic, Homeopathic, Siddha medicine dispensaries in the health sector, local residents or voluntary agencies operating locally , Anganwadi workers and private practitioners where cases reporting to them are suspected and diagnosed for malaria.National antimalaria drug policy essentially provides a framework for the safe and effective treatment of uncomplicated and severe malaria as well as prevention of malaria in vulnerable groups, such as pregnant women and young children.
According to the revised drug policy, there is no scope of presumptive treatment in malaria control.(10) However, where microscopy is not possible within 24 hours and RDT is negative or not available, suspected malaria cases will be considered as clinical malaria cases due to P. vivax and treated with the full 3 day course of chloroquine (1500 mg). The drug policy is changed in areas/block PHCs having 10% or more treatment failure (ETF+LTF) to the currently used antimalarial drug in therapeutic efficacy studies in a minimum sample of 30 patients. The current National Drug Policy recommends the use of ACT (Artesunate plus Sulfadoxine Pyrimethamine) for treatment of P.falcipuram cases in chloroquine resistant areas/block PHCs. The vivax cases are treated with a full course of chloroquine for 3 days and primaquine for 14 days.
Chemoprophylaxis is to be started a week before arriving at malarious area for visitors. For pregnant women in high risk area prophylaxis should be initiated from second trimester. In chloroquine sensitive areas chloroquine is to be given In chloroquine resistant areas it is to be supplemented by proguanil. Start with loading dose of 10 mg/kg bw and followed by a weekly dose of 5 mg/kg bw. This is to continue till 1 month after delivery in case of pregnancy and in travelers till one month after return from endemic area. The terminating dose should be 10 mg/kg bw along with 0.25 mg/kg bw of primaquine for five days.Chemoprophylaxis with chloroquine is not recommended beyond 3 years because of its cumulative toxicity. In chloroquine resistant areas chemoprophylaxis is recommended with chloroquine 5 mg/kg bw weekly and proguanil 100mg daily
In India the main species of mosquito transmitting malaria are Anopheles culicifacies, Anopheles fluviatilis, Anopheles stephensi, Anopheles dirus, Anopheles minimus and Anopheles sundaicus. Of these An.culicifacies is responsible for the transmission of 60-70% of cases in our country and hence control of malaria in India is practically the control of An.culicifacies. Each year 60-70% of the allotted budget is spent for control of malaria in those areas where An.culicifacies is the vector species for malaria transmission. Vector control programme in India, as in the case with many anti-malaria programme elsewhere, in the world, mostly rely on usage of natural and synthetic chemical molecules, which have potential to kill the target vectors. According to WHO Vector control measures can be grouped together as given in table1 (11):-
Table1: Malaria Vector control measures (11)
For individual and family
Reduction of human mosquito contact
Insecticide treated nets, repellants, protective clothing, screening of houses
Insecticide treated nets
Destruction of adult mosquito
Insecticide treated nets, indoor residual spray, space spray, ultra low volume spray
Destruction of mosquito larvae
Peri domestic sanitation
Larviciding of water surfaces, intermittent irrigation, sluicing, biological control
Small scale drainage
Environment sanitation, water management, drainage
Motivation for personal and family protection
Health education, community participation
Indoor Residual Spray (IRS) is the mainstay where the insecticide is sprayed indoors. The rationale behind IRS is that when the mosquitoes after having bite on an infective person will rest in the house will pick up sufficient insecticide particles sprayed on the walls and other indoor surfaces of the house and its longevity will be reduced so much so that it does not survive to become infective. In areas where the vectors are strongly endophilic, i.e. they tend to rest indoors, indoor residual spraying of human dwellings can give very effective control. Vectors that are exophillic i.e. they tend to rest outdoor but tend to feed or rest indoors briefly, can be effectively controlled by indoor residual spraying with insecticides that have good airborne effect. In areas where vectors are strongly exophilic and/or exophagic, i.e. they rest and bite outdoors, other control methods, such as use of insecticide treated mosquito nets or exterior space spraying (for emergency control), are considered. Presently different formulations of synthetic chemical insecticides are in the use for vector control. Wettable powder (WP) formulations are used for indoor residual sprays while emulsion concentrate (EC) formulations are used for larval control.
Insecticide formulations and dosages for IRS are given in table 2.
Table 2 Insecticide formulations and dosages for IRS
Name of Insecticide
Preparation of suspension in water
Dosage per sq.metre of active ingredient
Residual effect in weeks
Area to be covered by 10 lit.of suspension to get correct dosage
DDT 50% wp
1 kg/10 Lit
Malathion 25% wp
2 kg/10 Lit
Deltamethrin 2.5% wp
400 gm/10 Lit
125 gm/10 Lit
Lambdacyhalothrin 10% wp
125 gm/10 Lit
Bifenthrin 10% WP
Box 2: Possible ways of avoiding development of insecticide resistance in field
Avoid indiscriminate use of insecticides
Avoid use of insecticides that simultaneously select resistance to other chemically related insecticides.
Avoid use of insecticides that induce development of more than one type of resistance mechanism of broad spectrum of resistance.
Avoid use of the same insecticide both against adults and larvae.
Use of non chemical control methods, e.g. biopesticides, larvivorous fish.
Use of synergist with insecticides to reduce physiological resistance.
Malaria vectors in India are resistant to DDT alone
or double resistant to HCH or triple resistant to DDT,
HCH, malathion and quadruple resistant to DDT, HCH,
malathion and Deltamethrin (synthetic pyrethroid).
HCH has been phased out of the programme in 1997.
Of the six principal vector species, two, namely
An.culicifacies and An.stephensi have shown wide
spread resistance. Other vector species are mostly
susceptible to these insecticides. Development of
resistance to synthetic pyrethroid warrants a caution
of impending possibility of wide spread resistance
to other compounds of this group that are introduced
in public health programme for indoor residual spray
as well as insecticide treated bed nets. Possible ways of
avoiding development of insecticide resistance in field
are given in box 2 (12).
Larval control: It can be done by using chemical larvicides like abate, baytex or biological control by using larvivorous fishes. One of the most successful and widely used biological control agent against mosquito larvae is the top water minnow or mosquito fish Gambusia affinis. Fish other than Gambusia which has received the most attention as a mosquito control agent is Poecilia reticulata, the common guppy. These fishes are self-perpetuating after its establishment and continue to reduce mosquitoes larvi for long time. The cost of introducing larvivorous fish is relatively lower than that of chemical control. Also biological contol by using fishes is an environment friendly method. .they are easy to use as larvivorous fishes such as Gambusia and Poecilia prefer shallow water where mosquito larvae also breed.
Personal Prophylactic Measures These are the measures which can be used at the individual level like use of mosquito repellent creams, liquids, coils, mats, screening of the houses with wire mesh, wearing clothes that cover maximum surface area of the body and use of bed nets treated with insecticide.
Insecticide treated net(ITN): Ordinary untreated mosquito nets provide limited physical barrier between mosquito and man; mosquitoes may still bite through the net or get inside the net following improper use. Mosquito nets treated with insecticides provide better and effective protection by keeping away mosquitoes as well as killing them. Insecticide treated bed nets can be either conventional ITNs or Long Lasting Impregnated Nets (LLINs). Conventional ITNs must be treated once or twice a year (depending on the duration of the transmission season). LLINs are mosquito nets, whose fibres have been impregnated with insecticide by a special technique, so that the insecticidal effect is maintained through about 20 washes, or as long as the net can withstand daily usage, i.e. 3-5 years.
A list of actions that communities must are encouraged to undertake are spreading word about availability and reliability of diagnosis and treatment strategies, spreading word about need of early reporting for testing and treatment of fever cases, Facilitating quick transport of slides to the laboratory, informing people about necessity of IRS ,consistent and correct use of bed nets and arranging vehicle for patients with severe malaria to be transported to referral institution. The community should be sensitized and involved in detection of Anopheles breeding places and their elimination. Observance of anti malaria month in June should be done at the community level to create awareness among people about malaria prevention.
Environmental Management & Source Reduction Methods
People from engineering department have an important role to play as source reduction can be achieved by filling of the breeding places and channelization of breeding source. Other source reduction methods include filling and leveling depressions in kitchen garden, courtyard, roof, open spaces, ditches by the side of road and canals. All water containers, overhead tanks and wells should be well covered to prevent mosquito breeding.
Monitoring and Evaluation of the programme
Last but not the least is Monthly Computerized Management Information System (CMIS), Field visits by state the State National Programme Officers, Field visits by Malaria Research Centres and other ICMR Institutes and continuous feedback to states on field observations for correction actions.
It is expected that RTS-S, a pre-erythrocytic malaria vaccine, is likely to be available in a few years from now. Such a vaccine, when available, will be introduced in India after carrying out the vaccine trials. This is by far the most advanced vaccine candidate(10).
Remote Sensing in Vector Control
Remote Sensing (RS) technology is a tool for the surveillance of habitat, densities of vector species and even prediction of the incidence of disease that must be considered as new invention in the epidemiology of malaria and vector-borne diseases. Literal meaning of remote sensing is to sense any object from a distance. The Human eyes and cameras also act as a remote sensing device. However, scientist of NASA of USA used colour infrared aerial photography to identify the habitats of a nuisance mosquito, Aedes sollicitans in 1971. The principle of RS rests on the fact that every object absorbs some part of radiation received from sunlight(13). Depending upon its physical and chemical properties, the object absorbs some part of radiation while the remaining part is reflected in specific wavelength of the electromagnetic spectrum (EMS). This reflected energy is channelised through a telescope to detectors/sensors present on board of the satellites. The sensors are sensitive to different bands of EMS. The sensors convert the light energy into electrical voltages produces two-dimensional discrete pictures. These are different for different objects and the satellite pass over a particular part of earth at the fixed time intervals repeatedly making it possible to monitor changes in the lad use categories viz. Water bodies, vegetation, forests, soil mapping, geology, crop estimation, detection of fire in forest, mines, oil sleek in sea, etc. Such data is generated in National Remote Sensing Agency, Hyderabad, in India. A feasibility study using Satellite data in collaboration with the Indian Space Research Organisation in and around Delhi was carried out and correlation of changes in the areas of land use features viz. Water bodies and vegetations with mosquito density was found significant in some sites.
Whether the malaria map will keep shrinking, as it has in the past decade, or be reclaimed by the malaria parasites, depends, to a great extent, on the resources that will be invested in control efforts over the next years.Investments in malaria control have created unprecedented momentum and yielded remarkable returns in the past years. However, these gains are fragile and will be reversed unless malaria continues to be a priority. Sustaining malaria control efforts is an investment in development. Continued investment in malaria control near-zero deaths by 2015 and achieving the Millennium Development Goals.
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