Mosquito Control

Mosquito control is an important component of malaria control strategy, although elimination of malaria in an area does not require the elimination of all Anopheles mosquitoes. In North America and Europe for example, although the vector Anopheles mosquitoes are still present, the parasite has been eliminated. Socio-economic improvements (e.g., houses with screened windows, air conditioning) combined with vector reduction efforts and effective treatment have led to the elimination of malaria without the complete elimination of the vectors. On the other, controlling these highly adapted, flying and hiding vectors is indeed a formidable task. Development of resistance to insecticides has compounded the problem. Ban on non-biodegradable and non-eco-friendly insecticides like DDT also may have contributed to the resurgence of malaria.

Mosquito Control Measures: Every step taken to control the mosquitoes has a cumulative effect and contributes immensely to control malaria. The eggs developing within the female mosquito need human blood for nourishment and so the female mosquito bites humans. By personal protection against mosquito bites, this blood meal can be denied, leading to reduction in mosquito eggs and hence mosquito population. Personal protection includes closure of windows and doors to prevent entry; protection of humans against mosquito bite by using bednets (insecticide treated) and mosquito repellent. Female mosquitoes lay the eggs on water collections where they develop further over a week into adult mosquitoes. By preventing water logging, destroying unwanted water collections and keeping the water containers closed, sources of egg laying (Source Reduction) can be denied and breeding of mosquitoes can be prevented. Further, different types of chemical (insecticides) or biological (Guppy or Gambusia fish or bacteria or fungii) larvicides can be used on such breeding grounds to kill the developing larvae and pupae. It is far easier to kill the non-flying forms of the mosquitoes than going after the adults that can fly a kilometer or more. The adult mosquitoes can live up to 4-10 weeks depending on the ambient temperature and humidity. Space sprays are used to instantly kill the adults and residual sprays, on their resting places such as walls, are used for residual mosquitocidal effect. But most of such insecticides have effects on the human beings as well as the environment and other life forms. The adult mosquitoes enter the human dwellings between 5 pm and 10 pm and early morning and hide in dark corners, to come out and bite human beings at night, mostly between 11pm-4am. The entry of the adult mosquitoes can be prevented by keeping the doors and windows closed between 5-10pm and early morning. Screening of all the windows and vents is a very easy and sure method of controlling the entry of adult mosquitoes. The hiding places of the mosquitoes, such as clothes hanging in the open, can be minimised. Personal protection by covering the body with clothes and use of mosquito nets and repellents will further help in preventing mosquito bites. All these in turn will deny the blood meal and development of eggs. 

Source reduction involves preventing development of mosquito larvae. The female mosquitoes need a blood meal from a vertebrate host to nourish their eggs. About 50-200 eggs are laid per oviposition on the surface of stagnant water and these eggs develop into adult mosquitoes in a span of about 5-14 days, passing through the stages of larvae and pupae. High humidity and ambient temperature between 20-30ºC provide ideal conditions for breeding of Anopheline mosquitoes. Common sites of breeding for Anopheles mosquitoes include rainwater pools and puddles, borrow pits, river bed pools, irrigation channels, seepages, rice fields, wells, pond margins, sluggish streams with sandy margins, hoof prints, tyre tracks etc. Water stagnation due to construction of dams, reforestation, shrimp farming, fish ponds etc., have also been identified as possible sites of Anopheles breeding. An. stephensi is a well adapted urban vector, being a container breeder, making use of man-made sites such as building-construction sites, wells, garden ponds, cisterns, overhead tanks, ground level cement tanks, water coolers, tyres, barrels and tins, intra-domestic containers etc. Anopheles breeding sites increase with rainfall and resultant water stagnation, ; however, some larvae and pupae may be washed away by heavy rainfall.

The best method of mosquito control is preventing the development of the eggs into adult mosquitoes, by reducing the sources of breeding. These anti larval measures are not only simple and cost effective, but also environment friendly.

a. Preventing egg laying: The easiest, cheapest and most environment-friendly method to control malaria is by preventing the mosquito from laying eggs. This is done by avoiding or eliminating the clean water collections. As mentioned, most such collections are artificial, temporary and man made.

It is a common habit to throw the unutilized utensils, buckets, bottles, tyres etc., into the open. During the rains, water gets collected in these containers and provides ample breeding locations for the female anopheles mosquito.

In the cities, the other sites for mosquito breeding are the water tanks. Shortage of water supply in large cities makes it necessary to have these tanks in virtually every building. Overhead tanks, sump tanks, storage tanks, ornamental tanks etc. are often left uncovered and this provides scope for mosquito breeding. Also, it is common to find puddles of water everywhere during the rainy season. This is the reason why malarial transmission is at its peak during the monsoon.

There is abundant scope for water collection in and around the construction sites: water stored in tanks; the layer of water on the surface of the cement concrete (used for ‘curing’ the concrete and left as such for 3 weeks); puddles of water in and around the place of construction – all these provide scope for mosquito breeding. To add to the problem, construction workers tend to harbour the malarial parasite, due to frequent infections owing to their poor standards of living. Thus, construction sites not only provide for mosquito breeding but also supply the parasites. This is the reason why malaria tends to be more common in cities where construction activities are in full swing.

The older houses have tiled roofs that are sloping. This helps easy drainage of water during rains, thus minimising water logging. In the recent years, most new constructions have concrete roofs and terraces that tend to be flat and non-sloping. These roofs/terraces may not have proper drains for water-flow. As a result, water tends to collect on these rooftops during the rains and this provides ample scope for mosquito breeding. In addition, there are the natural collections of water like the wells, lakes, ponds, paddy fields, marshlands etc. where mosquito breeding occurs in abundance.

Therefore, unless these breeding sites (most of which are man-made and temporary) are taken care of, it is impossible to control mosquito breeding and hence malaria. And it is impossible to achieve this without the participation of the general public. Education of the people is thus very important for any meaningful action. The following measures are called for to minimize mosquito breeding and these measures require only a trifle of human efforts:

• Do not throw utensils, vessels, buckets, tyres, bottles, tender coconut shells etc. in the open. They should be either destroyed or buried or at least kept inverted so that water cannot collect in them. All such things should be cleared during the rainy season.
• All tanks should be kept tightly closed. A black plastic sheet can be used for the purpose. Also, all tanks should be emptied, cleaned and allowed to dry for at least half an hour, once every week.
• Terraces and roofs should ideally have a slope, particularly in places where monsoon tends to be heavy. All such roofs/terraces should have adequate drainage for water. Any collection of water on these surfaces should be cleared at least once a week.
• At construction sites, all the care should be taken to avoid collection of water at one place for more than a week. The layer of water on the surface of the concrete, used for concrete curing, should be cleared at least once a week and allowed to dry for half an hour. All other puddles should be cleared regularly. Collections of water in the toilets and closets under construction should also be cleared. All tanks should be kept snugly closed. All labourers should be frequently checked for parasitemia and adequately treated. They should also be provided with mosquito nets.
• All unused wells and tanks should be closed or destroyed. Engine oil or kerosene has been used as a larvicidal on these collections. Another method to prevent egg laying on unused wells is by adding EPS polyesterene beads onto the surface of water. These beads are non-toxic, cheap and long lasting. They coat the water surface and prevent the mosquito from laying eggs.
• Wells that are being used and ornamental tanks can be treated with biological larvicides that do not harm the quality of drinking water. Also, these wells should be covered with either mosquito-proof nets or with plastic sheets.

How engineers can help in malaria control?
Public Health Engineering has lot to do with malaria control, especially by means of Source Reduction.

• Prevent water logging – Design the buildings with sloping roofs to aid easy drainage of rain water; provide drains in adequate numbers and sizes in buildings with flat roofs
• Prevent entry of insects – Screening of all windows and vents should be made mandatory. It is observed that this simple, common sense measure followed in every construction in the U.S.A. has in a big way helped in control of all insects including mosquitoes and hence malaria.
• Engineering skills are also called for in draining and flushing of water collections; deepening or filling of water logged areas; proper maintenance of water levels and intermittent irrigation in dams and canals and in changing salt content of water so as to make it unsuitable for mosquito breeding. Mosquitoes that breed in irrigation water can be controlled through careful water management.

b. Use of Larvicides: If the above mentioned measures are not adequate or difficult to achieve, then measures should be taken to destroy the larvae developing in the breeding sites. This can be done by either larvicidal chemicals or by biological larvicides like fish or bacteria.

i. Chemicals: Themiphos and Fenthion are the two commonly used larvicidal agents. Themiphos is used on potable water collections and Fenthion, being more toxic, is used on non-potable water collections. Oils may be applied to the water surface, suffocating the larvae and pupae. Most oils in use today are rapidly biodegraded. Insect growth regulators such as methroprene is specific to mosquitoes and can be applied in the same way as chemical insecticides.

ii. Biological larvicides: One of the safest and interesting methods in mosquito control is the use of biological agents that eat or destroy the larvae.

Eco-friendly larvivorous fish such as the top water minnow or mosquito fish (Gambusia affinis) or the common guppy (Poecilia reticulate) can be effectively used to control the mosquito population. These fish can be introduced into all collections of potable water like wells, tanks, ponds and lakes, particularly in rural and peri-urban areas and in freshwater bodies in rural areas.

Bacteria such as Bacillus sphaericus and Bacillus thuringiensis var israelensis are also effective larvicides. However, they need to be re-introduced every 15 days and their culture may need expertise.

Mermitid Nematod (Romanomermis culicivorax), Notonectid (Bug), Ambylospora (Protozoa), Coelomomyces (Fungus), Nuclear Polyhedrosis (Virus), and Cyclopoid copepods (Crustacean) are the other biological larvicides found to be effective.

A ‘saline solution’ from Kochi:

The Kochi Corporation in Kerala tried out a novel and cost effective method of reducing the mosquito population at the larvae stage itself. It has conducted experiments suggested by the retired National Institute of Oceanography (NIO) scientist, Dr. U.K. Gopalan, where the salinity of water in canals and stagnant pools is increased by adding sea water. The experiment was successful and mosquito larvae were found morbid in the canal portions where salinity was increased. When the salinity level reaches 30 parts per thousand or PPT (the normal percentage of salt in the sea), mosquito larvae cannot survive beyond 3 hours. Even at lower concentrations of 15 PPT, they are dead in 12 hours. And when the concentration is upped to 60 PPT, the larvae perish within the hour.[http://www.cochingateway.com/mkingdom.htm]

Further reading:

1. CDC. Malaria: Anopheles Mosquitoes. Available at http://www.cdc.gov/malaria/about/biology/mosquitoes/index.html
2. White NJ. Malaria. In Cook GC, Zumla AI. (Ed). Manson’s Tropical Diseases. 22nd Edition. Saunders Elsevier. 2009. pp 1201-1300
3. Dash AP, Adak T, Raghavendra K, Singh OP. The biology and control of malaria vectors in India. Current Science. 2007;92(11):1571-78. Full text at http://www.ias.ac.in/currsci/jun102007/1571.pdf
4. Operational Manual for Implementation of Malaria Programme. Government of India, Directorate of National Vector Borne Disease Control Programme; Directorate General of Health Services, Ministry of Health and Family Welfare. 2009. Available at http://nvbdcp.gov.in/Doc/Malaria-Operational-Manual-2009.pdf
5. Singh N, Mehra RK, Sharma VP. Malaria and the Narmada-river development in India: a case study of the Bargi dam. Annals of Tropical Medicine and Parasitology 1999;93:477-88.
6. Lindsay S, Kirby M, Baris E, Bos R. Environmental management for malaria control in the east Asia and Pacific (EAP) region. The International Bank for Reconstruction and Development / The World Bank. Washington. 2004. Available at http://www.who.int/water_sanitation_health/publications/whowbmalariacontrol.pdf
7. Maheu-Girouxa M, Casapía M, Soto-Calle VE et al. Risk of malaria transmission from fish ponds in the Peruvian Amazon. Acta Tropica. 2010;115(1-2):112-118
8. Kumar A, Thavaselvam D. Breeding habitats and their contribution to Anopheles stephensi in Panaji. Indian Journal of Malariology. 1992;29:35-40
9. CDC. Malaria: Larval Control and Other Vector Control Interventions. Available at http://www.cdc.gov/malaria/malaria_worldwide/reduction/vector_control.html
10. Kolsky P. Engineers and urban malaria: part of the solution, or part of the problem? Environment and Urbanization. 1999;11(1):159-163. Full Text at http://eau.sagepub.com/cgi/reprint/11/1/159.pdf
11. NVBDCP. Guidelines on the use of larvivorous fish for vector control. Available at http://nvbdcp.gov.in/Doc/Guidelines-larvivorous-fish.pdf

Control of Adult Mosquitoes

Control of adult mosquitoes is not an easy task, considering their varied habits, their ability to fly all over and to hide in nooks and corners. Whereas vectors such as An. gambiae and An. funestus are highly anthropophilic (prefer human blood meal), the Indian anopheline vectors such as An. culicifacies, An. fluviatilis, An. minimus, An. philippinensis, An. dirus, and An. stephensi are essentially zoophilic (preferring blood meal from animals such as cattle) and feed on human beings when high densities build up. During the day, these mosquitoes rest in human dwellings and cattle sheds and enter the human dwellings between 5pm-10pm. They start biting indoors soon after, with peak biting at midnight, between 11 pm and 4 am. Adult female anopheles mosquitoes survive for 1-2 weeks or more depending on the ambient conditions and have a flight range of 0.5-3 kms.

Control of adult mosquitoes involve the following measures:

• Preventing entry of adult mosquitoes into human dwellings
• Mosquito nets (regular and insecticide treated)
• Personal protection measures
  • Protective clothing
  • Mosquito repellents
• Adult insecticides
  • Space sprays – for instant results
  • Residual sprays – for sustained effects
  • Combined
  • Insecticide vaporizers

The Global Malaria Action Plan enlists insecticidal nets (LLINs), indoor residual spraying (IRS) with long-lasting chemical insecticides, and other vector (mosquito) controls such as larviciding and environmental management as the key tools of the global malaria control strategy.
Preventing entry of adult mosquitoes into human dwellings: Measures to make the human dwellings inaccessible to the vector mosquitoes so as to reduce man-mosquito contacts are important in controlling malaria transmission. Mosquitoes do not fly more than about 2-4km from their breeding habitats and therefore positioning houses 1.5 to 2 km from large breeding sites will reduce the risk of transmission substantially. Villages at higher elevations and exposed to the wind tend to have fewer mosquitoes compared to sites situated in the lowlands that are less windy and have many small water bodies. As most mosquitoes fly close to the ground, raising buildings off the ground or on silts can help in preventing mosquito entry. Sitting on raised platforms or keeping the feet off the ground also help in minimizing mosquito bites.

Keeping the windows and doors closed during evenings and early morning hours can prevent the mosquitoes from gaining entry into households (it is important to close the doors of the toilets, which always open to the exterior through windows or vents). Modifying the house structure and mosquito-proofing of the houses were used by Manson, Ross, Celli and others to protect people from malaria in Italy, Greece, Panama and the USA and there is ample evidence that house screening contributed to the elimination of malaria from many parts of the world. Homes with ceilings or closed eaves also protect from mosquitoes and malaria; a study using experimental huts in Gambia demonstrated that installing a ceiling made of netting reduced transmission by 80%. As Anopheles mosquitoes tend to hide in the dark corners and amidst the clothes and other linen left hanging in the rooms, such hiding places should be avoided by keeping all the clothes and linen inside wardrobes and cupboards.

Mosquito nets: Mosquito nets act as physical barriers by blocking the vector mosquitoes. Application of pyrethroid insecticides adds a chemical barrier to the physical one, further reducing human–vector contact and increasing the protective efficacy of the mosquito nets. Pyrethroid insecticides have a long residual action and low mammalian toxicity and provide prolonged protection by their excito-repellent effect. As mosquitoes are positively attracted by the odour of the sleeper inside the net, these insecticide treated nets (ITNs) acts like a baited trap and the mosquitoes that come into contact with the ITN are, most often, killed. As the ITNs shorten the mean mosquito life span, very few mosquitoes can survive long enough for the sporogonic cycle to be completed, thus reducing the transmission. As the ITNs also inhibit mosquito feeding, the reproductive potential of highly anthropophilic vectors is also reduced. Due to these multiple effects, the ITNs have been shown to avert around 50% of malaria cases and provide at least double the protection than that provided by untreated nets.

The community-wide use of ITNs has been reported top reduce the vector population significantly and when used by a majority of the target population (around 60%), to provide protection for all people in the community, including those who do not themselves sleep under nets. ITNs have been found to be the most cost-effective interventions against malaria, and long-lasting insecticidal nets LLINs were found to be significantly cheaper to use than conventionally treated nets. ITNs/LLINs are particularly useful for high-risk populations that cannot be reached by residual spraying, for people in forest-fringe areas who are at risk of infection from forest stay, and for pregnant women who are highly vulnerable to malaria. Under NVBDCP, ITNs/LLINs are provided free to the target population.

Currently, most mosquito nets are made of polyester and rarely last longer than 2–3 years under field situations. Conventional ITNs, treated with pyrethroids such as alpha-cypermethrin, cyfluthrin, deltamethrin, lambda-cyhalothrin or permethrin, need to be re-treated after three washes, or at least once a year to ensure continued insecticidal effect. Long-lasting insecticidal nets [LLINs] are factory-treated mosquito nets, made with netting material that has the insecticide incorporated within or bound around the fibres and the insecticide is progressively released so that the net retains the efficacy after repeated washings. The LLINs are expected to retain their effective biological activity without re-treatment for at least 20 standard washes and for three years of recommended use under field conditions. Permethrin (high density polyethylene monofilament yarn blended with 2% permethrin), Deltamethrin (multifilament polyester netting treated with deltamethrin 55mg/m2), and alpha cypermethrin (multifilament polyester netting treated with alpha cypermethrin 200mg/m2) are used in LLINs.

Zooprophylaxis intends to control vector-borne infections by diverting vectors from humans to domestic animals such as cattle that act as dead-end or decoy hosts. Although this method has been suggested by WHO as one of the measures to control anopheline vectors, some of which are indeed zoophilic, studies on its efficacy have yielded varying results.

Indoor Residual Spraying:

IRS is an integral component of the Global Malaria Action Plan and currently DDT, pyrethroids (Deltamethrin 2.5% WP, Cyfluthrin 10% WP, Alphacypermethrin 5% WP and Lambdacyhalothrin 10% WP) or Malathion 25% are used in different parts of the world for this purpose. All the interior walls and ceilings as well as the underside of furniture, back of the doors and porches of permanent human dwellings as well as Jhoom huts where people sleep during the plantation or harvesting season are sprayed. For protection during the entire transmission season, two rounds of DDT or synthetic pyrethroids or three rounds of Malathion are used.

DDT has once again staged a comeback after nearly thirty years of being phased out from the widespread use in indoor spraying to control malaria. A 1990 cost comparison by the WHO found DDT to be considerably less expensive than other insecticides, which cost 2 to 23 times more on the basis of cost per house per 6 months of control and this advantage remains even today. In September 2006, the WHO once again recommended the use of DDT for indoor residual spraying, not only in epidemic areas but also in areas with constant and high malaria transmission, including throughout Africa with an assurance that DDT presents no health risk when used properly. The tough campaign by public health officials and malaria experts who had argued for years that DDT was a necessary public-health weapon in poor tropical countries, signature campaign by hundreds of physicians from all over the world urging resumption of DDT spraying and arguments of Amir Attaran, of Harvard University’s Center for International Development, that unlike agricultural uses which inject tons of DDT into the outdoors, the indoor residual house-spraying with DDT at minimal (2g/m2) quantities was an inexpensive and highly effective practice against malaria, all helped in making this decision.

See

• Attaran A, Roberts DR, Curtis CF, Kilama WL. Balancing risks on the backs of the poor. Nature Medicine July 2000;6(7):729-731. Available at http://www.malaria.org/attarannaturemed.html or at http://www.nature.com/index.html?file=/nm/journal/v6/n7/full/nm0700_729.html
• Roberts D et al. The United Nations’ Scientific Fraud against DDT. [Full Text]

Space sprays: These insecticides instantly kill the mosquitoes, but lack any residual effects. They are therefore sprayed into the air. By killing adult mosquitoes, not only bites are prevented, but breeding is also prevented, resulting in net reduction in the mosquito population. Space sprays must be repeated often, at least once every week. Pyrethroids are commonly used for this purpose.

Space spraying involves the application of small droplets of insecticide into the air, but recent studies have demonstrated that the method has little effect on the mosquito population. Moreover, when space spraying is conducted in a community, it creates a false sense of security among residents, which has a detrimental effect on community-based source reduction programmes. (In fact, in Mangalore, the ward level committees formed in the year 1995-96, lost steam and became defunct after fogging operations were introduced in late 1996!) Although it is highly visible and conveys the message that the government is doing something about the disease, this can be only a poor justification for using space sprays. (Often, members of the City Corporation order fogging in their constituencies to ‘satisfy’ their voters!).

Space spraying operations should be carried out at the right time, at the right place, and according to the prescribed instructions with maximum coverage, so that the fog penetration effect is complete enough to achieve the desired results. Fogging should be primarily reserved for emergency situations: halting epidemics or rapidly reducing adult mosquito populations. It must be timed to coincide with the peak adult activity, because resting mosquitoes are often found in areas that are difficult for the insecticide to reach (e.g., under leaves, in small crevices). Generally, there are two forms of space-sprays, namely thermal fogs and cold fogs and both can be dispensed by vehicle-mounted or hand-operated machines.

Thermal fogs: Thermal fogs are produced when an insecticide formulation condenses after being vaporized at a high temperature. These formulations can be oil-based or water-based; the oil (diesel)-based formulations produce dense clouds of white smoke, whereas water-based formulations produce a colorless fine mist.

Ultra-low volume (ULV), aerosols (cold fogs) and mists: ULV involves the application of a small quantity (<4.6 litres/ha) of concentrated liquid insecticides. Aerosols, mists and fogs may be applied by portable machines, vehicle-mounted generators or aircraft equipment.

House-to-house application using portable equipment: Portable spray units can be used when the area to be treated is not very large or in areas where vehicle-mounted equipment cannot be used effectively. This equipment is meant for restricted outdoor use and for enclosed spaces (buildings) of not less than 14m³. Congested low-income housing areas, multistoried buildings, godowns and warehouses, covered drains, sewer tanks and residential or commercial premises are some examples.

Vehicle-mounted fogging

Vehicle-mounted fogging can be used in urban or suburban areas with a good road system. One machine can cover up to 1500-2000 houses (or approximately 80 ha) per day. An educational effort may be required to persuade the residents to cooperate by opening doors and windows. The best time for application is in the early morning (6am-8.30am) or evening (5pm-7.30pm).

Insecticide formulations for space sprays

Organophosphate insecticides

• Malathion
  • Undiluted technical grade malathion (active ingredient 95%+) for ULV spraying (0.5 liters per hectare for vehicle-mounted operations)
  • One part technical grade diluted with 24 parts of diesel for thermal fogging respectively
• Fenitrothion
• Pirimiphos methyl

Pyrethroids

• Permethrin
• Deltamethrin
• Lambda-cyhalothin

Low dosages of pyrethroid insecticides are usually more effective indoors than outdoors.

Novel Genetic Methods: Sterile male release has been successfully applied in several small-scale areas. However, the need for large numbers of mosquitoes for release makes this approach impractical for most areas. Genetic modification of malaria vectors aims to develop mosquitoes that are refractory to the parasite. This approach is still several years from application in field settings.

Wolbachia Fungus to Control Malaria Vector Mosquitoes

Evolution, Resisted: Article by Elie Dolgin

Fungus fights malaria Science February 25, 2011 Abstract | Podcast | Report]

Further Reading:

1. The Global Malaria Action Plan For a malaria free world. Roll Back Malaria Partnership, WHO. Geneva. 2008. Available at http://www.rollbackmalaria.org/gmap/gmap.pdf
2. Lindsay S, Kirby M, Baris E, Bos R. Environmental management for malaria control in the east Asia and Pacific (EAP) region. The International Bank for Reconstruction and Development / The World Bank. Washington. 2004. Available at http://www.who.int/water_sanitation_health/publications/whowbmalariacontrol.pdf
3. Charlwood JD, Pinto J, Ferrara PR et al. Raised houses reduce mosquito bites. Malaria Journal 2003;2:45. doi:10.1186/1475-2875-2-45 Full text at http://www.malariajournal.com/content/2/1/45
4. Lindsay SW, Emerson P, Charlwood JD. Reducing malaria by mosquito-proofing homes. Trends in Parasitology 2002;18:510-514.75.
5. Lindsay SW, Jawara M, Paine K, Pinder M et al. Changes in house design reduce exposure to malaria mosquitoes. Tropical Medicine and International Health. 2003;8(6):512–517.
6. Ogoma SB, Kannady K, Sikulu M et al. Window screening, ceilings and closed eaves as sustainable ways to control malaria in Dar es Salaam, Tanzania. Malaria Journal 2009;8:221. doi:10.1186/1475-2875-8-221. Full Text at http://www.malariajournal.com/content/8/1/221
7. WHO. Malaria vector control and personal protection: report of a WHO study group. (WHO technical report series: no. 936) World Health Organization. Geneva. 2006 Available at http://malaria.who.int/docs/WHO-TRS-936s.pdf
8. WHO. Insecticide-Treated Mosquito Nets: a WHO Position Statement. WHO. Geneva. 2007. Available at http://www.who.int/malaria/publications/atoz/itnspospaperfinal.pdf
9. WHO. Long-lasting insecticidal nets for malaria prevention: A manual for malaria programme managers. World Health Organization. Geneva. 2007. Available at http://www.who.int/malaria/publications/LLINmanual.pdf
10. Operational Manual for Implementation of Malaria Programme. Government of India, Directorate of National Vector Borne Disease Control Programme; Directorate General of Health Services, Ministry of Health and Family Welfare. 2009. Available at http://nvbdcp.gov.in/Doc/Malaria-Operational-Manual-2009.pdf
11. Kaburiae JC, Githutob JN, Muthamic L. Effects of long-lasting insecticidal nets and zooprophylaxis on mosquito feeding behaviour and density in Mwea, central Kenya. J Vector Borne Dis. 2009;46:184–190.Full text at http://www.mrcindia.org/journal/issues/463184.pdf
12. Saul A. Zooprophylaxis or zoopotentiation: the outcome of introducing animals on vector transmission is highly dependent on the mosquito mortality while searching. Malaria Journal. 2003;2:32. doi:10.1186/1475-2875-2-32. Full text at http://www.malariajournal.com/content/2/1/32
13. Bøgh C, Clarke SE, Walraven GE, Lindsay SW. Zooprophylaxis, artefact or reality? A paired-cohort study of the effect of passive zooprophylaxis on malaria in The Gambia. Trans R Soc Trop Med Hyg. 2002;96(6):593-6.
14. WHO gives indoor use of DDT a clean bill of health for controlling malaria. Available at http://www.who.int/mediacentre/news/releases/2006/pr50/en/index.html
15. Walker K. Cost-comparison of DDT and alternative insecticides for malaria control. Medical and Veterinary Entomology.2000;14(4):345–354
16. Attaran A, Maharaj R. Ethical debate: Doctoring malaria, badly: the global campaign to ban DDT. BMJ 2000;321:1403-1405. Full text at http://www.bmj.com/cgi/content/full/321/7273/1403
17. http://www.cdc.gov/malaria/control_prevention/vector_control.htm
18. http://w3.whosea.org/en/Section10/Section332/Section554_2569.htm

 ©malariasite.com ©BS Kakkilaya | Last Updated: Jan 2, 2018