Indoor residual spraying
This article's factual accuracy may be compromised due to out-of-date information. (August 2012) |
Indoor residual spraying or IRS is the process of spraying the inside of dwellings with an
World Health Organization recommendations
The World Health Organization (WHO) recommends IRS as one of three primary means of malaria control, the others being use of insecticide treated bednets (ITNs) and prompt treatment of confirmed cases with artemisinin-based combination therapies (ACTs).[2] While previously the WHO had recommended IRS only in areas of sporadic malaria transmission, in 2006 it began recommending IRS in areas of endemic, stable transmission as well.[3]
According to the WHO:[4]
[N]ational governments should:
- Introduce and/or scale up coverage of targeted IRS as a primary malaria control intervention in countries where available data indicates that it can be effective towards achieving malaria targets.
- Take all necessary steps to ensure effective implementation of IRS interventions, including selecting the appropriate insecticide, spraying where and when necessary and sustaining a high level of coverage, and to prevent unauthorized or un-recommended use of public health insecticides.
- Strengthen the managerial capacity of national malaria control programmes and improve human, technical and financial resources for the timely delivery and high coverage of effective interventions including IRS, with adequate monitoring and evaluation.
Furthermore, for IRS to be effective:[4]
- There must be a high percentage of sprayable surfaces within each dwelling.
- The vector(mosquitos) must feed or rest indoors.
- The targeted vectors must be susceptible (i.e. not resistant) to the insecticide being sprayed.
The WHO further states that "insecticide susceptibility and vector behaviour; safety for humans and the environment; and efficacy and cost-effectiveness" are factors that must be considered when selecting an insecticide for IRS.[4]
Approved insecticides
Currently, the WHO has approved 13 different insecticides for IRS.
Insecticide | Class | Recommended dosage of active ingredient (g/m2)[5] | Duration of effective action (months) | Estimated cost per house per 6 months (US$)[6] | WHO toxicity rating[7] |
---|---|---|---|---|---|
DDT | Organochlorine
|
1–2 | >6 | 1.60 | II |
Fenitrothion | Organophosphate | 2 | 3–6 | 14.80 | II |
Malathion | Organophosphate | 2 | 2–3 | 8.20 | III |
Pirimiphos-methyl | Organophosphate | 1–2 | 2–3 | III | |
Propoxur | Carbamate | 1–2 | 3–6 | 18.80 | II |
Bendiocarb | Carbamate | 0.1–0.4 | 2–6 | 13.80 | II |
Alpha-cypermethrin | Pyrethroid | 0.02–0.03 | 4–6 | II | |
Cyfluthrin | Pyrethroid | 0.02–0.05 | 3–6 | II | |
Deltamethrin | Pyrethroid | 0.02–0.025 | 3–6 | 1.60 | II |
Etofenprox | Pyrethroid | 0.1–0.3 | 3–6 | U | |
Lambda-cyhalothrin
|
Pyrethroid | 0.02–0.03 | 3–6 | 8.60 | III |
Bifenthrin | Pyrethroid | 0.025–0.05 | 3–6 | II | |
Clothianidin | Neonicotinoid |
Cost effectiveness and efficacy
According to 2010
Few studies have directly compared the
With regard to the cost effectiveness of various pesticides vis-a-vis each other for IRS, historically DDT has been considered the most cost effective, mainly because it lasts longer than alternatives and therefore dwellings can be sprayed less frequently. But actual studies on cost effectiveness are lacking, and none have taken into account the adverse health and environmental effects of DDT or its alternatives. The United Nations Environment Programme (UNEP) concluded in 2008 that "IRS with DDT remains affordable and effective in many situations but, with regard to the direct costs, the relative advantage of DDT vis-à-vis alternative insecticides seems to be diminishing. The contextual evidence base on cost-effectiveness needs strengthening, and the external costs of DDT use vis-à-vis alternative insecticides require a careful assessment."[3]
Residents' opposition to IRS
For IRS to be effective, at least 80% of homes and barns in an area must be sprayed,[4] and if enough residents refuse spraying, the effectiveness of the whole program can be jeopardized. Many residents resist spraying of DDT in particular. This is due to a variety of factors, including its smell[10] and the stains it leaves on the walls.[10][11][12][13] While that stain makes it easier to check whether the room has been sprayed, it causes some villagers to resist the spraying of their homes[13][14][15] or to resurface the wall, which eliminates the residual insecticidal effect.[12][15] Pyrethroid insecticides are reportedly more acceptable since they do not leave visible residues on the walls.[13]
In addition, DDT is not suitable for this type of spraying in Western-style plastered or painted walls, only traditional dwellings with unpainted walls made of mud, sticks, dung, thatch, clay, or cement.[10][15][16] As rural areas of South Africa become more prosperous, there is a shift towards Western style housing, leaving fewer homes suitable for DDT spraying, and necessitating the use of alternative insecticides.[15]
Other villagers object to DDT spraying because it does not kill
As a result,
Use of DDT
As discussed above, DDT is one of several insecticides currently approved by the WHO for use in malaria control. The following table shows recent per country use of DDT for IRS. Unless otherwise noted, data for 2003–2007 is from the 2008
Country | 2003 use ( tonnes )
|
2005 use ( tonnes )
|
2007 use ( tonnes )
|
2008 use | 2009 use ( tonnes )
|
Notes |
---|---|---|---|---|---|---|
Botswana | 0 | 0 | 0 | 0 | Use suspended in 1997, plans to introduce in 2009 [19][20] | |
Cameroon | 0 | 0 | 0 | 0 | plan to introduce in 2009 | |
China | 0 | 0 | n.a. | 0 | 0 | discontinued use in 2003 |
DR Congo | 0 | 0 | 0 | some | plan to reintroduce | |
Eritrea | 13 | 15 | 15 | some | ||
Ethiopia | 272 | 398 | 371 | some | 1350 | Spraying stopped in 2010 because of resistance[17][21] |
Gambia
|
0 | 0 | 0 | 0 | some | plan to introduce in 2008 |
Guyana | n.a. | n.a. | n.a. | some | listed in World Malaria Report 2013 as not using DDT for IRS[22] | |
India | 4444 | 4253 | 3188 | some | 3415 | includes use for both malaria and leishmaniasis |
Madagascar | 45 | 0 | 0 | 0 | 0 | plan to reintroduce in 2009 |
Malawi | 0 | 0 | 0 | 0 | plan to introduce in 2009 | |
Mauritius | 1 | 1 | 0 | 0 | some | |
Morocco | 1 | 1 | n.a. | 0 | 0 | |
Mozambique | 0 | 308 | n.a. | some | reintroduced in 2005 | |
Myanmar | 1 | 1 | n.a. | some | 0 | phasing out |
Namibia | 40 | 40 | 40 | some | ||
North Korea | n.a. | n.a. | 5 | some | some | (an additional 155 tonnes is used in agriculture) |
Papua New Guinea | n.a. | n.a. | n.a. | some | unknown amounts used | |
South Africa | 54 | 62 | 66 | some | reintroduced in 2000 | |
Sudan | 75 | n.a. | 0 | 0 | ||
Swaziland
|
n.a. | 8 | 8 | some | ||
Uganda | 0 | 0 | 0 | some[23] | IRS with DDT was briefly implemented in 2008[23] | |
Zambia | 7 | 26 | 22 | some | some | reintroduced in 2000 |
Zimbabwe | 0 | 108 | 12 | some | reintroduced in 2004 | |
Global Total | 4953 | 5219 | 3725 | 4783 | 2009 use includes only India, Ethiopia, Zambia, and Mauritius |
References
- ^ a b World Health Organization, World Malaria Report 2009, 2009.
- ^ World Health Organization. "WHO – Malaria". Retrieved 2008-11-22.
- ^ Stockholm Convention/United Nations Environment Programme. Archived from the original(PDF) on December 17, 2010. Retrieved 2008-11-22.
- ^ a b c d Indoor Residual Spraying: Use of Indoor Residual Spraying for Scaling Up Global Malaria Control and Elimination. World Health Organization, 2006.
- PMID 18165500.
- ^ "Excluding operational costs and freight and other external costs"
- ^ Ia = Extremely Hazardous; Ib = Highly Hazardous; II = Moderately Hazardous; III = Slightly Hazardous; U = Unlikely To Be Hazardous. Source: World Health Organization, The WHO Recommended Classification of Pesticides by Hazard, 2005.
- PMID 20393950.
- PMID 19091114.
- ^ Wall Street Journal, July 26, 2001
- ^ a b DDT and Africa's war on malaria, BBC
- ^ PMID 15303988.
- ^ a b c d e Control of Malaria Vectors in Africa and Asia Archived 2007-10-02 at the Wayback Machine C.F.Curtis
- ^ a b c Gladwell, Malcolm (July 2, 2001). "The Mosquito Killer". The New Yorker. Archived from the original on February 6, 2009..
- ^ a b c d e f South Africa's War against Malaria Lessons for the Developing World, Richard Tren and Roger Bate, Cato Institute
- S2CID 22748077.
- ^ a b DDT Expert Group of the Stockholm Convention (15 Dec 2010). "UNEP/POPS/COP.5/5. Report of the expert group on the assessment of the production and use of DDT and its alternatives for disease vector control". United Nation Environment Programme. Retrieved 11 April 2011.
- ^ "DDT-Eg4".
- ^ Letsididi, Bashi (July 7, 2009). "Gov't reintroduces DDT chemical". Sunday Standard. Archived from the original on October 23, 2014. Retrieved 2009-07-08.
- ^ NGWANAAMOTHO, MARANYANE (November 24, 2009). "DDT benefits outweigh risks - Ntebela". Mmegi Mobile. Retrieved 27 January 2010.
- ^ ZENEBE, WUDINEH (March 14, 2010). "DDT Ban Forces Pesticide Co to Export Stockpile". Addis Fortune. Retrieved 16 March 2010.
- ^ Who.int,. (2014). Retrieved 2 November 2014, from http://www.who.int/malaria/publications/country-profiles/profile_guy_en.pdf?ua=1
- ^ a b Das, Devapriyo (1 October 2008). "Health - DDT Experiment Fails Its First Test". The Observer. Retrieved 15 January 2010.
External links
- MALARIA VECTOR CONTROL AND PERSONAL PROTECTION, WHO Technical Report Series No. 936. 2006.