Editing DDT (section)

===Mosquito resistance===
In some areas, resistance reduced DDT's effectiveness. WHO guidelines require that absence of resistance must be confirmed before using the chemical.<ref name="IRS-WHO">"
[http://whqlibdoc.who.int/hq/2006/WHO_HTM_MAL_2006.1112_eng.pdf Indoor Residual Spraying: Use of Indoor Residual Spraying for Scaling Up Global Malaria Control and Elimination] {{Webarchive|url=https://web.archive.org/web/20081002173139/http://whqlibdoc.who.int/hq/2006/WHO_HTM_MAL_2006.1112_eng.pdf |date=October 2, 2008 }}". World Health Organization, 2006.</ref> Resistance is largely due to agricultural use, in much greater quantities than required for disease prevention.

Resistance was noted early in spray campaigns. Paul Russell, former head of the [[Allies of World War II|Allied]] Anti-Malaria campaign, observed in 1956 that "resistance has appeared after six or seven years".<ref name="Gladwell"/> Resistance has been detected in Sri Lanka, [[Pakistan]], [[Turkey]] and [[Central America]] and it has largely been replaced by [[organophosphate]] or [[carbamate]] insecticides, e.g. malathion or [[bendiocarb]].<ref name="Curtis">{{cite web | vauthors = Curtis CF | url = http://ipmworld.umn.edu/chapters/curtiscf.htm | title = Control of Malaria Vectors in Africa and Asia | archive-url =  https://web.archive.org/web/20071002124232/http://ipmworld.umn.edu/chapters/curtiscf.htm | archive-date = October 2, 2007 | url-status = dead | date = February 1996 | publisher = University of Minnesota }}</ref>

In many parts of [[India]], DDT is ineffective.<ref>{{cite journal | vauthors = Sharma VP | title = Current scenario of malaria in India | journal = Parassitologia | volume = 41 | issue = 1–3 | pages = 349–353 | date = September 1999 | pmid = 10697882 }}</ref> Agricultural uses were banned in 1989 and its anti-malarial use has been declining. Urban use ended.<ref>{{cite journal |title=No Future in DDT: A case study of India |last=Agarwal |first=Ravi | name-list-style = vanc | journal=Pesticide Safety News |date=May 2001}}</ref> One study concluded that "DDT is still a viable insecticide in indoor residual spraying owing to its effectivity in well supervised spray operation and high excito-repellency factor."<ref name="mrc">{{cite journal | vauthors = Sharma SN, Shukla RP, Raghavendra K, Subbarao SK | title = Impact of DDT spraying on malaria transmission in Bareilly District, Uttar Pradesh, India | journal = Journal of Vector Borne Diseases | volume = 42 | issue = 2 | pages = 54–60 | date = June 2005 | pmid = 16161701 }}</ref>

Studies of malaria-vector mosquitoes in [[KwaZulu-Natal Province]], [[South Africa]] found susceptibility to 4% DDT (WHO's susceptibility standard), in 63% of the samples, compared to the average of 87% in the same species caught in the open. The authors concluded that "Finding DDT resistance in the vector ''An. arabiensis'', close to the area where we previously reported pyrethroid-resistance in the vector ''An. funestus'' Giles, indicates an urgent need to develop a strategy of [[insecticide resistance]] management for the malaria control programmes of southern Africa."<ref name="Hargreaves">{{cite journal | vauthors = Hargreaves K, Hunt RH, Brooke BD, Mthembu J, Weeto MM, Awolola TS, Coetzee M | title = Anopheles arabiensis and An. quadriannulatus resistance to DDT in South Africa | journal = Medical and Veterinary Entomology | volume = 17 | issue = 4 | pages = 417–422 | date = December 2003 | pmid = 14651656 | doi = 10.1111/j.1365-2915.2003.00460.x | s2cid = 22748077 }}</ref>

DDT can still be effective against resistant mosquitoes<ref name=PLoS1/> and the avoidance of DDT-sprayed walls by mosquitoes is an additional benefit of the chemical.<ref name="mrc"/> For example, a 2007 study reported that resistant mosquitoes avoided treated huts. The researchers argued that DDT was the best pesticide for use in IRS (even though it did not afford the most protection from mosquitoes out of the three test chemicals) because the other pesticides worked primarily by killing or irritating mosquitoes – encouraging the development of resistance.<ref name="PLoS1">{{cite journal | vauthors = Grieco JP, Achee NL, Chareonviriyaphap T, Suwonkerd W, Chauhan K, Sardelis MR, Roberts DR | title = A new classification system for the actions of IRS chemicals traditionally used for malaria control | journal = PLOS ONE | volume = 2 | issue = 8 | page = e716 | year = 2007 | pmid = 17684562 | pmc = 1934935 | doi = 10.1371/journal.pone.0000716 | doi-access = free | editor1-last = Krishna | editor1-first = Sanjeev | bibcode = 2007PLoSO...2..716G }}</ref> Others argue that the avoidance behavior slows eradication.<ref name="Musawenkosi">{{cite journal|vauthors=Mabaso ML, Sharp B, Lengeler C|date=August 2004|title=Historical review of malarial control in southern African with emphasis on the use of indoor residual house-spraying|journal=Tropical Medicine & International Health|volume=9|issue=8|pages=846–856|doi=10.1111/j.1365-3156.2004.01263.x|pmid=15303988|doi-access=free|s2cid=10018052}}</ref> Unlike other insecticides such as [[pyrethroid]]s, DDT requires long exposure to accumulate a lethal dose; however its irritant property shortens contact periods. "For these reasons, when comparisons have been made, better malaria control has generally been achieved with pyrethroids than with DDT."<ref name="Curtis"/> In India outdoor sleeping and night duties are common, implying that "the excito-repellent effect of DDT, often reported useful in other countries, actually promotes outdoor transmission".<ref>{{cite journal |title=DDT: The fallen angel |first=V. P. |last=Sharma |name-list-style=vanc |journal=Current Science |volume=85 |pages=1532–1537 |issue=11 |date=December 2003 |url=http://www.ias.ac.in/currsci/dec102003/1532.pdf |url-status=dead |archive-url=https://web.archive.org/web/20050518063647/http://www.ias.ac.in/currsci/dec102003/1532.pdf |archive-date=May 18, 2005 |df=mdy-all }}</ref>