LongLasting Insecticidal Nets: an overview

1
Long-Lasting Insecticidal Nets an overview

• Dr Pierre Guillet
• Vector Biology Control
• WHO Regional Office for Africa
• Harare, Zimbabwe

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Use of nets in Africa
lt 5 of nets properly treated
Source Africa Malaria Report 2003, Figure 2.3
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What is a long-lasting insecticidal net?

• A mosquito net usually treated at factory level
• - with insecticide, either incorporated into or
  coated around fibres,
• - which resists multiple washes (al least 20),
• - and whose biological activity for personal
  protection and/or vector control lasts as long as
  the life of the net itself (e.g. around 3 years
  for polyester nets, 5 years for polyethylene).

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Two main treatment technologies

• Incorporation insecticide is mixed with a
  polymer subsequently used to extrude a mono or a
  multifilament yarn
• Monofilament strength, durability, production
  capacity, equipment,
• Multifilament easy transfer, equipment
  available, QC issues
• Both occupational health issues (handling)
• Surface treatment insecticide (mixed in a resin
  or a polymer) is bound to netting fibres by
  dipping or spraying techniques
• Advantages safety, ease of application,
  possibility for field use
• Limitations suitability with different nettings,
  long-term efficacy under various field conditions

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WHOPES evaluation

• Phase I laboratory testing (bioefficacy, wash
  resistance, dynamics of insecticide)
• Phase II field testing in experimental huts
  (mortality, impact on vector behaviour comparing
  unwashed, washed LLINs with conventionally
  treated nets)
• Phase III field test at village scale
  (entomological and epidemiological evaluation as
  necessary)

WHO recommendations only valid for products
meeting WHO specifications
Only Phases I II needed for insecticides
already recommended by WHO for treatment of
mosquito nets
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WHOPES evaluation

• Phases I II testing and provisional
  recommendations 1 to 2 years
• Provisional recommendations revisited after few
  years (effective lifespan of the LLIN) and
  confirmed or eventually changed on the basis of
  results obtained under programme conditions

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Two LLINs currently recommended by WHO

• Olyset netR wide mesh netting (mesh 56), made of
  high-density polyethylene monofilament yarn (150
  denier) with 2 permethrin incorporated
  (equivalent to 1 gr/m2)
• Recommended since 2001, WHO/CDS/WHOPES/2001.4
• PermaNetR multifilament polyester netting (mesh
  156, 75 or 100 denier), surface treated with a
  wash resistant deltamethrin mix (55 mg a.i./m2)
• Recommended since 2003, WHO/CDS/WHOPES/2004.8

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Olyset lab testing wash resistance and heat
regeneration (Phase 1, WHO cones 3 min. exposure)
Heat regeneration
0
1
60C, 1H
2
3
WHOPES
CDC
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Chemical analysis migration of permethrin in
tropical conditions (30C) (industry data)
mg/kg
Surface concentration
Minimum active
surface concentration
Weeks
10
Bioassay with Olyset washed 5 times spontaneous
regeneration at 22-25C
WHOPES
CDC 30C
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Results of CDC field trial in Kenya(Kaplan Meyer
estimate)
1.0
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Olyset efficacy epidemiological impact at
village scale in West Africa

• Senegal vectors susceptible to permethrin
• reduction of transmission by 93 and malaria
  morbidity by 58 (Faye et al., 1998, Med. Trop.,
  58, 355-360)
• Côte dIvoire vectors highly resistant (kdr)
• reduction of malaria morbidity by 60.9 (Henry
  et al., 1999, Med. Trop., 59, 368-372), without
  detectable entomological impact (Doannio et al.,
  1999, Med. Trop., 349-354)

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Olyset long-lasting efficacy, field data

• Côte dIvoire
• When tested in experimental huts, Olyset efficacy
  remained unchanged after 3 years of continuous
  use by villagers
• (N'Guessan et al., 2001, Medvet, 15,
  97-104)

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Olyset residual permethrin content after 4, 5
and 7 years of continuous use in the field

1
3
2
(13)
(30 10)
(21 nets)
Years
1 Senegal
3 Senegal Tanzania
2 Côte dIvoire
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Olyset residual permethrin content after 4, 5
and 7 years of continuous use in the field

1
3
2
(13)
(30 10)
(21 nets)

• 4 Years
• WHO cone test 62 of the nets
• still effective (KD 60 min gt 95 )

1 Senegal
3 Senegal Tanzania
2 Côte dIvoire
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Olyset residual permethrin content after 4, 5
and 7 years of continuous use in the field

1
3
2
(13)
(30 10)
(21 nets)

• 5 Years
• Who cone test 65 of the nets
• still effective (KD 60 mins gt 95 )

1 Senegal
3 Senegal Tanzania
2 Côte dIvoire
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Olyset residual permethrin content after 4, 5
and 7 years of continuous use in the field

1
3
2
(13)
(30 10)
(21 nets)

• 7 Years Tanzania
• (Tami et al., 2004, Malaria Journal, 3-19)
• - WHO cone test 9 out of 10 nets still effective
  (KD 60 min gt 95 )
• (without heat regeneration).
• - Village survey (103 households) 97 of the
  nets still in place
• and used, 62 in a relatively good shape.
• - 51 of villagers would buy an Olyset net
  because of its durability.

1 Senegal
3 Senegal Tanzania
2 Côte dIvoire
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Evaluation of PermaNet 1

• Heterogeneous results observed in the field
• Insecticide uptake and wash resistance vary
  according to polyester fabrics
• Low wash resistance observed in a large scale
  field trial in Uganda (Kilian et al., 2002)

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Field testing in Colombia, An. darlingi A.
Kroeger et al., 2001
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PermaNet2 wash resistance, laboratory and field
test
CDC, lab test with WHO cones
Field test, experimental huts, Benin
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Key advantages of LLINs

• A practical option to rapidly increase coverage
  of target populations with properly treated nets
• LLINs are more cost-effective than conventionally
  treated nets

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LLIN cost-effectiveness
Comparison of conventional nets retreatment
with LLIN (MSH)

1 net delivered
3.5
2.33 5.33
2.97
3
2.78
2.68
2.63
2.59
2 treatments/year
2.5
2.4 /year delivered
2.67
2
1.5
1.78
1
1.33
1.07
0.89
0.5
Duration of a net
0
2 Years
3 Years
4 Years
5 Years
6 Years
conventional
LLIN
Cost per year
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Rapid increase in demand for LLINs ITN request
from African countries to The Global Fund
Numbers
Proportion
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Next steps in LLIN technology development
testing protocols

• Further refinement of test methods and protocols
  for accelerated testing (working group early
  2005, scientists, industry WHO)
• Capacity strengthening for laboratory and field
  testing
• Facilitating access to information on long-
  lasting efficacy under programme conditions

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Priorities for facilitating technology access and
scaling-up local production

• Insecticide incorporated multifilament yarns
  (polypropylene, polyester...)
• Kits for long-lasting dipping of nets already in
  use or for treatment of finished nets at factory
  level
• Possible use of weaving machines to produce
  long-lasting netting materials
• Assessment of potential for local production of
  LLINs in Africa (Business Plan)
• Development of standard operating procedures for
  local production
• Strengthening capacity for quality control

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Priorities for further developments, technology
transfer scaling-up local production

• Pyrethroid resistance combination of
  insecticides on LLINs to prevent or limit the
  development of pyrethroid resistance and to
  enhance mass impact of ITNs on vector populations

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Other applications (netting or weaving)

• Curtains
• Window, door and eave screening
• Jar covers (dengue)
• Screens in agriculture (shading, "netting green
  houses"..)

Photo A to Z, Tanzania
Photo Elastic Enterprise, India
Photo M. Nathan
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Photos P. Carnevale
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Protective clothing and fabrics

• Long-lasting treatment of fabrics (etofenprox,
  permethrin, repellents..)
• Clothing to prevent tick borne diseases, to
  protect travellers, refugees, military forces,
  residents in nuisance areas
• Long lasting treated hammocks for prevention of
  forest malaria
• Tsetse traps
• Curtains and screens

Photo USDA
Photo M. Coosemans
Photo Y. Séchan
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LLITMs a new approach in vector control and
personal protection

• Wide range of technologies and potential
  applications for highly targeted and selective
  application of active ingredients (insecticides,
  repellents)
• Multi-disease prevention
• Providing comfort and improving domestic
  environment as a motivating factor and a vehicle
  to deliver interventions
• Creativity, inter-activity and multi-sectoral
  collaboration needed

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Partnership opportunities for the development and
transfer of new technologies for local
production of LLINs
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A chain of multiple private and public partners
Pesticide industry
Extruders
Retail market
Oil industry
Marketing PSI..
Net manufacturers
Fibre industry
Netmark Plus
Technology development Production
Distribution use
UNICEF, WHO
WHO
WHO / WHOPES
NGOs
Academic institutions
National governments
Technology transfer Strengthening local industry
Enabling environment procurement
subsidy, national programmes
Research technology development
Use of public resources, partnerships
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Transfer Olyset technologyto Tanzania
African population
Retail market
Sumitomo Insecticide technology
UNICEF procurement subsidy
Acumen Fund management funding
WHO technical advice
A to Z production distribution
PSI marketing
ExxonMobil polymer
WHO, UNICEF Acumen MSH business plan
Raise interest additional capital investment
for scaling up local production stimulating
competition
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With less than 5 of nets properly treated the
way forward

• Development of LLINs to be seen as a dynamic
  process market growth, economies of scale and
  competition will result in improved performances
  and/or reduced prices
• Technology development requires innovative
  alliances and partnerships
• Private and public sectors joining forces through
  a network of collaboration
• Public resources are needed to stimulate
  technology development, strengthen testing
  capacity and facilitate technology transfer
• Industry's and private sector are instrumental
  for scaling up production and distribution of
  LLINs

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Jointly promoting public healthand strengthening
industry for
healthy children and sustainable development