slide of blind man led by child - california state water ......public health importance • 25...
TRANSCRIPT
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Slide of blind man led by child
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Onchocerciasis = river blindness
• caused by the parasitic roundwormOnchocerca volvulus
• transmitted by female black flies of the Simulium damnosum complex
• Solution: control the vector (the black fly)
• Solution: control the parasite through chemotherapy with ivermectin
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Slide of parasite
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Slide of abandoned villages
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Control of Onchocerciasis
• United Nations Development Program, World Bank, and World Health Organization funded theOnchocerciasis Control Program in 11 West African countries, 1974-2002 (extended to 2007)
• Goal: Control river blindness, resettle abandoned valleys, increase food and crop production, raise GNP, and reduce severity of future droughts
• African Program for Onchocerciasis Control in 19 central African countries, 2000-2010
• Goal: Disease elimination through drug therapy
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Onchocerciasis Control Onchocerciasis Control Programme Programme (OCP)(OCP)
African Programme for African Programme for Onchocerciasis Control Onchocerciasis Control (APOC)(APOC)
MOROCCO
Former Spanish Sahara
MAURITANIA
MALISENEGAL
THE GAMBIA
GUINEA BISSAU GUINEA
SIERRA LEONE
LIBERIA
CÔTE D’IVOIRE
BURKINA FASO
GH
ANA
TOGO
BEN
IN
NIGERIA
NIGER
ALGERIA
TUNISIA
LIBYAARAB REP. OF EGYPT
CHAD SUDAN
CAM
EROO
N
CENTRAL AFRICAN REPUBLIC
ERITREA
ETHIOPIA
DJIBOUTI
SOMALIA
KENYAUGANDA
RWANDA
BURUNDICO
NG
O
GABON
EQUATORIAL GUINEA
SAO TOME AND PRINCIPE
ANGOLA
NAMIBIABOTSWANA
ZAMBIA
TANZANIA
MALAWI
ZIMBABWE
MOZA
MBI
QUE
SOUTH AFRICA
SWAZILAND
LESOTHO
MAD
AGAS
CAR
MAURITIUS
COMOROSMAYOTTE (Fr.)
SEYCHELLES
CAPE VERDE
DEM. REP.OF CONGO
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Strategy of Vector Control:The First Approach
• stop black fly transmission of parasite to humans
• over time, the human “reservoir” of parasites decreases
• 9-11 year parasite life cycle, 14-20 years of insecticide applications needed
• 30,000 miles of river sprayed weekly
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Helicopter spraying
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Slide of insecticides used
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Fish are the Essential Protein Source in this Region
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Slide of monitoring stations
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Evaluation of Fish
• species richness and composition• catch per unit effort• size distribution• population densities• condition factor (length-weight relationship)
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Evaluation of Benthic Macroinvertebrates
• species richness and composition• densities• night-time invertebrate drift patterns• recovery of sensitive species• toxicity tests (black flies and non-target
organisms)
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Slide of gutters
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Slide of stream gutters
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Socio-Economic Impact of Controlling River Blindness
• onchocerciasis is no longer a disease of public health importance
• 25 million onchocerciasis-free hectares (67.5 million acres) are now being resettled
• food production has increased to support 17 million additional people
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Slide of Leraba
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What is the environmental sustainability of resettlement in
onchocerciasis-free areas?• resettlement is spontaneous, little
infrastructure such as schools or roads exist• settlers try to occupy largest possible areas• few sustainable soil, water, fisheries, or
crop-management techniques are practiced
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Habitat Assessments
• conducted at all sites where fish and benthic macroinvertebrates are collected
• existing habitat is compared to descriptions that describe optimal, suboptimal, marginal, or poor conditions
• within each category, a high, medium, or low score is applied
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At the program’s inception an “environmental catastrophe”
resulting from the large-scale, long-term applications of
insecticides to West African Rivers was feared
Were the fears justified?
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Concepts of River Zonation
• Fish and invertebrate communities occur in different river zones
• Therefore, application of insecticides could eliminate taxa and change ecological status
• However, in African rivers, there are no species replacements; species richness increases downstream
• Species are distributed over large areas; recolonization potential is high
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Insect life cycles in tropical Africa were unknown
• 4-12 weeks for hydropsychidcaddisflies and dragonflies
• Adult life of aquatic insects is longer
• Recolonization occurs more rapidly than expected
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Boundary Layer Concept
• Boundary layer is 1-3 mm thick; affects contact and uptake of insecticides
• Non-target benthos should have higher uptake than black fly larvae
• Flow is complicated; boundary layer is transient and very thin
• Insecticide contact should be higher for black flies than for non-target organisms
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Rivers are in an equilibrium condition
Rivers are driven by disturbance, no steady state or equilibrium
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Monitoring was based entirely on on fish and macroinvertebrates
• Dynamic aspects of river discharge, metapopulations, and biota should be studied as part of an overall assessment
• Today, a systems approach would be used(Mekong River Commission)
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Water flow downstream (quantity, quality)
Water flow upstream (quantity, quality)
Industrial & urban waste
diversion
Flooding
transportation Dam
Fisheries
irrigation
agricultural runoff
Forests
Mekong River
Basin EcosystemL. Bêche
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Mekong River: Evaluating Effects of Large Dams
• Biological Assessment• In-stream flows• Ecological risk assessment• Water quality• Sediment toxicity
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Bioassessment
• Fish• Benthos• Zooplankton• Algae• Macrophytes• Primary Production• Respiration
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Lessons Learned from West African Biomonitoring
• Large-scale programs start from political decisions, not necessarily with a scientific basis
• Programs hindered by what cannot be done (higher-level identifications) and tradition (sampling devices)
• Monitoring can only tell us so much; a complementary research program reveals underlying effects
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Slide of end of road
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Outcomes of OnchocerciasisControl
• African Program for Onchocerciasis Control now in 19 more countries (ivermectin only, Merck donation)
• coordinate distribution of drugs for lymphatic filariasis (SKB donation)
• potential distribution of anti-malaria nets• reductions in parasitic-induced anemia
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