Options for malaria vector reduction

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Options for malaria vector reduction

• Larval Stage
• Source reduction
• Larviciding
• Biological control
• 2. Adult Stage
• Insecticide Treated Nets
• Indoor Residual House Spraying
• Repellants
• House improvements

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Biological Control

• Use of natural enemies to regulate pests
  population at a lower level than would occur in
  its absence
• BC control measures involve the introduction of
  various pathogens and predators
• Such agents range from viruses, bacteria, fungi
  and nematodes to natural predators such
  larvivorous fish

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Success of BC

• BC is not 100
• Despite this, BC has a great potential and can
  produce spectacular results when and where
  appropriately executed
• Careful application of other control measures as
  Integrated Vector Control is desirable

• In medical/ veterinary entomology, BC has limited
  success than in agriculture
• Reasons Include
• Lack of any real data on threshold
• High variability of disease /vector relations
  among different areas
• Targeted against immature stages
• Difficult sampling
• Complexity of aquatic systems
• Lack of research

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Desirable Characteristics of BC organisms

• Should be good searcher and disperser
• Able to regulate is host at low densities
• Should have a high reproductive rate
• Life cycle of the natural enemy must be well
  synchronized with that of the host
• Should be able to persist in the environment in
  the absence of its primary host (able to utilize
  alternative food)
• Should specific to the host
• Easy to culture colonize

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BC with Fish

• Of all the biological control methods, the use
  larvivorous fish has been the most successful in
  many parts of the world
• Hundreds of spp are used to control various spp
  of mosquitoes around the globe and using
  indigenous fish remained to be the best option.
• There are certain traits that make fish species
  a good candidate for mosquito control

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Use of fish against mosquitoes

• Fish were first proposed as mosquito control
  agents in the late 1800s
• The most widely used fish, Gambusia, was
  introduced in the US (Hawaii), the Philippines,
  Japan, Spain, Italy, then to Africa and elsewhere
• In Somalia, the idea of larvivorous fish use
  dates back to the colonial era against Aedes
• Early 1970s biological control by using
  larvivorous fish gained momentum and NMCP
  undertook massive search
• Seven genera of Nothobranchius , Oreochromis and
  aphainus were identified

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Desirable traits

• Fish must eat mosquito larvae
• Behavioral and physical adaptation for surface
  feeding
• Small size
• Mode of reproduction (short maturation and high
  fecundity)
• Hardiness, disease resistance and adaptability

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Gambusia

• Most widely used biological control agent for
  mosquitoes and probably the most widely used
  fresh water fish in the world
• Proposed as mosquito control agent in the late
  1800s
• Best in small permanent water bodies
• Very aggressive fish (attack native fish)
• Give live birth (3-6 cm)

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Good BC

• Opportunistic feeders and can survive by feeding
  on another prey in the absence of mosquitoes
• Voracious predators on mosquito larvae
• Rapid increase in population density
• Easy mass production (15)
• Broad tolerance to temperature changes, salinity,
  organic pollution, overcrowding and poor food
  supply
• Small size good disperser

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Negative factors

• Handicapped by vegetation
• Difficult to maintain effective numbers in
  running water
• Some breeding habitats of important vectors may
  not be accessible/suitable for the fish
• Not compatible with insecticides
• Population reduced by predators

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Oreocromis spilurus spilurus

• East Central Africa formerly known as Tilapia
• Indigenous fish successfully used in Somalia
• Somali Government, WHO/EMR and TDR (1980-82) in
  Buroa district
• Collected from permanent streams in Behin
• Carry eggs in the mouth
• 1 fish/3 square meters
• Very effective in vector reduction
• Extremely rapid growth (16-20cm)

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Nothobranchius

• East Africa
• Annual or kilifishes
• Spawns on substratum
• Drought resistant eggs
• Ideal for temporarily flooded pools (wars)
• Immediate hatching of eggs with first rains
• No re-stocking required
• Easy transportation and seeding (2 fish per
  square meter)

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Aphanius dispar

• Fresh water, brackish and marine
• Widely distributed (Egypt, Yemen, Somalia,
  migrated through the Suez Canal to the
  Mediterranean also in Persian Gulf-Iran, India
• Mainly herbivorous
• Spawn in areas with floating debris
• Rapid growth rate (size of 5-7cm)
• Studies supported by TDR in UAE
• In Somalia used in the central regions and
  coexisted with Oreochromis

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Collection

• A dip net on a small scale
• Minnow seines for large numbers
• Both collect every thing (content sorted out)
• May cause bruises, scrapes (not kill but can
  cause fetal fungal infections)
• Mosquito nets, Minnow traps

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Transportation

• Variety of container including boxes, plastic
  containers(Jeri cans, bags)
• Regardless of the container used, it should be
  screened to avoid jumping
• Plastic bags reduce the injury
• Should not be fed on the day before or the day of
  transportation to prevent waste build-up in the
  container
• Anesthetic have been added to the water to slow
  metabolism and decrease activity

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Adel Al-Balisha