Transcript Malaria Control and prevention

Malaria control
and prevention
Controlling malaria.
• When trying to control malaria there are three main
approaches that you can take:
• Control against the adult mosquito
• (stopping people from being bitten by them)
• Control against the eggs and larve
• (to stop the adult mosquito from being born)
• Control against the plasmodium
• (by treating people)
1. AGAINST ADULT MOSQUITOES
INSECTICIDE
SPRAYS
(SUCCESSFUL…BUT)
INSECTICIDE
TREATED BED
NETS
GENETIC
ENGINEERING
(VERY LIMITED SUCCESS)
(VERY SUCCESSFUL)
DDT
STERILE
MALES
KILLER
MALES
Insecticide sprays
• This is when the
chemical DDT is sprayed
on the walls of homes.
• This is the most widely
used method and it is
recommended by the
WHO.
• Sprays must be applied
repeatedly for long term
effectiveness.
Insecticide sprays
• DDT is unfortunately
poisonous to humans.
• It can get into water
supplies and can be
passed on to young
children through breast
milk.
• MOST IMPORTANTLY:
• The mosquitoes can
quickly become immune
to the chemical making
the spraying worthless.
• Even though it is cheap
very poor villages can
not afford to pay for this
treatment.
• The effect of stopping the use of DDT in Sri Lanka (Ceylon). Was the
banning of DDT one of the costliest mistakes of all time?
• One estimate suggests that 50 million children have died of malaria
since the use of DDT was greatly reduced in the 1960s.
Effectiveness of DDT
• There is no denying that DDT can be effective as the
graph on the last slide highlighted.
• Also there was around a 60% drop in cases of
malaria when D.D.T. was introduced to Ecuador in
1993 and a 90% increase when it was withdrawn
from Bolivia in 1993.
• Overall it is a good method but can’t halt the spread
of malaria entirely.
A simple mosquito net.
Mosquito net
• Mosquito nets are a
great way to combat the
spread of malaria.
• First of all they
physically stop the
mosquito from landing
on you when you sleep
and feeding.
Mosquito net
• The women in this
picture are treating the
mosquito net with
insecticide.
• The most common
chemical to use is
Permethrin, which is
harmless to humans,
but deadly to
mosquitoes.
Mosquito net
• This is a very popular
way of combating
malaria with the charity
“Roll back malaria”
• It can be extremely
effective but it is up to
three times as
expensive as DDT.
• Several African
countries are endorsing
this method and
removing tax on the
nets.
Genetic engineering
• Labs produce sterile male mosquitoes so that the
breed die out.
• This is very time consuming and it can not be
replicated on a large scale.
2. AGAINST EGGS AND LARVAE
PHYSICAL
CHEMICAL
DRAINING
BREEDING
SITES
SPRAYING
WITH
LARVICIDES
BIOLOGICAL
ADDING OIL, EGG
WHITES OR
MUSTARD SEEDS
FLUSHING
BREEDING
SITES
ADDING FISH TO
PONDS AND PADI
FIELDS
PLANTING
EUCALYPTUS
TREES
ADDING Bti
IN
COCONUTS
PHYSICAL CONTROL
Flushing
out breeding
by weekly
release
Draining
breedingsites
places:
because
Planting
Eucalyptus
trees
to absorb
excess
of
water
can
drown
the
larvae,
but
can
only
be
mosquitoes need so little water in which
to lay
water
from
the soilareas
helps and
drain
breeding
sites.
done
in
suitable
where
there
their eggs, it can be virtually impossible is
to
surplus water.
Draining/flooding stagnant water
• In theory this is a good idea. However the scale on
which it would have to be done is too great.
• Pools of water would have to be drained once every
5-7 days as the mosquito breading period is 8-10
days.
• Mosquitoes only need a pool of water the size of a
footprint to breed so it is unlikely that all pools of
water would be drained.
• Also LEDC can’t afford to empty their reservoirs on
a regular basis.
Spraying with Lavicides
• This is very similar to the spraying of DDT but on to
the breeding grounds.
• It suffers from the same success’ and failures of
DDT as well as the fact that it is unlikely that all
pools of water will be found.
BIOLOGICAL CONTROL
Can you think
of any other
benefits of this
method?
Adding larvae-eating fish, such as the Muddy
Loach, to padi fields and pools, can clear
them of larvae within a day.
Adding larvae eating fish
• Although it is initially expensive it can provide a
source of food for local people.
• Unfortunately it can endanger local wildlife species.
A number of techniques can be
used to drown the larvae
Drowning Larvae
• Adding mustard seed to the water will drag the
larvae down.
• Spraying the water with egg whites clogs up the
breathing system of the larvae.
• Spraying oil on the water also causes them to
suffocate.
After all the problems with effectiveness that
we have looked at what do you think the
limitations of these methods could be?
BIOLOGICAL CONTROL - Bti
The bacillus Bti (Bacillus Thuringiensis Israelensis !!!)
can be incubated in coconuts, where it multiplies. The
coconuts are then broken open and thrown into pools,
where the bacilli are eaten by the mosquito larvae. They
kill the larvae by destroying its gut.
The
incubation
stage
Adding
to
pools
Spraying Bti
from a boat
BIOLOGICAL CONTROL - Bti
You can
even buy
Bti over the
counter in
the U.S.
3. AGAINST THE PLASMODIUM…
An ingredient of Tonic Water (check in the
supermarket), Quinine was often taken with
Gin to mask its bitter taste. However, you
1.Quinine:
Originally
would need to drink about 25 Gin and Tonics
extracted
from
a day to
getthe
the recommended dose.
bark of the South
American Cinchona
(Fever Tree), it was
for a long time the
main anti malarial
drug.
AGAINST THE PLASMODIUM…
2. Chloroquine: Now
the most common anti
malarial drug, but, like
Quinine, becoming
ineffective as the
Plasmodium mutates
and becomes immune
to it.
..AGAINST THE PLASMODIUM
3. Artemisia
(Wormwood): Used as an
anti malarial herbal
remedy by the Chinese
for hundreds of years
(known there as
Qinghaoshu), it was
“rediscovered” during
the Vietnam war and
may prove to be a major
weapon in the fight
against malaria, as
plasmodium do not seem
to become immune to it.
VACCINATION
At the moment, there is no effective vaccine
against malaria, although scientists all over the
world are trying to develop one.
New discovery
• A recent discovery has been made in a vaccine that
claims to half the chances of a human contracting
malaria.
• There is no proven test yet but initial findings are
positive.
• The WHO has admitted the battle against malaria is
currently being lost and the must do more to stop it.
It is clear that the problems will not stop any time
soon.