Malaria Control
 
A second major sanitation-related disease is malaria. A serious resurgence of
malaria is taking place in many countries. Between 300 and 400 million people
suffer from malaria, and five million die from it annually. The disease is caused
by the malaria parasite, Plasmodium falciparium (and three other Plasmodium
species), which are transmitted by anopheline mosquitoes from an infected person
to a healthy person. Tropical and subtropical regions of the world suffer the most
from malaria.
 
COMMUNITY PREVENTIVE MEASURES
 
Mosquitoes generally stay within about one mile (1.6 km) of where they hatch.
The cycle from egg laying to hatching as mosquitoes usually takes about eight
days. These facts make it easier for local mosquito eradication or control
programs to be effective. But over time, persons infected with malaria can visit
the local area or mosquitoes carrying the malaria parasite can be brought in with
vegetable baskets, water containers, etc. Therefore, to be effective, anti-mosquito
programs must be ongoing, and any spraying should be done on a regular basis.
Other community based anti-malaria activities include:
 
o   Eliminate or reduce the amount of stagnant water near the community by
    digging drainage ditches. The malaria mosquitoes must have water for their
    egg, larval, and pupal stages of development. Even small accumulations of
    water, as in wheel ruts or hoofprints of cattle may increase mosquito
    breeding if the water remains a week or more.
 
o   Plan for the elimination of standing water in new water and flood control
    projects.
 
o   "Supercharge" unlined irrigation ditches about every 6 days. To do this, raise
    the water level of the irrigation ditch three inches (8 cm) or more for a
    period of about an hour. This will cause mosquitoe larvae to float upward on
    the vegetation that lines the ditch. Do this in the morning on a sunny day.
    Then quickly drop the water level about five inches (13 cm.) or more and
    leave it at this level for several hours. The mosquito larva will be hung up
    on the dry vegetation and will die.
 
o   Develop a voluntary reporting system for persons in the community who
    develop fevers, so that health care can be provided to them, and so that
    trends in the occurrence of malaria will be evident.
 
Mosquito-eating fish can reduce the number of mosquitoes in rice fields. This is
not practical where rice cultivation includes alternate flooding and drying.
 
Regular use of mosquito-proof bed nets by all or most community inhabitants has
been shown to reduce malaria rates. Programs with community participation in
local production and repair of bed nets deserve field trials.
 
PERSONAL PREVENTIVE MEASURES
 
To reduce the probability of malaria:
 
1.  Inspect your living and sleeping quarters and install or repair screens in
    doors and windows.
 
2.  Spray the walls, floors, and ceilings of your residence with insecticides.
 
3.  Sleep under a mosquito-proof bed net.
 
4.  Use mosquito repellents when you walk in the woods or other likely
    mosquito areas.
 
To reduce the risk of malaria, you should begin taking chloroquine two weeks
prior to departing for regions of the world where malaria is found. Up to date
information on the status of malaria and drug resistance can be obtained from
references (1) and (2) below.
 
TREATMENT
 
No vaccine is currently available against malaria. Breakthroughs have been made,
but pharmaceutical availability is still many years away. The most effective drug
against malaria is chloroquine, but in some areas of the world, the parasite is
beginning to show some resistance to the drug. An alternative drug that is much
more expensive is sold under the label "Fansidar." This drug is effective, but can
cause serious allergic reactions in some people. Local health care providers should
be consulted as to what drug to use.
 
The search for a vaccine against malaria is complicated by the fact that while
Plasmodium falciparium is responsible for most malaria deaths, there are other
plasmodium species, and each species may react differently to the drugs used to
treat it.
 
In addition, the parasite goes through a series of stages of growth as it passes
from the mosquito into the human bloodstream, back to the mosquito, and then
back into a human host. Each stage requires its own separate defense.
 
For example, at one stage of the parasite's life it is called a gametocyte, a tiny
body that will produce gametes or mature sexual reproduction cells. The gametocytes
must pass into an anopheles mosquito to develop.
 
The mosquito bites a person whose blood contains the gametocytes. The gametocytes
develop in the body of the mosquito and eventually produce sporozoites,
tiny bodies that will grow into adult plasmodia. The infected mosquito then passes
the sporozoites to another human host and the cycle begins again.
 
A vaccine against the sporozoite would keep the second person from getting the
disease from the mosquito. It would not, however, defend against, say, contaminated
blood used in a transfusion, nor one of the other infectious stages of the
parasite's life.
 
The challenge to scientists is to develop vaccines that would be effective in three
different ways. One would work against the sporozoite, preventing it from
developing in its human host. Another would work against the gametocyte to
prevent its growth in the body of the mosquito. Both of these vaccines could
effectively block the transmission of the disease.
 
They would not, however, protect the person who was infected as a result of a
blood transfusion. Such a person could become ill with malaria and would then be
a source of infection to mosquitoes and ultimately to other people. Thus scientists
are also working on a third type of vaccine, which would protect against this
type of transmission.
 
In the meantime, the best protection for people living in malaria areas is to
interrupt the cycle by getting rid of the mosquitoes or by trying to keep from
being bitten. Malaria control is a community problem, not just a challenge to
science. Use the measures described above to eliminate mosquito breeding areas
around your home, farm, and community. Remember to protect yourself and your
family from the mosquitoes by using window screens and mosquito-proof bed nets.
Use mosquito repellents, and spray with appropriate insecticides where needed.
 
Sources:
 
Dr. Donald Pletsch, VITA Volunteer, Gainsville, Florida
 
Dr. Alan Greenberg, Center for Disease Control, Atlanta, Georgia
 
"Taking the Bite Out of Malaria," VITA News, January 1986, pp. 4-5.
 
References:
 
1.  Tropical Disease Office, Pan American Health Organization (PAHO/WHO), 525
    23rd Street, N.W., Washington, D.C. 20037 USA
 
2.  Malaria Division, U.S. Public Health Service Center for Infectious Diseases,
    Chamblee, Georgia 30333 USA
 
3.  "Malaria: Meeting the Global Challenge," USAID Science & Technology in
    Development Series. Boston, Massachusetts: Oelgschlager, Gunn & Main Inc.,
    1985
 
4.  Viajar con Salud, Division of Public Information, World Health Organization,
    Geneva, Switzerland.
 
5.  Manual on Environmental Management for Mosquito Control, World Health
    Organization, 1211 Geneva, Switzerland.