Auut1,11 H AAM AA uut1,13


The fight against mosquitoes probably will never end on the
 Canal Zone, The examination of stagnant water for the
 larvae is being made here under the direction of one of the
 sanitation experts of the Health Department.
were rarely completely empty and served to
make Aedes breeding continuous throughout the
year.
 In very recent years it has been learned that
there exists, perhaps throughout most of tropical
South America, a form of yellow fever in the
transmission of which the Aedes aegypti may at
times play no role, and which disease may have
jungle animals for its natural reservoir rather
than man. Monkeys have been found to be
infected with jungle yellow fever, and several
varieties of jungle mosquitoes have been found
to be infected with the virus. Whether this
jungle yellow fever is of recent origin or has per-
sisted for centuries in tropical America is largely
of academic interest. It is of considerable signifi-
cance, however, that when introduced into
urban populations, in the presence of Aedes
aegypti, the disease may assume its classical
epidemic form.
 That malaria is also a mosquito borne disease
was demonstrated forty years ago. Instead of one
variety of mosquito carrier, however, it was
learned that malaria is transmitted by various
members of a large family of mosquitoes, the
Anopheles, whose life habits and' habitats differ
greatly, thereby rendering more complex the
methods of extermination and greatly increasing
the magnitude of prevention measures.
 In all tropical and in most sub-tropical coun-
tries, malaria is, a one time or another, an out-
standing cause of sickness and death. On the
Isthmus, since the beginning of history, malaria
has caused more disabling illness than any other
single disease. Several factors contributed to the
continued prevalence of malaria: an almost uni-
versal infection of the native population with
chronic malaria; large collections of naturally
impounded water in lowlands or along the banks
of sluggish streams furnishing economically un-
controllable breeding places for mosquitoes; and,
of greatest importance, the introduction through

Page thirty-four


the centuries, of continuous influxes of suscep-
tible persons.
 The sanitarian's attack upon malaria has been
carried on with one practically unattainable
object-the complete riddance of malaria from
the Zone. The plan of attack that has been con-
sistently followed consists of: Anti-mosquito
screening; removal, in so far as possible, of entire
settlements of infected natives to sites outside
the Zone; prompt treatment of all persons suffer-
ing from malaria; attempted medical prophy-
laxis; and attempts at mosquito eradication by
preventing their breeding. That this combined
method of attack has been successful is evident
from the gradual, but yearly demonstrable, dim-
inution in the rate of infection, so that in recent


One of the forms of malaria control which has proved effective
 on the Isthmus is spraying open ditches or other places
 where standing water provides a breeding place for malaria
 carrying mosquitoes. This worker is engaged in this type of
 work. During the construction days this was most impor-
 tant. This picture was taken in 1910 at Miraflores.

years it has become commonplace to hear the
statement, "This is the best malaria year in
history."
 In a campaign against a yellow fever epidemic,
prompt destruction of the Aedes mosquito is of
paramount importance and relatively easy. In a
campaign against malaria, however, destruction
of the Anopheles mosquitoes, in terrain such as


August 15, 1914


THE PANAMA CANAL


August 15, 1939