INSECTS AS CARRIERS OF DISEASE
[Sidenote: Some insects that carry disease]
Certain diseases are given to human beings by the bites of insects.
We know that certain ticks and mosquitoes carry certain germs. It
is also probable that disease germs are transferred from diseased
to well persons by bedbugs and other insects that bite.
[Sidenote: How yellow fever is transmitted]
For a long time it was thought that yellow fever was carried
through the air, but now it has been proved that yellow fever is
not carried in this way. A well person can sleep with one who has
yellow fever and not catch the disease. Yellow fever infection is
carried from a yellow fever patient to a healthy person only by a
certain mosquito. Keep this mosquito away from the yellow fever
patients and there can be no spread of the disease.
[Illustration: FIG. 48. The mosquito that carries yellow fever.]
It is not many years since yellow fever was one of the most dreaded
diseases in warm countries. To-day there is not the same fear of
it, for the source of the disease has been discovered and practical
methods have been devised to get rid of the mosquito which carries
it.
[Sidenote: How malaria is transmitted]
Malarial fever is another disease transmitted by the bite of a
mosquito, but the mosquito that carries malarial fever is not
the same as the one that carries yellow fever. For a long time
it was supposed that malaria came from the gases which rise from
marshes. To-day it is known that it is not the gases that cause
the sickness, but a mosquito which lives and grows in the marshes.
Many countries that have heretofore been practically worthless on
account of malarial fever, are being made valuable by draining the
marshes and doing away with places where mosquitoes can hatch.
[Illustration: FIG. 49. One of the places where mosquitoes hatch.]
[Sidenote: How to get rid of the mosquito]
It might seem a very hard task to get rid of mosquitoes in
countries where there are so many of them; but it can be done.
The mosquito must have still water in which to lay her eggs. In
countries where there is danger of yellow fever or malaria, the
rain barrel and the cistern should be screened, and the swamps and
water holes filled up. Puddles of water should not be allowed to
form anywhere, and low places where water might stand should be
drained. By giving her no place in which to lay her eggs, we can
get rid of the mosquito; and when the mosquito disappears, yellow
fever and malaria disappear also.
[Sidenote: How wood-ticks transmit disease]
In certain portions of Montana, Washington, Idaho, Utah, and
Wyoming, there is a peculiar disease known as Rocky Mountain
spotted (tick) fever. It is now known that this disease is
transmitted to people by the bite of a wood-tick. Not all
wood-ticks carry this fever, and for people living in districts
where this disease does not exist there is no danger in the bite
of a wood-tick; but in a part of the country where the disease
prevails, the wood-tick should be avoided.
[Sidenote: How disease-bearing insects can be destroyed]
All insects that are known to transmit diseases can be destroyed.
If we will do away with stagnant water, the mosquito cannot hatch;
if we will cut out underbrush and oil the domestic animals, the
wood-tick will not find a place to grow. If we wish to get rid of
disease, we must spend money and labor; but it is worth while, for
human life is at stake.
=Questions.= 1. What insects are known to transmit diseases to
man? 2. How is yellow fever transmitted? 3. Malarial fever? 4.
What disease is transmitted by the wood-tick? 5. How can we get
rid of the mosquito? 6. How can we get rid of ticks?
=Remember.= 1. It is a proved fact that diseases are transmitted
to man by the bites of mosquitoes and wood-ticks. 2. It is
possible to do away with both the mosquito and the wood-tick
almost completely, although it requires a great deal of work and
the expenditure of a large amount of money. 3. Health is the most
valuable thing we have, and it is foolish to hesitate in giving
the work and money necessary to exterminate disease-bearing
insects, as well as the many other causes of sickness.