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.
Fig. 49. One of the places where mosquitoes hatch.
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.
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.
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?