. Elementary textbook of economic zoology and entomology. Zoology; Insect pests. 374 ECONOMIC ZOOLOGY AND ENTOMOLOGY quito and in no other way. Since that time many other ex- periments have been made, and it is now definitely known how this disease spreads through an infected region. The virus that causes the fever occurs in the blood plasma of the human host, but the yellow-fever patient is a source of infection for the mosquito only during the first three or four days after the fever manifests itself. The virus must undergo an incubation period of twelve to fourteen days in the mosquito befo
. Elementary textbook of economic zoology and entomology. Zoology; Insect pests. 374 ECONOMIC ZOOLOGY AND ENTOMOLOGY quito and in no other way. Since that time many other ex- periments have been made, and it is now definitely known how this disease spreads through an infected region. The virus that causes the fever occurs in the blood plasma of the human host, but the yellow-fever patient is a source of infection for the mosquito only during the first three or four days after the fever manifests itself. The virus must undergo an incubation period of twelve to fourteen days in the mosquito before she is capable of transmitting the disease. After this incubation period the mosquito is infective for the rest of her life. The parasite. FIG. 164.—Yellow-fever mosquito, Stegomyia fasciata. (About eight times natural size.) that causes the disease has never been seen, probably because it is too small, but it is believed that it is one of the large group of Sporozoan parasites. One of the members of the Yellow Fever Commission died of yellow fever during the course of the experiments, and another member contracted the disease but recovered. The applica- tion of the knowledge gained by these studies enabled the officers soon to check the epidemic of yellow fever then existing in Cuba. A few years later when the disease appeared in virulent form in New Orleans it was stamped out in a re- markably short time by waging a ceaseless war against the mosquitoes. The Panama Canal Zone has long been regarded as one of the worst regions in the world for yellow fever and malaria. Since the United States began work on the Canal persistent efforts have been made to control the mosquitoes there. These efforts have been so successful that there has been no yellow fever in the Canal Zone for several years, and cases of malaria are comparatively Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and
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