Handbook of Medical Entomology

by William A. Riley; O. A. Johannsen

Methods of control of various diseases have been revolutionized by the discovery that they were insect-borne, but in no other case has the change been as radical or the results as spectacular as in the case of yellow fever. The "shot-gun quarantine," the sufferings and horrors, the hopelessness of fighting absolutely blindly have given way to an efficient, clear-cut method of control, based upon the knowledge that the disease is carried from man to man solely by the mosquito, Aëdes calopus. The lines of defense and offense are essentially as follows:

In the first place, when a case of yellow fever occurs, stringent precautions must be adopted to prevent the infection of mosquitoes and the escape of any already infected. This means that the patient must be removed to a mosquito-proof room, or ward beyond reach of the insects, and that the infected room must be thoroughly fumigated at once, to kill the mosquitoes hiding within it. All cracks and openings should be closed with strips of paper and fumigation with burning sulphur or pyrethrum carefully carried out.

It should be remembered that if the first case noted is that of a resident rather than imported, it means that the mosquito carriers became infected more than two weeks before the case was diagnosed, for as we have seen, the germ must undergo a twelve-day period of development within its insect host. Therefore a careful search must be made for mild cases which, though unrecognized, may serve as foci for the spread of the disease.

In face of a threatened epidemic one of the most essential measures is to educate the citizens and to gain their complete coöperation in the fight along modern lines. This may be done through the schools, the pulpit, places of amusement, newspapers and even bulletin boards.

Emphasis should be placed on the necessity of both non-immunes and immunes using mosquito curtains, and in all possible ways avoiding exposure to the mosquitoes.

Then the backbone of the fight must be the anti-mosquito measures. In general, these involve screening and fumigating against adults, and control of water supply, oiling, and drainage against the larvæ. The region involved must be districted and a thorough survey undertaken to locate breeding places, which must, if possible, be eradicated. If they are necessary for water supplies, such as casks, or cisterns, they should be carefully screened to prevent access of egg-laying adults.

The practical results of anti-mosquito measures in the fight against yellow fever are well illustrated by the classic examples of the work in Havana, immediately following the discoveries of the Army Commission and by the stamping out of the New Orleans epidemic in 1905.

The opportunities for an immediate practical application of the theories of the Army Commission in Havana were ideal. The city had always been a hotbed of yellow fever and was the principal source from which the disease was introduced year after year into our Southern States. It was under martial law and with a military governor who was himself a physician and thoroughly in sympathy with the views of the Commission, the rigid enforcement of the necessary regulations was possible. The story of the first campaign has been often told, but nowhere more clearly than in Dr. Reed's own account, published in the Journal of Hygiene for 1902.

Closer home was the demonstration of the efficacy of these measures in controlling the yellow fever outbreak in New Orleans in 1905. During the spring and early summer of the year the disease had, unperceived, gained a firm foothold in that city and when, in early July the local Board of Health took cognizance of its existence, it was estimated that there had been in the neighborhood of one hundred cases.

Conditions were not as favorable as they had been under martial law in Havana for carrying on a rigid fight along anti-mosquito lines. The densely populated city was unprepared, the public had to be educated, and an efficient organization built up. The local authorities actively began a general fight against the mosquito but in spite of their best efforts the disease continued to spread. It was recognized that more rigid organization was needed and on August 12th the United States Public Health and Marine Hospital Service was put in absolute charge of the fight. Up to this time there had been one hundred and forty-two deaths from a total of nine hundred and thirteen cases and all of the conditions seemed to threaten an outbreak to exceed the memorable one of 1878 when, as we have seen there were four thousand and forty-six deaths.