Dr. Finlay, in a reprint from the Journal of the American Medical Association, April 19, 1902, says:
The final confirmation of the rôle which appertains to the culex mosquito deso (now included in the genus stegomyia of Theobald) in the transmission of yellow fever, has now been sanctioned by the experiments of Drs. Reed, Carroll, Agramonte and the lamented Dr. Lazear, at Quemados de Marianao, during the winter of 1900, and afterwards by those of Dr. Guiteras at the Experimental Station of Las Animas, last summer, and finally by the splendid practical results obtained by the Chief Sanitary Officer of Havana, Major W. C. Gorgas, during the epidemic year which has just been completed. With those facts and the ones which I had gathered in former years, it is now possible to determine with some degree of precision the conditions which are necessary in order that yellow fever may develop in an epidemic form in a given locality, not too highly situated above the sea level and where temperatures between 25° and 35° C. (77° and 95° F.) either temporarily or habitually prevail.
Dr. Reed and I discussed on several occasions the possibility of making practical application of his discoveries. It did not seem to us possible to destroy the adult mosquito in sufficient numbers to be of any practical use. And we were not sufficiently familiar at that time with the life history of the mosquito to think of any other way in which the subject could be approached with a fair prospect of success.
We, of the Sanitary Department, after a great deal of discussion and thought given to the matter, decided that we should adopt all measures that seemed likely to be useful, being guided in our plans principally by the life history of the mosquito.
After the first two cases—in all some twenty-six—all the Board’s cases had been very light. We concluded, therefore, that our strongest measure would be vaccination; that is, to have an infected mosquito bite a non-immune and give him a light case. If this proved as successful as had vaccination in smallpox, we could see that this measure alone would entirely protect against yellow fever, just as had vaccination against smallpox. We consulted the military governor, General Wood, on the subject, and he agreed to let us try it as one of the several preventive measures which we were putting into effect against yellow fever.
We announced that we were ready at Las Animas Hospital to immunize against this disease anyone who wished to be treated in this way. There was no lack of applicants. This was in February, 1901. Most of the work of the Army Board had been done during the preceding fall, and at this time we had only one infected mosquito left, which had been given us by Dr. Reed. This old lady was a veteran in every sense. She had given several people yellow fever, but her greatest claim to celebrity was the fact that it had been fifty-seven days between the first case of fever and the last one which she had given.
The weather is cool in Havana during January, February and March, so that the stegomyia under ordinary conditions become quite sluggish in their movements and a great many die. Mosquitoes decrease so much during these months that yellow fever becomes more or less rare, and it was very difficult for us to infect our mosquitoes. While for one hundred and forty years there had never been a single month in which there had not been some reported case of yellow fever in Havana, still only a very small proportion of these cases was recognized during the first three days, and it must be remembered that a mosquito has to bite within that period of the disease in man to become infected. We were, therefore, keeping our only infected mosquito with a great deal of care and tenderness, knowing that we had to depend upon her to start our vaccination work.
In all Havana there is probably not a single fireplace or other means of artificial heat, so we sent to the United States and imported an oil-stove wherewith to keep her ladyship’s room always at summer temperature. Her home was a large glass jar on a table in the center of a sunshiny room. In this jar was hung a lump of white sugar on which she fed when hungry, and to this was added now and then a small piece of banana. A small vessel containing water was also kept in the jar. In order that she might have a plentiful supply of fresh air, the glass top was not placed upon the jar, but a sleeve of mosquito-netting was tied over its top.
Within the last fifteen years a great deal of study has been given to mosquito life. It is now known that there are some seven hundred different species of mosquitoes; that in all species of mosquitoes the natural food is the various vegetable juices. In all species the female has to have a feed of blood before she can lay eggs. Blood does not seem to be necessary for life, but merely stimulates the function of ovulation. In order that the female may get this blood, she is furnished with biting apparatus not possessed by the male. The male never bites, not being physically able to do so. The female stegomyia, therefore, is alone concerned in the transmission of yellow fever.
Las Animas Hospital being the yellow-fever hospital for the city of Havana was a center of attraction for most of the doctors of the Health Department. Dr. John W. Ross, Dr. John Guiteras and myself were at this hospital almost every day. Dr. Guiteras had charge of the vaccination work and of the laboratory where the mosquitoes for this work were being bred. Our lady mosquito was therefore directly under his charge. She had given so many people yellow fever and was therefore so valuable for our prospective work that we all when at the hospital would drop in to see how she was coming along and to pay our respects.