STUDIES ON TYPHUS FEVER VIII. TicI~s As A POSSIBLE VECTOR OF THE DISEASE FROM ANIMALS

In his study of the epidemiology of typhus in the southern United States, published in 1926, Maxcy (1) came to a number of important conclusions, the most significant of which was that the epidemiological characteristics observed by him were at variance with the idea that the disease is kept alive by man to man transfer through lice. He suggested at that time, on the basis of case studies, that there might be an animal reservoir of infection, possibly in rodents--rats or mice from which the disease is occasionally transmitted to man. The most likely manner of such transmission, of course, would be by means of an insect, and in a previous study by the writers of this paper (2) experiments were reported on the infection of bedbugs with typhus virus, an insect which was investigated as the most likely possibility suggested by Maxcy's results. I t was found at that time that bedbugs experimentally infected per rectum or permitted to feed on benzol-treated typhus rats could harbor the virus in potent form for from 5 to 9 days (the limits of the actual experiment). The viscera of such bedbugs injected into guinea pigs produced typical typhus infection with Rickettsiae, subsequent immunity to both European and Mexican typhus and characteristic brain lesions. We did not succeed in transmitting the disease to guinea pigs by the natural process of allowing the infected bedbugs to feed upon them. But the guinea pig is more resistant than man, and our cycle was in other respects complete in that we proved the possibility of natural infection of the insects and the viability of the potent virus within them for at least 9 days. These facts we took to be of considerable epidemiological importance