Ricketts, Howard Taylor (1871-1910)

US pathologist who discovered the Rickettsia (named after him), a group of unusual micro-organisms that have both viral and bacterial characteristics. The ten known species in the Rickettsia genus are all pathogenic in human beings, causing such diseases as Rocky Mountain spotted fever and typhus.

Ricketts was born in Findlay, Ohio, and educated at the University of Nebraska and Northwestern University, Chicago. From 1902 he worked at Chicago University. In 1909 he went to Mexico City to investigate typhus, and while there he became fatally infected with the disease.

Ricketts began studying Rocky Mountain spotted fever in 1906 and discovered that the disease is transmitted to human beings by the bite of a particular type of tick that inhabits the skins of animals. In 1908, he found the causative micro-organisms in the blood of infected animals and in the bodies and eggs of ticks. In his studies of typhus in Mexico, Ricketts demonstrated that the micro-organisms are transmitted to humans by the body louse. Before he died from the disease, he also showed that typhus can be transmitted to monkeys, and that, after recovery, they are immune to further attacks.