The Rickettsiae 379 



virus-like in that they require Hving cells for growth. They are 

 normally found only inside other living cells. The original studies 

 of Ricketts were concerned with the cause of Rocky Mountain 

 spotted fever, and a year later in Mexico he discovered the etiolog- 

 ical agent in typhus fever, also a rickettsial disease. He found short, 

 rod-like forms of organisms in the blood of patients suffering from 

 typhus, and infected lice were found harboring similar organisms 



Fig. 66. Howard T. Ricketts (1870-1910). (From Principles of 

 Microbiology, F. E. Cohen and E. J. Odegard. Copyright 1941, C. V. 

 Moshij Company, St. Louis, Missouri.) 



in their intestines. Unfortunately, during the course of his investi- 

 gations Ricketts contracted typhus and died in 1910. Typhus fever 

 should not be confused with typhoid fever which is a bacterial 

 disease caused by gram negative rods reported in 1880 by Eberth, 

 who discovered the organisms in the spleen of typhoid fever 

 patients. 



It was a Rrazilian, Rocha-Lima, who demonstrated the louse- 

 borne nature of typhus in 1916. He is also the person who named 

 the etiological agent Rickettsia prowazekii in honor of Howard 

 Ricketts and an Austrian, von Prowazek, both of whom lost their 



