Ricketts, Howard Taylor

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(b. Findley, Ohio, 9 February 1871: d. Mexico City, Mexico, 3 May 1910)


In his short and brilliant career Ricketts pioneered research on a group of diseases that were later named after him. The rickettsial diseases are those caused by obligate, intracellular, parasitic, and pleomorphic microorganisms. Ricketts brought them to the attention of microbiology. He provided the basis for a rich understanding of Rickettsia by working intensively with Rocky Mountain spotted fever and Mexican typhus fever. The genus now includes all the very small, gram-negative, bacterium-like organisms found in arthropods and capable of transmission to some vertebrates. Difficult to stain, with Machiavello’s technique, Rickettsia appears red against a bluish background. Henrique da Rocha-Lima named them in honor of Ricketts in 1916, and fundamental explorations of the genus were made by S. B. Wolbach shortly thereafter.

Ricketts, the son of Andrew Duncan and Nancy Jane Ricketts, was born on a farm. A husky and vigorous youth, he was motivated by deep Methodist conviction. In 1890, after completing preparatory school, he entered Northwestern University. Two years later he transferred to the University of Nebraska. The panic of 1893 destroyed his family’s modest fortune, and from that time on Ricketts worked his way through school. In 1894 he entered Northwestern Medical School. His patron, W. H. Allport, helped him secure employment there in the medical museum.

During his third year of medical school, Ricketts suffered a nervous breakdown. After his recovery he interned at Cook County Hospital, and in 1898 he received a pathology fellowship at Rush Medical College. In 1900 he married Myra Tubbs.

At the suggestion of L. Hektoen, head of the pathology department at the University of Chicago. Ricketts studied in Berlin, where his son, Henry, was born. He later went to the Pasteur Institute. These experiences in Europe perfected Ricketts’ laboratory techniques and gave him a broader appreciation for theoretical microbiology.

In 1902 Ricketts became associate professor of pathology at the University of Chicago. His research there on blastomycosis was published in Infection. Immunity, and Serum Therapy (1906). When Ricketts traveled to Missoula, Montana, in the late spring of 1906, his vacation in the Rockies led to unexpected and exciting work. Accounts of a deadly spotted fever intrigued him, and he immediately began examining patients. He learned that the disease was geographically quite restricted and that 80 to 90 percent mortality rates were not uncommon.

The infective agent of spotted fever was thought to be Piroplasma, and several modes of transmission were suspected. Over the next three years Ricketts showed that the tick Dermacentor andersoni was responsible for transmission, but he failed to find Piroplasma and thus began to formulate a new theory. His work upset several real estate agents who were concerned lest land prices drop. One entomologist from the U.S. Department of Agriculture denied emphatically that the tick was responsible. By 1909 Ricketts thought he had seen the causative bacillus, and he outlined a control program that he hoped would destroy the reservoir of the disease. He based his ideas on the successful model of Texas tick fever that had been worked out by Theobald Smith and others. Although there were too many natural hosts for control to be effective, Ricketts’ techniques and ideas were bringing him closer to the truth.

In 1910 Montana suffered an outbreak of typhoid fever and smallpox, and money ordinarily spent on preventing spotted fever was diverted to fight these other diseases. Ricketts thus accepted an invitation to examine typhus in the Valley of Mexico. Similarities between typhus and spotted fever would perhaps provide him with the key to the etiology of the diseases. He discovered that lice transmitted the fever, and he worked closely and rapidly with severely infected patients. He and two associates contracted the disease and Ricketts died. He had shown, however, that typhus (tabardillo) was distinct from spotted fever. He was buried in Kirkwood, Illinois.

Ricketts also pioneered the use of laboratory animals for inoculation experiments and disease identification. His work on immunity and serums became the basis for further advances in vaccine development. Wolbach of the Harvard Medical School wrote an apt eulogy: “Ricketts brought facts to light with brilliance and accuracy and indicated by the methods he used, most of the major lines of development subsequently employed in the study of rickettsial diseases.”


The Howard Taylor Ricketts Memorial Collection in ten boxes is in the Harper Memorial Library, University of Chicago. Important photographs, letters, drawings, and laboratory notes and protocols are reproduced in a family scrapbook on loan to the archives of the Rocky Mountain Laboratory (National Institute of Allergy and Infectious Diseases) in Hamilton, Montana. This scrapbook was assembled by the family in 1941 and materials relating to typhus were added in 1947. A permanent collection of Ricketts’ work is: Contributions to Medical Science by Howard Taylor Ricketts 1870–1910 (Chicago, 1911).

Secondary citations are in Frank L. Horsfall, Jr., and Igor Tamm, Viral and Rickettsial Infections of Man, 4th ed. (Philadelphia, 1965), 1059–1129. Also see Selected Papers on Pathogenic Rickettsia, Nicholas Hahon, ed. (Cambridge, Mass., 1968), xv-xxiii, 27–36, 41–46.

Pierce C. Mullen

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