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Howard Taylor Ricketts

Born  1871
Died  1910

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American bacteriologist and pathologist, born February 9, 1871, Findlay, Ohio; died May 3, 1910, Mexico City, Mexico.

Biography of Howard Taylor Ricketts

Howard Taylor Ricketts is remembered for discovering the causative organism of Rocky Mountains spotted fever and abardillo, both forms of typhus fever, and how they are transmitted.

Ricketts was born on a farm, the son of Andrew Duncan and Nancy Jane Ricketts. In 1890, after completing preparatory school, he entered Northwestern University. Two years later he transferred to the University of Nebraska, where he received an undergraduate degree in zoology. 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, Walter H. Allport, helped him secure employment there in the medical museum.

During his third year of medical school, Ricketts suffered a nervous breakdown. After the recovery he interned for two years at Cook County Hospital, and in 1897 he was conferred doctor of medicine at the Northwestern University. In 1898 he received a pathology fellowship at Rush Medical College. In 1900 he married Myra Tubbs.

At the suggestion of Ludvig Hektoen (1863-1951), 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 in Paris. These experiences in Europe perfected Ricketts’ laboratory techniques and gave him a broad appreciation for theoretical microbiology.

A young professor in Montana
In 1902 Ricketts became associate professor of pathology at the University of Chicago. That same year, the state of Montana began funding medical research into the aetiology of Rocky Mountain spotted fever. While this disease rarely claimed more than a dozen lives in a year, it was particularly virulent in Bitterroot Valley, an increasingly prosperous and influential community.

In 1906, with funding from the McCormick Memorial Institute, the State of Montana, the University, and the American Medical Association, Ricketts travelled to Montana to study the disease, which had a mortality of 80-90 percent. For the next four years, Ricketts divided his life between campus-based laboratories and his research in the field. As part of his research, he contacted victims of the disease, collected and studied affected animals, and raised additional funds for his project.

Not until the second year of his investigation, however, did Ricketts and his assistant J. J. Moore make a critical breakthrough by discovering that wood ticks were the primary carriers of the bacillus that caused the fever.

By 1909, using laboratory animals, Ricketts was able to demonstrate that ticks transmitted the disease and this finding led to a public health campaign to 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 (1859-1934) and others. Rickett’s work suggested that bacterial diseases could be biologically transmitted from pests to people.

Death in Mexico
In 1910 Montana suffered an outbreak of typhoid fever and smallpox, and money ordinarily spent on preventing spotted fever was diverted to fight these 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 aetiology of the diseases. He discovered that lice transmitted the fever, and he worked closely and rapidly with severely infected patients.

In 1909 Ricketts and his assistant, Russell M. Wilder, went to Mexico City to study tabardillo - a Mexian form of typhus. There he discovered that typhus closely resembled spotted fever, leading him to argue that insects spread both diseases. Unknown to Ricketts, this same conclusion had been reached by the French surgeon Jules Henri Nicolle (1866-1936, winner of the 1928 Nobel Prize in Physiology or Medicine), who identified lice as the culprits. Ricketts's final stint of research was cut short by a critical illness. Just days after isolating the microorganism he contended was the cause of typhus, Ricketts died on May 5, 1910, most likely from an infected insect's bite.

Rickets and Wilder, achieved a lot in the short period prior to the death of Ricketts. They found that tabardillo can be transmitted by the body louse (Pediculus humanus) and that it was caused by an organism similar to the one causing Rocky Mountains spotted fever. Ricketts also demonstrated that tabardillo can be transmitted to monkeys, which, after recovering, would develop immunity to the disease.

Prowazek – another victim of typhus
The Austrian bacteriologist and zoologist Stanislaus Joseph Mathias von Prowazek (1875-1915) found that the same organisms were present in lice taken from typhus-patients during an investigation in Serbia in 1913. von Prowazek suffered the same fate as Ricketts, as he died of typhus in 1915. This organism has since been called Rickettsia-prowazeki. There are at least six diseases which are caused by these organisms: Typhus (Rickettsia-prowazeki), Rocky Mountains spotted fever (Rickettsia), trench fever (Rickettsia quintana), murine typhus of Mexican tabardillo (Rickettsia-muricolor); tsutsugamushi disease, also known as Japanese river fever or scrub typhus (Rickettsia orientalis, and Q-fever (Rickettsia burnetti).

“Ricketts brought facts to life …
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. Simeon Burt Wolbach (1880-1954) of the Harvard Medical School wrote a eulogy: “Ricketts brought facts to light with brilliance and accuracy and indicated by the method he used, most of the major lines of development subsequently employed in the study of rickettsial diseases.”


  • Henrique da Rocha-Lima (1879-1956):
    Zur Aetiologie des Fleckfiebers.
    Berliner klinische Wochenschrift, 1916, 53: 567-569.
    Rickettsia prowazeki, the cause of typhus, was first isolated by da Rocha-Lima, who named it after Ricketts and Prowazek, both of whom died of the disease. Howard Taylor Ricketts:
  • The transmission of Rocky Mountain spotted fever by the bite of the wood-tick (Dermacentor occidentalis).
    The Journal of the American Medical Association, Chicago, 1906, 47: 358.
    Ricketts demonstrated that the wood tick Dermacentor andersoni is a vector of Rocky Mountain Spotted fever.
  • Infection, immunity and serum therapy.
    Chicago, A. M. A. Press, 1906; 2nd edition, 1913.
  • A micro-organism which apparently has a specific relationship to Rocky Mountain spotted fever. A preliminary report.
    The Journal of the American Medical Association, 1909, 52: 379-380.
  • The relation of typhus fever (tabardillo) to Rocky Mountain spotted fever.
    With Russell Morse Wilder (1885-1952).
    Archives of Internal Medicine, Chicago, 1910, 5: 361-370.
    Ricketts and Wilder differentiated Rocky Mountain spotted fever and typhus.
  • The etiology of the typhus fever (tabardillo) of Mexico City. A further preliminary report.
    Howard Taylor Rocketts and Russell Morse Wilder (1885-1952).
    The Journal of the American Medical Association, 1910, 54: 1373-1375.
    Demonstration of the causal organism of typhus.
  • Contributions to medical science.
    Memorial paper published by the Chicago Pathological Society in 1911. Biographical etc:
  • Howard Taylor Ricketts. Science, Washington, 1910, 32 (826): 585-587.
  • Isidor Fischer (1869-1943), publisher:
    Biographisches Lexikon der hervorragenden Ärzte der letzten fünfzig Jahre.
    Berlin – Wien, Urban & Schwarzenberg, 1932.
  • Harry Wain (1907-1970):
    The Story Behind the Word. Some Interesting Origins of Medical Terms.
    Springfield, Illinois, Charles C. Thomas, 1958.
  • Pierce C. Mullen:
    Ricketts, Howard Taylor.
    In: Charles Coulston Gillispie, editor in chief: Dictionary of Scientific Biography. Charles Scribner’s Sons. New York, 1970.
  • Barry G. Firkin and Judith A. Whitworth:
    Dictionary of Medical Eponyms.
    The Parthenon Publishing Group. 1989. New edition in 2002.
  • Encyclopædica Britannica.
  • Richard Toellner:
    Illustrierte Geschichte der Medizin. Andreas & Andreas Verlag, Salzburg, 1990.
    Original title: Histoire de la Médicine, de la Pharmacie, de l'Art Dentaire et de l'Art Vétérinaire. Paris 1978.
  • P. C. Mullen:
    Bitterroot enigma: Howard Taylor Ricketts and the early struggle against spotted fever. Montana, 1983, 32 (1): 2-13
  • Jeremy M. Norman, editor:
    Morton’s Medical Bibliography. An annotated Check-list of Texts Illustrating the History of Medicine (Garrison and Morton).
    Fifth edition. Scolar Press, 1991.

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