Theobald Smith

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Theobald Smith
Theobald Smith 2.jpg
Born(1859-07-31)July 31, 1859
DiedDecember 10, 1934(1934-12-10) (aged 75)
Alma materCornell University, Albany Medical College
Known forTexas cattle fever, Salmonella
AwardsManson Medal (1932)
Copley Medal (1933)
Scientific career
InstitutionsUS Department of Agriculture, Harvard University, Rockefeller University

Theobald Smith FRS(For)[1] HFRSE (July 31, 1859 – December 10, 1934) was a pioneering epidemiologist, bacteriologist, pathologist and professor. Smith is widely considered to be America's first internationally-significant medical research scientist.[2][3]

Smith's research work included the study of babesiosis (originally known as Texas cattle fever) and the more-general epidemiology of cattle diseases caused by tick borne diseases. He also described the bacterium Salmonella enterica (formerly called Salmonella choleraesuis), a species of Salmonella, named for the Bureau of Animal Industry chief Daniel E. Salmon. Additional work in studying the phenomena of anaphylaxis led to it being referred to as the Theobald Smith phenomenon.[1]

Smith's contribution that is well known even by many laypeople is called the "law of declining virulence". This is based on his disproved notion that there is a “delicate equilibrium” between host and pathogen and that they develop a "mutually benign relationship" over time.[4] This was at most an educated guess (in other words a hypothesis) and never became a scientific theory, but it became accepted as conventional wisdom and was even called the "law of declining virulence". It has been disproved and replaced by the trade-off model, which explains that each host-pathogen relationship must be considered separately and that there is no general pattern that predicts how each of these relationships will develop, and definitely no inevitability of decreased virulence.[4][5]

Smith taught at Columbian University (now George Washington University) and established the school's department of bacteriology, the first at a medical school in the United States.[1] He later worked at Harvard University and the Rockefeller Institute.

He was a trustee of the Carnegie Institution from 1914 until his death in 1934.[6]


Smith was born in Albany, New York, the son of Philip Smith and his wife, Theresa Kexel.[7]

He received a Bachelor of Philosophy degree from Cornell University in 1881, followed by an MD from Albany Medical College in 1883.[2] After his graduation from medical school, Smith held a variety of temporary positions which might broadly be considered under the modern heading of "medical laboratory technician". After some prodding by his former professors, Smith secured a new research lab assistant position with the Veterinary Division of the US Department of Agriculture (USDA) in Washington, D.C., beginning his position there in December 1883.[8]


Smith became the Inspector of the newly created Bureau of Animal Industry (BAI) in 1884. Established by Congress to combat a wide range of animal diseases—from infectious disease of swine to bovine pneumonia, Texas cattle fever to glanders—Smith worked under Daniel E. Salmon, a veterinarian and Chief of the BAI.[9] Smith also discovered the bacterial type species which would eventually form the genus Salmonella. After two years of work studying the efficacy of bacterial vaccination in pigs, Smith erroneously believed he had found the causative agent of hog cholera.[10]

Smith turned his attention to Texas fever, a debilitating cattle disease; this work is detailed in a chapter in Microbe Hunters, by Paul de Kruif. In 1889, he along with the veterinarian F.L. Kilbourne discovered Babesia bigemina, the tick-borne protozoan parasite responsible for Texas fever. This marked the first time that an arthropod had been definitively linked with the transmission of an infectious disease and presaged the eventual discovery of insects as important vectors in a number of diseases (see Tick-borne disease, Mosquito-borne disease yellow fever, malaria, etc.).

Smith also taught at Columbian University in Washington, D.C. (now George Washington University) from 1886 to 1895, establishing the school's Department of Bacteriology. In 1887, Smith began research on water sanitation in his spare time, investigating the level of fecal coliform contamination in the nearby Potomac River. Over the next five years, Smith expanded his studies to include the Hudson River and its tributaries.[11]

While Smith's work at the BAI had been highly productive, he found the rigid federal government bureaucracy stiffing and complained about the lack of leadership from his supervisor. In 1895 Smith moved to Cambridge, Massachusetts to accept a dual appointment serving as professor of comparative pathology at Harvard University as well as directing the pathology lab at the Massachusetts State Board of Health.[8]

Smith joined the Rockefeller Institute for Medical Research as Director of the Department of Animal Pathology in 1915 and remained there until his retirement in 1929.

In 1933, Smith was awarded the Royal Society's prestigious Copley Medal "For his original research and observation on diseases of animals and man.".


  • Parasitism and Disease (1934)

Other discoveries[edit]

  • Observed differences between human and bovine tuberculosis (1895).
  • Discussed the possibility of mosquitos as a malaria transmission vector (1899).
  • Variation and bacterial pathogenesis (1900).
  • Discovered anaphylaxis (1903), which is also sometimes referred to as "Theobald Smith's phenomenon".[12]
  • Brucellosis infections
  • Used toxin/antitoxin as a vaccine for diphtheria (1909).
  • In the process of investigating an epidemic of infectious abortions of cattle in 1919, Smith described the bacteria responsible for fetal membrane disease in cows now known as Campylobacter fetus.[13]


  1. ^ a b c Nuttall, G. H. F. (1935). "Theobald Smith. 1859-1934". Obituary Notices of Fellows of the Royal Society. 1 (4): 514–521. Bibcode:1935SciMo..40..196W. doi:10.1098/rsbm.1935.0014. JSTOR 768981. Retrieved 17 March 2022.
  2. ^ a b Dolman, C.E.; Wolfe, R.J. (2003). Suppressing the Diseases of Animals and Man: Theobald Smith, Microbiologist. Boston Medical Library. ISBN 0-674-01220-8.
  3. ^ Middleton, James (July 1914). "A Great American Scientist: Dr. Theobald Smith, Head of The New Department Of Animal Diseases At The Rockefeller Institute". The World's Work: A History of Our Time. Doubleday, Page & Co. XLIV (2): 299–302. Retrieved 17 March 2022.
  4. ^ a b Fall, Ed; Yates, Christian (1 February 2021). "Will coronavirus really evolve to become less deadly?". The Conversation. Retrieved 29 November 2021. The trade-off model is now widely accepted. It emphasises that each host-pathogen combination must be considered individually. There is no general evolutionary law for predicting how these relationships will pan out, and certainly no justification for evoking the inevitability of decreased virulence.
    There is little or no direct evidence that virulence decreases over time. While newly emerged pathogens, such as HIV and Mers, are often highly virulent, the converse is not true. There are plenty of ancient diseases, such as tuberculosis and gonorrhoea, that are probably just as virulent today as they ever were.
  5. ^ Orent, Wendy (16 November 2020). "Will the Coronavirus Evolve to Be Less Deadly? - History and science suggesting many possible pathways for pandemics, but questions remain about how this one will end". Smithsonian Magazine. Retrieved 29 November 2020.
  6. ^ Carnegie Institution of Washington. Year Book No. 47, July 1, 1947 – June 30, 1948 (PDF). Washington, DC. 1948. p. vi.
  7. ^ Biographical Index of Former Fellows of the Royal Society of Edinburgh 1783–2002 (PDF). The Royal Society of Edinburgh. July 2006. ISBN 0-902-198-84-X.
  8. ^ a b Kruif, Paul De (2002) [1926]. Microbe Hunters. Harvest Books. ISBN 0-15-602777-1.
  9. ^ J.H., Brown (1 July 1935). "Theobald Smith 1859-1934". J Bacteriol. 30 (1): 196. Bibcode:1935SciMo..40..196W. doi:10.1128/JB.30.1.1-3.1935. PMC 543631. PMID 16559815.
  10. ^ "Theobald Smith, 1859-1934: A Fiftieth Anniversary Tribute" (PDF). ASM News. 50: 577–80. 1984. Archived from the original (PDF) on 2004-09-07.
  11. ^ T., Smith (1893). "A new method for determining quantitatively the pollution of water by fecal bacteria". 13th Annual Report of the State Board of Health of New York for 1892: 712–22.
  12. ^ "Whonamedit - dictionary of medical eponyms". Retrieved 2018-04-18.
  13. ^ Smith, T.; Taylor, M.S. (1919). "Some morphological and biological characters of the Spirilla (Vibrio fetus, n. sp.) associated with the disease of the fetal membranes in cattle". J Exp Med. 30 (4): 299–311. doi:10.1084/jem.30.4.299. PMC 2126685. PMID 19868360.

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