Theobald SmithFRS(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]
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.[5]
Research
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.[6] Smith also discovered the bacterial type species which would eventually form the genusSalmonella. 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.[7]
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 protozoanparasite 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 such as ticks and mosquitoes as important vectors in a number of diseases.
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.[8]
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.[5]
Smith's best-known contribution was the notion, long since disproved, that there would be a “delicate equilibrium” between hosts and pathogens such that they would develop a "mutually benign relationship" over time.[10] This was at most an educated guess 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, that there is no general pattern that predicts how all of these relationships will develop, and that there is definitely no inevitability of decreased virulence.[10][11]
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.[16]
12Dolman, C.E.; Wolfe, R.J. (2003). Suppressing the Diseases of Animals and Man: Theobald Smith, Microbiologist. Boston Medical Library. ISBN0-674-01220-8.
↑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.
12Fall, 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.
Paul de KruifMicrobe Hunters (Blue Ribbon Books) Harcourt Brace & Company Inc., New York 1926: ch. VIII Theobald Smith: Ticks and Texas Fever (pp. 234-251)
