Paul-Louis Simond (30 July 1858 – 3 March 1947) was a French physician, chief medical officer and biologist whose major contribution to science was his demonstration that the intermediates in the transmission of bubonic plague from rats to humans are the fleas '' Xenopsylla cheopis'' that dwell on infected rats.

Early life

Paul-Louis Simond was born in Beaufort-sur-Gervanne, ( Drome,

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

) on 30 July 1858. His father was a

pastor A pastor (abbreviated to "Ps","Pr", "Pstr.", "Ptr." or "Psa" (both singular), or "Ps" (plural)) is the leader of a Christianity, Christian congregation who also gives advice and counsel to people from the community or congregation. In Lutherani ...

of the Reformed Church. From 1878 to 1882 Simond was an assistant in Medical and Biological Sciences at the School of Medicine and Pharmacy in

Bordeaux Bordeaux ( ; ; Gascon language, Gascon ; ) is a city on the river Garonne in the Gironde Departments of France, department, southwestern France. A port city, it is the capital of the Nouvelle-Aquitaine region, as well as the Prefectures in F ...

, and he began his medical training there. From 1882 to 1886 he served as director of the

leprosarium A leper colony, also known by #Names, many other names, is an isolated community for the quarantining and treatment of lepers, people suffering from leprosy. ''Mycobacterium leprae, M. leprae'', the bacterium responsible for leprosy, is believ ...

in Acarouany near Saint-Laurent-du-Maroni,

French Guiana French Guiana, or Guyane in French, is an Overseas departments and regions of France, overseas department and region of France located on the northern coast of South America in the Guianas and the West Indies. Bordered by Suriname to the west ...

, where he contracted an attenuated form of yellow fever. He returned to Bordeaux in 1886 and the following year he received his medical doctorate with a prize-winning thesis on

leprosy Leprosy, also known as Hansen's disease (HD), is a Chronic condition, long-term infection by the bacteria ''Mycobacterium leprae'' or ''Mycobacterium lepromatosis''. Infection can lead to damage of the Peripheral nervous system, nerves, respir ...

Career

Paul-Louis Simond injecting plague vaccine June 4th 1898 Karachi

In 1895 he began work at the

Pasteur Institute The Pasteur Institute (, ) is a French non-profit private foundation dedicated to the study of biology, micro-organisms, diseases, and vaccines. It is named after Louis Pasteur, who invented pasteurization and vaccines for anthrax and rabies. Th ...

Paris Paris () is the Capital city, capital and List of communes in France with over 20,000 inhabitants, largest city of France. With an estimated population of 2,048,472 residents in January 2025 in an area of more than , Paris is the List of ci ...

and while working in the laboratory of Elie Metchnikoff, he was the first to provide a comprehensive description of the sexual reproductive processes of

Coccidia Coccidia (Coccidiasina) are a subclass of microscopic, spore-forming, single-celled obligate intracellular parasites belonging to the apicomplexan class Conoidasida. As obligate intracellular parasites, they must live and reproduce within a ...

. This work provided experimental support for the theory of evolutionary dimorphism which had been put forward by R. Pfeiffer. In 1897, when Alexandre Yersin was transferred by the Pasteur Institute to a post in

Vietnam Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...

, his position in

Bombay Mumbai ( ; ), also known as Bombay ( ; its official name until 1995), is the capital city of the Indian States and union territories of India, state of Maharashtra. Mumbai is the financial centre, financial capital and the list of cities i ...

was filled by Simond, who was to test the efficacy of an experimental antiserum against the outbreak of plague in that city. The following year, Simond was in

Karachi Karachi is the capital city of the Administrative units of Pakistan, province of Sindh, Pakistan. It is the List of cities in Pakistan by population, largest city in Pakistan and 12th List of largest cities, largest in the world, with a popul ...

where, despite limited resources, he was able to demonstrate that fleas transmit the bacterium Yersinia pestis, the agent causing bubonic plague, from rat to rat, and from rat to human. His ingenious experiments are described in his report to the Pasteur Institute on the spread of plague ("La propagation de la peste"), which was published in 1898 by Pierre Paul Emile Roux in the ''Annales de l'Institut Pasteur''. For this work Simond was awarded the Barbier prize from the French Academy of Medicine. His findings were not initially accepted by the scientific community, but were validated later by others and by 1907 his conclusions were accepted as scientific fact. From 1898 to 1901 Simond served as director of the Pasteur Institute in

Saigon Ho Chi Minh City (HCMC) ('','' TP.HCM; ), commonly known as Saigon (; ), is the most populous city in Vietnam with a population of around 14 million in 2025. The city's geography is defined by rivers and canals, of which the largest is Saigo ...

organizing a modern vaccine service; he received the distinction of Knight of the Legion of Honour. From 1901 to 1905 he participated on a mission to study yellow fever in

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

where he and his colleagues confirmed the results that the U.S. Army Commission led by Walter Reed had just obtained in Cuba. These revealed that the amaril virus is the pathogen present in the blood of patients, and that this virus can be conveyed to humans by the mosquito species, ''Stegomyia fasciata'' (later renamed ''Aedes aegypti''). In 1908-09 he conducted yellow fever research in

Martinique Martinique ( ; or ; Kalinago language, Kalinago: or ) is an island in the Lesser Antilles of the West Indies, in the eastern Caribbean Sea. It was previously known as Iguanacaera which translates to iguana island in Carib language, Kariʼn ...

. From 1911 to 1913 he served as Director of the Imperial Bacteriology Research Institute in

Constantinople Constantinople (#Names of Constantinople, see other names) was a historical city located on the Bosporus that served as the capital of the Roman Empire, Roman, Byzantine Empire, Byzantine, Latin Empire, Latin, and Ottoman Empire, Ottoman empire ...

. In 1917, Simond was installed in Valence to study tuberculosis. Simond also had a keen interest in

botany Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who s ...

; during his stay as a colonial doctor in Indochina from 1914 until 1917, he collected orchids and had a local artist create watercolor paintings of them. He amassed a collection of 226

watercolor Watercolor (American English) or watercolour (Commonwealth English; see American and British English spelling differences#-our, -or, spelling differences), also ''aquarelle'' (; from Italian diminutive of Latin 'water'), is a painting metho ...

paintings of 3,226 different species of orchids which were presented to the ''Phanerogamie'' of the ''

Muséum national d'histoire naturelle The French National Museum of Natural History ( ; abbr. MNHN) is the national natural history museum of France and a of higher education part of Sorbonne University. The main museum, with four galleries, is located in Paris, France, within the Ja ...

'' on 1947.

Death

Paul-Louis Simond died in Valence (

Drôme Drôme (; Occitan: ''Droma''; Arpitan: ''Drôma'') is the southernmost department in the Auvergne-Rhône-Alpes region of Southeastern France. Named after the river Drôme, it had a population of 516,762 as of 2019.

) on 3 March 1947 at the age 88. After his death, a fellow biologist, René Dujarric de la Rivière, presented Simond's eulogy at the Academy of Medecine. There is a street in Valence named after him.

Early life

Career

Death

References

Further reading