History and Geography

Tularemia enjoys a unique place in medical history as it is the first disease to be identified and entirely described by American investigators. In 1910 G. W. McCoy of the U.S. Public Health Service, while studying plague in California ground squirrels, reported a "plague-like disease of rodents" in these animals. The following year, he and C. W. Chapin, using a special nutrient medium, succeeded in cul-turing the causative organism and named it Bacterium tularense after Tulare County, California, where infected squirrels were first discovered. W. B. Wherry and B. H. Lamb were the first to diagnose bacteriologically a human case of the disease in 1914. The infected patient, an Ohio meat cutter, showed ulcerative conjunctivitis and lymphadenitis.

Earlier, in 1911, R. A. Pearse had described several cases of deer-fly fever in humans from Utah and suggested that the disease was caused by the bite of Chrysops discalis, the common deer fly. It was left to Edward Francis, a surgeon with the U.S. Public Health Service, to piece together the complicated etiologic connection among deer-fly fever in humans, the plaguelike disease of rodents in California, and similar illnesses in small mammals of Utah and Indiana. Francis isolated the organism in 1921 and proved that it was indeed spread by the bite of the deer fly as well as by direct contact with infected meat. The role of the tick in the spread of tularemia was determined in 1924 by R. R. Parker, R. R. Spencer, and Francis. It was also Francis who coined the term "tularemia" after finding the organism in the blood of infected individuals. In the late 1950s the genus name of the organism was changed to Pas-teurella because of a supposed relationship to the causative organism of plague. In 1974, upon recommendation of microbiologists in the Soviet Union and the United States, the genus name was changed to Francisella to honor Francis who, through more than 30 years of investigation into tularemia, was the man most responsible for sorting out its complexities and many manifestations.

In 1925, Hachiro Ohara, a Japanese scientist, published a paper entitled "Concerning an Acute Febrile Disease Transmitted by Wild Rabbits," followed shortly by a second paper describing how an illness that would become known as Ohara's disease was successfully transmitted to humans. Other papers by Japanese scientists soon followed, but none made reference to American investigations of tularemia.

Francis and a colleague, recognizing that Ohara's disease seemed similar to tularemia in every way, requested serums from convalescent Japanese patients. Examination of the sera quickly confirmed that Ohara's disease and tularemia were actually the same illness.

The first isolation of F. tularensis outside North America and Japan occurred in the Soviet Union in 1926, and by 1928 almost 800 cases were reported, rising to a peak incidence in 1941-2 of approximately 100,000 cases, but, as in North America, there has subsequently been a dramatic delcine in cases.

Although tularemia is often described as a "new disease," it is perhaps best to consider it new only in terms of its discovery. Medical historians believe there is good evidence that tularemia was endemic in the United States, Scandinavia, and the Soviet Union in the eighteenth and nineteenth centuries. Many travelers in Russia as early as 1741 noted a disease with all the characteristics of tularemia and termed "Siberian ulcer."

In the United States at least three written records survive describing the disease, including one from California in 1904 and another from Arizona in 1907. In fact, the wide distribution of the disease and its adaptation to a wide variety of animals suggest that the disease is ancient in nature, perhaps dating to the latter end of the Miocene or early Pliocene periods.

Despite the dramatic decline in the incidence of tularemia since the 1950s, it would appear that tularemia will remain a hazard to humans for many years to come. In spite of the great amount of research over the past 70 years, numerous questions remain unanswered because of the very complex interactions among hosts, vectors, and varied environments. Because of these complex ecological interactions, eradication of tularemia seems unlikely.

Patrick D. Home

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