Researchers Use Genomic Analysis to Study the Deadly Bacteria Responsible for “Rabbit Fever”

A team of researchers used genomic analysis techniques to separate harmful bacteria from harmless relatives. Specifically, the researchers used genomic data to compare dangerous Francisella tularensis strains to harmless varieties. Francisella bacteria are classified as potential bioweapons and are considered a high priority in biological warfare research. Interestingly, it appears that the genus includes four new species. The findings were just published in the journal Applied and Environmental Microbiology.

Tularemia is a highly infectious disease caused by Francisella tularensis bacteria. It’s also known as “rabbit fever” and is spread by many mammal species but mostly affects lagomorphs (rabbits, hares, and pikas) and rodents. Technically, the true vectors are the ticks, fleas, and other parasites living on the host. Tularemia is a zoonotic disease that occasionally affects humans and requires treatment. Although rare, some strains of F. tularensis can be deadly if the patient doesn’t receive immediate medical care. These bacterial strains can also spread through the air and could be used as biological weapons. Most strains are harmless, however, and it can be difficult to tell the difference until it’s too late.

Researchers from the Los Alamos National Laboratory collaborated with the Centers for Disease Control and Prevention to perform genomic analyses of over 90 strains of Francisella bacteria. The team discovered four brand new and genetically separate species: F. opportunistica, F. salina, F. uliginis, and F. frigiditurris. The team was also able to identify the most harmful, virulent strains but classified most as harmless or simply opportunistic (strains that might harm an immunocompromised patient).

The team’s findings will provide a framework for studying zoonotic diseases and their uses as biological weapons. Researchers can now develop a test to determine the present species in a sample of Francisella bacteria. Tularemia outbreaks are still common in certain parts of the world so any new information is potentially life-saving.


Challacombe et al. Whole genome relationships among bacteria of diverse origin define new species and provide specific regions for detection. Applied and Environmental Microbiology (2016).

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