SCIENCE ALERT – Case numbers of the infectious disease tularemia, also termed ‘rabbit fever’, have jumped in the United States over the past decade, according to a new report from the US Centers for Disease Control and Prevention.
The disease, caused by the bacterium Francisella tularensis, can be transmitted to humans in many ways, including bites from infected ticks and deer flies, and skin contact with infected rabbits, hares, and rodents, all of which are particularly susceptible to the disease.
But there are far gnarlier routes of transmission possible: lawn mowing over the nests of animals infected with the disease has been reported to aerosolize the bacteria, infecting the unwitting gardener.
This phenomenon was first recorded at a Massachusetts vineyard in 2000, where the resulting tularemia outbreak lasted six months and resulted in 15 identified cases and one reported death.
At least one of another handful of cases reported in Colorado in 2014 and 2015 was also linked to a lawn-mowing incident.
The CDC keeps a close eye on this bacterium, in part because it’s classified as a Tier 1 Select Agent by the US government for its bioterrorism potential, and also because even when it’s transmitted naturally, it can be lethal without treatment.
“The case fatality rate of tularemia is typically less than 2 percent but can be higher depending on clinical manifestation and infecting strain,” the report’s authors note.
Tularemia is relatively uncommon in the scheme of things: across 47 states, 2,462 cases were recorded for the decade 2011-2022. By comparison, the CDC estimates around 1.35 million cases of Salmonella bacterium poisoning occur across the country each year.
While those 2,462 tularemia cases amount to just one case among every 200,000 people, it’s a 56 percent higher incidence rate than records from 2001-2010 …
More detail from the CDC’s Morbidity and Mortality Weekly Report.
Risk for tularemia persists throughout the United States, particularly in some central states.
Although the demographic groups most at risk for tularemia remain consistent with those identified in previous decades, AI/AN persons continue to face substantially higher disease risk than do other groups.
The findings in this report highlight the need for tailored prevention education given the myriad of potential exposures to F. tularensis in the environment, including via inhalation, ingestion, contact with animals, or arthropod bites.
In addition, increasing tularemia incidence underscores ongoing needs for clinical education regarding diverse clinical manifestations of tularemia, options for laboratory testing, and importance of early and appropriate treatment with aminoglycoside, fluoroquinolone, or tetracycline classes of antimicrobials, particularly for health care providers serving tribal populations.
Although the signs and symptoms of tularemia are broad and often nonspecific, health care providers should consider tularemia in patients with clinically compatible illness (e.g., fever accompanied by lymphadenopathy) after possible exposure to F. tularensis, and laboratories should be alerted to suspicion of tularemia when possible to enable specific diagnostic considerations and ensure appropriate safety precautions.
