When you’re in a medical technology program, you quickly learn that there are some microbiology test questions that you only need to skim for key words before you can guess at an answer. Has the patient been feeding pigeons? Cryptococcus! Sleeping next to an old window air conditioner? Legionella! One of my favorites, which has stuck with me through the years, is tularemia: brought to you by your friendly neighborhood bunny rabbits.

The bacterium to blame here is Francisella tularensis, a tiny Gram-negative aerobic coccobacillus. The bacterium is carried by deer flies and several species of ticks, and can easily infect rabbits, prairie dogs, and other wild rodents. People are at risk of infection when they are bitten by an insect vector, or when they handle a sick or dead animal. Symptoms include fever, fatigue, swollen glands, and ulceration where the skin was punctured. If inhaled, the bacteria can cause a devastating and sometimes fatal pneumonia, although cases like this are extremely rare.

Isolating the organism in laboratory culture is the best way to confirm the infection, but blood cultures can often give false negative results. Scrapings or swabs from ulcerated skin are the best specimen sources, in cases where the transmission occurred by insect or animal bite. Alternatively, the lab can test a patient’s antibody titers and compare levels in acute and convalescent serum as a means of confirming the infection, but those results are not helpful in initial diagnosis and management of the disease.

Because of the extreme pathogenicity of F. tularensis – only a dozen or so organisms need to be inhaled or otherwise acquired to cause disease – the CDC has added the bacterium to its list of possible agents of bioterrorism. It’s not easy to spread from person to person, but if it were to be dispersed in the air or into a city’s water supply, it could cause widespread disease. Suspected cases of F. tularensis should be reported to state public health laboratories immediately.

Unfortunately for laboratory professionals on the front lines, F. tularensis is also very infectious when grown in laboratory culture, and there are many cases of laboratory-acquired infections on record. Because of this, the CDC and Association of Public Health Laboratories recommend that procedures likely to create aerosols or droplets (e.g., grinding, centrifuging, vigorous shaking, animal studies) always be conducted under Biosafety level 3 precautions. Commercial identification systems aren’t recommended if F. tularensis is suspected, because of the potential for the spread of aerosols.

Tularemia cases are fairly rare in the United States, with only 314 cases reported in 2015. Most laboratories will likely never see a case. However, there is concern that climate change may lead to an increase in tick-borne diseases in general, as mild winters allow tick populations to increase and to spread to new areas. Laboratory professionals who work with microbiology specimens and may have been exposed to F. tularensis in the lab can be treated prophylactically with a course of antibiotics, or can wait and watch for the appearance of a fever before beginning the medication.

About The Author

Jen is the Post Survey Team Leader with COLA, where she provides valuable consultation to laboratory clients regarding regulatory compliance and quality lab practices, and guides member laboratories through the Accreditation process. She is a licensed Medical Laboratory Scientist with over a decade of experience in high-volume hospital blood banks and core laboratories. She holds a Bachelor of Science degree in Human Physiology from McGill University and a Medical Technology degree from Dawson College. She is also a freelance science writer whose articles are featured on websites dedicated to consumer safety, STEM outreach, and science communication.