Case Presentation: An 83-year-old male with a history of renal cell carcinoma s/p nephrectomy, chronic kidney disease, and hypertension presented to the Emergency Department with several weeks of recurring fevers to 103°F, chills, malaise, fatigue, night sweats, anorexia, and an unintentional weight loss of 4.5 kg. He denied arthralgias, myalgias, neurologic symptoms, rashes, diarrhea, or enlarged lymph nodes. The patient had an extensive exposure history. He lives on a farm in Michigan with access to a community lake in a woodland area, in which he swam for the first time one week prior to developing symptoms. He has seasonal tick exposures and was bitten one month prior to symptom onset. He routinely sweeps bird and bat droppings in his barn. He collects rabbit skins while hunting and regularly eats large game animals native to the Midwest. He catches field mice using traps, disposes of their carcasses, and cleans the blood off the traps for reuse. He had no recent travel history but had remote trips to Brazil and China. During his admission, the patient had intermittent fevers that defervesced with acetaminophen and was otherwise hemodynamically stable. Fevers occasionally occurred with bradycardia consistent with a positive Faget sign. Both standard blood cultures and viral panels were negative. Given his oncologic history, CT imaging was performed but revealed no evidence of malignancy. The patient was afebrile for 48 hours without antipyretics and discharged home on a 14-day course of empiric antibiotics (doxycycline) while additional infectious laboratory testing was pending. Days later, his serum immunoglobulin M (IgM) returned positive for Francisella tularensis.

Discussion: Tularemia is a rare bacterial infection, historically endemic to the central-southern United States. F. tularensis is a fastidious gram-negative coccobacillus commonly acquired via exposure to animal or arthropod vectors in the setting of hunting, skinning, or handling mammals. Symptoms can be nonspecific with a clinical presentation that varies depending how the bacteria enters the body. Most commonly, infected patients present with ulceroglandular disease secondary to tick bites, characterized by a single central eschar at the site of inoculation and tender lymphadenopathy often requiring incision and drainage. All forms are accompanied by fever. Faget sign, which refers to the unusual pairing of fever and bradycardia, has been observed in tularemia. Antimicrobial therapy is required for treatment. Clinical efficacy has been demonstrated with aminoglycosides, tetracycline, doxycycline, and fluoroquinolones. Here, we describe a patient who likely developed the typhoidal disease variant, a systemic illness without localizing features. Per CDC reports, six cases of tularemia were reported in Michigan between 2011 and 2020 compared to a total of 2,134 in the United States. Recent data suggests a possible, albeit subtle, northward geographical shift of tularemia in the setting of ongoing climate changes.

Conclusions: While exceedingly rare in the midwestern United States, tularemia represents one of several zoonotic pathogens whose geography is subject to expansion into more northern states in the face of changing climate. We report this case to encourage providers to broaden the differential diagnosis for fever of unknown origin to include infectious diseases not historically observed in their geographic area of practice.