Tularemia is a zoonotic bacterial infection caused by Francisella tularensis, a highly virulent gram-negative intracellular coccobacillus and a CDC Category A bioterrorism agent due to its extreme infectivity (as few as 10-50 organisms can cause disease via inhalation), ease of aerosolization, and potential for causing severe illness and death if untreated. F. tularensis survives and replicates within macrophages by escaping from the phagosome into the cytoplasm, evading intracellular killing mechanisms. This intracellular survival allows the organism to disseminate via the reticuloendothelial system to lymph nodes, liver, spleen, and lungs. There are two clinically important subspecies: F. tularensis subspecies tularensis (Type A — more virulent, found in North America, associated with higher mortality) and F. tularensis subspecies holarctica (Type B — less virulent, found in Europe and Asia). Transmission occurs through multiple routes: tick/deer fly bites (most common in the US), handling infected animals (rabbits, hares, muskrats — hence the name rabbit fever), inhalation of contaminated aerosols, ingestion of contaminated water/food, and direct inoculation through skin breaks. The clinical forms depend on the route of entry: ulceroglandular (most common — painless...