North American Veterinary Licensing Examination (NAVLE) Practice Test

The clinical diagnosis in this case is purpura hemorrhagica, which is an immune-mediated condition that can occur as a complication following infections such as strangles, particularly in horses that have been vaccinated or exposed to strep equi. The presentation of urticaria and respiratory distress in the Arabian mare strongly suggests an allergic or hypersensitivity reaction, commonly associated with this syndrome.

When a horse has strangles, particularly if there has been vaccination or recent infections, an exaggerated immune response can lead to vasculitis, resulting in the urticaria and petechiation that are hallmark signs of purpura hemorrhagica. The respiratory distress could stem from edema and inflammation in the upper respiratory tract, reflecting how systemic illness affects respiratory function.

In contrast, Potomac Horse Fever primarily causes fever and diarrhea and would not typically present with respiratory distress in that context. Equine salmonellosis is more associated with gastrointestinal signs such as diarrhea and colic rather than respiratory problems. Equine viral arteritis can present with fever and respiratory distress, but it is less commonly associated with urticaria and does not directly link to the recent strangles treatment. Thus, purpura hemorrhagica is the most fitting diagnosis given the combination of symptoms and the