Zoonotic infections are caused by an extremely diverse group of microorganisms. A myriad of classification approaches focus on the pathogen, animal vector, mode of transmission, geographic range, and clinical syndrome. For emergency physicians, the best approach is one of clinical syndrome presentation, but systemic zoonoses are most difficult to diagnose. Often, they present as an undifferentiated febrile illness with pyrexia, cephalgia, myalgia, malaise, and weakness. This presentation is very common in patients in an emergency department and can indicate pathology other than that of a zoonotic infection. The concern is how to differentiate a zoonotic infection from a benign febrile illness. In this regard, risk factors for acquiring a zoonotic infection are very important, as is recognizing the seasonal variation of most zoonotic infections. In the United States, most zoonoses show an increased incidence in the spring and summer. 8 However, systemic zoonotic infections should be included in the differential diagnosis of any seriously ill patient who presents with an undifferentiated fever. Specific zoonoses that can present as an undifferentiated febrile illness or septic presentation include Aeromonas spp, Brucella canis, Capnocytophaga, Chlamydia psittaci, Leptospira sp., Francisella sp., Salmonella enteritidis, Streptococcus pyogenes, Yersinia pestis, Coxiella burnetii, Ehrlichia sp., and Rickettsia rickettsi. (Table 1.45.-2).
TABLE 145-2 Systemic Zoonotic Infections
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