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Chapter 161: Zoonotic Infections

Bryan B. Kitch; John T. Meredith

INTRODUCTION

Zoonoses are diseases caused by bacteria, viruses, parasites, or fungi transmitted from vertebrate animals or insects to or from humans. Ticks are one of the most important vectors of human infectious diseases in the world. Exposures or occupations that involve animal contact are risk factors for disease (Table 161-1). Recent travel, particularly in spring, summer, and early fall, or history of habitation in an underdeveloped country are additional risk factors. Zoonoses can occur at any time of the year, but in temperate climates, most zoonoses happen in the spring and summer. A patient with a zoonotic infection has signs and symptoms similar to many acute infections: fever, headache, myalgias, malaise, and weakness (Table 161-2).

TABLE 161-1Risk Factors for Zoonotic Infection
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TABLE 161-1 Risk Factors for Zoonotic Infection
Risk Category Examples
Agricultural workers Farmers, cattle ranchers, sheep ranchers, and migrant workers
Animal processing workers Slaughterhouse workers, animal hide processors, and workers in manufacturing who deal with animal products
Outdoor enthusiasts Forestry workers, lumbermen, surveyors, park rangers, hunters, spelunkers, and fishermen
Pet owners Those living alongside a dog, cat, bird, rodent, rabbit, reptile, or fish
Professionals Veterinarians, animal researchers, and animal handlers
Immunocompromised patients Those with congenital immunodeficiencies, diabetes mellitus, alcoholism, renal failure, liver failure, cancer, splenectomy, or human immunodeficiency virus
TABLE 161-2Common Systemic Zoonotic Infections
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TABLE 161-2 Common Systemic Zoonotic Infections
Agent Animal Reservoir Physical Findings Diagnostic Tests Treatment
Aeromonas species Fish, reptiles Nonspecific fever, severe crepitant cellulitis with systemic toxicity, gastroenteritis — See Chapter 160, “Food and Waterborne Illnesses”
Brucella canis Dogs Nonspecific fever Serologic testing, blood culture Doxycycline plus gentamicin or rifampin. TMP-SMX plus gentamicin in children
Capnocytophaga Dogs and cats Fever, septic shock, and meningitis from infected bite Culture of bite wound Amoxicillin-clavulanate or clindamycin. Pip-Tazo or a carbapenem plus clindamycin/vancomycin for shock
Chlamydophila psittaci Birds Fever, flulike illness, pneumonia, endocarditis, sepsis Serologic testing and sputum culture Doxycycline. Azithromycin and levofloxacin are alternatives
Coxiella burnetii Cattle, sheep, goats, and occasionally cats Fever, pneumonia, hepatitis, meningitis, endocarditis Serologic testing, PCR Doxycycline, with the possible alternative of a fluoroquinolone or macrolide
Ehrlichia species Ticks Nonspecific fever, sepsis, meningitis, hepatitis Clinical diagnosis, serologic testing, peripheral blood smear, immunocytologic testing, PCR Doxycycline recommended for all patients (even children and pregnancy). Rifampin is alternative
Leptospira species Birds, dogs, rodents Fever, pneumonia, conjunctivitis, lymphadenopathy Darkfield microscopic examination of body fluids, serologic testing Penicillin G IV. Ceftriaxone IV alternative. Mild disease: oral doxycycline or amoxicillin or azithromycin
Francisella tularensis Rabbits, cats, wild animals, biting insects Fever, sepsis, meningitis, pneumonia, hepatitis, rash Serologic testing (poses hazards to laboratory staff) IV aminoglycosides. Alternative: Doxycycline or ciprofloxacin
Rickettsia rickettsii Ticks Fever, diarrhea, or typical presentation of Rocky Mountain spotted fever Clinical diagnosis, rise in antibody titer between acute and convalescent serum, skin biopsy Doxycycline or chloramphenicol
Salmonella enterica...

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