Respiratory Zoonotic Infections

Respiratory zoonotic infections can be divided into two distinct syndromes of upper respiratory infections (pharyngitis) and lower respiratory infections (pneumonia). Recurrent culture-proven streptococcal pharyngitis in a household member can have a zoonotic source—often the household pet. 34 For complete eradication of this form of streptococcal pharyngitis from a family, the family pet, in addition to family members, may require a course of antistreptococcal antimicrobial therapy. Prolonged exudative pharyngitis raises the suspicion of a zoonotic origin or atypical pharyngitis, particularly if the exudative pharyngitis includes systemic symptoms and leukocytosis, and is refractory to standard antistreptococcal therapy. In this case, it is pertinent to inquire about animal exposure. Dogs and domesticated farm animals can be the source of Streptococcus sp., Corynebacterium ulcerans, Yersinia sp., and viral vesicular stomatitis. All of these zoonoses can present as an exudative pharyngitis.5 Nondomesticated animals can be a source of exudative pharyngitis as a result of Bordetella sp., Francisella tularensis, Streptobacillus moniformis, and Yersinia pestis.5 Both pet birds and wild birds carry Chlamydia psittaci, which can cause an atypical exudative pharyngitis in humans.

Zoonotic pneumonia presents as an atypical pneumonia with systemic symptoms. Most often the presentation consists of productive or nonproductive cough, fever, chills, headache, myalgias, and a nonspecific rash. These pneumonias are community acquired. Of concern to emergency physicians is that zoonotic pneumonia can often be rapidly lethal, as is the case in pneumonic plague. Zoonotic pneumonia should be considered in any case of gram-negative community-acquired pneumonia and in any case of atypical pneumonia with systemic symptomatology (T§ble...14.5i5.).35 A detailed history provides the data necessary for the consideration of zoonotic pneumonia. Inquiries about animal exposure, occupation, and recent travel are warranted for patients with an atypical pneumonia. Particular attention should be paid to slaughterhouse workers and those individuals exposed to ticks, birds, and other fowl. Additionally, a history of outdoor activity, recreational history, and food-contact history should be obtained.

Anthrax (Bacillus anthracis) is extremely rare in North America. The pulmonary form—inhalation anthrax—is acquired most often from handling unsterilized, imported animal hides or imported raw wool. Inhalation anthrax is universally fatal. Not a true pneumonia, inhalation anthrax is a mediastinitis without alveolar involvement.

Initial symptoms are flulike in character and progress to respiratory failure in 3 to 4 days, with a marked mediastinal and hilar edema. One of the serious concerns to emergency physicians is the potential use of B. anthracis as a biologic warfare agent. Though B. anthracis can be readily cultured, the delivery system that can generate 5 p particles and disperse large volumes of culture material is not easily deployable in a large population center. Currently, active-duty US military personnel are being immunized against anthrax. Treatment is with either ciprofloxacin (750 mg PO bid for 7 to 10 days) or doxycycline (100 mg PO bid for 10 to 14 days). Penicillin or erythromycin can be used as alternative antibiotics. 36

Brucellosis (Brucella sp.) occurs most often in slaughterhouse workers exposed to the aerosol of Brucella bacteria. The consumption of unpasteurized dairy products is another way of acquiring brucellosis. Pneumonia with frank pulmonary infiltrates as a result of brucellosis is uncommon. Often the presentation is one of an upper respiratory infection with a cough, hoarseness of voice, and wheezing. Typically, peritracheal and hilar lymph node involvement is seen. With long-standing resolution, calcified granulomas and lymph nodes are characteristic findings. 37 Doxycycline (100 mg PO bid for up to 6 weeks) combined with rifampin (10 mg/kg/day up to 600 mg per day) is effective therapy.38

Chlamydia psittaci is common to most birds and fowl. Psittacosis is also known as parrot fever, parrot disease, or ornithosis. Human acquisition is from the inhalation of dust from dried bird feces, feather dust, or aerosolized avian respiratory secretions. Psittacosis is characterized by an incubation period of 5 to 14 days followed by abrupt onset of fever chills, cephalgia, myalgia, and generalized malaise. Pneumonia is atypical, with a nonproductive cough and lobar or interstitial infiltrates on chest radiograph. Extrapulmonary manifestations involving the heart, central nervous system, liver, and kidney are common. Tetracyclines (doxycycline 100 mg PO bid for 10 to 14 days) are the drugs of choice for treatment, with erythromycin (250 mg PO qid for 10 to 14 days) for patients intolerant to tetracycline. 3940

Q fever (Coxiella burnetii) is unique because it is the only rickettsial infection acquired by aerosol inhalation rather than by an arthropod vector. Q fever is common among domesticated farm animals in the United States and is shed in urine, afterbirth products, and feces. Feed lots are often contaminated with C. burnetii, which is highly resistant to environmental degradation. The disease is often self-limiting, with variable pulmonary manifestations and extrapulmonary findings. In addition to pulmonary infiltrates, pericarditis, myocarditis, endocarditis, and granulomatous hepatitis can occur. Treatment is with doxycycline (100 mg PO bid for 10 to 14 days), with erythromycin (250 mg PO qid for 10 to 14 days) as an alternative antibiotic. 41

Pasteurellosis (Pasteurella multocida) is endemic to the normal oral flora of cats and most dogs. Often associated with necrotizing cellulitis from bite wounds, bronchitis, bronchopneumonia, and suppurative pleural effusion can occur as a result of pulmonary infection. Treatment is with amoxicillin with clavulanate (500 mg/125 mg PO tid for 10 to 14 days), tetracycline (doxycycline 100 mg PO bid for 10 to 14 days), penicillin (penicillin V 500 mg PO qid for 10 days), or a third-generation cephalosporin.42

Rocky Mountain spotted fever (Rickettsia ricketsii), an arthropod-vectored rickettsial infection, can result in a pulmonary capillary vasculitis with associated bronchiolitis.11 Often a nonproductive cough is present. The chest radiographic findings vary from a normal radiograph to one that shows diffuse interstitial infiltrates and pleural effusions. A secondary bacterial pneumonia is commonly associated with this rickettsial pneumonia. Treatment is with tetracycline or chloramphenicol. 43

Plague (Yersinia pestis) is endemic to the United States and is most often found in rock squirrels and ground rodents of the Southwest. Cats can also be carriers of plague. The principal vector is the rodent flea. Humans and household pets can become infected when bitten by an infected flea. Often an eschar is found at the site of the flea bite, followed by the development of a bubo, an enlarged proximal lymph node. Sepsis and pneumonia from hematologic spread then follow the bubo formation. The pneumonic form is highly contagious and rapidly fatal if not aggressively treated. Additionally, the pulmonary plague can be disseminated from one person to another through aerosolization of respiratory secretions. Treatment is with gentamicin [2.0 mg/kg intravenous (IV) loading dose followed by 1.7 mg/kg IV tid for 10 to 14 days], streptomycin (1 gram IM bid for 10 to 14 days), or a combination of tetracycline and an aminoglycoside. 44

Influenza accounts for the major viral zoonotic pneumonia. Influenza viruses of the Orthomyxoviridae family are classed as types A, B, and C, and "Thogoto-like" virus. Influenza types A, B, and C infect humans, but zoonotic infections are limited to influenza type A. 45 Migrating aquatic fowl are thought to be the natural animal reservoir for influenza type A. Horses and marine mammals can also serve as reservoirs for this zoonotic virus. Additionally, there is very strong epidemiologic and biologic evidence for transmission of influenza between specific species, such as between pigs and humans. 46 Antigenic drift of the viral surface proteins hemagglutinin and neuraminidase in conjunction with a zoonotic reservoir accounts for the frequent human pandemics of influenza. The most noted of these pandemics have been the Spanish influenza of 1918, the Asian influenza of 1957, and the Hong Kong influenza of 1968. It is estimated that 20 to 40 million deaths worldwide were attributed to the Spanish influenza pandemic.46 Influenza pneumonia carries a high morbidity for all age groups. The mortality rate is greatest in those older than age 70. This age group accounts for 90 percent of the deaths from influenza. 47 Treatment of influenza pneumonia is supportive care. Though amantadine and rimantadine have shown to be effective against influenza A, these two antivirals are not effective against types B and C. Antibiotic therapy for superimposed bacterial pneumonia can contribute to the reduction of mortality and morbidity from influenza. Prevention is by annual vaccination and by preventing influenza introduction into domestic poultry and pigs.

Hantavirus, identified in 1977, is a viral zoonosis. The recognized etiologic agent in North America is the Sin Nombre virus, which belongs to the Bunyaviridae family of viruses. To date, at least 10 distinctive serotypes have been identified, each with a specific rodent vector, geographic distribution, and clinical manifestation. 47 The deer mouse (Peromyscus maniculatus) is the primary vector in the United States.48 Infected rodents excrete Hantavirus in feces, urine, and saliva. Human infection occurs with the inhalation of dried, particulate feces contact with urine, or by a rodent bite. The majority of Hantavirus serotypes have a predilection for the kidney, and the most common worldwide presentation is that of acute renal failure with concurrent thrombocytopenia, ocular abnormalities, and flulike symptoms. In the United States, the presentation of this zoonosis is that of Hantavirus pulmonary syndrome,4748 and 49 which consists of an initial flulike prodromal illness of 3 to 4 days' duration, rapidly followed by pulmonary edema, hypoxia, hypotension, tachycardia, and metabolic acidosis. Dizziness, nausea, vomiting, absence of cough, and thrombocytopenia are common and may help to differentiate Hantavirus pulmonary syndrome from adult respiratory disease syndrome, bacterial pneumonia, and influenza pneumonia.2 Hantavirus pulmonary syndrome carries a very high mortality rate of 50 to 70 percent. Diagnosis is with an immunofluorescent or immunoblot assay. Treatment consists of supportive care with attention to adequate oxygenation and possibly the use of an inhalation solution of ribavirin. 47,4 and 49

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