Zoonotic concern: Psittacosis in Birds

Introduction

Individuals that work or live with birds may be at risk for zoonotic diseases (Fig 1). Psittacosis, also known as parrot fever or ornithosis, is caused by Chlamydia psittaci, an obligate intracellular bacterium (1,6). During 2003–2014, 112 human cases of psittacosis were reported to the Centers for Disease Control (1).

Figure 1. Psittacosis, also known as parrot fever, is caused by Chlamydia psittaci, an obligate intracellular bacterium of birds.

How do human infections occur?

Most human cases result from exposure to infected psittacine birds, although poultry, pigeons and doves, and many other avian species can also transmit disease (4,7). Infected birds shed bacteria through feces and oculonasal discharge (1,6).

Individuals at risk include (1):

• Pet bird owners and breeders
• Veterinary health professionals
• Wildlife rehabilitators
• Poultry slaughter and process plant workers
• Zoo, laboratory, and avian quarantine employees
• Farmers
• Gamekeepers

Humans can be infected during transient exposure to infected birds and contact may be so brief the individual may forget. Person-to-person transmission of C. psittaci is possible but rare (5,8). Clinical signs typically follow a 5 to 14 day incubation period (1,6).

What are the signs of psittacosis in humans?

Psittacosis in humans may range from asymptomatic infection to flu-like signs to severe disease, including pneumonia, endocarditis, myocarditis, hepatitis, arthritis, keratoconjunctivitis, and encephalitis (1,6).

Flu-like signs may include (1):

• Sudden onset fever
• Headache
• Lethargy
• Muscle pain
• Non-productive cough
• Breathing difficulty
• Chest tightness

Splenomegaly and a non-specific rash are also sometimes observed (6). Fatality occurs in less than 1% of appropriately treated humans, however mortality rates can reach 10% to 20% where antimicrobials are not provided (6).

What should I do if suspect psittacosis?

Seek medical attention if you develop flu-like symptoms or respiratory problems after exposure to birds diagnosed with avian chlamydiosis (1). Physicians should consider psittacosis in all ill human patients exposed to birds (1). Early, specific treatment for psittacosis should be initiated (1). Most states require physicians to report psittacosis cases to public health authorities (1,3).

What can I do to minimize my risk in the veterinary hospital?

Specific control measures to prevent transmission of C. psittaci and other infectious agents to humans include (1):

• The Centers for Disease Control recommends at-risk personnel wear protective gear and an appropriately fitted respirator with N95 or higher rating when handling birds infected with  psittacior when cleaning their cages (1). Surgical masks may not prevent transmission of Chlamydia (1).
• Before performing necropsies, wet carcasses with detergent and water to prevent aerosolization of infectious particles (1).
• Isolate ill birds and use standard quarantine protocols (1).
• Thoroughly remove organic debris before disinfection (1). Chlamydia psittaciis susceptible to most disinfectants and detergents as well as heat, however many disinfectants are respiratory irritants and should be used in a well-ventilated area (1).

Regular, prophylactic use of antibiotics is not recommended due to the growing risk of developing drug-resistant strains (1).

For more information on zoonoses in birds, visit “Zoonotic Avian Infections” by Neil Forbes, BVetMed DECAMS FRCVS.

References