Definition
Psittacosis is an uncommon infectious disease that is most often transmitted to humans through exposure to infected birds, especially parrots, cockatiels, parakeets and similar pet birds. Psittacosis can affect the lungs and may cause inflammatory illness of the lungs (pneumonia). Additional common symptoms include fever, muscle pain (myalgia), headaches, and a dry cough.
Psittacosis is caused by infection with the bacterium, Chlamydia psittaci, and may also be known as ornithosis. It is rare among humans. People who own birds as pets are most likely to be affected by psittacosis. In addition, psittacosis may affect people who work in environments with birds that may be carriers of the infection such as pet store workers, farmers, veterinarians and ranchers.
History
Late in the year of 1929, Simon S. Martin of Baltimore purchased a parrot for his wife as a Christmas gift. He asked relatives to care for it until Christmas day. The parrot looked increasingly ill as time passed. By Christmas day, the bird was dead. Soon after, two relatives who cared for the birds became ill. Lillian, Martin’s wife, also became ill. Their doctor had recently read about parrot fever and suspected it was the cause. When the doctor asked the U.S. Public Health service for medication to treat it, he was told that there was no known treatment.
The case was featured in a newspaper, and the fear of parrot fever spread rapidly. The overall number of cases also increased dramatically. This is because doctors began to look for pet birds in the homes and businesses of people with symptoms resembling flu or pneumonia. The American media created a panic about this new mysterious illness, and inaccurate reports of the number of related fatalities only increased this panic. However, the heightened awareness of parrot fever also presented scientists with enough subjects to eventually isolate the germ and find a treatment for it.
Epidemiology
Chlamydia psittaci is responsible for pulmonary and systemic infections that occur sporadically and as outbreaks. Exposure to infected birds is a common cause for psittacosis. Outbreaks are more common among workers on duck or poultry farms, and in abattoirs and processing plants. Veterinarians are also at increased risk.
There has been an increased prevalence of disease in England, Wales, Sweden, and the US, from infected exotic birds kept as pets, although worldwide epidemiologic studies have not been performed. Approximately 5% to 8% of birds are infected, and 465 avian species are susceptible to this organism. C. psittaci strains that infect psittacine birds and poultry are more virulent and can infect all age groups through aerosolized particles or direct contact with infected nasal secretions, feces, or tissue. Human-to-human transmission is thought to be rare and can cause more severe disease.
Risk factors
Working in, or buying from, a pet shop. Psittacosis is the most common zoonosis acquired through a pet shop according to a recent study of available literature.
- Pet bird ownership.
- Pigeon fancying.
- Contact with ill birds.
- Certain occupations:
- Poultry farmers.
- Poultry processing plant workers.
- Vets.
- Bird breeders and those selling birds.
- Zoo and bird park keepers.
- Street cleaners.
- Those working on building demolition or conservation where birds have been nesting.
Causes of Psittacosis
- Psittacosis is caused in humans by exposure to the bacterium, Chlamydia psittaci, which is most often transmitted to humans from infected birds, especially parrots and poultry, especially turkeys.
- Most infections occur from handling of infected birds themselves or by working in areas where such birds are kept or butchered (occupational exposure). Anyone in contact with an infected bird is at risk of psittacosis. However, cases have occurred in pet store workers, veterinarians, ranchers, and breeders of parrots, parakeets, love-birds, and macaws. Poultry workers handling the insides (viscera) of butchered turkeys also run a high risk of contracting the disease from blood and tissue.
- Another source of infection is the dried feces of birds and poultry and the dust from feathers and cages. Protective gloves and masks can often prevent transmission of the disease to these workers.
- The respiratory system is the most likely manner through which individuals are affected. Individuals inhale airborne organisms either from dried droppings or respiratory secretions from infected birds.
- The infected birds may be outwardly ill, or may show no signs of illness. Other animals such as cows, goats and sheep can be infected by the bacterium and can potentially transmit infection to humans. Human-to-human transmission is extremely rare, but has occurred and is usually associated with more severe symptoms than bird (avian)-to-human transmission.
Symptoms
Symptoms are very varied, but commonly include:
- Fever
- Cough, usually without much phlegm
- Headache
- Rash
- Muscle aches
- Chest pain
- Shortness of breath
- Sore throat
- Swollen lymph glands.
- Illness ranges from mild through to severe and is sometimes fatal.
Complications of Psittacosis
Complications of psittacosis may include:
- Brain involvement
- Decreased lung function as a result of the pneumonia
- Heart valve infection
- Inflammation of the liver (hepatitis)
Diagnosis and test
Since parrot fever is such a rare condition, your doctor may not suspect this disease at first. Be sure to tell your doctor if you have recently been exposed to any potentially sick birds or if you work in a pet shop, veterinarian’s office, poultry-processing plant, or any other workplace that puts you in contact with birds.
To diagnose parrot fever, your doctor will generally perform several tests. Blood and sputum cultures can reveal whether you have the type of bacteria that causes this infection. A chest X-ray can show the pneumonia that is sometimes caused by the disease.
Your doctor will order an antibody titer test to see if you have antibodies to the bacteria that causes parrot fever. Antibodies are proteins that the immune system produces when it detects a foreign, harmful substance (antigen) such as bacteria or a parasite. Changes in the level of antibodies can indicate that you have been infected with the bacteria that causes parrot fever.
Treatment and medications
The infection is treated with antibiotics. Doxycycline is used first. Other antibiotics that may be given include:
- Macrolides
- Fluoroquinolones
- Other tetracycline antibiotics
Note: Tetracycline and doxycycline by mouth are usually not given to children until after all their permanent teeth have started to grow in, because they can permanently discolor teeth that are still forming. These medicines are also not given to pregnant women. Other antibiotics are used in these situations.
Antibiotic treatment
After diagnosis, antibiotic treatment typically continues for 10 to 14 days after the fever resolves.
Most people who are treated for parrot fever make a full recovery. However, recovery may be slow in people who are older, very young, or who have other health issues. Still, parrot fever rarely causes death in humans who have received proper treatment.
Prevention of Psittacosis
- Exclusion from childcare, preschool, school or work is not necessary
- sick birds should be treated promptly by a veterinarian
- close contact with birds, especially kissing, should be discouraged
- clean bird cages regularly, including water and food trays, using gloves and a wet cleaning method to minimise inhalation of bird droppings
- exclude birds from roof spaces prior to blocking access to the birds
- tissues used by patients should be disposed of carefully.