Introduction
Psittacosis (aka Ornithosis) is an infectious disease, sometimes associated with an atypical pneumonia, caused by the gram-negative bacterium Chalmydia psittaci. It is usually transmitted to humans from birds.
It is contracted through inhalation of bacteria – usually from bird droppings and feather dust from infected birds. Infection may also be passed when handling birds, or in the case of a well-loved pet, mouth-to-beak contact. Humans can catch the illness from many types of bird, but pet birds are most commonly implicated. This means that those at risk include pet owners, vets, and those working with birds in other contexts. About 70% of cases are thought to from pets to their owners.
- There are cases of humans contracting the disease as a result of inhaling dust from bird faeces that has been stirred by by a lawn mower
Person-to-person spread is possible but is rare.
Birds themselves may be asymptomatic, or can be very sick. Birds may show symptoms such as diarrhoea, ruffled feather, poor feeding and runny eyes / nose.
It is a rare disease – there are about 50 confirmed cases in the UK each year – although this is likely an underestimation.
It is not related to bird fancier’s lung (aka pigeon fanciers lung) which instead refers to a chronic pneumonitis caused by exposure to bird faeces, and is non-infectious in origin.
Presentation
Incubation period varies from 4 days to about 4 weeks, usually within 14 days following exposure. It typically produces a flu-like illness.
- Headache
- Fever
- Cough
- Myalgia
- Sore throat
- Malaise
- Dry cough
- SOB
- Chest pain
Severe cases can cause sepsis and require ICU care. Most cases are mild.
- Mortality is <1% in treated cases, around 15% if untreated
Investigations
- CXR
- Signs of pneumonia
- Often the CXR findings are no concordant with the clinical findings on examination
- There are no specific sings that identify psittacosis as the cause
- Sputum culture
- Often not much sputum is produced and thus no often reliable
- Serological testing. Severe methods are available:
- Compliment fixing
- Micoimmunofluorescent antibody test
- May cause fate positive due to cross-activity with other chlamyida species
- Often two samples are required to show an increasing number of antibodies between the times the samples were taken
- PCR testing
- Quick
- Sensitive and specific
- Requires specialist reagents and equipment. Often needs to be sent away to specialist laboratory
Differentials
- Bird Fancier’s Lung
- Pneumonia
- Q fever
- TB
- Avian influenza
Management
Sensitive to:
- Tetracyclines – e.g. doxycycline, tetracycline
- Often not suitable for children
- 2-3 weeks required
- Macrolides
- Azithromycin
- Clarithromycin
- Erythromycin
- This is the usual second-line agent
You may need to seek advice from the local infectious diseases specialist / microbiologist.
Pet bird owners should be advised of ways of treating their bird, and reducing the risk of transmission. Remember that infected birds may not show any symptoms.
- Wash hands after handling birds
- Don’t let faeces build up in the bottom of cages
- Wear a respirator and gloves when cleaning cages
- Wash hands after cleaning cages
- Avoid mouth-to-beak contact
- Good ventilation of bird cages
- Avoid overcrowding of birds
References
- Psittacosis – patient.info
- Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
- Psittacosis – NSW Health
- Psittacosis – CDC
- Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.