Control of Psittacosis (Ornithosis)

Pet birds as a source of psittacosis.
In the UK in recent years there has been an increasing trend for birds, and other pet animals, to be sold through large store chains in addition to more conventional high street pet shops. This may encourage purchase without adequate preparation and planning. Many of the birds sold in this way originate from a small number of suppliers. Chlamydophila psittaci is transmitted primarily by aerosols so the presence of strong air currents, especially in large out-of-town stores, may be a factor in the spread of infection. The transmission of infections from birds to humans may be dose-dependent; cages should be regularly cleaned, ensuring that faeces do not accumulate for long enough to dry out and become aerosolised (airborne).

Infections in pet birds and pigeons continue to present a significant hazard to human health; however, eradication or elimination of chlamydial infections in birds is impossible as these infections are carried by a wide range of avian hosts throughout the world. Improved methods of diagnosis and treatment, quarantining of imported birds, and improvements in hygiene in the poultry industry have resulted in a reduction in the number of outbreaks in the poultry industry since the 1960's. Relaxation or breakdown in any of these control measures could lead to the re-emergence of avian C. psittaci infections and their transmission to humans.

Dealing with infected birds
Birds with probable or confirmed infection should be destroyed or treated under the supervision of a veterinarian. If treated with medicated feed, the treatment is considered to have commenced only when the birds accept medicated feed as the sole food in their diet. This may be an unsatisfactory method of freeing birds from infection since wild-caught birds will often not accept unfamiliar food. They may also have a suppressed immune system after becoming stressed in transit, enabling an increase in the number of organisms carried.

For treatment of infected birds the drug of choice is chlortetracycline, which is usually delivered as impregnated seed. Small pet birds are usually treated with millet containing the antibiotic at 0.5mg/g for 30-45 days. Intramuscular or subcutaneous administration of tetracyclines is only recommended for up to one week due to the risk of local tissue damage.

There is no vaccine for avian chlamydiosis.

Control measures
In order to prevent transmission of C. psittaci from birds to humans, a number of control measures are recommended, including isolation of newly acquired birds and implementation of rigorous disinfection measures to prevent the spread of infection. It is essential that people potentially exposed to infected birds should seek medical advice if they develop influenza-like symptoms or other respiratory illnesses.

Control measures include the quarantine, surveillance and antibiotic treatment of imported birds. During antibiotic treatment, appropriate disposal of infected material and disinfection of housing may help to eliminate Chlamydophila and reduce the risk of re-infection. In the UK there are two Statutory Instruments (Importation of Birds, Poultry and Hatching Eggs Order 1979 and, Psittacosis or Ornithosis Order 1953) that allow for the Official Control of outbreaks of chlamydial infection in, for example, poultry processing plants, pet shops, quarantine stations or breeding aviaries. For imported captive birds entering quarantine in the European Community, decision 2000/666 now applies, which requires specific action to be taken when the infection is detected in psittacines during quarantine. If, during quarantine, it is suspected or confirmed that psittacines are infected with Chlamydophila psittaci, all birds in the consignment must be treated by a method approved by the Divisional Veterinary Manager (DVM), and the quarantine must be prolonged for at least two months after the last recorded case.

Control and disinfection in C. psittaci infection

1. Practice preventive husbandry
Position cages to prevent the transfer of faecal matter, feathers, food and other materials between cages. Do not stack cages; use solid-sided cages or barriers if cages are adjacent to each other. The bottom of the cage should be of wire mesh. Litter that will not produce dust (e.g. newspaper) should be placed underneath the mesh. Clean all cages, food bowls and water bowls daily. Soiled bowls should be emptied, cleaned with soap and water, rinsed, placed in disinfectant solution, and rinsed again before re-use. Between occupancies by different birds (or bird groups), cages should be thoroughly scrubbed with soap and water, disinfected and rinsed in clean running water. Exhaust ventilation should be sufficient to prevent accumulation of aerosols and prevent cross-contamination of rooms.

2. Control the spread of infection
Isolate birds requiring treatment. Rooms and cages where infected birds were housed should be cleaned immediately and disinfected thoroughly. When the cage is being cleaned, transfer the bird to a clean cage. Thoroughly scrub the soiled cage with detergent to remove all faecal matter, rinse the cage, disinfect (allowing a minimum of 5 minutes contact with the disinfectant), and re-rinse the cage to remove all disinfectant. Discard all items that cannot be adequately disinfected (e.g., wooden perches, ropes, nest material and litter). Minimise the circulation of feathers and dust by wet-mopping the floor frequently with disinfectant and preventing air currents and draughts in the area. Reduce contamination from dust by by spraying the floor with disinfectant or water before sweeping it. Do not use a vaccuum cleaner as this will aerosolise infectious particles. Remove waste material from the cage at frequent intervals (moisten first) and incinerate or double-bag the waste for disposal. Deal with healthy birds before handling isolated or sick birds. Observe good personal hygiene.

3. Disinfection
All hard surfaces should be cleaned thoroughly before disinfection. Chlamydophila psittaci is susceptible to most disinfectants and detergents as well as heat; it is however, resistant to acid and alaklai. A 1:1000 dilution of quaternary ammonium compounds is effective, as are 70% isopropyl alcohol, 1% lysol, 1:100 dilution of household bleach, and chlorophenols. Many disinfectants are respiratory irritants and should only be used in a well ventilated area, following the manufacturers instructions. Avoid mixing disinfectants with any other product.

Further information

European Commission Scientific Committee on Animal Health and Animal Welfare (2002). Avian chlamydiosis as a zoonotic disease and risk reduction strategies. Report Number SANCO/AH/R26/2002. Available at: http://ec.europa.eu/food/fs/sc/scah/out73_en.pdf

American Veterinary Medical Association (2010). Compendium of measures to control Chlamydophila psittaci (formerly Chlamydia psittaci) infection among humans (psittacosis) and pet birds, 2010.
Available at http://www.nasphv.org/Documents/Psittacosis.pdf

Last reviewed: 15 July 2011