Avian chlamydial infections
Chlamydophila psittaci : Treatment
and control
The drug of choice is
chlortetracycline [see: tetracyclines], which is usually delivered as impregnated seed
or in cooked mash. The following doses are generally used: 400-790 g/ton to control disease in turkeys or ducks for 45 days, with up to 2800 g/ton for tissue clearance. Smaller pet birds are usually treated with millet containing the antibiotic at 0.5 mg/g for 30-45 days.
Of the other tetracyclines, oxytetracycline can be administered by intramuscular
injection for one week only, due to the risk of local tissue damage (Flammer,
1987). Doxycycline, may be used for intramuscular or subcutaneous injection or for oral treatment.
A quinolone, enrofloxacin®, can also be used for the treatment of chlamydial infections in birds. When supplied in medicated food for 3 weeks, it was shown to eliminate
chlamydiae from parakeets (Dorrestein, 1989).
Control measures include
the quarantine, surveillance and antibiotic treatment of imported birds. During antibiotic treatment,
the disposal of infected material and the disinfection of avian quarters is helpful in eliminating chlamydiae and reducing the risk of
reinfection. 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 epidemics,
for example in poultry processing plants, pet shops, quarantine stations or breeding aviaries.
Similar legislative measures exist in the US and other countries. Eradication or elimination of chlamydial infections in birds
is impossible, as these infections are harboured by many diverse avian hosts throughout the world.
Infections in pet birds and pigeons continue to present a
significant hazard to human health (Grimes and Clark,
1986). Improved methods of diagnosis and treatment as well as
the quarantine of imported birds and improved hygiene in the poultry industry have
reduced disease outbreaks since the 1960s. As stated by Storz
(1988), relaxation or breakdown of any one of these control measures could lead to
the re-emergence of avian C. psittaci infections and their transmission
to humans.
A vaccine for avian chlamydiosis is not currently available. Research efforts concerning the preparation of a DNA vaccine for use in birds are in progress. Vaccines based on plasmid DNA expressing
C. psittaci MOMP, and inoculated systemically or locally, have been used in turkeys.
MOMP-based DNA vaccination was shown to prevent severe clinical signs and chlamydial excretion in turkeys challenged with the same serovar
(Vanrompay et al., 1999).
For guidelines on
controlling avian and human C. psittaci infections see:
AVMA Compendium on
measures to control C. psittaci infections in birds and humans
2002 [National association of state public health
veterinarians]
[PG] updated by MEW
June 2002
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