[ This section is primarily concerned with chlamydial infection of domestic or farm animals, though note is made where humans may be incidentally infected.
The Everett Andersen 1999 classification has been particularly helpful in the veterinary field, rationalising the old dumping ground of C. psittaci. This classification's distinction between Chlamydia and Chlamydophila, causing primarily human or animal infections respectively, is also helpful. Accordingly this classification is used throughout this section. ].
[ Thanks to Dr Peter Griffiths, formerly of the Central Veterinary Laboratory at Weybridge, in the UK, who wrote this section originally].