Chlamydial infections in animals
Chlamydophila psittaci in birds: Epidemiology
Infections with chlamydial agents have been described in 130 species of birds from 10 orders
(Meyer, 1965).
Chlamydial infections in birds are important as they represent a biological hazard to
human health as well as economic loss to the poultry industry. C. psittaci has
been recovered from symptomatic and from apparently healthy birds. Infection
principally involves the gastrointestinal tract and the chlamydiae are shed in
faeces or via infectious respiratory tract discharges. Clinically inapparent, latent infections may be the predominant state. Overt clinical disease
may be activated by stress factors, including overcrowding, poor nutrition, other bacterial and viral infections, and
transportation.
Apparently healthy birds shedding chlamydiae,
can infect other birds or humans through contact. Infectious chlamydiae in respiratory secretions or faeces may remain viable for several months. Transmission of disease is mainly through aerosols of faecal or feather dust, but oral infection is an alternate route. Transmission through eggs has been shown in chickens, ducks, seagulls and
psittacine birds. However, most infected eggs do not hatch (Shewen,
1980). In the nest, parent birds may infect their young, which
may carry the infectious agent for many years. Young birds are more susceptible to infection than older birds, and some species seem to be more susceptible than others. Often, disease carriers may be identified
by the transmission of disease to other susceptible birds or by the sudden death of young nestlings with apparently healthy parents.
Although outbreaks of C. psittaci
infection in feral birds appear uncommon, it is possible that wild birds may act as natural reservoirs of the
agent and introduce chlamydiae into farmed bird populations such as turkeys and ducks, with potentially devastating consequences.
Wild and racing pigeons, the psittacine bird trade, and migrations of wild birds such as seagulls, finches, sparrows and waterfowl may all contribute to the dissemination of chlamydiae throughout avian populations.
NEXT: C. psittaci: Clinical
signs
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