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on farm level
Livestock
P
sittacosis is a disease that can be contracted by people
who come into close contact with birds and more particu-
larly those of the parrot family (psittacine birds). The mico-
organism causing pstittacosis is
Chlamydophila psittaci
.
Infections occur naturally worldwide and have been identified in at
least 400 avian species, particularly caged birds, colonial nesting
birds, raptors, ratites and poultry. Pigeons, turkeys and ducks are
most often affected. Among cage birds affected, more than 70% be-
long to the parrot family.
For practical purposes, all species of birds are a potential source
of infection, although the prevalence of infection is significantly
greater in caged birds than in wild ones. Some birds carry this organ-
ism asymptomatically. Others become mildly to severely ill, either
immediately or after they have been stressed (nutritional deficien-
cies, handling, overcrowding or egg laying).
The micro-organism lives within the cells (intracellular) of the body.
In people, parrot fever is readily treated with antibiotics, but it can
be fatal if it is left untreated. Other potential hosts of
Chlamydophila
species include sheep, goats, cattle, dogs, pigs and horses. The dis-
ease is also known as bird’s fever and avian chlamydiosis.
How do people contract the disease?
Psittacosis is a direct zoonosis contracted as a result of close con-
tract with birds, usually by inhalation of the infectious agent. The
droppings of infected birds, which may be symptomless carriers
or noticeably sick, contain large numbers of organisms. When the
droppings dry out an aerosol is formed in which in the organisms
are suspended and can be inhaled by people. Contaminated feathers
also play an important role in spreading the disease.
Transmission from one bird to another also occurs by inhalation
of contaminated droppings and by the ingestion of infectious ma-
terial, but transmission via the eggs (transovarial) of infected birds
to the chicks is also possible.
A person is an incidental victim of the disease and transmission
between people (person-to-person) is rare. Dogs can be infected
with
C. psittaci
if they eat infected bird carcasses or faeces. They are
probably also infected via inhalation.
The disease in birds
The disease in birds may not be obvious and apparently healthy
birds may carry and excrete the organisms in their droppings. When
stressed, such birds show severe symptoms of illness. Birds that
have a lowered resistance due to overcrowding and unhygienic con-
ditions in their cages, nutritional deficiencies, or prolonged trans-
portation are more prone to the disease. Birds with the disease may
show fever, greenish diarrhoea, inappetence, emaciation, respira-
tory distress, discharges from the eyes and nose and listlessness.
Source of infection
The natural sources of infection are wild as well as domesticated
birds, other animals of both types may also possibly constitute a
source of infection. If the host animal, usually a bird, is exposed to
stressful conditions, the micro-organism multiplies readily and is
consequently excreted in large numbers.
Birds excrete the organism intermittently and at times continuously
for weeks or months in faeces; this applies to a lesser extent to na-
sal secretions. There are several strains of
C. psittaci
, which vary in
their capacity to cause disease. This may explain why the disease in
humans varies so much in severity.
Symptoms in humans
The interval between infection and first signs of illness is usually
about ten days but varies from four to 15 days. Symptoms include
fever, headache, muscular pains, chills, respiratory signs such as
coughing or pneumonia and malaise, among others. The disease in
humans may vary from a minor to a serious illness. Parrot fever in
humans and birds often starts with flu-like symptoms and becomes
a life-threatening pneumonia.
Prevention and control
Psittacosis is a controlled animal disease in South Africa in terms
of the Animal Diseases Act, 1984 (Act No. 35 of 1984).
Total prevention and control of psittacosis is impossible in
practice because of the large number of host animals, including
wild birds, which may serve as source of infection. To date no
successful vaccine has been developed for use in host animals
and birds to prevent dissemination of infection.
Strict implementation of efficient quarantine measures, espe-
cially those applicable to birds imported from areas or countries
is essential.
Preventive treatment of birds (chemoprophylaxis), using spe-
cific medication, is successfully used during transport to prevent
excretion and dissemination of the causative organism.
Good control, hygiene, care and ventilation for birds in captivity
(cages) is essential to minimise stress and thus keep the level of
infection as low as possible.
People who keep birds in their homes, especially those of the
parrot family, and who are therefore in close daily contract
with these animals, should consult their veterinarian about the
health of the birds.
For more information on zoonotic diseases contact Dr Jan du Preez
at
drjanh.dupreez@gmail.com
or visit
www.zonooses.co.za.
Animal diseases that can affect humans
Part 5: Psittacosis or parrot fever
Dr Ja du Preez,
veterinary specialist, Public Health
Psittacosis is a
disease that can
be contracted by
people who come
into close contact
with birds and
more particularly
those of the parrot
family.