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Psittacosis, also known as parrot fever and
ornithosis, is a bacterial infection of humans that can cause severe
pneumonia and other serious health problems . It is caused by Chlamydophila psittaci
(obligate intracellular bacterium)
, formerly known as Chlamydia psittaci .
Visit:
Chlamydial Infection
;
Chlamydial Conjunctivitis (Inclusion
Conjunctivitis).
;
Chlamydial Infection of the Genital Tract
;
Trachoma
;
Lymphogranuloma Venereum
.
Once thought to
infect only psittacine birds, C. psittaci is harboured by many other
birds, including chickens, turkeys, pigeons and sea gulls and by many
mammals. Many usually acquires the disease by contacting infected
birds.
C. psittaci
causes systemic disease in man, but pulmonary involvement is most
prominent.
The organisms are
inhaled with dust-borne contaminated excreta or aerosolized droplets.
The organisms are carried to the reticuloendothelial cells of the
liver and spleen, proliferate, and disseminate to the lungs and other
organs.
Clinical
presentation:
The disease
ranges in severity from subclinical to fatal.
After an
incubation period of 7 to 21 days, an intense headache and fever
herald the disease. A faint macular rash (Horder's spots), resembling
the rose spots of typhoid fever , may be present.
Pharyngitis,
malaise, anorexia and painful myalgias and arthralgias are common, as
is hepatosplenomegaly. A persistent dry, hacking cough, fine crepitant
rales, and tachypnea are typical.
Morphological
features:
Infectious Disease Online
Lungs:
Psittacosis begins as an inflammatory process in the lung and
progresses to consolidation, primarily lobular but occasionally lobar.
It progresses through a sequence of congestion, edema and red and gray
hepatization.
Histopathologically, fibrin, erythrocytes and neutrophils appear early
in the alveolar exudate. Later the alveoli contain large mononuclear
cells and epithelial cells. Interstitial infiltration is not
present in early stages, but as the disease progresses lymphocytes and
monocytes invade the alveolar walls.
Hyperplasia of
alveolar type 2 pneumocytes is typical. In severe disease abscesses
form in alveolar septa and hemorrhage and fibrin may fill the alveoli.
The hilar lymph nodes show lymphadenitis and reticulo-endothelial
hyperplasia.
Elementary bodies
in the alveolar lining cells appear as clusters of minute,
intracytoplasmic, basophilic, coccobacillary inclusions upto 0.8
micrometer in greatest dimension. The organisms are dark blue with the
Van Gieson and Giemsa stains and red against a blue backround with the
Gimenez or Machiavello stains. They are also demonstrated by direct
immunofluorescence.
Rarely, severe
extrapulmonary
manifestations
may occur.
Dissemination is characterized by foci of necrosis in the liver and
spleen and diffuse mononuclear cell infiltrates in the heart, kidneys
and brain.
Liver:
In the
liver, swelling, vacuolization, and phagocytic activity of Kupffer's
cells are prominent, and intracytoplasmic elementary bodies can be
seen in the Kupffer cells. Focal necrosis in the spleen is accompanied
by diffuse reticuloendothelial hyperplasia and desquamation of
mononuclear cells into the splenic sinuses. Pericardial and myocardial
inflammation have been described.
Heart:
Chlamydial infection should be considered in cases of
idiopathic dilated cardiomyopathy,
myocarditis ,
pericarditis,
and
endocarditis of unknown origin. An early diagnosis has
important therapeutic and prognostic implications.
C. psittaci myocarditis is probably a
rare disease, but the exact prevalence remains obscure.
Brain:
It is rarely involved and shows edema, congestion and focal
hemorrhage.
Ocular adnexal
non-Hodgkin lymphoma :
A recent report suggests that ocular adnexal non-Hodgkin lymphoma (NHL) may be related to Chlamydia
psittaci infection. The distinctive patterns of ocular NHL call for
further studies to identify risk factors and mechanisms, including the
potential role of C. psittaci or other infections. Studies from Italy
showed Chlamydia psittaci infection in 87% of ocular adnexal MALT
lymphomas and complete or partial regression of the lymphoma after C.
psittaci eradication in a nuber of cases.
In pregnancy:
Chlamydia psittaci is associated with
significant morbidity and mortality during pregnancy, and its rarity
can delay early diagnosis and treatment.
Vasculitis:
Some authors suggest the role of
Chlamydia in the pathogenesis of atherosclerosis and some vasculitis.
There is a possible
association between C. psittacci infection and temporal
arteritis.
Diagnosis of
the disease:
The clinical
signs and symptoms are not diagnostic and routine laboratory findings
are not specific ; a history of exposure to birds may be the best
clue. Radiographs of the chest usually reveal a patchy lower lobe
infiltrate, but findings vary. The diagnosis is made either by
isolating C. psittacci from sputum, blood or tissue specimens or by
serologic tests..
The possibilities for diagnostic detection of chlamydiae
have considerably improved following the introduction of molecular
methods, particularly the polymerase chain reaction (PCR), which
permits direct identification from clinical specimens and
differentiation of species.
Information
about psittacosis is essential for public health officials,
physicians, veterinarians, the pet bird industry, and others concerned
about controlling these diseases and protecting public health.
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