J. Comp. Path. 2016, Vol. -, 1e3
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Aspergillosis in Domesticated Birds*
Neumann
NUMEROUS observations have shown that certain
fungi belonging to the genus Aspergillus of Michel
may penetrate into and grow within the respiratory
tract of birds, and, in rare cases, in that of mammals,
producing serious changes. According to the position
they occupy, they produce diseases described under
the terms bronchomycosis, pneumomycosis, cytomycosis (that is, mycosis of the air sacs), etc.
The aspergilli are fungi belonging to the order Ascomycetes. They consist of a thallus or mycelium
divided by partitions, and are reproduced by means
of spores formed by partial division within the interior
of mother cells (asci), which are contained in almost
all cases in special organs (perithecæ).
The family of Perisporiaceæ, to which the genus
Aspergillus belongs, is characterised in its order by
the presence of a completely closed peritheca with
dense walls, the destruction or rupture of which is
necessary before the asci can be set at liberty, and
together with them the spores (asco-spores). The Perisporiaceæ are reproduced, and almost exclusively reproduced, by free globular cells, termed conidia,
grouped on the surface of special modifications of
the thallus.
The aspergilli are endowed with great powers of
vegetation, and consist of filaments or hyphæ of colourless mycelium with thin transparent walls divided
by irregularly spaced partitions; from the filaments
spring lateral branches of the same nature. These filaments form on the surface on which they grow a
branched mass, the superficial portions of which
resemble a tuft of grass. From this mycelium the fertile
filaments arise. They contain few partitions, and
exhibit a swollen club-like head. This swollen extremity becomes covered with short hairs, called sterigmata, each of which is terminated by a chaplet of
conidia, the whole forming a kind of capital which
*
This article was originally published in the Journal of Comparative Pathology
and Therapeutics (1908, 21: 260-264) and is republished with permission of
the Journal of Comparative Pathology.
0021-9975/$ - see front matter
http://dx.doi.org/10.1016/j.jcpa.2016.07.003
has been compared to a bottle-brush. The perithecæ,
which have only been detected in a few species, are
represented by little, lounded, hard grains, in the
centre of which develop oval asci containing four to
eight lenticular spores.
Several species of aspergilli have been mentioned as
existing in the respiratory tract of birds, but so far as
the domestic birds are concerned it seems well established that all cases of aspergillosis are due to one species, namely, the Aspergillus fumigatus of Fresenius. The
Aspergillus fumigatus forms a somewhat raised clump,
greenish, or sometimes bluish or grey, in colour. The
filaments or hyphæ are 2 to 3 mm in diameter, and
at points exhibit swellings varying between 8 and
30 mm in diameter. The conidia are upright, 100 to
300 mm in length, 5 to 6 mm broad at the base, and increase in size towards the summit, which consists of a
slightly elongated spheroidal head, 10 to 40 mm in
size, covered in the upper two thirds with powdery
sterigmata, 6 to 15 mm in length, sometimes shorter
towards the extreme end. The conidia are round or
oval, 2 to 3 mm in size, ordinarily bronzed, readily
detachable from the conidiophore, on which, however, the sterigmata remained fixed. Perithecæ have not
often been observed. The species develops most
readily at a temperature of 37 C.
The first recorded case of pneumomycosis was
observed in 1815 by Meyer in a jay. Its publication
was followed by that of a large number of others
embracing all orders of the class of birds. So far as
the domestic species are concerned, the guinea-fowl
and peacock stand alone in not yet having furnished
any case. Aspergillosis was detected, in the fowl by
Rousseau and Serrurier (1841), Bollinger (1881), Perroncito (1883); in the pheasant by Ch. Robin (1853),
Rivolta (1887), Lucet (1844), Perroncito (1896); in
the turkey by Lignieres and Petit (1898); in the pigeon by Rousseau and Serrurier (1841), Bonizzi
(1876), Generali (1879), Bollinger (1881), Kitt
(1881), Dieulafoy, Chantemesse, and Widal (1889),
Renon (1893); in the duck by Hayem (1873); in goose
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Please cite this article in press as: Neumann, Aspergillosis in Domesticated Birds, Journal of Comparative Pathology (2016), http://dx.doi.org/
10.1016/j.jcpa.2016.07.003
2
F.E. Neumann
by Reinhardt (1842), Lucet (1894); in the swan by
J€
ager (1816), Zschokke (1887), Lienaux (1894).
The frequency of aspergillosis in birds as compared
with mammals is evidently connected with the formation of the respiratory apparatus in the former species,
the air sacs affording conditions favourable to the
vegetation of fungi. Living in close, confined henroosts, etc., favours the development of fungi, and
certainly plays an important part in the etiology.
For this reason all the cases of aspergillosis observed
in non-domesticated species have been found in birds
kept in captivity. Forced feeding is also an occasional
cause of infestation. Aspergillosis is particularly common in pigeons so fed, the food sometimes being
forced into the trachea, and passing thence in varying
quantity into the bronchi and air sacs. Young birds
may perhaps be specially predisposed, and Megnin
states that aspergillosis of the respiratory tract sometimes rages in an epidemic form in nestling pigeons
( poussins), which die in two to three days. Finally, according to Generali, the finer bred and more delicate
races of pigeons are more prone than the common
breeds to pneumomycosis and mycosis of the air sacs.
The Aspergillus fumigatus is a fungus of very common
occurrence in nature. It develops and reaches maturity in an infinite variety of media. Its spores are found
in countless quantities in forage and on straw, and
they exhibit great resistance to atmospheric conditions. In birds, contamination most commonly follows
the ingestion of grain charged with spores, and the
entrance of the latter into the air passages is favoured
by dryness of the grain.
It is possible that in some cases the Aspergillus obtains its foothold in the respiratory organs, thanks to
some already existing disease, but as a general rule
it is truly and primarily pathogenic. The spores
conveyed by food find in the mucous membrane of
the respiratory tract a moist, warm nidus favourable
to their development. They there develop their mycelium, the presence of which causes inflammatory
changes. This view is based on numerous investigations, instituted first by Schutz and repeated principally by Lucet and by Renon. These investigators
showed that the Aspergillus fumigatus grows perfectly
at the normal temperature of birds (40 to 42 C.).
The spores develop well at 37 to 38 C., and even at
40 C.
The investigations undertaken by Dieulafoy,
Chantemesse, and Widal in 1890, and later by Lucet,
Renon, etc., confirm the pathogenic part played by
Aspergillus fumigatus. The spores of a culture of this fungus obtained from the lung of a diseased pigeon when
injected into the axillary veins of healthy pigeons produced a hepatic and pulmonary “tuberculosis,”
which proved fatal in three to four days. Injected
into the trachea, they killed the animals after a somewhat longer time, varying from ten to twenty days,
according to the dose. The lesions were then principally located in the lung, where they resembled tracts
of pneumonic infiltration or formed caseous blocks.
The histological lesions closely resembled those of
true tuberculosis, and sections revealed the presence
of nodules surrounded by giant cells.
The most recent nodules were formed of an
agglomeration of leucocytic or epithelioid cells
around one or several mycelial filaments. The older
granulations presented a central mass of mycelium,
the filaments of which appeared more vigorous at
the periphery than at the centre. In certain cases
the nodule was simply represented by a large giant
cell, the protoplasm of which contained a network
of mycelium either in a living state or having undergone changes indicating digestion by phagocytes.
Some nodules had undergone fibrous changes, the
centre being represented by a fibrillar protoplasm,
containing mere vestiges of the fungus, or being
even completely free from it, as if the lesion had
entirely destroyed the parasite.
The Aspergillus fumigatus produces its effects in an
entirely different way from bacteria. The latter act
principally through the medium of their toxins, but
the Aspergillus operates simply by its presence. It
does not appear to form products capable, when
experimentally injected, of producing toxic effects.
It sets up, in fact, an infestation and not an infection,
and it does not appear that a neighbouring or distant
centre can give birth to a centre of aspergillosis, in the
interstices of the tissues at least. Such a method of
reproduction only occurs on the surface of mucous
membranes or in open cavities.
The symptoms of aspergillosis of the air-tracts
consist primarily in acceleration of the breathing,
more or less serious catarrh of the trachea and
bronchi, and in a rough breathing sound heard
chiefly during expiration. The breathing gradually
becomes more and more impeded and difficult, the
rough breathing sound louder and, as in diphtheria,
snoring. Fever develops, appetite diminishes or
almost disappears, and thirst is marked. The sick birds
withdraw from their fellows and appear feeble. The
eyes are partially shut, the feathers ruffled, the head
is held low, and the animal appears sleepy. Wasting
proceeds more and more quickly and diarrhoea
soon sets in, causing death in from one week to two
months. In mycosis of the air sacs wasting is sometimes the only indication of the disease.
The lesions are found in the trachea, bronchi,
lungs, and air sacs; rarely in the nasal cavities or in
the air sacs of the bones. They consist of tuberclelike or membranous formations, irregular or discoid
Please cite this article in press as: Neumann, Aspergillosis in Domesticated Birds, Journal of Comparative Pathology (2016), http://dx.doi.org/
10.1016/j.jcpa.2016.07.003
Aspergillosis in Domesticated Birds
in shape, 3 to 10 mm in thickness, of a dirty yellow or
greenish tint, and are at first soft, later becoming more
consistent, and forming a fibrino-purulent exudate.
The discoid lesions are greenish or bluish in colour,
closely resembling the spots of fungus which develop
accidentally on artificial culture media employed in
the laboratory. Sometimes the air cavities are more
or less obstructed by these formations, which are
then thicker and firmer. They may undergo caseous
or calcareous degeneration. In their substance, but
particularly on or near their surface, one finds mycelium and the conidial development of Aspergillus. The
exudate is formed of fibrin containing numerous leucocytes, a great number of which are infiltrated with
fat, and countless micrococci. In the lungs one finds
agglomerated or disseminated nodules, the organ presenting the appearance of caseous pneumonia or true
phthisis. Perroncito saw one case where the disease
was localised in the membrane lining the thoracic
sacs and the peritoneum. The lesions consisted of nodules not larger in size than a pin’s head, and exactly
representing acariasis due to Laminosioptes cysticola.
The centre of each contained a mycelium of Aspergillus.
In young pigeons the lesions of aspergillosis are
most commonly found in the lung and liver, more
rarely in the oesophagus, intestine, and kidneys.
They are sometimes localised in the buccal cavity,
which is rarely free from them. The lesions in the
buccal membrane assume the form of whitish, apparently caseous, nodules, varying in size between a pea
and a hazel nut. In the lung they appear as miliary,
transparent, or opaque tubercles, isolated, disseminated, or agglomerated into caseous masses similar
to the tubercles described by La€ennec. These growths
contain no tubercle bacilli, but in their centres may be
found a fungus, which on culture proves to be the
3
Aspergillus fumigatus (Dieulafoy, Chantemesse, and
Widal, 1890).
Aspergillosis is common in the Italian pigeons sold
in Paris. A good number of these show large disseminated mycosic swellings. The buccal form had
already been noted in a pigeon by Rivolta and Delprato. Its localisation in the beak of the pigeon gives
its special importance. According to Dieulafoy,
Chantemesse, and Widal, pigeon-feeders probably
contract the contagion of the peculiar chronic lung
disease, from which they so frequently suffer, from
these birds. In certain establishments in Paris men
are employed who feed thousands of pigeons per
day by filling their mouths with a mixture of water
and grain, and then, by applying their lips to the
open beak of the bird, injecting a portion of the
mixture into the bird’s crop. It is probable that the
germs of Aspergillus are conveyed to them either
from the surface of the grain with which they fill
their mouths or from direct contact with the buccal
swelling in diseased pigeons. Cultural and inoculation experiments made with the sputum of such persons confirm this explanation.
The prevention of aspergillosis (which sometimes
assumes an epizootic form) evidently consists in rigid
cleanliness in the poultry-roosts, runs, etc., in disinfecting them by means of boiling water, and in destroying any kind of material which may harbour
the particular fungi.
The disease is usually fatal. In the early stages,
however, improvement occasionally follows the use
of vapour of tar. A tablespoonful of vegetable tar is
mixed with half a litre of water, and a piece of redhot iron is plunged in the mixture and stirred about.
The vapour should not be so dense as to cause irritation of the air passages. (Neumann, Rev. Vet., 1st July
1908, p. 417.)
Please cite this article in press as: Neumann, Aspergillosis in Domesticated Birds, Journal of Comparative Pathology (2016), http://dx.doi.org/
10.1016/j.jcpa.2016.07.003