PART 2
MYCOSIS
This is a general term applied to the infections with Hyphomycetes, but in the zoological material discussed here it refers chiefly to the growth of aspergillus in the air sacs and viscera of birds. A few cases of cutaneous mould growth have been seen in mammals but are of trifling importance; brief mention will be made of them on a later page.
Under the names of Aspergillosis and brooder pneumonia, the infection with _Aspergillus fumigatus_, _A. glaucus_ and others is well known to breeders of chickens, ducks and ostriches. Literary references to its occurrence in zoological collections are numerous, but there seems to be no record indicative of its frequency in the various orders nor discussion of the pathological types best exhibited by different birds. There has indeed been some discussion of the actual entity, mould disease, the picture found at autopsy being referred to secondary contamination with fungi in the presence of bacterial infection. Experiments by DeLong and others have been indifferently successful in the production of the disease by inhalation of mould spores. The appearance of groups of cases in breeding places, apparently all exhibiting the same organism, in the absence of other varieties of avian epizoötics seems to warrant the conclusion that the hyphomycetes can at least be associated with a fatal morbid lesion of quite uniform character whether or not they be the original invaders.
Judging by our experience it would seem probable that the aspergillus can, under conditions not fully explained, cause inflammation of the avian air sac and tubercles in viscera, in the absence of other evident causes of illness and death. Over three-fourths of our cases have no other diagnosis than “mould disease”; this may be in part due to overlooking other things, but to a much greater extent to the very extensive mould growth which obscures all other changes. That unexplained preparatory conditions may exist is indicated by general observation and some experimental work. Whereas in breeding establishments this disease occurs in epizoötics, or in groups of cases, with us it is enzoötic, constantly present, never, however, bursting forth in virulent form with high mortality. Nor is the condition highly contagious.
In an attempt to explain its source I examined over forty varieties of feed and found therein several strains of aspergillus and of mucor; the latter occurs occasionally in the avian air sac. The infective material is therefore constantly present, and it would seem that if it were capable of initiating a fatal disease many more cases should come to our attention. Perhaps these moulds do gain access to the avian air sac and are killed off, or only assume a pathogenic rôle when they are in large numbers or a preëxisting disease assists them. Since our records do not support the idea that a preceding condition must exist for a growth of mould to be successful, and yet pathological and experimental observations suggest that something helps its colonization in the air sac, what are such conditions? Moulds grow on feed and litter in which birds pick; from this it is quite possible for a piece of grain or even inorganic matter laden with spores to be inhaled and lodged in a secondary alveolus near the air sac whence extension into the air spaces could occur. In addition I think it quite conceivable that a whole colony of mould might be inspired with the same result, the mechanical obstruction being sufficient physical damage to incite inflammation. The continuous moist surfaces of the bronchial passages and air sacs afford conditions favorable to the growth of mould and as inflammation is not vigorous, little resistance is presented to its spread.
The mode of operation of these hyphomycetes has usually been assumed to be a mechanical one, local colonization replacing healthy tissue or spreading along surfaces so that function is physically impossible. A support of this idea is to be found in the fact that inflammation, as produced by schizomyces, is trifling or absent; the necrosis that occurs is due to choking off of tissue by the intricately tangled masses of mycelia and blocking off of air or blood supply. The existence of an infiltrating and necrotizing form in some parrots and gallinaceous birds, suggested to me that a toxin might be responsible for some part of mould action. Proof for this speculation was sought by injecting into the pectoral muscles of pigeons an emulsion of a dead mould and a filtered broth culture. Necroses occurred but only to an extent which I interpreted as due to the physical destruction of muscle by the injected material; they were larger with the dead mould than with broth filtrate. I concluded therefore that aspergillus perhaps has no toxin as usually described for bacteria.
TYPES OF MYCOSIS.
Avian mycosis occurs in three different forms, two of which are probably of similar nature and two are frequently combined. The first variety, most often seen in gallinaceous and anserine birds, consists of thickening and opacity of the air sac walls, upon the surface of which either a curd-like pseudocoagulum or a velvety or fluffy mould growth appears. This variety usually begins about the anteroinferior pulmonary stoma on the right side extending thence to the related sac, upward toward the wing and downward to the abdominal spaces. Occasionally the middle thoracocervical space is involved, probably _via_ the opening in the syrinx. Extension takes place by the way of normal passages, but when the growth is dense it also seems to occur by continuity through tissue. This variety may or may not be associated with the second, an infiltrative type of lesion best seen in the lung. Under what seems to be a true picture of mycotic pneumonia, dirty gray consolidated areas will be found around the bronchial space, infiltrating in all directions and without definite boundaries. A similar lesion has been seen also in the liver on rare occasions, but the lung is its usual seat. Judging from microscopic appearances this is a process complicated by the addition of bacteria.
[Illustration:
FIG. 59.—NODULAR OR TUBERCULAR MYCOSIS IN THE LUNGS OF A DUCK. ONE- HALF OF THE LUNG IS CUT AWAY AND LAID ON THE INTESTINES TO CONTRAST THE PLEURAL AND SECTION SURFACES. ]
The third variety is nodular or tubercular mycosis, a process of probably more chronic nature since around the isolated lesions connective tissue is perceptible, it being absent or inconspicuous in the other types. The formation of gray or yellow-white nodules from a few millimetres to a centimetre in cross section, is the characteristic production in this variety. Lungs, liver, spleen, intestines and air sacs are involved in about this order. Attempts at explanation of this peculiarity of growth were made in the direction of identification of the species of mould, kind of bird and probably degree of resistance. No conclusions could be drawn since the same variety of mould was found in this as in other types; no bird showed a special susceptibility or resistance to it. It is quite difficult to obtain a culture from nodular mycosis, it being necessary to crush or grind the solid masses before making cultural implants. This variety should always be differentiated from tuberculosis by staining for the organisms.
Histologically studied these three types are not as easily separated as the gross appearances would warrant one to expect. The original mould nodule begins in essentially the same manner in all, a small colonization of mycelia and spores which grow centrifugally, but ever becoming more intricately wound in their first location. As the tissue is invaded, total necrosis takes place, no recognizable cellular architecture being left. When fully formed the mycotic tubercle consists from the centre outward of a necrotic mass, in which spores and mycelia stain indifferently well, surrounded by a dense zone of fully formed mould beyond which mononuclear cells and a few loose fibrils may be found. The circumferential tissue of the viscus supplies a mild congestion and perhaps a moderate connective tissue capsule. Giant cells, as known for tuberculosis, do not appear.
Where the process involves loose tissue like the lung, especially when growing rapidly, the sporulating heads of the mycelia stretch out in advance of the main mass and resemble rays. So too in a rapidly growing nodule radiating mycelia are sometimes seen but never with the regularity of arrangement typical for actinomycosis. Diffuse and irregular mycelial spread is characteristic of the second or infiltrative type of lesion and between the mould stalks one may discover well preserved tissue cells and at times bacterial forms like cocci or bacilli. This picture, suggesting as it does bacterial admixture and more active inflammation, leads one to the conclusion that the morbid process in which it is found does not represent mould disease _per se_, but a mixed infection. Whether or not the bacterial disease exists first and paves the way for the mould I am unprepared to say; I am inclined to the view that mycosis can start by itself.
INCIDENCE IN AVIAN ORDERS.
Mycosis may be said to occur in all birds although the appended list fails to show cases in a few of the orders included in this study; the sum total of autopsies from missing orders is only 45, so that they may be ignored.
═══════════╤═══════════ │ per cent. Passeres │ 3.7 Picariæ │ _1.2_ Psittaci │ 3.9 Striges │ 6.7 Accipitres │ 5.1 Columbæ │ .6 Galli │ 2.7 Fulicariæ │ _8.6_ Alectorides│ _2.7_ Gaviæ │ _10._ Impennes │ _40._ Herodiones │ _2._ Anseres │ 6. Struthiones│ _9.4_ ───────────┴─────────── For meaning of italics see foot note Table 1.
[Illustration:
FIG. 60.—MICROSCOPIC APPEARANCE OF ONE OF THE NODULES. NOTE THE CENTRAL NECROSIS AND THE CLOSE FIBROCELLULAR PACKING IN THE RESTRAINING CAPSULE. ]
[Illustration:
FIG. 61.—MYCELIAL GROWTH IN AN ALVEOLUS IN THE RAPIDLY SPREADING VARIETY OF PULMONARY MYCOSIS. SEVERAL FRUIT-HEADS ARE VISIBLE. ]
These figures hardly permit conclusions as to relative vulnerability unless the large percentage of cases for the small number of Impennes, Gaviæ and Struthiones be permitted to stand. Judging from orders upon which there are at least one hundred autopsies, owls, ducks and eagles are most likely to suffer with mycosis. The percentages are, however, not very convincing, and it would seem better with these data to conclude for the present that any variety of bird is susceptible to mould. Ostriches have long had the reputation of succumbing to this affection, so that their outstanding position in the list is more easily credited.
It was to be hoped that the various susceptibilities would assist in an explanation of the genesis of mould disease, but the result of the analysis is suggestive only in one direction which can be stated quite briefly. Ostriches, owls, shore and swimming birds have large stomata between the lungs and the lateral air sacs and show a high mould disease incidence. The natural thought is that access of mycelia and spores to the air sacs is facilitated. More comparative data is being assembled upon this point. Water birds are more susceptible to mould than land birds; the percentages based upon cases and totals for orders is 5.4 to 3.7.
The hygiene of mycosis is that of scrupulous cleanliness. Being hampered by incomplete knowledge as to its genesis one can only apply common sense measures. The germs having been found upon all the vegetable feeds, it naturally follows that they cannot be eradicated, but their colonization in large numbers can be prevented by repeated cleansing or sterilization of bins and pans so that no mouldy or musty material is given to the animals. At times of serious outbreaks sterilization by burning all old feed, starting fresh with good material in bins painted or saturated with disinfectant and then deodorized, is the only salvation. Where the blast lamp can be applied, it is the safest procedure. Autoclave sterilization should be thorough if practiced. By constant vigilance we believe that our large exhibition house is protected, but the sanitation of the pond, where many ducks have the disease, can never be so satisfactory.
Mycosis among mammals as an organic pathological entity is certainly a rare condition, indeed almost always to be considered an accidental or secondary one. In so far as human pulmonary disease is concerned it is among the pathological curiosities deserving of individual report. Moulds of several varieties have been found in intestinal ulcers, in cranial sinuses and in the ear, while generalized mycosis from thrush and favus are reported (cases of thrush in kites with fatal outcome has been described on page 168). Cutaneous infestation with mould is quite another matter for ring worms and similar conditions are now believed to be due solely to the penetration by spores and mycelia into the superficial dermis and into hair follicles. Numerous small lesions have been detected on dogs and cats that correspond to the ring worms described for them; to these we have devoted little study, because when discovered the animal is removed, treated or killed to protect others. Doctor Weidman has discovered several varieties of hyphomycetes which he will report upon at a later time. No case of generalized mould disease has been found in mammals, but Doctor Weidman has discovered a hitherto undescribed mould in ulcers and cutaneous abscesses of seals; no extension beyond subcutaneous areolar tissue occurred in these cases.
Botryomycosis, while not strictly belonging to the foregoing group, may be mentioned here because of its nodular tumor-forming superficial growths. The case to be cited certainly belongs to this illy defined group of diseases even if the organism was not isolated. It cannot be accepted as wholly demonstrated that the disease described under this name is always the same or that it has a single cause.
California Hair Seal (_Zalophus californianus_) ♀ . Had sore spots on side for several months. Ate well up to three days before death but ate something to time of death.
DIAGNOSIS.—Chronic enteritis with acute hemorrhagic exacerbation. Low grade chronic diffuse nephritis. Botryomycosis. General condition poor, subcutaneous fat practically absent. On the left side of the thorax there is a warty and nodular thickening of the skin overlying diffuse and flat thickening of subcutaneous tissues. There are warty, pustular, fistulous communications in four places between surface and deep mass. They are covered over with light crust. On dissection mass is found to be in subcutaneous tissue well outlined and encapsulated and consisting on section of dense, white, firm trabeculæ forming a mesh around yellow, soft areas which can be squeezed out. An adjoining lymph node is much enlarged, dense, tough, resilient, on section showing great connective tissue increase and solid brown medulla. The thyroids are solid, brown, 3. x 2. x .6 cm. and 3.7 × 1.8 x .6 cm. Trachea and bronchi contain pink froth but mucosa is negative. Anterior edges of lungs are distinctly emphysematous. Remainder of lung is uniformly congested and lobules are quite prominent. No consolidations. Bronchial lymph nodes are slightly large, anthracotic and wet. The heart is dilated, filled with mixed clot, muscle firm and deep brown color. The liver surface is smooth, edges sharp, size normal, color dull brown with greenish cast, consistency firm and tough. Section surface is glistening, smooth, moist, lobules indistinct but probably normal. The gall-bladder is full of fluid yellow bile. The common duct is patulous. The spleen is of normal size and shape, capsule opaque gray. The trabeculæ are prominent, the pulp stippled rusty brown. The kidney is of normal size, capsule is smooth, strips easily leaving a smooth purple surface. The organ is firm. The lobules and lobular markings are distinct. The adrenal has a narrow regular brown cortex and gray homogeneous medulla. The stomach contains whole fish. The mucosa shows digestion, congestion and mucus formation. Beginning at the pylorus and extending to the colon the mucosa is swollen and edematous, yellow brown. In the lower part it is quite firm and opaque. In the upper part it is more translucent except where there are diffuse hemorrhagic mottlings of the submucosa. Here and there are shallow erosions but no ulcers. The lymphatics of the mesentery are definitely enlarged, white, pale and very firm. Smear from the surface of the growth in side fails to show any definite yeasts or moulds by Loeffler’s or Gram’s stains. It is largely made up of polynuclear cells with many large mononuclears, many of which are phagocyting polynuclears and nondescript bodies. Cultures failed to grow. Microscopic section of liver shows marked congestion with slight hydropic degeneration of the epithelium. The kidney capsule is not thickened. Interstitial tissue not grossly exaggerated but connective tissue nuclei fairly numerous. Some tufts have decidedly more elongated nuclei than others and connective tissue around the stalk vessels seems hyaline. Capsule for most part not thickened but space contains cells and detritus in many instances. Epithelium of the tubules for the most part swollen, loosened and without nuclei. Some imperfectly formed casts. The intestine shows distinct congestion of the whole mucosa with here and there definite small hemorrhages well out in the villi. Slight round cell increase but no definite fibrosis. In submucosa around vessels connective tissue is hyaline in many places. The tumor on side consists of dense strands of connective tissue forming alveoli of varying size containing an exudate of fibrin and cells, about three-fourths of the latter being mononuclears. Neither connective tissue nor cells are arranged in a characteristic or peculiar manner so the observer is forced to conclude that this is one of the conditions of the group called Botryomycosis.
SECTION XVII—