Part 52

The value of the test can best be estimated by a recital of the mortality of monkeys, from tuberculosis, since its inception. Before the test was started practically every monkey in the collection for sufficient length of time to be exposed died from the disease. The average duration of exhibition life of all specimens up to 1903 did not exceed eleven months. The time has risen almost uninterruptedly until now it is thirty-five months. There are, at time of writing, sixty-eight specimens in the cages which have been on view from one to one hundred and eighty-five months with an average of fifty-four months. These figures speak for themselves as evidence of the reduction of infection. The average mortality from enteritis and degenerative bone disease has remained about the same through all these years. Percentage figures such as are recorded in our yearly report are misleading because all monkeys written into the property record of the Garden are listed and since some of these specimens remain in quarantine, they do not properly belong to the exhibition collection. Up to 1906 when the test technique was perfected nearly all deaths were due to tuberculosis, the figure for 1906 (including experimental animals) being 78 per cent. However from February 1906 to October 1907 and from then until May 1910 no case of tuberculosis occurred in the exhibition cages and both deaths at these given times seem like infection from visitors. During the next three years thirteen monkeys died of the disease in the exhibition and many more in quarantine. By 1913 the outbreak was stamped out. Its explanation is not so very far to seek. In the fall of 1910 we obtained some suspected monkeys which were kept in one of the quarantine rooms. After repeated testing two were passed. From them five cases are known to have originated and it was not until in 1912 when the whole exhibition house was cleaned of specimens, thoroughly disinfected and fumigated and until every specimen was retested, that the infection passed. In 1914 no cases occurred, while in 1915 a case either slipped through undetected or was a visitor infection; 1916 two cases, 1917 one case, 1918 one case (see orangutan charts), 1919 and 1920 none and 1921 one case, 1922 no cases. Since 1912 the whole monkey collection has been tested every two years, a method which enabled us to catch a small group in 1916 and has protected the collection since then. Three of the six monkeys specified above were never placed free in the general cages of the exhibition house, they being segregated in smaller cages. One, the orang, was with its mate in an isolated cage. The other two were in larger cages and their history suggests visitor infections.

We have never underestimated the possibility that an occasional very early case might evade detection by this test but we believe the history just outlined warrants us in depending upon it for the protection of the exhibition. By the tuberculin test we have detected the existence of the disease in twenty-three per cent. of specimens. Every condemned specimen, forty-one, showing tuberculosis, gave a positive test. Fifteen monkeys condemned on their temperature charts failed to show the disease. Eight per cent. of the tests resulted in suspicious charts, and the animals finally died of the disease in quarantine. Fifty-six tuberculous monkeys died on exhibition, of which thirty-one were original there and twenty-five their contacts. Twelve of the thirty-one were in the early stages of the work, thirteen due to our misadventure of 1910 and the remainder, six, scattered over nine years.

Another interesting experience concerns the exhibition of a group of Rhesus Macaques in an open “band stand” cage. The idea arose in an attempt to find a separate exhibition space for some good specimens that gave unsatisfactory charts, with the purpose of applying at the same time the “open air” treatment if tuberculosis existed. The experiment has been entirely successful since in the eleven years during which this enclosure has been used there has been but a single case of tuberculosis among twenty-six monkeys. Curiously enough this exception gave a good chart and we suspect it was a visitor infection; no secondary case arose from it. The animals housed in this cage keep in excellent condition, their coats responding to our severe winter by increasing in thickness and glossiness. Frozen toes, fingers and tails are sometimes seen but these monkeys seem just as happy as the others. Breeding is active and the young are lusty and husky. Practically the only deaths are due to accident, or to abuse of old and less vigorous members of the colony. We are unable to give comparative exhibition periods and death rates for monkeys in the large house and this open cage because some specimens have been changed from one to the other but it is certain that the appearance of the “band stand” monkeys is better than those in the house and there are four of eleven animals in the former which have been there eleven years and only four among the seventy in the exhibition house for that length of time.

The results of the foregoing work seem to demonstrate that the tuberculin test permits the separation of tuberculous and non- tuberculous monkeys and that its employment serves the purpose of maintaining a healthy exhibition by excluding infected specimens. These experiences form further corroboration of the facts that tuberculosis begets tuberculosis, that a healthy individual is not a source of infection. It follows that an obviously tuberculous animal should not, need not, be a source of danger; the hidden or unrecognized case is the menace. There is little or no problem when an unequivocally good or bad temperature record is obtained; it is when there are slight variations from the standard for the group that decision as to the disposition of the specimen must be made. Nearly always such specimens are retested until the records are definite. If they be constantly irregular the animal is either sacrificed or exhibited in a separate cage far from other monkeys. It is by the sacrificing of infected specimens or the segregation of suspected ones that our collection is kept clear of disease.

Hygiene of a general character must be maintained also. Our quarantine rooms are disinfected by formaldehyde and mechanical cleansing after every case detected as tuberculosis, and painted every two years. Monkeys associated with infected ones, are retested and then given a bath of carbolized water before being put on exhibition. The exhibition house is mechanically and chemically disinfected at the injection time each two years. All keepers are examined for tuberculosis upon beginning their employment and those handling monkeys, periodically thereafter. When a case of tuberculosis dies, all animals in the same and adjoining cages are removed for retest and the enclosure scrubbed and disinfected.

There is a source of tuberculosis upon the importance of which we can only speculate—the visitor. There were two isolated cases in animals which had passed the test with unexceptionable charts, three and four months on exhibition; curiously enough no other cases occurred in their cages. These we have laid to visitor infection since no previous exposure can be traced for the specimens and no secondary cases occurred.

I can conclude this discussion of the tuberculin test and of the control of tuberculosis by its use, by mentioning the possibilities for the solution of the problem in man. While the eradication of the disease cannot be accomplished as easily as if a potential source could be eliminated by sacrifice, it will come in direct relation to the earliness of detection of infection and isolation of the sources of danger. Not so much the cough-racked consumptive but the unrecognized early lesion whose bearer hawks and spits in public places or at home, unaware of his malign power!

THE SKIN AND EYE TESTS WITH TUBERCULIN.

The first of these can be dismissed briefly, for in a few cases it was absolutely of no value. A known tuberculous monkey was injected _into_ the skin of the chest with 0.5 mg. of old tuberculin. The small bleb disappeared in a few hours and was followed by no reaction whatsoever. Other attempts likewise failed, some of them I believe due to the technical difficulty of injecting into the skin. This tissue is very thin, delicate and loose at the less hairy places where a reaction might be read—arm, chest, abdomen. The hairless parts of the rump might be used, but are so often scratched and soiled with dirt that readings might be misleading. The Von Pirquet test was done on the first mentioned specimen and was likewise negative. His tuberculin test was afterward positive.

The ophthalmic reaction is highly spoken of in the New York Zoological Park and has been used elsewhere. It was tried by me at the time Doctor Blair first discussed it, but with variable results. One set of two monkeys was treated with Calmette’s purified tuberculin into the conjunctival sac and given a subcutaneous dose of old tuberculin. Another set received 1 per cent. old tuberculin into the conjunctivæ and the usual subcutaneous dose. Although all these monkeys gave a temperature reaction only one gave a conjunctival reaction. Fearing that the two tests simultaneously might be an unfair trial, another poor specimen was given an eye test which resulted negatively; a later subcutaneous test and autopsy revealed the disease. Because of these experiences and the fear that any reacting conjunctivæ might become secondarily infected from the uncertain personal hygiene of the beast, we decided to omit this method and rely upon the temperature test.

PATHOLOGICAL EFFECTS OF THE INJECTION OF TUBERCULIN.

It is generally believed that tuberculin injected into tuberculous animals, in doses large enough to produce a marked reaction at the site of disease, may stimulate the process to growth and spread and that certain parenchymatous organs in such bodies undergo degenerative changes. We can give little information concerning the first point because known infected animals have not been sacrificed during the test and we are not informed of the degree of morbid lesion in those dying, since we had no previous knowledge of its existence.

An interesting and practically useful observation has, however, been made upon the kidneys of several monkeys dying shortly after tuberculin injection. It consists in a marked cloudy swelling of the renal epithelium and a congestion or even thrombosis of the glomerular capillaries, accompanied sometimes by increase of nuclei in the tuft and by amorphous material in the space of Bowman. Grossly such kidneys are but little changed, albeit the cortical zone may be dull and opaque and swell out slightly on section; very occasionally bloody streaks may separate the cortical and medullary striæ. In a few kidneys there have been suggestions of preëxisting nephritis but usually the findings are confined to those given above. At all events true glomerulonephritis is not often found. Monkeys which have this condition may or may not exhibit a behavior suggesting its existence. Sometimes it will be noted that the animal is dull and eats little, at other times the keeper will report that the cage is seldom wetted and we know of cases in which only an ounce or two of urine has been passed in a day. Two monkeys were distinctly ataxic and incoördinate and one of these had a convulsion. From one a specimen of urine showed albumen but no casts.

These signs of renal affection are not always alone nor are the kidneys necessarily the only part diseased since postmortem records show a variety of accompanying lesions, bronchitis and enteritis, for example. There are, however, several cases dying in a few days after tuberculin injection, both with and without tuberculosis, in which the renal changes were quite prominent; two examples, without tuberculosis, exhibited the damage to the kidneys very well and with no other evident visceral pathology. The relation of cause and effect may not be unequivocal, but these findings suggest that the condition of the kidneys deserves attention when tuberculin is to be injected. My associate, Dr. Corson-White, is firmly convinced that the substance whips up a preëxistent parenchymatous disease and wants to see a urinalysis from every monkey that is in any way abnormal.

THE TUBERCULIN TEST IN OTHER ANIMALS.

Two cases of tuberculosis occurred in White nosed Coatis (_Nasua narica_) so that it was decided to test their neighbors in the next cage. There is reproduced a composite (Y) of the temperature record of three of these animals after receiving 2 mg. of tuberculin under the skin. No tuberculosis was found in them at death, all dying within two years. The similarity to the primate type of temperature curve is striking.

Chart Z shows the course of temperature before and after tuberculin injection in a Bactrian Camel (_Camelus bactrianus_) ♀ which lived for some months and showed no infection at autopsy.

Charts AA and BB show the temperature ranges of respectively a healthy and a tuberculous Bison (_Bison bison_.)

Chart CC is that of a Malayan Sambur Deer (_Cervus equinus_) which died a week after injection, showing fibrocaseous tuberculosis. The failure to make an initial rise is noteworthy, but the fall in temperature may be explained by the severity of the lesions and the approaching death.

Chart DD represents daily and post-injection records of a Virginia Deer (_Cervus virginianus_) which at death was found free of the disease. Chart EE is that of a healthy American Elk (_Cervus canadensis_).

SECTION XVII—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.

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.