Part 50

Lesson’s Motmot (_Momotus lessoni_). The region above and behind the right clavicle in front of the brachial plexus on the internal surface of the thorax, exterior to the first and second ribs, and on the internal surface of the ribs at the junctions of ribs with the alæ of the sternum, there are many small, irregular, smooth, firm, yellowish white nodules varying in shape from spherical to sweet potato and in size from 3 × 3 mm. to 3 × 7 mm. These are found quite homogeneous on cross section. They do not resemble tubercle or mould infection but make one think of neuromata. There are also a few present in the left lateral air sacs, close to but not joining the intestine. The lungs are apparently normal. Histological section of the masses described as distributed along the nerves consist of sharply outlined but not well encapsulated masses made up of irregularly disposed bunches of large cells with vesicular nuclei in a stroma of loose connective tissue very inconspicuous in amount. There is also quite a number of small round cells and a few leucocytes. The large cells first described have the nucleus eccentric for the most part. Many of them have two nuclei and a few three and occasionally a giant cell is observed. Blood vessels have a very delicate wall and are frequently encountered in the centre of these masses. Atypical mitoses can be found. Here and there a seal ring placement of the nucleus can be found. A few eosinophiles are present not definitely placed. Necroses, with large quantities of nuclear fragments, are scattered irregularly through the mass. The diagnosis rests between an infectious granuloma, false neuroma and sarcoma. Tubercle bacilli were found by stain in great numbers both within and without the cells.

Psittaci. Tuberculosis occurs in this order somewhat more frequently in the varieties whose habitat is the Eastern world, although South American birds also suffer from it in the characteristic manner. There seems to be no difference in the pathology of these two groups. Parrots present very beautifully the separate solid or semisolid nodules of avian tuberculosis, whether they be in the lungs, liver, or spleen. When the lung becomes riddled with masses, coalescence occurs and the whole mass turns into a cast of the hemithorax. Lesions in the liver are mostly isolated, but the spleen often appears like one large pink tuberculous nodule. The liver occupies as usual the first place in organic incidence.

Striges. Owls (and Struthiones—see below) present the interesting exception to the rule of intestinal origin of tuberculosis in birds. Perhaps the platting is incorrect but the birds in the order under discussion had older and much more advanced lesions in the lungs and thoracic serosa than they did in the abdominal organs. That this was true in all three examples is in itself noteworthy. Perhaps they possess less pulmonary and more intestinal resistance. One of these birds showed a small recent cavitation in the posteroinferior angle of one lung.

Accipitres. With one exception the cases of this order occurred among the Falconidæ, that is in hawks, buzzards, and eagles. Their lesions are usually generalized as indicated by the figures for visceral distribution, but that half the number should have the oldest, most prominent lesions in the lungs is curious. Their intestinal tuberculosis seems mostly of the diffuse infiltrative type.

Columbæ. These birds are obviously the most susceptible of all the varieties of which there are sufficient autopsies to make a comparison. Generalized nodular lesions emanating from the intestinal tract comprise their usual form, while most of the hepatic lesions are small miliary and nodular; occasionally one sees caseous masses destroying large sections of the organ. Their intestinal lesions may assume any of the three forms described.

Galli. This is an order of something over the average percentage incidence for the birds but containing families that seem very susceptible to tuberculosis. The small number of Brush Turkeys (_Catheturus lathami_) had 60 per cent. of the disease, while South American Cracidæ had 44 per cent. These two groups raise the incidence for the order. Galli as a group have generalized nodular tuberculosis originating by the intestinal route. This is especially seen in the Phasianidæ, while the very susceptible Cracidæ have much more prominent lesions in the lungs, often of a massive caseous type. It is really astonishing at times how much of the pulmonary tissue is occupied by infiltrate before death has supervened.

Fulicariæ are represented by a special contingent of rails and gallinules. Avian characters are well illustrated in the order. So too the succeeding order, Alectorides, another variety of shore birds, run true to the avian form. It is interesting to note that in the two cases from each of these orders tuberculosis and aspergillosis have been combined. The former has assumed the firm nodular type, while the mycosis has been of the air sac variety. The following case is worth citing as possibly illustrating infection _per cloacam_. There is, however, no trace of this bird having been with a male with the disease.

Demoiselle Crane (_Anthropoides virgo_) ♀ . General tuberculosis including the oviduct. All organs are thickly beset by caseous tuberculous nodules except the lungs which have only a few scattered ones. The oviduct is, for its lower two-thirds, much enlarged, firm, tough, pale yellow, thickly beset with caseous nodules; upper parts uninvolved. The kidneys are definitely enlarged, irregular, almost mulberry-like, brownish yellow, firm and tough. On section the lobules are irregular, connective tissue increased, urates in pelves. Tubercles in intestines seem to be wholly peritoneal. This seems like a tuberculosis of genital origin judging from condensation of tubercles in the lower abdomen (mass around cloaca). The ovaries are not involved. Lungs and thoracic air sacs relatively free. The pericardium shows a whitish thickening of both layers due to the presence of whitish granules like urates. Histological section of kidney shows the capsule not greatly altered. Glomeruli largely negative but a few show hyaline capsular thickening of vacuoles in tufts or fibrosis in tufts or obliteration of whole structure. Tubules largely degenerated, distended or distorted. Interstitial tissue between the tubules definitely but irregularly increased. No real attempt at regeneration. Few vessels show perivascular fibrous change. One tubercle seen.

Anseres. These birds present no especial features so far as percentage or organic incidence are concerned. The individuals are mostly geese and swans, ducks being somewhat more often affected by mycosis than by tuberculosis. However, both these diseases tend to assume the nodular type in Anseres so that the diagnosis should be supported by bacteriological discovery of the respective organisms.

Struthiones. The marked feature of this order is the prominence of the isolated and confluent nodules in the lungs, of apparently greater age, certainly of great size, than similar lesions in the abdominal viscera. Caseation of the avian variety is well illustrated in these birds. The thyroid body was involved in two of the three cases, the ovary in one. The representatives of the Crypturi, two tinamous, came at the same time and lived only a few months. Miliary tuberculosis of the small precaseous variety was the form exhibited by both specimens.

HISTOLOGY OF THE TUBERCULOUS LESIONS.

The initial and characteristic unit of tuberculosis, the miliary tubercle, seems to be constructed upon the same general principles in all cases of the disease and in all members of the zoological groups in our study and in a manner entirely comparable to that well known for man and for the domestic animals. There are, however, certain minute differences which are interesting and may at some time become important. It is customary to speak of the bovine tubercle and of the human variety, but there are also slight variations of the microanatomy of each of these, while one may find on occasion a tubercle of the human type in a cow and _vice versa_. Not all the domestic animals show the bovine form, although in sheep and swine it is approximated very closely. In the horse there is much greater tendency to a central softening and fibrosis is not so common as in the bovine tubercle. I have attempted to study the histological anatomy of each of the zoological orders, but it has not resulted in any profitable discovery. It is, however, possible to contrast the type commonly found in monkeys with that characteristic for man and the ungulates and also to emphasize the construction of the avian tubercle that it may be distinguished from mammalian tuberculosis and from avian mycosis.

The tubercle of the Primates is a loosely constructed affair lacking the fibrous mixture of the bovine and the close cellular packing of the human form. Studied from the periphery to the centre, there will be found very little fibrocellular reaction in the immediately surrounding organ, while the mantle of round cells, rather prominent in the human tubercle, is often quite inconspicuous. The principal cellular component of the miliary granuloma is the large pale endo- or epithelioid cell, which is abundant, loosely arranged and without apparent purpose. In the centre is an irregular necrosis usually retaining some chromatic matter, probably the remains of recently destroyed nuclei, but this caseous midpoint does not assume the dense acid staining common for many milia. Giant cells of the Langhan’s or foreign body type are often entirely missing, and when present are scanty. There may be large cells, resembling the aforementioned epithelioid cells, with two or even three large palely staining nuclei, but these latter are arranged irregularly and not like the spokes of a wheel near the cell wall.

This picture suggests a rapidly growing inflammatory mass and indeed this is the type that tuberculosis follows in monkeys. In a few cases gross evidence of fibrosis in the serous surfaces and in the lungs has been observed, but they are too rare to permit one to think that connective tissue activity is an important part of the reaction of this beast to the disease.

The avian tubercle as it rests in the tissue seems like a sharply outlined almost encapsulated body. This is in part due to the homogeneity of its structure and in part to the fibrocellular condensation around the caseous part of the growths. Examined from without inward, there is a round cell mantle, between the elements of which course fine but easily perceptible fibrils; elastic tissue has been seen among them. The small cells continue more deeply than the fibres, to be succeeded in prominence by epithelioid cells of rather dense character, the nuclei especially seeming quite rich in chromatin and round. The rotundity of the nuclei remains not only in the single separate cells forming the middle zone of the cellular cortex, but can be found in the nuclei of the compound or giant cells which comprise the internal layer lying upon the necrotic centre. These giant cells are characteristic for the avian tubercle in assuming a form like syncytia with nuclei arranged in irregular radiating columns. This internal large cell area may completely surround the central necrosis or it may be interrupted by the large single cells. Tubercle bacilli are more common in and between single cells than multinuclear ones. Within the cellular zone lies the necrotic centre, often, indeed usually, full of chromatic debris. This centre is commonly quite amorphous but occasionally one will see what is probably the remains of a coarse coagulum. Between the necrosis and the cells one usually finds a split, a sort of separation of the gangrenous from the living part. Old tubercles with denser fibrous capsule retain this microanatomy in part, but the cellular zone gradually becomes thinner and thinner until all that remains is a narrow cortex of round cells and imperfectly retained multinuclear cells.

Tuberculous granulation tissue without definite milia consists entirely of the round cells with small vacuoles and a fine but definite fibrosis. Tuberculomata consist of cells of varying sizes with small round nuclei. Interstitial fibrosis is delicate and barely visible unless especially sought. Giant cells may be encountered but are not so large as in milia. Necrosis occurs but not in an orderly manner in relation to cells as in an isolated tubercle. Tubercle bacilli are very numerous.

TYPES OF BACILLARY INFECTION.

According to experimental and statistical research, all the tubercle bacilli of the higher vertebrate classes can be infective for any member of these classes. Thus, for example, human bacilli have been found in many orders of mammalia and in birds. The bovine form has been found in swine. The lesson from this is that while the special predilection of a variety of the tubercle bacillus may be for one kind of animal, it is potentially a virus for other kinds. Hygienic principles have therefore been laid down at the Garden which aim at the protection of all specimens from every variety of tubercle bacillus. For this reason and because the laboratory has not attempted extensive research on bacteriology, few type determinations have been made and those at hand offer nothing new or unusual; they are noted here as a matter of record. Bovine bacilli have been judged by their slow growth and infectivity for rabbits, human bacilli by the reverse of these characters. Avian tubercle bacilli can be cultivated with reasonable ease directly from lesions not bearing a mixed bacterial flora, and grow in a yellow, moist, even, spreading colonization. In our two attempts at infection of guinea-pigs, no success was had, although Rabinowitsch and others had no difficulty in so doing; this strain may vary in virulence as do other tubercle bacilli. No avian culture was obtained from a mammal, but a bovine was found in a parrot and a human in a duck. Bovine bacilli were isolated once from a monkey (see page 496) and in another case of lymphatic type, bacilli of the short heavy blunt shape, supposed to be characteristic of this variety of the germ, could be stained. Monkey tuberculosis in our experience is usually due to the human tubercle bacillus, judging by the staining characters and two successful cultures.

DISCOVERY OF TUBERCULOSIS DURING LIFE.

Fully developed chronic tuberculosis may be recognized with reasonable ease in the human being and some domestic animals. The diagnosis rests largely upon the history and symptoms and partly upon the appearance of the individual and upon signs elicited by physical examination. There is good reason to believe that these latter methods are entirely applicable to certain wild animals, notably those that can be caught and held quiet, but because of their naturally great reserve many specimens offer little reason for suspicion as to their tuberculous condition until near death. Certain ungulates with chronic pulmonary disease get thin and weak but remain on their feet with good appetite and satisfactory discharges for many months. Primates, Carnivora, Rodentia and Aves not uncommonly come to autopsy with very good coats and without great emaciation and yet are heavily infected. It can be stated with fair positiveness that no chain of historical data or gross observations are certainly known to us as indicative of tuberculosis in the wild beast. Coughing is not necessarily characteristic of chronic pulmonary infection, although when continuous it rouses considerable suspicion, especially in the Ungulata. It is to be interpreted with care in all animals that have loose bedding as bits of straw or seeds get into the throat causing irritation; the dust of hay may cause coughing in horses.

However much chronic or fatal tuberculosis may be interesting from the standpoint of pathology or of zoological or visceral incidence, the most important factors in our knowledge of the disease are its early recognition and treatment, either for curative or hygienic purposes. Since we have learned that advanced lesions may exist in an animal without materially affecting its external appearance and behavior, it naturally follows that early cases, possibly of an “open” or infectious character are still less likely to give evidence of their existence. This is well recognized by veterinarians as being true of cattle, but is perhaps less well known, or possibly admitted, by those who handle the very susceptible monkey.

Upon a visit to a foreign garden I was told that experience alone is sufficient to enable an observer to detect tuberculosis, and that the disturbance entailed in physical examination and tuberculin tests is prejudicial to the well-being of all varieties, but especially the delicate ones. I learned later that they had the disease in their exhibition cages all the time but decided to put their method to the test. Shortly after my return from abroad a splendid specimen of Grivet Monkey (_Cercopithecus sabæus_) was condemned by the tuberculin test. He was well studied by the superintendent and two very experienced keepers, all of whom pronounced him one of the finest specimens they had ever seen, and stated that he was behaving quite normally. Despite their protests he was sacrificed, tuberculosis with early cavitation being found in the upper lobe of the left lung. Incidentally vague physical signs were found by auscultation, but as the monkey was unruly and had long pectoral hairs little weight was placed on the observation. However, it is frequently possible to make very thorough physical examination of the lungs of the more tractable specimens, diagnoses of pneumonia and bronchitis being frequently made in this and other parks, so that treatment may be instituted.

IMPORTANCE OF TRANSMISSION AND KNOWN SUSCEPTIBILITY.

Some light upon possible reasons for the poor condition of an individual animal is of course shed by a knowledge of the disease to which that particular variety is most susceptible, to which may be added the data obtained from previous deaths in the same group or enclosure. Thus, for example, a sickly monkey would be suspected of having tuberculosis or early osteomalacia, whereas no suspicion of these diseases would fall upon the marsupials. The same position would be assumed if a dove and a heron were out of condition.

In so far as enclosures are concerned, the matter is somewhat different. Whenever a case of tuberculosis occurs in a cage, the remaining specimens if any are removed and the place cleaned by soap and water and disinfectant and paint. The naked flame from a blast lamp is used when possible. Out-of-doors enclosures are vacated, spread with lime and allowed to lie fallow for as long a time as practicable. These methods have been in the main successful in clearing a cage of the disease, and all our experience demonstrates the effect of cage hygiene and the selection of non-infective replacements. A few places such as those occupied by doves and guans have not been freed of infection, if one judge by its appearance when new specimens are placed in them, but they may of course be due to the infection from elsewhere. The history of seven years in the new bird house where the hygienic conditions are excellent, seems to indicate that a cage thoroughly cleaned is no longer a source of danger, and that a repetition of tuberculosis in such an enclosure is due to its importation with new exhibits.

The spread of the disease to nearby cages seems to depend upon two factors. If the number of cases has been large and the infection virulent, immediately adjoining cages are involved, but the tendency to spread is directly proportional to the proximity of orders or families that have a high susceptibility for tuberculosis. This second factor seems to be the more important and is illustrated by our experience in one corner of the new bird house. In this area are exhibited certain doves and pheasants, among which are many cases, while the passerine varieties nearby are little affected. So too in the flying cage the disease has occurred in varieties with high general susceptibility. There are at the present writing ten orders on exhibition in this large enclosure and there have been more. An occasional case of the disease occurs, but only in the orders which show it elsewhere. The Herodiones, of which we have had nearly one hundred autopsies and many now are on exhibition, are always well represented in this cage and yet show no tuberculosis. In the ten orders mentioned above three show no cases of the disease.

These observations illustrate the spread of tuberculosis, especially to the most susceptible varieties, and how non-susceptibles under good hygienic conditions fail to become infected even when infected animals are near them. The freedom of activity in the large enclosure is doubtless an important factor.

The history of the past three years with regard to the control of tuberculosis in the small cages shows that twenty-nine were infected, but by the measures employed nineteen have remained free of the disease for one year; three of the remaining ten are known to have received newly arrived and possibly infected specimens.

The accredited method of transmission in birds, the swallowing of material soiled with the feces richly laden with germs, is the principal reason why infected enclosures and their immediate environment are the principal breeding places for tuberculosis. To be sure air currents may blow the virus around, allowing it to light upon food in other cages but this cannot be a great menace if for no other reason than that we have had no epizoötic outbreak of the disease, when there were groups of deaths in doves and guans.