Disease in Captive Wild Mammals and Birds

SECTION I. Introduction

INTRODUCTION

“We have also parks and enclosures of all sorts, of beasts and birds; which we use not only for view and rareness, but likewise for dissections and trials, that thereby we may take light what may be wrought upon the body of man.”

The purpose of a menagerie under the auspices of a zoological society can scarcely be put into better words than those found in this quotation from Sir Francis Bacon’s New Atlantis. Apt as this description of the mythical island’s collection may be, it is but a reflection of the teachings of Plato’s original legend of a perfected community, and the practical applications of these teachings by Aristotle in his Anatomy and Physiology of Animals. The history of human study shows a constant investigation of lower forms of life, ever broadening in its scope, ever more satisfying in its explanation of biologic problems and ever increasing in value from an economic standpoint.

If, however, all animals are to be subjected to “dissections and trials” there inevitably will come under observation many specimens presenting variations from the accepted mean or standard or even from an average for their kind and therefore approaching what may be called pathological.

The desire to explain the abnormal has had the effect, during the half century since Virchow defined cellular pathology and Darwin systematized the world’s knowledge of comparative biology, of directing attention to comparative pathology and of stimulating the study of veterinary medicine. Moreover in the past twenty-five years much work has been done and many isolated publications have appeared upon the diseases of wild animals, notably Bland-Sutton’s work, Evolution and Disease (1895), a thoroughly scientific and most charmingly written book, but rather elementary in its approach of the subject of pathology, and Wood Hutchinson’s Diseases of Animals, a more or less popularly presented treatise. I am unaware, however, of any systematic monograph upon the subject wherein we may find data showing the character of pathology in the various animal groups or the incidence of the various lesions. The reports of some zoological gardens contain the result of medical and pathological data collected for the report period. The publication of greatest merit and value is that from the Zoological Society of London, whose huge collection studied by a large official personnel makes it possible to present valuable data. The New York Zoological Park uses its material in a similar manner and has been able to explain some of the knotty problems so frequently met in wild animal collections.

Here at Philadelphia it has been our practice now for twenty years to perform an autopsy upon every mammal and bird that dies, and upon all of the large or important reptiles. There is no aquarium connected with the Garden. The office of the society keeps a record of the arrival and a general description of every animal so that a brief history of the specimen is usually available. The keepers are required to observe their charges regularly and closely and to report any abnormalities to the officials of the Garden. Somewhat detailed discussions upon signs of sickness will be given at appropriate places, where also a few remarks upon treatment will be included, but as this work is not intended to be a treatise on therapy and since this subject does not differ from that referable to domesticated animals, little space will be devoted thereto. Upon death a complete autopsy is performed and the findings are recorded upon a printed form from which, when the histological, bacteriological and parasitological studies have been completed, a set of cross index catalogue cards are typed; these are divided into the principal diagnoses and determinations. The report of the Zoological Society, appearing at the end of their fiscal year, February 28th, contains a résumé of the observations for the year, together with notes of interesting cases and experimental work.

There have accumulated the records of nearly six thousand autopsies and upon them as a basis has been founded the following report of the incidence and nature of pathological manifestations in the various animal groups, using also as additional data, published reports from other gardens. The book might be described as a collection of our studies, parts of which have appeared as separate articles, but most of which are entirely new, put together with as much connection as the subject matter will permit. The zoological and pathological literature has been consulted very extensively, but except for the reports of zoological societies and the publications of special students, it usually represents isolated notes by travellers and veterinarians so that many articles may have been overlooked. Therefore no claim of perfect completeness of reference is made, the statements resting chiefly upon our own records. The subject will be approached from the standpoint of description and incidence, but it is inevitable that comparisons and contrasts must be noted.

Into the realm of evolution I shall not venture because I appreciate a lack of adequate preparation for such an attempt, and because, even if such were not the case, the material at hand is lacking in data upon fishes, many kinds of reptiles and invertebrates.

A direct and practicable application of these data will be in the direction of explaining some of the pathological states in domestic animals and man. There are indeed many disease entities or syndromes in these groups for which no useful hypothesis has been advanced, while for others a partial explanation has been offered, usually, however, inadequate wherewith to form the basis of rational prevention or therapy. Thus, for example, essential emphysema seems to be limited to the animals of civilization; on the other hand, the anatomical basis of exophthalmic goitre may be seen throughout nearly the whole animal kingdom yet the clinical phenomena belong characteristically to man, and are occasionally seen atypically in the dog. While it may be impossible to give a complete comparative anatomy and physiology for each of the pathological states, the attempt will be made to treat all subjects analogically through the zoological orders.

The experimental pathologist may find the records of the Garden useful in his work. For example, he can know that rodents are not prominent among the orders showing spontaneous arteriosclerosis, but that nephritis occurs among them in about a quarter of natural deaths; or he may learn that the Primates have a good cardiac reserve while the Marsupialia have not. Too often experimental work is not based upon facts including natural probabilities.

A collection of pathological data such as is presented in the following pages may be of assistance to veterinarians and managers of zoological gardens in the diagnosis of sickness in animals, both wild and domesticated. We do not presume to offer a system of veterinary medicine, but it is possible to introduce certain objective findings of practical hygienic and therapeutic value. Such observations are, however, limited and in our experience at the Philadelphia Garden the diagnosis of disease in a wild animal, excepting of course those which are perfectly self-evident, is more often speculation and conjecture than at all well grounded. It is not uncommon for animals to come to autopsy presenting a perfect galaxy of abnormalities, yet the closest antemortem observation failed to reveal unusual conduct or appearance. On the other hand specimens are frequently opened whose organs fail to contain any lesions discoverable even by careful study. Dr. Henry Chapman, sometime prosector to the Society, once made a remark in this connection—“Why do they die or how can they live so long.” Space is given to this phase of the observation of wild animals in order to emphasize the difficulties of interpreting their conditions, but of course it should be understood that certain data of value may be gained by close attention to the details of their normal behavior and to changes which occur indicating that something is wrong.

The naturalist and the trained animal keeper are, in our opinion, better judges of a wild animal’s condition than is the veterinarian, unless he be at the same time a zoologist and have long experience with a menagerie. My own observation of dogs and horses leads me to think that more acumen is needed to interpret the actions of wild animals since they seem to have greater natural reserve, and of course in regard to them there are many more variables since we see fewer specimens of each species than we know familiarly among domestic varieties. The principal objects for observation are, as in veterinary medicine, the eyes, the hair and skin, the mucous surfaces, the droppings, the condition of the abdomen, the appetite and the desire for water. Physical examination is limited to tractable beasts and those which can be caught and handled without danger to the personnel or unusual fright and damage to themselves. In the interpretations of physical signs in tractable animals, such as many ungulates and some monkeys, the experience of the trained veterinarian is of the greatest value, but this fails amongst carnivores and birds. It might be said that anesthetics could be used for a thorough examination, but this would be undesirable for a seriously sick animal and it is, in our experience, none too safe a procedure although often perfectly practicable. Animals do not like to be molested much as they may seem to enjoy attention, and when it is possible it is our practice to avoid handling them.

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