Part 62

FIG. 81.—ARACHNID (CYTOLEICHUS PENROSEI) IN A BRONCHOPNEUMONIC FOCUS IN THE LUNG OF A PRAIRIE DOG (CYNOMYS LUDOVICIANUS). ]

PHYSALOPTERA IN OPOSSUMS AND BADGERS.—These worms were frequent findings for a period of years and were particularly impressive on account of the large number of parasites present. The stomach often contained scores, more or less securely attached to the mucosa by the head. The worms average an inch or two in length and perhaps an eighth of an inch in thickness. _P. turgida_ is the only species we have identified (three examinations). As to pathogenicity we have not observed that definitely constant lesions are induced by the parasites. In several instances the gastric mucosa has shown the mosaic appearance indicative of chronic gastritis, a condition not necessarily incited by, but certainly aggravated by, these worms; at least significant is the habit of the worm to imbed its head in the gastric mucosa. In one instance the microscope has revealed a most severe fibrosis of the submucosa. The fibrosis was not so much diffuse as it was local or nodular, and in favorable places the ova of physaloptera could be discovered in the centres of the nodules, and thus betrayed the previous presence of the adult worm there. In this individual animal the case against the physaloptera is clinched by direct evidence. In other cases we have circumstantial evidence. Whereas it is not a deeply burrowing parasite, it is still a penetrative one, and this is sufficient to compromise the all important “integrity of the mucosa.” It should therefore be considered pathogenic in all cases, because open to suspicion in several directions—abstraction of tissue juices, irritation by its products or movements and by opening up an avenue for bacterial infection.

TROPIDOCERCA IN BIRDS.—This is a blood-red nematode of the size of a mustard seed to that of a peppercorn which inhabits the depths of the proventricular mucosa. At first sight its spheroidal form suggests that of a fluke, but under the microscope it is found to be a nematode hugely ballooned out by ova, and coiled up into a ball. In spite of its dangerous appearance—being red—it is most likely quite innocuous, for microscopic sections show no sign of inflammation around the worm. Moreover, we know that a Concave Casqued Hornbill (_Dichoceros bicornis_) now on exhibition has harbored the worms, as indicated by ova in the droppings, for eight years and yet seems perfectly well. I have made wax reconstructions of three of the worms and find that the coils are not very intricate and that they assume no regular or constant arrangement.

SYNGAMUS TRACHEALIS.—Our worst experience with this picturesque parasite was in common crows (_Corvus b. brachyrhynchos_). In 1914 and 1915 alone we lost five such birds. Some geese, swans and a pheasant complete the short list of birds affected in addition to the crows. In no case was it a young bird that was affected. Shipley[145] reports this parasite in two grouse at the London Gardens, and Plimmer’s tables show that three deaths were directly charged against them in one year[146].

EXTRA-INTESTINAL TAPEWORMS.—This discovery is worthy of record because it is rare for cestodes to appear anywhere save in the intestines. We have observed three instances where they had backed up into the bile duct—twice in the Cape Hyrax (_Procaria capensis_) and once in a Livingston’s Eland (_Taurotragus oryx livingstonii_). At the London Gardens they were mentioned in the gall-bladder of a wallaby and in Cape Hyraces. Beddard[147] carefully describes four new species of these cestodes from the hyrax.

TABLE 28. _Occurrence of Blood Parasites._ (Adapted from Plimmer, nine year period) _Animals examined—12,241 Mammalia—2,924 Aves—6,619 Reptilia—2,698._ ══════════════════════════════════╤══════════════════╤════════╤════════ Parasite. │ Host │ No. │ % │ │Infested│Infested ──────────────────────────────────┼──────────────────┼────────┼──────── 1. Hemogregarines │Reptilia │ 316│ 11.8 2. Microfilaria │Mammalia │ 33│ 1.1 │Aves │ 191│ 3. │Reptilia │ 24│ 1. 3. Hemoproteus │Aves │ 140│ 2.1 4. Trypanosomes │Mammalia │ 1│ 0.003 │Aves │ 28│ 0.4 │Reptilia │ 4│ │Amphibia │ 3│ 5. Plasmodia │Mammalia │ 2│ │Aves │ 39│ 0.6 │Reptilia │ 5│ 6. Leucocytozoa │Aves │ 16│ 0.2 7. Intestinal organisms[148] │Reptilia │ 16│ 0.5 8. Toxiplasma │Mammalia │ 1│ │Aves │ 1│ │Reptilia │ 1│ 9. Spirochæta │Mammalia │ 1│ 10. Babesia │Mammalia │ 1│ 11. Hæmocystidium │Reptilia │ 1│ ──────────────────────────────────┼──────────────────┼────────┼──────── Grand Total │ │ 824│ ──────────────────────────────────┴──────────────────┴────────┴────────

SUMMARY OF TABLE 28. ═══════════════════════════════════╤═══════════╤═══════════╤═══════════ │Parasitized│ Animals │ % │ │ examined │Parasitized ───────────────────────────────────┼───────────┼───────────┼─────────── Mammalia │ 39│ 2,924│ 1.5 Aves │ 415│ 6,619│ 6.5 Reptilia │ 367│ 2,698│ 14.0 ───────────────────────────────────┼───────────┼───────────┼─────────── Total │ 821│ 12,241│ 6.7 ───────────────────────────────────┴───────────┴───────────┴───────────

FILARIASIS IN WILD CATS (_Felis ruffus_).—This parasite was named _Filaria fasciata_ because it coils in the fascia between the muscles— generally those of the thigh and abdomen. The worms are easily detected on skinning the animal and separating thigh and other muscles. Microfilaria were always present in the blood. The grade of pathogenicity is only conjectural.

PERITONEAL FILARIA IN MONKEYS.—Thread worms have been encountered eleven times, largely in Cebidæ. In several instances _F. gracilis_ has been the species identified, always inhabiting the peritoneal cavity, and in one instance also the lung. Microfilaria were always present in the blood. We have never seen lymphangitis or elephantiasis in our filarial cases.

BLOOD PARASITES.—I justify this paragraph on the basis of the usefulness it might have in the clinical direction, for while the taking of blood specimens is not as easy as with man it can still be done with some animals. From time to time we have encountered blood parasites in this Garden, but the large numbers occurring in the experience of special searchers in the London Garden and Plimmer’s particular interest in this direction make their data much the more valuable. In one report of 6,430 animals examined he found 7 per cent. infested with blood parasites of one sort or another. I have constructed the foregoing table (28) from his various reports to show which animal classes were affected by the several blood parasites.

This table (28) brings out that considering them as a whole and without respect to host, just as the animals come day in and day out to the autopsy table, blood parasites will be met in 6.7 per cent. of all cases. They are seen most commonly in the form of hemogregarines of reptiles (2.5 per cent. of all animals and 12 per cent. of all reptiles) while microfilaria run a close second, being found in 2 per cent. of all animals but much more commonly in birds. Hemoproteus of birds while ranking third, should be emphasized on account of its acknowledged blood-destructive properties. The remaining infestations were too infrequent to be useful statistically.

Turning to individual groups of blood parasites, microfilariæ of birds deserve special comment. They occurred four times more often in birds than in other animals, or, put in another way, one out of every twenty- two birds was affected, and only one out of every ninety other animals. The high figure for birds is significant in relation to what we have already said about periproventricular filaridæ in our Garden, indicating that the same infestment probably also exists in London.

A point brought out by Plimmer is to the effect that, of the several blood parasites, the microfilariæ were the least harmful, and that of these the adult forms were the only ones to produce symptoms; yet in one place[149] he records microfilaria as plugging the cerebral capillaries of birds. This is a very important lesion if permanent, and especially so when affecting cerebral capillaries as do the organisms and pigment of malaria. The adult forms were found in one-fourth of the cases where microfilaria were demonstrated.

As to the pathogenicity of these blood parasites in general, it will be unsafe to arrive at a definite conclusion, recalling the pitfalls that I have already outlined in discussing pathogenicity of parasites in general. Keeping in mind the wonderful adaptability on occasion of animals to unfavorable circumstances we must hesitate to declare unqualifiedly the importance of even blood parasites as morbid agents. Where the parasite is known to destroy the blood cells of birds and mammals it is otherwise, but even here experimental work would be necessary to settle the question. The element of “racial” immunity and of phylogeny is the fly in the ointment of our deductions.

TRANSMISSION OF ANIMAL PARASITISM FROM WILD ANIMALS TO MAN.

Examples of direct transmission will be only occasional, due to the relatively infrequent contacts between the two hosts. Pets threaten the most. Several such examples have been touched upon in the preceding pages and it but remains to gather them into one place. There is one concrete instance in the form of clear cut simian scabies being transmitted to a keeper in this Garden[150] and a similar lot fell to the keeper of a wombat at the Paris Garden[151] as well as to the taxidermist who preserved its skin. We know that the skin and feathers of our parrots and pigeons harbor mites[152] (plumicoles of Megnin) and, recalling the occasional cases of poultrymen’s itch, a transient affection might be conceded from pet parrots and other birds. Pediculi are not as numerous on monkeys as popularly supposed—we see very few at the autopsy table. We have seen _Trichinella spiralis_ in the polar bear (_Ursus maritimus_)—an animal whose flesh is edible. The hydatid cysts in the camel appear unimportant, but in the livers of deer it is otherwise. Neither of these infestments is dangerous if the meat is sufficiently cooked before eating.

Hookworm disease points thus far only to _Anchylostoma duodenale_ in the chimpanzee and _Uncinaria ceylanicum_ in the lion and tiger. Both serve as reservoirs of the disease, the ova being discharged by way of the feces. Similarly the _Strongyloides intestinalis_ infestment which we have seen in the orang might be transferred to man. Indirectly, Europeans traveling in Africa have made the crucial test that certain ungulates and other wild animals of Africa are the reservoirs of _Trypanosoma gambiense_, the parasite of the well known African sleeping sickness; for this example the blood stream of the beast is the reservoir and a biting insect the means of transmission.

The above examples are cited to emphasize the possibility that parasites of wild animals may have a pathogenic significance for man. They do not exhaust the subject. Many more instances might be cited but the foregoing bring out the important ones which have come to our attention.

TREATMENT.

The recognition of the existence of parasites during the life of an animal, especially those of the skin and intestinal tract whose discovery is easiest, suggests that some means of combating them should be employed. But we are by now quite satisfied that medicinal and disinfective therapeutic procedures, while they have their field of usefulness, are much less to be depended upon for the protection of exhibits than are preventive measures of general hygienic nature. Under the latter heading come the prompt removal of excreta, frequent changes of drinking water, routine examinations of feces of certain varieties, autopsy examinations and incineration of autopsy remains—all of which are part of the requirements of common cleanliness and general disease prevention. I wish to amplify the matter of disposal of feces and general cage-police. Our ideas as to what constitutes thoroughness in this work have changed considerably since Fulleborn’s recent demonstration that ascarid ova[153] could live in formaldehyde for four or five years, and the older one of Galli-Valerio[154] that those of _Hepaticola hepatica_ lived one month in 2 per cent. formaldehyde solution. Evidently the same substances which disinfect do not invariably disinfest; and if the occasion should arise for the most exacting control in this respect, a special investigation of the susceptibility of the individual ova in question would have to be undertaken.

In addition to these general measures we have put up certain special safeguards against parasites. Thus, each specimen of the large Carnivora (lions, tigers, leopards, etc.), has received routinely a dose of santonin every month over a period of several years. We have no figures on which to base comparison with previous periods, but an examination of feces of all the inmates of the Carnivora house in 1916[155] showed that less than one-third of the animals were infested, and of these all save the jaguars showed either small numbers of ova in the feces or relatively non-pathogenic forms. The jaguars had been badly infested for many years with dibothriocephalus. Prior to this examination we had been under the impression that nearly every one of the felidæ ordinarily was infested and if this impression was well founded, due credit must be given, in company with general hygienic precautions, to the routine santonin dosages. It goes without saying that where animals are detected at autopsy with unequivocal transmissible and dangerous parasites (coccidia, amebæ, etc.), the contacts are isolated, examined and if necessary treated for the affection or even sacrificed.

To continue the preventive measures, it would be most desirable to examine at least the blood and feces of all newly arrived animals, but at present this is not practicable on account of the labor involved in the laboratory and in collecting the material, and because all animals do not stand the restraint involved when blood specimens are being taken. At present we are limiting special examinations to the droppings of newly arrived parrots and toucans for _Spiroptera incerta_ and to the feces of certain monkeys for amebæ.

Further preventive measures will depend on the nature of individual infestments as they crop up. Food inspection, screening, sulphur dips, etc., are but a few examples of what might be found necessary hygienically after investigating or establishing the life cycle of our numerous parasitic groups. However we cannot forbear to emphasize again the value of the blast lamp and of paint in the hygiene of animal enclosures—means we believe to be much more potent and quite as practicable as chemical disinfectants.

Turning now to the active curative side of the subject, what medical means we have against parasites appertain for the most part to the intestinal ones. The treatment of tapeworms is very hazy and unsatisfactory—areca nut is perhaps more useful in animals than any one other drug. For round worms santonin is most to be depended on although turpentine is useful against the round worm of the Equidæ. The dosage of santonin per month has been—for large bears, ten grains; for lions, tigers, large pumas, six grains; for jaguars, leopards, hyenas, four grains; for wild cats, etc., two grains. The dose of areca nut recommended for Carnivora is two grains per pound of body weight. Since ungulates do not stand areca nut well, iron sulphate may be used. For animals the size of a horse the dosage is two drams, and to this one or two grains of arsenic trioxide may be added. On the basis of very carefully controlled experiments on dogs, Hall recommends carbon tetrachloride for hookworms in these animals—0.3 mils per kilo of body weight, without purging. Its efficacy has been confirmed lately but we have not had the occasion to test it.

From time to time we have broached other lines of medication against worms which may be worth while relating if for nothing more than to illustrate the uncertain ways of our vermifuges when applied to wild animals.

I can speak first of thymol as employed on parrots parasitized by _Spiroptera incerta_. The first thing that impressed us was the large dosage which birds could endure. The lethal dose for pigeons was four grains, suspended in mucilage of acacia. After we had established that certain parrots withstood fourteen grains in mucilage, we administered on one occasion twelve grains and on another sixteen grains, suspended in glycerin. The drug is reputed to be absorbed when exhibited in the latter vehicle and we hoped to get a certain anthelmintic effect on the parasites from the blood side as well as from the lumen of the gut. The bird itself, a very heavily infested cockatoo, showed no ill effects and passed two dead female spiroptera and enormous numbers of ova. But thereafter it passed even greater numbers of ova than before (we estimated 182,000 per day for this bird over a five day period and 288,000 on a single subsequent day), and was obviously unimproved by the treatment. The explanation of failure was clear, for the worms can retire into the protecting mucus or mucous membrane lining the proventricle until the thymol has passed by, and even though paralysed may not be flushed out. In a later test on a toucan which died twenty minutes after thymol administration we found at the autopsy that worms deeply imbedded in the proventricle were translucent and motionless from the effects of the thymol-glycerin mixture, _i.e._, saturated with the medicament and apparently dead. Twenty minutes later they were placed in normal salt solution in the incubator, and next morning were found actively motile. Thymol evidently does not kill—it only stupefies, and in the absence of means for flushing the parasites out, as we do in human hookworm cases, this class of vermifuge will have to be abandoned in work against this parasite.

Not with any serious hope of success, but feeling that arsenic was the most promising drug available for parenteral use, we tried atoxyl hypodermically and arsphenamine intravenously but without success. The only positive results were to emphasize the tolerance of some lower animals to arsenic. Thus in preliminary work pigeons received sixty drops of Fowler’s solution by mouth without embarrassment, but five minims killed a pigeon when administered hypodermically. The organic arsenical, arsphenamine, was withstood intravenously by pigeons in six times the proportional human dosage.

One of our drug trials was instructive in that it worked quite a different effect from that in man, besides being most amusing. In earlier diagnostic work on spiroptera we tested the practicability of examining the vomitus for the worms, hoping thereby to get a greater concentration of ova, which would facilitate the microscopic examination. Hypodermic injections of apomorphine (0.1 grain) into an amazon did not induce vomiting from the gizzard as hoped—only a regurgitation from the crop, but it did cause some dizziness and most ludicrous talking and laughter.

To illustrate further the difficulties of animal medication I quote our experience with four red howling monkeys (_Alonatta seniculus_). One of these died of intestinal obstruction from large ascarids—the case which has been already cited. Ova were found in the stools of the remaining three, and one of the monkeys was treated twice with santonin. It died in thirty hours after the second dose—not of santonin poisoning, for none of the clinical symptoms were present, but most likely from absorption of toxic substances originating in the decomposing ascarids which crowded the gut. It profits not to destroy these parasites, then, unless we feel assured that they may thereafter be removed immediately.

If, for the sake of brevity, I were asked to state in a single sentence the practical status of animal parasitic disease in this Zoological Garden I would put it thus: Since there are various animal parasitic diseases continuously present here of which we know, and since fresh ones are from time to time cropping out, and since these are on the whole of economic importance, it behooves us to continue and extend our efforts against an issue extant—somewhat through therapeutic means, but far more through clinical laboratory examinations, careful autopsy searches, and by rigid general hygienic measures such as cage-police, new quarters, isolation, or if necessary, destruction of the exhibit.

INDEX

Abortion, 305

Abscess of liver, 231 of lung, 155

Acariasis, lungs, 647 of monkeys, 647

Actinomycosis, 138, 568 in deer, 368, 568 tapirs, 568 treatment, 570

Adenoma, 474

Adrenal body, 336

Alimentary tract, 166

Amblyopia, 403

Amœbæ, 606, 644 dysentery from, 644

Amyloid, liver, 227 spleen, 128

Anatomy of labor, 290

Anchylostomum, see hookworms

Anemia, 87 primary, 98 secondary, 88

Aneurysms, 65, 80

Animal Parasitism, hygiene, 656 prevention, 656 treatment, 655

Animal Parasites, 614 disappearance of, 627 frequency, 628 of groups, 633 in blood, 652 incidence, 628–636 modes of action, 617 occurrence in wild, 627 transmission animals to man, 653 visceral distribution, 637

Angina pectoris, 49

Aorta, 72 fatty deposits in, 71

Arteries, 66

Arteriosclerosis, 71

Arteritis, 70

Arthritis, 347 gouty, 347, 411

Ascending nephritis, 276

Aspergillosis, 558

Aspergillus, varieties, 558

Ataxia, 375

Atrophy, acute of liver, 228

Autopsy list, 47

Avian spiropteriasis, 172, 640

Bacterial flora, 418

Basal cell carcinoma, 475

Beriberi, 439

Biliary tract, 225 calculi, 238