Part 61

As to the individual organs which are most commonly parasitized our records show that with Aves as well as Mammalia the intestines are the parts most commonly affected. The stomach ranks second for both—the proventricle rather than the gizzard of birds corresponding, parasitologically speaking, to the stomach of mammals. We have found but one parasitic species in the gizzard of birds, _i.e._, immature forms of _Spiroptera incerta_ lying under the chitinous lining of the gizzard and only discoverable after the lining has been peeled off. The peritoneum comes third (air sacs of birds) due to the presence of filaridæ, and the blood fourth for the same reason. It is to be emphasized that, in our data, identical organs of mammals and birds should be about equally liable to infestment with the possible exception of the lungs. But in view of the small number of cases available there is no justification for speculating about the reason for this last difference, albeit the radical difference in the anatomy of the two classes is very inviting.

Now that our spiroptera enzoötic has subsided, the order above given will be changed, and in view of like disturbing factors other gardens should not expect the same order to hold invariably for their collection, since their enzoötics will depend somewhat on the preponderance of animals of one or another family which are likely to compose their exhibits. A single such enzoötic may suffice to disarrange the whole fabric, and if two or three are taken into account the order of organ involvement can be quite disrupted. To attempt to construct statistically an “order of frequency involved” which would stand for every garden would only lead to interminable adjustments on the basis of animals exhibited and of parasitic enzoötics, so that I have finally been reduced to a combination of our Garden statistics and the bloodparasitic ones of the London Garden. Doing this I have arranged in Table 27 the frequency of organ involvement as follows and estimated the percentage of animals infested. These figures are computed upon a different basis from that of Table 24. They naturally cover all animals and not the “susceptible” ones as in Table 24.

TABLE 27. ═══════════════════════════════════╤═══════════════════════════════════ Mammalia │ Aves ───────────────────────┬───────────┼───────────────────────┬─────────── │ per cent. │ │ per cent. Intestines │ 9.0│Blood │ 6.5 Stomach │ 3.7│Intestines │ 3.5 Peritoneum │ 2.3│Proventricle │ 1.7 Blood │ 1.5│Air sacs │ 1.3 Lungs │ 1.0│Liver │ 0.3 Muscles │ 1.0│Gizzard │ 0.3 Liver │ 0.5│Scattering │ 0.4 ───────────────────────┼───────────┼───────────────────────┼─────────── Total │ 20.0│Total │ 14.0 ───────────────────────┴───────────┴───────────────────────┴───────────

The effect of this is at first sight startling in that it places the blood parasites of birds so far in the fore, but it must be at once recalled that the inquiries upon the blood parasites were much more searching—microscopic, than in the case of the other organs. If similar methods were applied to the others their percentage of parasitism might be notably raised—particularly that of the intestines.

SPECIAL PARASITOLOGIC CONSIDERATIONS.

At this point the statistical considerations of parasitism will give way to descriptions of certain specific infestments that have given us more or less concern.

The occurrence of single parasitic varieties or of well known species in an isolated host may occasionally be of practical importance, but usually they amount to little more than an academic study, whereas the repeated discovery of single parasitic kinds, or infestment of similar hosts, especially when grouped, raises the matter to a very practical level demanding attention. Such findings being not infrequent in our experience, it has been possible to study our material in a manner designed to show the frequency of various parasites in a certain host, the susceptibility of certain animals to parasites in general and the infestment of dissimilar hosts by the same parasite. The more important of these now follow.

AVIAN SPIROPTERIASIS.

This disease concerned parrots particularly but toucans, pigeons, and such widely separated species of birds as the starling, quail, thicknee and barbet have been occasionally affected. To the naked eye the parasite resembles the human hookworm, but differs in location, being a resident of the proventricle where it produces a swelling of the mucosa which interferes with the passage of food. Up to a hundred worms may be present in the one bird, and immature forms are occasionally found under the chitinous lining of the gizzard. The parasite burrows into the mucous membranes, occasionally penetrates quite through the wall into the air sacs, and on one occasion induced an adenomatous hyperplasia of the mucous membrane, and an adjacent “peritonitis.” Mucus is sometimes present in the droppings. Death may occur either acutely, or with emaciation. Spiroptera incerta Smith[132] is the common parasitic species of parrots, but I have found at least one other as yet unidentified species in the toucan, and there are probably more. In the eight year period 1906–1913 from 25 to 50 per cent. of our dead parrots showed this parasite every year, the total loss being 113 birds for this period—a most important infestment.

We approached the problem by diagnosing and isolating the infested birds through a microscopic examination of droppings, finding that by boiling the droppings in 5 per cent. NaOH solution we clarified them and made examination easier and more certain without at the same time destroying the parasitic ova. The result of the examination of all our parrots was the isolation of 14 per cent. of the parrot population; and as these died off the diagnosis of infestment was found confirmed at autopsy in every case. The parrot house was thoroughly renovated and no newly arrived parrots were admitted until after quarantining and examining droppings for ova. The toucans and other species, being housed elsewhere, were not quarantined. Following this, we were gratified to experience no more spiroptera deaths in parrots for seven years. Then, in 1920 and 1921, a new outbreak occurred in four toucans and several other scattering species, including two parrots; but none of these came from the main parrot house and probably represented a fresh importation. We attempted to cure the isolated verminous birds by medication but were unsuccessful. Likewise attempts at determining the life cycle of the parasite brought us no farther than that the ova developed larvæ in moist sand in six days. Feeding of ova, freshly passed and larvated did not produce infestment in parrots or pigeons. On the whole we can quote our experience with spiroptera as a most satisfactory example of the value of hygiene and as a result which could never have been accomplished by medication.

HEPATICOLA (TRICHOSOMA) HEPATICA IN PRAIRIE DOGS.

Bancroft[133] and Hall[134] have given us details concerning this parasite and the disease it causes. It is threadlike, several inches long, and permeates the livers of the gray rat, white rat and wild hare.[135] We first saw it in the more or less cirrhotic livers of several prairie dogs; later we observed it in a beaver and the gray rats of the Garden. In the prairie dogs and beaver the liver resembled that of fatty cirrhosis and was so considered on naked eye examination at our first autopsy. We were only set right when we came to the histological examination. It was remarkable how well conditioned some of the prairie dogs were in in the face of very extensive liver destruction; but on the other hand some were emaciated and a few of the spontaneously diseased showed at autopsy an enormous ascites. The outstanding features at autopsy were the large size of the liver and its pallor and hardness; and fine yellow lines could sometimes be made out twisting over the surface.

The disease affects wild rats differently from prairie dogs. In both the spontaneous and experimental disease the infestment was insignificant, amounting to perhaps three or four foci the size of a split pea near the anterior margins of the liver. Diagnosis may be easily confirmed by crushing the yellow infested portions of the liver between glass slides and examining microscopically for ova.

We have seen such a small number of cases of this disease because so few prairie dogs reach the autopsy table, yet there must be some important mortal factor in our prairie dog enclosure, for the Superintendent states that the population there does not increase in spite of the frequent births and additions from dealers. The animals almost invariably die under ground and their bodies are not recovered.

In order to test out the origin of the infestment we trapped two of our exhibition specimens, and the liver of both was found infested on surgical examination whereas six newly purchased ones had normal livers. The latter were secured fresh from their native habitat in the West, and their livers were examined through long surgical incisions and found free of infestment. Later we fed the ova (embryophores) from rat livers to these prairie dogs and on destroying them found them infested. We were also successful in transmitting the disease in the opposite direction, _i.e._, from prairie dog liver to white rat. From all this we feel sure that the prairie dog disease in our Garden was transmitted from the rat and that here is another reason for rat extermination in a zoological garden.

The adult _Hepaticola hepatica_ of prairie dogs I have not seen in sufficient entirety to compare with the rat species and therefore cannot affirm that the two are identical species. It is presumably like that of the rat, being threadlike and most difficult to separate from the liver substance through which it ramifies. At maturity it dies and disintegrates, leaving the ova distributed more or less in tracts through the liver substance, so that we are limited to a certain period wherein to obtain the mature form. The ova are not passed into the intestine, but remain _in situ_, just as in the case of hydatid disease, and therefore diagnosis cannot be achieved by examination of feces. For the disease to be transmitted the host must die and its carcass be eaten or otherwise so disintegrated that the ova are distributed abroad. Another interesting observation is the long incubation period of the ova. Confirming Bancroft, we found that the ova only became larvated after they had lain in water at least three months.

HOOKWORMS.

These important parasites have been taken from several foxes: Gray Fox (_Canis cinero argenteus_), Arctic Fox (_Canis lagopus_), Swift Fox (_Canis velox_), Red Fox (_Canis vulpes pennsylvanicus_), a Gray Wolf (_Canis mexicanus_), divers members of the Felidæ-Eyra (_Felis eyra_), Jaguarundi (_Felis jaguarundi_), American Wild Cat (_Felis ruffus_), Spotted Wild Cat (_Felis ruffus texensis_), Ocelot (_Felis pardalis_), from two Giraffes (_Giraffa Camelopardalis_, _Giraffa capensis_), a Malayan Tapir (_Tapirus indicus_), and a young California Hair Seal (_Zalophus californianus_). It has been a most serious infestment in American wild cats (_Felis ruffus_ and _Felis ruffus texensis_)—animals which generally also harbor other species of worms. In view of the petechial hemorrhages of the intestines and analogous circumstances in dogs and human beings, it must be conceded that this worm is pathogenic.

At this point it is fitting to note the infestment as it affects hair seals. The parasite concerned, _Uncinaria lucasi_, has long been a scourge among the fur seals (_Otoes alaskanus_) of the Pribiloff Islands. Its punctures are bloodless, being signalized instead by small edematous plaques in the intestinal mucosa, The animal we autopsied was a young California Hair Seal born in the Garden, and is singularly the only hair seal in which we have seen it. The natural habitat of the hair seal is the coast of California which means that the range of _U. lucasi_ may extend farther southward than at first suspected. We have none of the northern variety.

I point out two giraffe cases only because they are unique as to the organ (liver) affected. So far as I know, mature hookworms have never been reported from other organs than the intestines.

From the prophylactic standpoint it will be advisable to have as little moist earth as possible, particularly sandy ground, in and around the enclosures for the above mentioned susceptible animals because it is in such soil that the earlier stages of the life cycle of the parasite are passed.

We have never found any of the human hookworm species in our animals, but it must be recognized that transmission is possible to a certain degree. _Anchylostoma ceylanicum_ Lane[136] was found in man, cats, dogs, and a lion; Leiper[137] reports _A. duodenale_ in a dog, and von Linstow[138] states that the latter parasite also occurs in the chimpanzee.

AMEBIC DYSENTERY IN MONKEYS.—We recently lost six monkeys in a small outbreak of this disease—four black spider monkeys (_Ateles ater_), a Pinche marmoset (_Leontocebus edipus_), and a woolly monkey (_Lagothrix lagotricha_). Except for non-characteristic looseness of stools, there were no symptoms until the usual terminal lethargy set in. Living amebæ were found in feces. At autopsy only the colon was found to be anatomically affected. It was hugely distended, fully an inch in diameter, and there were numerous confluent ulcers of the mucosa covered by a thick slough. The liver showed no abscesses. In the histological sections amebæ were found in the interstices of vital gut tissue just as they are in corresponding human lesions. I have not diagnosed the species yet, but can vouch that it is not _Endameba histolytica_ or _coli_.

According to Leidy’s recommendation, grated nutmeg was administered and was followed by an improvement in symptoms. The animals became brighter and the stools firmer, but the amebæ were not eradicated. Emetin hypodermically and by mouth had no obvious effects on the disease or the amebæ. One monkey thus treated with nutmeg recovered, but died the next year of another affection and disclosed the scars of the old ulcers in the colon. Our experience with this disease, however, is not unique. At Washington, D. C.,[139] eight spider monkeys were affected, and sporadic cases come to light from the West Coast[140], Manila, Khartoum and Ceylon. Prowazek’s report concerned a young orang[141]. Liver abscesses in addition to the intestinal lesions were found by three different observers.

As to the transmissibility of monkey amebiasis to man, reporters are divided. Both sides are probably right, in as much as _Endameba histolytica_ was concerned in some cases and non-human species in others. It is an infestment to be feared, and calls for examination of stools from such newly arrived animals as are known to be susceptible (spider and woolly monkeys, orangs).

PARASITES OF MARMOSETS AND SQUIRREL MONKEYS.—I give a special place to this subject because Table 24 shows that these monkeys are so commonly infested and because they are so commonly used as household pets. In this connection the questions arising are, first, whether the infestment is a menace to life, and second, whether it is existent outside the Garden or only acquired here. The following lists set forth the parasitic status as shown at autopsy. The figures indicate how long the animal lived in the Garden:

═════════════════════════════════════════╤═══════════════════════════ Marmosets │ Squirrel Monkeys ─────────────┬───────────────────────────┼─────────────┬───────────── Infested │ Not infested │ Infested │Not infested ─────────────┼───────────────────────────┼─────────────┼───────────── 1 day│ 6–15 days ( 4 animals)│ 2 days│ 3 months 1 day│ │ │ 2 months│ 1 month ( 6 animals)│ 14 days│ 3 months 6 months│ 3–5 months ( 9 animals)│ 26 months│ 5 months 12 months│ 6 months ( 2 animals)│ │ 14 months 12 months│ 7 months ( 2 animals)│ │ 15 months 12 months│ 8 months ( 1 animal)│ │ 13 months│ 9 months ( 2 animals)│ │ │ 10 months ( 1 animal)│ │ │ 12 months ( 1 animal)│ │ │ 14 months ( 1 animal)│ │ │ 15 months ( 1 animal)│ │ │ 17 months ( 1 animal)│ │ │ 18 months ( 2 animals)│ │ │ 20 months ( 1 animal)│ │ │ 21 months ( 1 animal)│ │ ─────────────┼───────────────────────────┼─────────────┼───────────── Totals 8 │ 35 animals│ 3 animals│ 5 animals animals │ │ │ ─────────────┴───────────────────────────┴─────────────┴─────────────

Reverting to the questions above raised, the data show that some of the animals were certainly infested on arrival here, and that others probably were; but since these animals were not examined for parasites on arrival in the Garden the duration of infestment remains unknown, and accordingly we are not justified in going farther in our conclusions. In the case of the marmosets, though, if we confine ourselves to the non- parasitized animals, it would appear that the “acclimatization” period is within the first six months. I have attempted to arrive at a conclusion on this basis, but the average lifetime of the four parasitized marmosets which survived this period is the same as that of the sixteen non-parasitized survivors, and we do not know at what time the parasitized ones contracted the disease.

CYSTICERCUS TENUICOLLIS.—We have noted this bladder worm in the Aoudad (_Ovis tragelaphus_), Red River Hog (_Potamochœrus porcus_), domesticated Angora Goats and several deer (_Cervus alfredi_, _Capreolus capreolus_, _Mazama mexicana_, _M. hemionus_) located with one exception in the peritoneal cavity or membrane. One of the mule deer (_Mazama hemionus_) exhibited the parasite also in the lung and liver. This parasite is discussed because the very valuable Philippine spotted deer (_Cervus alfredi_) died from a peritonitis secondary to an infected cyst in the lesser omentum, and because the parasitism (_Tænia marginatum_) is contractible from canidæ which are also on exhibition in the Garden. It happens that the spotted deer did not become infested from the dogs, but it is quite probable that the goats did, since they passed many times daily in front of the wolf cages, drawing the children’s carriages over the walks, and were stabled nearby. We have not discovered any of the other tapeworm cysts in deer which might be transmitted to them from the canidæ. Camels which are parked directly opposite them have only exhibited echinococcus cysts, yet we have never found its adult form (_Tænia echinococcus_) or its ova in the canine feces. The danger of fatal disease from _C. tenuicollis_, even though the infestment be present, is remote; but we feel that it is better, if possible, not to exhibit the canidæ adjacent to susceptible animals.

PULMONARY ACARIASIS IN MONKEYS.—We have seen but two instances of this affection in the Philadelphia Garden. The offending parasite in our animals was a new species, _Pneumonyssus foxi_ Weidman[142]. It occurred sparingly in small cysts under the pleura and was certainly benign in our cases. The importance of the infestment consists in part in that these lesions may be mistaken for tubercles.

At the London Gardens[143] acariasis was found in forty-four young rhesuses dying of pneumonia, and the observers ascribed the inflammation to irritation of certain doubly refractile crystals which occurred in the excreta of the mite. There are four other recorded instances of such disease in monkeys, all caused by different species of parasites.

As to pathogenesis of these arachnids, the London experience is most illuminating in that it was young rhesuses that were affected. Our specimens were mature, and nothing was stated to the contrary in the other reported cases from various parts of the world. The parasites are perhaps inhaled from the straw used as bedding, since such vegetable material is a common habitat for mites. If the resultant acute pneumonia is weathered the relics might remain only in the form of the subpleural and parabronchial cysts such as we have seen at the Philadelphia Garden.

I am the more willing to accept the possibility that the simian arachnids can induce an acute pneumonia after studying a very definite case of bronchopneumonia in a prairie dog, which was induced by _Cytoleichus penrosei_ Weidman 1916.[144]

PERIPROVENTRICULAR FILARIDÆ OF BIRDS.—Every year we report a number of cases (up to twenty-three) of these worms, probably several species, coiled under the serosa of the air sacs and most commonly around the proventricle. Tentatively we have recognized two forms, a shorter (an inch or so long) and a longer (three to four inches). The latter is most inextricably coiled, but the former may be teased out. Microfilaria occur in the blood of the latter cases, but not in that of the former. The adults have been observed to penetrate from their position in the air sac serosa into the lumen of the proventricle (goose), to have caused rupture of the inferior cava (bulbul), to be associated with subserous cysts of the intestine (weaver) and with profound anemia (liothrix). The birds affected are mostly small, inexpensive ones, but the infestment is important because of its frequency and deserves study of the means of transmission.