Pneumostrongylus Tenuis Research Articles

Choroid plexitis in white-tailed deer (Odocoileus virginianus) in southern New York State.

Brains, spinal cords, nerve roots, nerves and muscle tissues were removed from deer in southern New York State and examined for histologic evidence of infection by the causative agent of Lyme disease, Borrelia burgdorferi. There was no histologic evidence of this infection and only four of 26 deer had serologic evidence of past infection despite the fact that all were parasitized by the tick vector, Ixodes dammini. Of these ticks, 21% were carrying B. burgdorferi. In contrast, most of the deer had choroid plexitis. All but one of 48 deer tested were infected with Trypanosoma cervi, 20 of 24 deer had sarcocystis in skeletal muscles and two had dural lesions probably due to the nematode Pneumostrongylus tenuis. The causal relationship between choroid plexitis and trypanosomiasis is discussed.

Distribution of the Meningeal Worm in White-Tailed Deer in Canada

Larvae indistinguishable from those of the meningeal worm (Pneumostrongylus tenuis) were recovered from feces of white-tailed deer (Odocoile2ls virginianus) in Quebec (63 percent), Ontario (63 percent), Manitoba (49 percent), and eastern and central Saskatchewan (9 percent) in 1971. Adult worms were found as far west as 31 miles from the Manitoba-Saskatchewan border. The parasite is established in deer of the aspen parkland, and there is no apparent barrier to its continued spread westward. MENINGEAL WORM IN DEER * Bindernagel and Anderson 1349 MUNRO, S. A. 1969. The breeding biology of the snowshoe hare during a high population in central New Brunswick. M.S. Thesis. Univ. Of New Brunswick. 85pp. NOWOSAD, R. F. 1968. An ecological study of important deer wintering areas in Nova Scotia. M.S. Thesis. Acadia Univ. 198pp. POTTER, J. G. 1965. Snow coverclimatologicaI studies No. 3. Meteorological Branch, Canada Dept. of Transport. 69pp. ROLAND, A. E. 194S. The flora of Nova Scotia. Truro Publishing Company, Truro, Nova Scotia. 552pp. RowE, J. S. 1959. Forest regions of Canada. Canada Dept. Northern Affairs and Natl. Resollrces, Forestry Branch, Bull. 123. 71pp. SHAFER, E. L., JR. 1963. The twig-count method for measuring hardwood deer browse. J. Wildl. Mgmt. 27 ( 3 ) :428437. SKINNER, W. R. 1968. Spring, summer and fall foods of the white-tailed deer in central and southern New Brunswick. M.S. Thesis. Acadia Univ. 95pp. TELFER, E. S. 1967. Comparison of moose and deer winter range in Nova Scotia. J. Wildl. Mgmt. 31(3):418-425. 1968. The status of moose in Nova Scotia. J. Mammal. 49(2):325-326. . 1971. Changes in carrying capacity of deer range in western Nova Scotia Cranadian Field-Naturalist 85(3):231-234. Received for publication December 27, 1971. New Brunswick (Smith and Archibald 1967). All of these records are from deer in the deciduous forest or coniferous forest biome or in the ecotone between these two biomes. In 1964, the meningeal worm was shown to be the causal agent of neurologic disease in moose ( Alces alces ), more commonly known as moose sickness or blind staggers (Anderson 1964). Since then, specimens of the meningeal worm have been recovered from the brain or spinal cord of moose with neurologic disease from the Fort Frances district of northwestern Ontario (Anderson 1965 ), Nova Scotia and New Brunswick (Smith et al. 1964, Smith and Archibald 1967), Maine (Behrend and Witter 1968), The nematode Pneumostrongylus tenuis, first described from white-tailed deer in New York State ( Dougherty 1945 ), has been reported in the United States from deer in Michigan ( Degiusti [DeGiusti] l9SS, 1963 ), Pennsylvania ( Alibasoglu et al. 1961, Samuel and Beaudoin 1966), western Virginia (Dudak et al. 1966), Minnesota ( Karns l967 ), Maine ( Behrend and Witter 1968), and Wisconsin (Samuel and Trainer 1969). It has also been reported from 12 states of the southeastern United States as far west as Arkansas and as far north as Maryland ( Prestwood and Smith 1969 ) . In Canada, it is known from the provinces of Ontario (Anderson 1963), Nova Scotia, and This content downloaded from 207.46.13.43 on Wed, 25 May 2016 05:34:58 UTC All use subject to http://about.jstor.org/terms 1350 Journal of Wildlife Management, Vol. 36, No. 4, October 1972 the parasite occurring west of southeastern Manitoba was a matter of speculation. The present study was undertaken to determine the distribution of the meningeal worm in Ganada west of New Brunswick. Our study was based primarily on the recovery of firststage larvae from deer pellet groups but was supported by the examination of heads from critical areas. This study was supported by funds from the Canadian National Sportsman's Show. We thank the personnel of the Quebec Wildlife Service, the Ministry of Natural Resources, the Manitoba Department of Mines, Resources and Environmental Management, and the Saskatchewan Department of Natural Resources for their assist-

A device to aid in examining the brain and meninges of deer for helminth parasites.

A vise-like apparatus consisting of movable plates with “teeth”, which can be clamped to a table top, has been found to be of value as an aid in securing the heads of white-tailed deer (Odocoileus virginianus) for examination for meningeal worms (Pneumostrongylus tenuis). This apparatus also has been valuable as an adjunct to necropsy procedures when studying various types of cranial injuries, cerebral abscesses, and for examining the turbinates for nasal bots (Cephenemyia phobifera).

Neurologic disease in reindeer (Rangifer tarandus tarandus) introduced into Ontario.

In May, 1969, a small herd of reindeer (Rangifer tarandus tarandus) from Norway was placed in a recently enclosed area formerly inhabited by white-tailed deer (Odocoileus virginianus). The animals subsequently developed signs of neurologic disease. An analysis of clinical and pathologic findings, as well as a consideration of the history of the introduction, indicates the reindeer became infected in June with meningeal worm (Pneumostrongylus tenuis Dougherty, 1945) harbored by molluscs which had survived during the winter in the enclosure.

Winter Habitat Selection by Moose and White-Tailed Deer

In January, 1967, activity of white-tailed deer (Odocoileus virginianus) in the central New Brunswick lowlands was concentrated in dense-canopied forest types with a high proportion of conifers. Moose (Alces alces) avoided these types in favor of more open forests. In March, 1967, most of the activity of both species occurred in stands of the dense coniferous type. Snow depths in January ranged from 28 to 48 cm, in March, from 76 to 112 cm. Although the mean March snow depth in the dense conifer type did not differ significantly (P < 0.05) from that of the other types, 83 percent of a series of systematic depth samples in this type were less than the maximum depth at cervid tracks. Only 33 percent of depths in the other types were less than this value. Deer and moose used 22 percent of the total study area in March. They were essentially exclusive in their use of habitat, sharing only 1 percent of the area. The ranges of moose and white-tailed deer overlap extensively in eastern Canada and a few adjoining states. Since the foods and feeding habits of these species are similar, interspecific competition for food is a possibility (Peterson 1955:168, Idstrom 1965:88). Anderson (1964) has shown that the parasite Pneumostrongylus tenuis may be transmitted from deer to moose causing high mortality in the latter. Studies by Parker (1966) and Telfer (1967b) suggested that the incidence of transmission of this parasite is related to the extent that moose and deer populations mingle in late winter and early spring. Habitat requirements of white-tailed deer in winter have been described by several authors (Severinghaus and Cheatum 1956, Hosley 1956, Gill 1957, Hepburn 1959, Behrend 1966). Winter habitat use by moose has been reported by Peterson (1955), Des Meules (1962), Telfer (1967a), and Prescott (1968). Little has been published on the comparative habitat choices and reaction to winter conditions of moose and white-tailed deer in areas they both occupy. Kelsall and Prescott (in press) and Telfer (1967b) have reported aspects of the relationship between these species in localities having considerable topographic relief. Both these studies found altitudinal separation between the species in winter. The present study compared early and late winter habitat choice by moose and deer in relatively flat country where altitudinal variation is not great enough to be a factor in cervid distributions. I acknowledge the assistance of J. Maxwell and the cooperation of B. Wile and his staff at the Acadia Forest Experiment Station of the Canada Department of Fisheries and Forestry.

Geographic Distribution of Gongylonema pulchrum, Gongylonema verrucosum, and Paramphistomum liorchis in White-Tailed Deer of the Southeastern United States

The upper digestive tracts of 788 white-tailed deer (Odocoileus virginianus) from 13 southeastern states and St. Croix of the U. S. Virgin Islands were examined for helminths. Gongylonema pulchrum was found in 457 (57.9%) deer from Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, and West Virginia. Gongylonema verrucosum was present in 131 (16.6%) deer from Alabama, Florida, Georgia, Louisiana, North Carolina, and South Carolina. Rumen flukes, Paramphistomum liorchis, were harbored by 58 (7.3%) deer from Alabama, Florida, Georgia, Louisiana, and South Carolina. No helminths were found in the upper digestive tract of 10 deer from St. Croix. During the past 10 years considerable attention has been given to the diseases and parasites of white-tailed deer (Odocoileus virginianus), the most important big game animal in the United States. Although several reviews of the parasite fauna of white-tails are available (Dikmans, 1939; Olsen and Fenstermacher, 1943; Anderson, 1962a, b), the geographic distributions of helminths of this host are not well known. Regional distribution records involving several adjoining states have been published for one helminth (Pneumostrongylus tenuis) of white-tailed deer (Prestwood and Smith, 1969). The incidence of helminths in the upper digestive tract of deer is poorly documented. Gullet worms, Gongylonema pulchrum, were reported in white-tailed deer from North Carolina (Dikmans and Lucker, 1935; Shillinger, 1938) and Pennsylvania (Samuel and Beaudoin, 1966), while G. verrucosum was found in deer of Marion (Dikmans and Lucker, 1935) and Orange counties, Florida (Dinaburg, 1939). The latter author recorded amphistome flukes from the rumen of Florida deer. North American deer were listed (Dikmans, 1939) as hosts Received for publication 27 June 1969. * This study was supported by an appropriation from the Congress of the United States. Funds were administered and research coordinated under the Federal Aid in Wildlife Restoration Act (50 Stat. 917) and through Contract Nos. 1416-0008-676 and 14-16-0008-777, Bureau of Sport Fisheries and Wildlife, U. S. Department of the Interior. to Paramphistomum cervi and flukes, identified as P. liorchis, were found in Florida and Louisiana white-tails (Price and McIntosh, 1944). This article presents additional information on the incidence and distribution of Gongylonema pulchrum, G. verrucosum, and Paramphistomum liorchis in white-tailed deer of the southeastern United States. MATERIALS AND METHODS From 1961 through 1969 the upper digestive tracts of 788 white-tailed deer were examined for helminths. Animals from 98 areas in 13 southeastern states and St. Croix of the U. S. Virgin Islands were examined (Fig. 1). Most deer were killed by a shot through the neck with a .222 caliber rifle. Deer dying of accidental or natural causes were also examined. Approximately twothirds of the deer were females since the latter were more numerous on areas where buck only hunting regulations prevailed. Ages ranged from 6 months to 9 years. Approximately 17% of the deer examined were 6 months old, 31% were 1 to 2 years old, 16% were 2 to 3 years old, and the remaining 36% were greater than 3 years of age. All animals were examined similarly. After recording appropriate vital statistics, the carcass was skinned and the abdominal and thoracic cavities opened. The mouth and pharynx were examined for helminths. The esophagus was severed at the throat and near the inlet to the rumen; it was then split longitudinally and inspected for nematodes. The rumen, reticulum, and omasum were freed of ingesta and the mucosal wall washed lightly. The wall was searched for flukes, and the lining was peeled to reveal nematodes. In early studies (1961-63) attempts were not made to determine the number of parasites present

Polioencephalomalacia in a white-tailed deer. (Odocoileus virginianus borealis).

In an adult white-tailed deer affected by polioencephalomalacia the lesions were acute ischemic-type necrosis, malacia, and hemorrhage in the cerebral cortex, vestibular nuclei, caudal colliculi, oculomotor nuclei, geniculate nuclei, thalamus, and ventral portion of the cerebellar vermis. The deer also had granulomas associated with Pneumostrongylus tenuis in the spinal leptomeninges.

Distribution of Meningeal Worm (Pneumostrongylus tenuis) in Deer in the Southeastern United States

Pneumostrongylus tenuis was found in the meninges of 1,197 (49.7%) of 2,409 white-tailed deer collected in Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Tennessee, Virginia, and West Virginia. Infected deer were not found in South Carolina and St. Croix of the U. S. Virgin Islands. In the southeastern United States, meningeal worm appears to occur mainly in deer of oak-pine subclimax and climax deciduous forest types. It was not found in areas having a sandy soil and a predominantly pine forest. During the past few years considerable attention has been given to the biology of Pneumostrongylus tenuis Dougherty, 1945, the meningeal worm of white-tailed deer (Odocoileus virginianus). This helminth, apparently restricted to eastern North America, is noteworthy because it is a neurotropic form which generally produces a silent infection in the normal host (Anderson, 1963, 1965b; Anderson and Strelive, 1967; Lankester and Anderson, 1968) but can cause neurologic disturbances including paralysis in unusual hosts. Neurologic disease caused by P. tenuis has been produced experimentally in moose (Anderson, 1964), wapiti and mule deer (Anderson et al., 1966), woodland caribou (Anderson and Strelive, 1968), sheep (Anderson and Strelive, 1966b), and guinea pigs (Anderson and Strelive, 1966a; Spratt and Anderson, 1968). Neurologic disease associated with naturally acquired infections of meningeal worm has been reported in domestic sheep (Kennedy et al., 1952; Whitlock, 1952, 1959; Nielson and Aftosmis, 1964), moose (Smith et al., 1964; Anderson, 1965a; Kurtz et al., 1966; Karns, 1967a; Smith and Archibald, 1967; Behrend and Witter, 1968), and caribou (Behrend and Witter, 1968). The same disease probably occurs in wild wapiti in certain Received for publication 15 April 1969. * This study was supported by an appropriation from the Congress of the United States. Funds were administered and research coordinated under the Federal Aid in Wildlife Restoration Act (50 Stat. 917) and through Contract Nos. 1416-0008-676 and 14-16-0008-777, Bureau of Sport Fisheries and Wildlife, U. S. Department of the Interior. parts of eastern North America (Anderson et al., 1966). Although P. tenuis occurs rather extensively in eastern North America, precise data concerning its abundance and distribution have not been available. In view of rapidly expanding white-tailed deer populations throughout this section of North America and the proven pathogenicity of P. tenuis to other animals which come into contact with deer, it is essential that more information be obtained on its distribution. This article presents results of an extensive survey to determine the distribution of meningeal worm among white-tailed deer of the southeastern United States. MATERIALS AND METHODS From 1960 through early 1969 heads of 2,409 white-tailed deer were examined for P. tenuis. Animals originated from 137 counties in 13 southeastern states and St. Croix of the U. S. Virgin Islands (Fig. 1). Most deer heads were from animals killed by hunters during annual harvests in each state but some were obtained from deer dying of natural causes or collected for research purposes. Approximately two-thirds of the deer were females. Since hunters were reluctant to donate heads of mature bucks, does and immature bucks were most prevalent in the samples. Heads from hunter-killed animals were frozen prior to examination, while others were examined within 12 hr following death. After thawing, frozen and fresh heads were examined similarly. For individual examination, the head was skinned and freed of extraneous tissue. Horizontal cuts were made immediately posterior to the eyes and at the external occipital protuberance, with care taken not to damage the meninges. Frontal bones were opened along the sagittal crest, and bones lifted with a screwdriver. Bits of bone were removed with needle-nosed pliers until the brain with intact meninges was exposed. The olfactory bulb was grasped with a large pair of forceps, and tissue severed adjacent to the cribriform plate.

Pneumostrongylus tenuis in Moose on a Deer-Free Island

Analysis of fresh moose (Alces alces) feces from Isle Royale, Michigan, a deer-free island in Lake Superior, and northeastern Minnesota, an area with a low white-tailed deer (Odocoileus virginianus) population, revealed incidences of 0.8 and 0.6 percent respectively of the first-stage larva of Pneumostrongylus tenuis, the etiological agent of cerebrospinal nematodiasis in moose. The report of this parasite is from an area that has been deer-free for 30 years. The common host of the nematode Pneumostrongylus tenuis is considered to be the white-tailed deer. The parasite is now recognized as the etiological agent of cerebrospinal nematodiasis in moose (Anderson 1964). Infection is often fatal to moose, and heavy mortality has been recorded in areas where deer are abundant (Anderson 1965a, Karns 1967, Smith et al. 1964). Anderson (1965a), finding no record, raises the ques1 Joint contribution of Minnesota Division of Game and Fish and Purdue University. Field work receiving principal support from the National Science Foundation (GB-5124), the National Geographic Society, and the National Park Service: D. L. Allen, project director. Purdue University AES Journal Paper No. 3377. tion of whether this parasite can exist independently of white-tailed deer. Isle Royale, Michigan, lies 12 miles from the nearest off-shore islands and 15 miles off the north shore of Lake Superior. Woodland caribou (Rangifer tarandus) were present on the 210-square-mile island at one time and disappeared about 19'25 (Mech 1966:16). Mech and others felt that moose immigrated to the island from the mainland in the early 1900's. Twelve white-tailed deer were introduced in 1906, and may have persisted until about 1936 (Johnsson and Shelton 1964). All that we can assume about the growth and continuity of the introduced deer population is that deer were present ether this parasite can exist intl of white-tailed d er. ale, ichigan, lies 12 miles from This content downloaded from 157.55.39.102 on Mon, 03 Oct 2016 04:08:52 UTC All use subject to http://about.jstor.org/terms 432 Journal of Wildlife Management, Vol. 33, No. 2, April 1969 Table 1. Summary of moose fecal samples collected from Isle Royale, Michigan, and examined for first stage larvae of Pneumostrongylus tenuis. FECES FROM WOLFRANDOM FECES KILLED MOOSE COLLECTION COLLECTION Larvae Larvae Larvae Larvae PEmOD Present Absent Present Absent

Pneumostrongylus tenuis in White-Tailed Deer in Maine

Eighty-four percent of 196 heads of white-tailed deer (Odocoileus virginianus) collected in Maine from October through December, 1967, contained adult specimens of the nematode Pneumostrongylus tenuis. The incidence of this parasite was significantly greater (P < 0.05) in females of all age-classes combined, but was not significantly greater among females in each individual age-class. In contrast to other studies, no significant differences in incidence were found between age-classes; and fawns, while having the lowest incidence of infection (66 percent), were still infected in large numbers. Worms were found in deer heads from all counties. The incidence was highest (100 percent) where deer populations are presumably the densest and have been expanding. The occurrence of Pneumostrongylus tenuis in white-tailed deer has long been recognized. However, as whitetails apparently harbor this parasite with little illeffect, the ecological significance of P. tenuis has been obscure. Anderson (1964) provided the first insight on this problem by experimentally inducing severe neurological disorders in moose (Alces alces americana) which he infected with P. tenuis larvae. More recently, Anderson et al. (1966) have reported similar findings with wapiti (Cervus canadensis) and mule deer (0. hemionus). These findings have stimulated interest in P. tenuis, particularly in regions where whitetails coexist with other cervids. The work reported in this paper represents the preliminary phase of a study of deer-moose relationships in

Gastropods as intermediate hosts of Pneumostrongylus tenuis Dougherty of white-tailed deer

From May to October, 1966, gastropods from three different habitats on Navy Island, Ontario, were examined for larvae of Pneumostrongylus tenuis. Of 9940 examined individually, 4.2% contained larvae. A mean of 2.9 larvae was recovered from each infected gastropod. Deroceras laeve and Zonitoides nitidas were the most abundant and commonly infected species. The incidence of infective larvae in adult D. laeve from a wet forested area rose to 25% by late June but dropped to 1.5% during July, coinciding with the disappearance of adult slugs. The level of infection in Z. nitidus (4.3%) remained relatively constant. The wet forested habitat where gastropods were abundant, commonly infected, and active from May to October was probably most important for transmission. Experiments showed that snails already containing larvae can be reinfected and there is some evidence that they are repeatedly infected in nature. Larval development was retarded in aestivating snails. Numbers of larvae recovered and their rate of development differed in various species of experimentally infected gastropods. Snails of the family Polygyridae were the most suitable intermediate hosts studied. Larvae passed by deer were situated in the film of mucus covering faecal pellets. In this location, larvae may be dispersed by high spring water or heavy rainfall. Snails became infected when exposed to larvae in wet and dried soil. Larvae on pellets survived freezing at −15 to −20 °C for up to 306 days.

The experimental transmission of Pneumostrongylus tenuis to caribou (Rangifer tarandus terraenovae).

Two caribou calves (Rangifer tarandus terraenovae) were infected experimentally with Pneumostrongylus tenuis Dougherty from white-tailed deer (Odocoileus virginianus borealis). The female calf showed slight neurologic signs from the 5th to the 14th day when she died from a mycotic infection. The male calf first showed neurologic signs on the seventh day. These signs became progressively more extreme and by the 29th day, when the animal was necropsied, it showed severe locomotory ataxia with knuckling and posterior weakness. Histological study of the spinal cord of the male revealed numerous worms in all regions of the spinal cord and in the brain stem and medulla oblongata. Traumatic lesions and worms were unusually numerous in lateral and dorsal funiculi. It is suggested that the more severe neurologic signs were caused by migration of worms into funiculi from dorsal horns of grey matter. The results are discussed in relation to the management of woodland caribou in eastern North America.

THE PENETRATION OF PNEUMOSTRONGYLUS TENUIS INTO THE TISSUES OF WHITE-TAILED DEER

Three fawns of white-tailed deer (Odocoileus virginianus), given 1500–2200 infective larvae of Pneumostrongylus tenuis Dougherty, 1945, were autopsied 65, 90, and 144 hours later. Detailed examination of these fawns indicated most larvae penetrated the ventral curvature of the abomasum and moved into the mesentery and omentum where some could be found up to 6 days after infection. The subsequent course of larvae was not established conclusively. Small numbers reached the liver and lungs. However, the high incidence of eosinophil infiltrations associated with nerves ventral to the lumbosacral region of the vertebral column suggests worms may migrate directly to the spinal cord from the peritoneal cavity. Evidence for any other route was not obtained. There was no evidence, in this and other published work, that larvae reach the central nervous system before 10 days.

Pneumostrongylus tenuis in Deer in Minnesota and Implications for Moose

Pneumostrongylus tenuis in Deer in Minnesota and Implications for Moose

Further experimental studies of Pneumostrongylus tenuis in cervids.

Two young wapiti (Cervus canadensis nelsoni) and a female mule deer fawn (Odocoileus hemionus hemionus) were infected experimentally with Pneumostrongylus tenuis from white-tailed deer (Odocoileus virginianus borealis). The male wapiti showed only slight clinical signs after infection, and first-stage larvae appeared in its faeces 92 days later. The female wapiti showed severe neurological signs that terminated in general paralysis on the 54th day. The mule deer showed severe neurologic signs and died of paralysis on the 62nd day. Numerous worms were found in the subdural space and neural parenchyma, especially in the dorsal horns of grey matter, of the female wapiti and the mule deer. Traumatic damage in the dorsal horns was extensive, especially in the wapiti. Histopathologic findings were similar to those reported earlier in moose calves (Alces americana americana) infected with P. tenuis. Study of worms recovered from experimentally infected cervids indicates that P. tenuis develops similarity in white-tailed deer, moose, wapiti, and mule deer although in the first species it causes little damage to the central nervous system. The possibility that P. tenuis could become established in wapiti introduced into eastern North America is noted.

Experimental cerebrospinal nematodiasis (Pneumostrongylus tenuis) in sheep.

Six lambs were each infected experimentally with 50–1000 infective larvae of Pneumostrongylus tenuis. Three animals displayed neurologic signs. Lesions and dead or living worms were found in the central nervous system of all infected lambs. It is concluded, however, that sheep have a good natural resistance to infection and that P. tenuis will not mature in them. Before P. tenuis is diagnosed in naturally infected sheep it would be advisable to establish whether the sheep have been in contact with white-tailed deer, the normal host.

The transmission of Pneumostrongylus tenuis to guinea pigs.

Pneumostrongylus tenuis developed partially in the central nervous system of infected guinea pigs, some of which developed severe neurologic signs, especially posterior paralysis. Damage to the central nervous system was noted in various regions of the brain and in the white matter of the spinal cord. There was no evidence that the worms will mature in guinea pigs and the number of worms recovered from infected animals was small. P. tenuis behaves in a rodent in the same way as in the normal ruminant host, in contrast to lungworms of carnivores in which the infective larvae become quiescent and encapsulated in the liver of small mammals without loss of infectivity. It is suggested that this ability to retain infectivity after encapsulation is not a general attribute of lungworms or other parasitic nematodes, but has had a long evolutionary history. It should clearly be distinguished from visceral larval migrans which it superficially resembles. Hypotheses to account for the origin of heteroxenous life cycles of nematodes of vertebrates are contrasted as they apply to the Metastrongyloidea.

The development of Pneumostrongylus tenuis in the central nervous system of white-tailed deer.

The central nervous systems of five fawns (Odocoileus virginianus borealis), infected experimentally with Pneumostrongylus tenuis, were studied histologically 10, 20, 25, 30, and 40 days after infection. In the 10–30 day fawns young developing worms were found in dorsal horns of the grey matter of all regions of the spinal cord. A few worms were found in white matter and in the medulla oblongata. In the fawn autopsied 40 days after infection all but one of about 25 worms found were in the subdural space. Worms in the grey matter usually lay in cell-free tunnels surrounded by compressed neural tissue. There was little reaction of, or cellular infiltration in, surrounding tissue. Malacia was absent in all parts of grey matter. The central canal was normal and the brain, other than the medulla oblongata, was not involved. In the white matter, scattered single myelin sheath degeneration as well as degeneration and disappearance of axis cylinders were common. Occasionally there were tiny malacic areas in white matter, especially near worms. Infiltrations of eosinophils, lymphocytes, and plasma cells were commonly observed in and on the dura mater, the epineurium, ganglion capsules, and other tissues of the epidural space. The relative dearth of histopathologic findings helps to explain the rarity and slightness of neurologic signs in infected fawns and is indicative perhaps of a long and well established host-parasite relationship. This is in contrast to the situation in moose (Alces a. americana) where severe traumatic damage to the spinal cord by P. tenuis is associated with ataxia and paralysis.

An examination of wild moose exhibiting neurologic signs, in Ontario.

The central nervous systems of three wild moose (Alces a. americana) exhibiting neurologic signs, in the Kenora district of Ontario, Canada, were studied histologically. A diagnosis of cerebrospinal nematodiasis (Pneumostrongylus tenuis) was made in all three animals.

Neurologie Disease in Moose Infected Experimentally with Pneumostrongylus tenuis from White-Tailed Deer

An experiment was undertaken to test the hypothesis that moose neurologic disease is cerebrospinal nematodiasis. Two moose calves ( Alces a. americana) were infected with Pneumostrongylus tenuis derived from white-tailed deer ( Odocoileus virginianus borealis). Two to three weeks later both calves became lethargic and seemed unwilling to rise. This weakness and ataxia became progressively more pronounced and terminated in paraplegia. One calf was autopsied on the 40th day, the other on the 60th day. Fifth-stage P. tenuis were found in saline in which the central nervous system of the first calf had been placed. Numerous subadult worms were found in subdural spaces of the cranium and vertebral column of the second moose. Histological study revealed additional worms and traumatic damage in the central canal and dorsal horns of the cord of both calves. Focal malacia with micro-cavitation was found in all regions of the cord. Infiltrations of round cells and eosinophils in the leptomeninges, the ventral fissure and the dorsal sulcus, perivascular cuffing with round cells, petechial haemorrhages, neuron degeneration and loss, as well as swelling and disappearance of axis cylinders and myelin sheaths were observed. The known distribution and characteristics of neurologic disease in wild moose supports the hypothesis that P. tenuis is the ætiological agent.