The guineapig as an experimental host of the meningeal worm, Pneumostrongylus tenuis Dougherty

Infective larvae ofP. tenuisgiven orally to guineapigs, penetrated the stomach wall and reached the body cavity. Some dispersed in the omentum extending along the greater curvature of the stomach. Others wandered into and through the liver. Some migrated through the diaphragm or along the mesentery ensheathing the hepatic vein and the vena cava. In the pleural cavity some penetrated the pericardium, and the pleura and parenchyma of the lungs. Numerous larvae were overcome by the host in the mesentery, particularly the omentum.

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.

Dirofilaria (Nochtiella) infestation in a human in Ontario

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The comparative morphology of cephalic structures in the superfamily filarioidea (Nematoda)

Cephalic structures in 62 genera of the nematode superfamily Filarioidea are compared. Vestiges of pseudolabia do not occur in filarioids and the persistence of internal cephalic papillae in some genera indicates that this superfamily branched off early from a stem which also gave rise to the Spiruroidea. The hypothesis of Chabaud (1955) on the formation of papillae patterns in filarioids is followed generally but Pseudofilaria is regarded as the most primitive type which links the filarioids to the spiruroid family Thelaziidae. The condition of only four papillae, known conclusively only in Splendidofilaria, may have resulted from fusion of pairs of external papillae since in several genera there is a tendency towards fusion. Tetracheilonema, Litomosoides, and perhaps other genera (e.g. Icosiella, Setaria equina) apparently fall outside the main line of evolution which led to the commonest pattern of four pairs of submedian papillae (external papillae). Study of the cephalic ends of filarioids reveals characters useful in the identification of species.

Congenital cardiac disease associated with polysplenia. A developmental complex of bilateral "left-sidedness"

The well-recognized association of congenital cardiac disease with asplenia has been termed "bilateral right-sidedness" or dextro-isomerism, since the spleen is absent, the liver is symmetrical, and each lung has three lobes and an epiarterial bronchus. In a study of pathological material from 12 patients with congenital cardiac disease associated with multiple spleens (as contrasted to accessory spleen), we found a definite tendency for the symmetrical development of organs but with a tendency for bilateral left-sidedness or levo-isomerism.

The abnormalities assumed one of three forms as follows: (1) absence of a normal right-sided structure, (2) bilateral organs, each with the structure of a left-sided organ, or (3) excessive tissue of a left-sided organ. Thus, in polysplenia we observed a tendency for (1) absence of the hepatic segment of the inferior vena cava and absence of the gallbladder, (2) two lobes in each lung with hyparterial bronchi, and (3) multiple spleens. Other noncardiac abnormalities were partial or complete abdominal heterotaxia and partial malrotation of the bowel. The cardiac malformations included dextrocardia, bilateral superior venae cavae, anomalous pulmonary venous connection with malposition of the atrial septum, and defects in the atrial septum and in the ventricular septum.

Our study suggests that the developmental complex of multiple spleens is closely related to the asplenic syndrome, with the important difference being left-sided symmetry rather than right-sided symmetry.

Sequence constraints and concept identification

128 Ss performed on two concept learning problems within which the sequence of relevant cues was essentially random. For one problem a constant proportion ( k) of irrelevant cues changed whenever the relevant cue remained the same on adjacent trials (S-transition) whereas the values of the irrelevant stimulus dimensions varied at random whenever different relevant cues appeared on adjacent trials (D-transition). Within the second problem, k irrelevant stimulus dimensions changed at D-transitions, while the values of the irrelevant dimensions varied at random at S-transitions. For independent groups, k ranged from .00 to 1.00. Trial of last error proved to be an increasing linear function of proportion of irrelevant dimensions changed at D-transitions whereas the proportion changed at S-transitions made no difference. These results are difficult to understand in terms of an all-or-none model of concept identification in which it is assumed that cues are sampled at random.

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.