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Observations on the Macroscopic Diagnosis of Fowl Paralysis
Observations on the Macroscopic Diagnosis of Fowl Paralysis ERWIN
JUNGHERE
Storrs Agricultural Experiment Station Storrs, Connecticut (Received for Publication September 23, 1932)
HE occurrence of fowl or range paralysis has been reported from Austria by Marek (1907), the United States by Kaupp (1921), Holland by Van der Walle and Winkler-Junius (1924), England by Galloway (1929), Germany by Seifried (1930), and Japan by Emoto and Miyamoto (1930). The literature indicates a remarkable agreement in the opinions of the investigators in different countries as to the characteristic features of the disease by which the disorder is recognized as an entity. Since the inciting agent of fowl paralysis is unknown, any diagnosis must of necessity be a pathological and not an etiological one, a fact that in itself provides a source of dispute. Furthermore, it can not be denied that the symptom complex of paralysis may be brought about by various pathogenic processes. Being the first to make a study of fowl paralysis, Marek (1907) had to cope with the problem of differential diagnosis in distinguishing the polyneuritis described by him from the nutritional form studied by Eijkman (1890, 1893, 1896). Later, coccidiosis was recognized by Beach and Davis (1925) as causing paralysis, and taeniasis by Stafseth (1931a), Bayon (1930) and others. Lesions which can be responsible for paralytic conditions may be found in the bone tissue, nervous system, or muscles and tendons, according to Doyle (1929). The present medical conception of fowl paralysis as an entity is due to the studies of Kaupp (loc. cit.), Doyle (1926) and the
monumental work of Pappenheimer, Dunn and Cone (1926, 1929), who introduced the term "neurolymphomatosis gallinarum" into the literature. According to Bayon (1932), all other diseased conditions accompanied by paralytic symptoms can be grouped under the term "symptomatic paralysis." The designation neurolymphomatosis defines the kind and locality of the principal cellular reaction. Since similar reactions occur frequently in the internal organs, either in the form of tumors or extravascular infiltrations, Warrack and Dalling (1932) regarded fowl paralysis as a subform of lymphomatosis, and Johnson (1932) differentiated a visceral and neural form of lymphomatosis. Certain differences in the epizoology of fowl paralysis and lymphomatosis make the general acceptance of the latter nomenclature doubtful. The fact that symptomatic forms of paralysis occur frequently in association with neurolymphomatosis has weakened the unit structure of the latter. Statistical studies of the coincidence of the two conditions, by Thomas (1930), Stafseth (1931b), Brandly (1930) and others, point to chronic intestinal irritation as a predisposing factor, if not a primary etiological one. Lee (1931) reached the conclusion that fowl paralysis is not a specific disease; he questioned the carefulness of Pappenheimer's autopsies because this investigator was unable to find lymph glands in chickens. It should be remembered that Baum's
[184]
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on April 5, 2015
T
185
(1930) monograph on the lymph system of fowls stated specifically that there are no lymph glands in chickens. Experimental evidence for the specific infectious nature of fowl paralysis has been furnished by Van der Walle, Pappenheimer, Galloway, Seifried, and Warrack and Dalling in the references cited. Several authors, whose transmission experiments were negative, still regard the disorder infectious in nature (Kaupp, Doyle, and Johnson). The disease observed by continental European authors was rather easily transmissible, while Pappenheimer {loc. cit.) and Warrack and Dalling (loc. cit.) observed a susceptibility of only 20-25 percent in the experimental birds. Under natural conditions fowl paralysis apparently does not spread from bird to bird, and it is usually accompanied by low mortality. When the losses in an outbreak exceed 10-15 percent contributory causes must be suspected, according to Bayon (loc. cit.). The disease tends to affect the progeny of certain strains or families, with both sexes possibly responsible for a transmission through the egg. This observation was first made by Doyle (1928), and confirmed by McGaughey and Downie (1930), McGaughey (1930), Warrack and Dalling (loc. cit.), Bayon (loc. cit.) and others. The inciting agent of fowl paralysis is thought to be in the nature of a filterable virus of low virulence, but of widespread distribution. As this contention cannot be incontrovertibly supported by transmission experiments, Johnson (loc. cit.) assumed that a certain susceptibility to the virus may be transmitted through the egg, and Bayon (loc. cit.) believed the virus to be present in a latent state in many birds, but that an additional set of favorable conditions is necessary for the production of the disease. Bayon was able to cure 18 of 34 affected birds by forced feeding of lettuce or water cress. He interpreted the results as an in-
dication that nutritional factors may play a part in releasing the potency of the virus. From the hygienic standpoint, the possibility of transmission of the inciting factor or factors through the egg gives the problem of diagnosis a new and important aspect. Although diagnosis is based primarily upon a critical microscopic study of the central nervous system, the necessity of preparing histological sections has been stressed so much that the gross pathological examination has fallen into disrepute. However, some observations which were made by the writer during his routine diagnostic work, and later checked by microscopic study, impressed him as being an argument in favor of a systematic application of a specific postmortem technique.
1933. VOL.
XII,
TECHNIQUE
.
It goes without saying that a study of the clinical history and a thorough postmortem examination of the optical, respiratory, and digestive apparatus are indispensable. In the specific search for nerve lesions in routine examination, it is convenient to begin with the inspection of the sciatic nerves. With the bird placed on its back (Figure 1), the thigh musculature offers an easy access. The caudal border of the thigh is formed by two band-shaped overlapping muscles, the semitendinosus and the semimembranosus; cranial to them and separated by a shallow groove extend the adductors of the thigh in the form of a triangle footing with its base on the outer surface of the ischium and pointing toward the tibia. By lifting up the caudal border of the adductors, the two parallel strands of the femoral part of the sciatic nerve become exposed. There are three pelvic roots of the sciatic trunk which usually have a paired origin; they can be seen by disecting out the middle lobe of the kidney. This part of the kidney is demarcated cranially by the arteria and vena iliaca, caudally by
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on April 5, 2015
No. 3
MAY,
186
FIG. 1. (X %) Normal sciatic trunk; left side exposed by partially dissecting away the adductors and the middle lobe of the left kidney. The light horizontal bars close to the nerve roots are the intervertebral cartilages.
SCIENCE
1i FIG. 2. (X %) Normal brachial plexus; rightnerve roots with ganglia and almost entire width of spinal cord exposed. The small globular bodies along the neck are the thymus lobes.
posure of the cord is increased by introducing one pointed blade into the spinal canal and dissecting away the bony side walls. For convenience, the bird is now turned 90 degrees and the muscles and fasciae covering the dorsal root ganglia are paired away: the distally exposed nerve strands of the brachial plexus furnish thereby a landmark for this last operation. The brachial plexus consists of three main roots, which are normally white, opaque, and well defined. The dorsal root ganglia are somewhat oblong and set off by a constriction; the width of the ganglia exceeds only slightly the diameter of the nerve originating from it; they appear to be not quite as opaque as the nerves, but rather somewhat glossy. In young birds the cutting operation of the bones with scissors presents no particular difficulty, although the edge of the instrument may not last very long. In view of the time consumed by other dissecting methods, the use of scissors seems justified. OBSERVATIONS
During the past two years over 100 lots of specimen birds having a definite history of paralysis were submitted for diagnosis.
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on April 5, 2015
the arteria and vena ischiadica, and laterally by the median prominence of the ischium opposite to the acetabulum. The normal sciatic nerve is a thick, opaque, white flattened strand with fine transverse striation in the femoral part. Following the examination of the sciatic trunk, the bird is placed on its breast (Figure 2) the skin is cut transversely in about the middle of the body, and pulled away in the cranial and dorsal direction. The first things of interest to note are the numerous lobes of the thymus along the lateral sides of the neck. The thymus lobes may be completely involuted, or may vary in size up to that of a small bean. The scapulae are then located parallel to the thoracic vertebrae. The muscles which fix the shoulder blades to the vertebrae, principally the trapezius, rhomboideus, and the serrati, are severed in such a way that by a slight pull on the scapulae the brachial plexus becomes exposed. For further operation the author prefers pointed 6^-inch curved scissors. With these the dorsal muscles and bony arches of the last cervical and the thoracic vertebrae are dissected away by longitudinal cuts, just deep enough to expose the dorsal plane of the spinal cord. The convex curve of the instrument facing downward acts as a guard against injuring the cord. Subsequently, the ex-
POULTRY
1933. VOL.
XII,
187
In an'attempt to determine the prevailing forms of paralysis, gross examinations were performed as described and, in addition, material of the viscera and nervous system was fixed for histological study. About 70 percent of the specimen lots showed definite lesions of intestinal coccidiosis, principally Eimeria necatrix and Eimeria maxima infections; about 20 percent revealed parasitic infestations, usually in such a degree as to indicate taeniasis or ascariasis. About 10 percent did not show any lesions in the internal organs. Macroscopic lesions of the nerves occurred in all three groups to the total extent of 40 percent being most pronounced perhaps in the last. Microscopic examinations have been completed so far on the material from 25 lots of specimen birds; while this latter study did not seem to raise the number of positive cases materially, all nerve lesions recognizable with the naked eye presented the typical infiltrative processes in histological sections which are considered to be pathognomic for neurolymphomatosis. In a number of instances two or more outbreaks of paralysis exhibiting the characteristic manifestations occurred in flocks which originated on the same premises. The owners of the parent stock usually enjoyed an enviable commercial reputation as breeders of highly developed strains of birds which were state-accredited for pullorum disease and had attained the "Record of Performance" (R. O. P.) standards. It is not intended here to analyze the collected data for the purpose of supporting or opposing prevailing etiological theories; however, the experience of the writer in making a systematic gross examination of the sciatic and brachial nerves may be of value to others. The gross lesions of the sciatic nerves consisted of thickening and edematous changes in various degrees. Affected nerves appeared somewhat gelatinous, grayish, and translucent. The lesions
were more likely to be found in the pelvic than in the femoral portion; on the whole, lesions were recognized with difficulty, excepting in very pronounced cases. Gross lesions of the brachial plexus were particularly noticeable in the dorsal root ganglia, and corresponded in quality to that of the sciatic nerves. Owing to the globular shape of the ganglia, deviations from the norm were much more easily recognized than in the sciatic nerves. While the normal size of the ganglia is more or less dependent on the size of the bird, in general, an estimated difference between the diameters of the ganglion and the corresponding nerve of over 1 mm. is to be viewed as suspicious, and over 2 mm. as positive. Of all the birds that showed gross lesions in the brachial plexus, only 10 percent showed changes in the sciatic nerves also. This finding would clearly indicate that the common autopsy practice of examining the sciatic trunks only is inadequate. Gross lesions often occurred which were unilateral; an examination can not be regarded as complete, therefore, without inspection of both sides. Another interesting point in the findings was the large size and turgidity of the thymus lobes in about SO percent of the positive cases, as compared with non-paralytic birds of the same age. Although retarded involution of the thymus is not regarded as a specific lesion, a parallel may exist between this and the status thymicolymphaticus of human beings as reported by Young and Tumbull (1931) In all lots of four birds or more which had a typical clinical history of fowl paralysis as to age, symptoms, season, and blindness, the gross lesions could be demonstrated in one or more birds. The extreme changes illustrated and described in the literature were found very rarely and are not likely to be expected if the specimens are submitted by an alert clientele of a highly developed poultry industry.
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on April 5, 2015
No. 3
MAY,
188
POULTRY
SUMMARY
In view of the complex etiology of paralytic conditions in birds, the recognition of the underlying disease factors is of utmost importance. According to a number of authorities there is a definite entity known as true fowl paralysis, range paralysis, or neurolymphomatosis gallinarum. The disease is probably not contagious in nature, but certain evidence points toward a transmission of the inciting factor through the egg. With this possibility in mind, the diagnosis of true fowl paralysis plays an important part in any contemplated program of eradication. Since the etiological factor is unknown, the only possible way of diagnosis is the examination of the nervous system by pathological and histopathological methods. Of the two methods the microscopic study is preferable if it can be carried out, but the gross examination of the sciatic trunk and brachial plexus is serviceable in routine diagnostic work and should be an established procedure. The gross examination should be conducted on at least four birds from each suspected lot. Nerve lesions consisting of changes in
size and consistency of the nerve tissue are most apt to be found in the dorsal root ganglia of one or the other side of the brachial plexus. A simple method of gross examination of the nerves is described which requires only a limited number of tools and is applicable in the field as well as the laboratory. REFERENCES
Baum, H., 1930. Das Lymphgefass System d. Huhnes. Berlin, J. Springer: 6. Bayon, H. P., 1930. Vet. Rec, 10:1129. , 1932. 12:457-467. Beach, J. R., and D. E. Davis, 1925. Cal. Agr. Exp. Sta. Circ. 300. Brandly, C. A., 1930. Kan. Agr. Exp. Sta., Bi. Rpt. for 1928-1930:123. Doyle, L. P., 1926, J.A.V.M.A. 68:622. , 1928. J.A.V.M.A. 72:585-587. •, 1929. Poul. Sci. 8 :159-160. , 1931. Poul. Sci. 10:393. Eijkman, C , 1890, 1893, 1896. Geneesk. Tijdschr. v. Ned. Ind. 30, 33, 36. Emoto O., and K. Miyamoto, 1930. J. Jap. Soc. Vet. Sci. 9 :309. Galloway, I. A., 1929. Proc. Roy. Soc. Med., 22 (Part 1 ) : 1167. Johnson, E. P., 1932. Va. Agr. Exp. Sta. Tech. Bui. 44. Kaupp, B. F., 1921. J. Am. Assoc. Instr. and Invest. in Poul. Husb. 7:25. Lee, A. M., 1931. J.A.V.M.A. 78:204-216. McGaughey, C. A., and H. W. Downie, 1930. J. Comp. Path, and Therap. 43 :63-76. McGaughey, C. A., 1930. Vet. Rec. 10:1143-1144. Marek, J., 1907. Deut. Tierarzt. Wochnschr. 15:417. Pappenheimer, A.M., L. C. Dunn, and V. Cone, 1926. Storrs Agr. Exp. Bui. 143. , 1929. J. Exp. Med. 49 :63-86. Seifried, O., 1930. Arch. Wiss. Tierh., 62:208-222. Stafseth, H. J., 1931 a. J.A.V.M.A. 78:423-429. , 1931 b. 78:793-809. Thomas, E. F., 1930. Fla. Agr. Exp. Sta. Rpt. 54. Van der Walle and Winkler-Junius, 1924. Tijd. V. Vergel. Geneesk. Enz. 10:34. Warrack, G. H., and T. Dalling, 1932. Vet. J., 88: 28-43. Young, M. and H. W. Turnbull, 1931. J. Path, and Bact. 34:213-258.
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on April 5, 2015
Since a thorough histological diagnosis of neurolymphomatosis would require the preparation of serial sections of practically the entire central nervous system, the gross examination was used as a working basis in routine diagnostic work. Whenever intestinal parasitoses occurred in association with nerve lesions the owner was informed of both findings; when only parasitoses were revealed the report was made accordingly. Practical experience seemed to justify this procedure in that losses from paralysis associated with parasitoses could be more easily stopped by remedial measures when no gross lesions in the nerves were found.
SCIENCE
JUNGHERE
Storrs Agricultural Experiment Station Storrs, Connecticut (Received for Publication September 23, 1932)
HE occurrence of fowl or range paralysis has been reported from Austria by Marek (1907), the United States by Kaupp (1921), Holland by Van der Walle and Winkler-Junius (1924), England by Galloway (1929), Germany by Seifried (1930), and Japan by Emoto and Miyamoto (1930). The literature indicates a remarkable agreement in the opinions of the investigators in different countries as to the characteristic features of the disease by which the disorder is recognized as an entity. Since the inciting agent of fowl paralysis is unknown, any diagnosis must of necessity be a pathological and not an etiological one, a fact that in itself provides a source of dispute. Furthermore, it can not be denied that the symptom complex of paralysis may be brought about by various pathogenic processes. Being the first to make a study of fowl paralysis, Marek (1907) had to cope with the problem of differential diagnosis in distinguishing the polyneuritis described by him from the nutritional form studied by Eijkman (1890, 1893, 1896). Later, coccidiosis was recognized by Beach and Davis (1925) as causing paralysis, and taeniasis by Stafseth (1931a), Bayon (1930) and others. Lesions which can be responsible for paralytic conditions may be found in the bone tissue, nervous system, or muscles and tendons, according to Doyle (1929). The present medical conception of fowl paralysis as an entity is due to the studies of Kaupp (loc. cit.), Doyle (1926) and the
monumental work of Pappenheimer, Dunn and Cone (1926, 1929), who introduced the term "neurolymphomatosis gallinarum" into the literature. According to Bayon (1932), all other diseased conditions accompanied by paralytic symptoms can be grouped under the term "symptomatic paralysis." The designation neurolymphomatosis defines the kind and locality of the principal cellular reaction. Since similar reactions occur frequently in the internal organs, either in the form of tumors or extravascular infiltrations, Warrack and Dalling (1932) regarded fowl paralysis as a subform of lymphomatosis, and Johnson (1932) differentiated a visceral and neural form of lymphomatosis. Certain differences in the epizoology of fowl paralysis and lymphomatosis make the general acceptance of the latter nomenclature doubtful. The fact that symptomatic forms of paralysis occur frequently in association with neurolymphomatosis has weakened the unit structure of the latter. Statistical studies of the coincidence of the two conditions, by Thomas (1930), Stafseth (1931b), Brandly (1930) and others, point to chronic intestinal irritation as a predisposing factor, if not a primary etiological one. Lee (1931) reached the conclusion that fowl paralysis is not a specific disease; he questioned the carefulness of Pappenheimer's autopsies because this investigator was unable to find lymph glands in chickens. It should be remembered that Baum's
[184]
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on April 5, 2015
T
185
(1930) monograph on the lymph system of fowls stated specifically that there are no lymph glands in chickens. Experimental evidence for the specific infectious nature of fowl paralysis has been furnished by Van der Walle, Pappenheimer, Galloway, Seifried, and Warrack and Dalling in the references cited. Several authors, whose transmission experiments were negative, still regard the disorder infectious in nature (Kaupp, Doyle, and Johnson). The disease observed by continental European authors was rather easily transmissible, while Pappenheimer {loc. cit.) and Warrack and Dalling (loc. cit.) observed a susceptibility of only 20-25 percent in the experimental birds. Under natural conditions fowl paralysis apparently does not spread from bird to bird, and it is usually accompanied by low mortality. When the losses in an outbreak exceed 10-15 percent contributory causes must be suspected, according to Bayon (loc. cit.). The disease tends to affect the progeny of certain strains or families, with both sexes possibly responsible for a transmission through the egg. This observation was first made by Doyle (1928), and confirmed by McGaughey and Downie (1930), McGaughey (1930), Warrack and Dalling (loc. cit.), Bayon (loc. cit.) and others. The inciting agent of fowl paralysis is thought to be in the nature of a filterable virus of low virulence, but of widespread distribution. As this contention cannot be incontrovertibly supported by transmission experiments, Johnson (loc. cit.) assumed that a certain susceptibility to the virus may be transmitted through the egg, and Bayon (loc. cit.) believed the virus to be present in a latent state in many birds, but that an additional set of favorable conditions is necessary for the production of the disease. Bayon was able to cure 18 of 34 affected birds by forced feeding of lettuce or water cress. He interpreted the results as an in-
dication that nutritional factors may play a part in releasing the potency of the virus. From the hygienic standpoint, the possibility of transmission of the inciting factor or factors through the egg gives the problem of diagnosis a new and important aspect. Although diagnosis is based primarily upon a critical microscopic study of the central nervous system, the necessity of preparing histological sections has been stressed so much that the gross pathological examination has fallen into disrepute. However, some observations which were made by the writer during his routine diagnostic work, and later checked by microscopic study, impressed him as being an argument in favor of a systematic application of a specific postmortem technique.
1933. VOL.
XII,
TECHNIQUE
.
It goes without saying that a study of the clinical history and a thorough postmortem examination of the optical, respiratory, and digestive apparatus are indispensable. In the specific search for nerve lesions in routine examination, it is convenient to begin with the inspection of the sciatic nerves. With the bird placed on its back (Figure 1), the thigh musculature offers an easy access. The caudal border of the thigh is formed by two band-shaped overlapping muscles, the semitendinosus and the semimembranosus; cranial to them and separated by a shallow groove extend the adductors of the thigh in the form of a triangle footing with its base on the outer surface of the ischium and pointing toward the tibia. By lifting up the caudal border of the adductors, the two parallel strands of the femoral part of the sciatic nerve become exposed. There are three pelvic roots of the sciatic trunk which usually have a paired origin; they can be seen by disecting out the middle lobe of the kidney. This part of the kidney is demarcated cranially by the arteria and vena iliaca, caudally by
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on April 5, 2015
No. 3
MAY,
186
FIG. 1. (X %) Normal sciatic trunk; left side exposed by partially dissecting away the adductors and the middle lobe of the left kidney. The light horizontal bars close to the nerve roots are the intervertebral cartilages.
SCIENCE
1i FIG. 2. (X %) Normal brachial plexus; rightnerve roots with ganglia and almost entire width of spinal cord exposed. The small globular bodies along the neck are the thymus lobes.
posure of the cord is increased by introducing one pointed blade into the spinal canal and dissecting away the bony side walls. For convenience, the bird is now turned 90 degrees and the muscles and fasciae covering the dorsal root ganglia are paired away: the distally exposed nerve strands of the brachial plexus furnish thereby a landmark for this last operation. The brachial plexus consists of three main roots, which are normally white, opaque, and well defined. The dorsal root ganglia are somewhat oblong and set off by a constriction; the width of the ganglia exceeds only slightly the diameter of the nerve originating from it; they appear to be not quite as opaque as the nerves, but rather somewhat glossy. In young birds the cutting operation of the bones with scissors presents no particular difficulty, although the edge of the instrument may not last very long. In view of the time consumed by other dissecting methods, the use of scissors seems justified. OBSERVATIONS
During the past two years over 100 lots of specimen birds having a definite history of paralysis were submitted for diagnosis.
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on April 5, 2015
the arteria and vena ischiadica, and laterally by the median prominence of the ischium opposite to the acetabulum. The normal sciatic nerve is a thick, opaque, white flattened strand with fine transverse striation in the femoral part. Following the examination of the sciatic trunk, the bird is placed on its breast (Figure 2) the skin is cut transversely in about the middle of the body, and pulled away in the cranial and dorsal direction. The first things of interest to note are the numerous lobes of the thymus along the lateral sides of the neck. The thymus lobes may be completely involuted, or may vary in size up to that of a small bean. The scapulae are then located parallel to the thoracic vertebrae. The muscles which fix the shoulder blades to the vertebrae, principally the trapezius, rhomboideus, and the serrati, are severed in such a way that by a slight pull on the scapulae the brachial plexus becomes exposed. For further operation the author prefers pointed 6^-inch curved scissors. With these the dorsal muscles and bony arches of the last cervical and the thoracic vertebrae are dissected away by longitudinal cuts, just deep enough to expose the dorsal plane of the spinal cord. The convex curve of the instrument facing downward acts as a guard against injuring the cord. Subsequently, the ex-
POULTRY
1933. VOL.
XII,
187
In an'attempt to determine the prevailing forms of paralysis, gross examinations were performed as described and, in addition, material of the viscera and nervous system was fixed for histological study. About 70 percent of the specimen lots showed definite lesions of intestinal coccidiosis, principally Eimeria necatrix and Eimeria maxima infections; about 20 percent revealed parasitic infestations, usually in such a degree as to indicate taeniasis or ascariasis. About 10 percent did not show any lesions in the internal organs. Macroscopic lesions of the nerves occurred in all three groups to the total extent of 40 percent being most pronounced perhaps in the last. Microscopic examinations have been completed so far on the material from 25 lots of specimen birds; while this latter study did not seem to raise the number of positive cases materially, all nerve lesions recognizable with the naked eye presented the typical infiltrative processes in histological sections which are considered to be pathognomic for neurolymphomatosis. In a number of instances two or more outbreaks of paralysis exhibiting the characteristic manifestations occurred in flocks which originated on the same premises. The owners of the parent stock usually enjoyed an enviable commercial reputation as breeders of highly developed strains of birds which were state-accredited for pullorum disease and had attained the "Record of Performance" (R. O. P.) standards. It is not intended here to analyze the collected data for the purpose of supporting or opposing prevailing etiological theories; however, the experience of the writer in making a systematic gross examination of the sciatic and brachial nerves may be of value to others. The gross lesions of the sciatic nerves consisted of thickening and edematous changes in various degrees. Affected nerves appeared somewhat gelatinous, grayish, and translucent. The lesions
were more likely to be found in the pelvic than in the femoral portion; on the whole, lesions were recognized with difficulty, excepting in very pronounced cases. Gross lesions of the brachial plexus were particularly noticeable in the dorsal root ganglia, and corresponded in quality to that of the sciatic nerves. Owing to the globular shape of the ganglia, deviations from the norm were much more easily recognized than in the sciatic nerves. While the normal size of the ganglia is more or less dependent on the size of the bird, in general, an estimated difference between the diameters of the ganglion and the corresponding nerve of over 1 mm. is to be viewed as suspicious, and over 2 mm. as positive. Of all the birds that showed gross lesions in the brachial plexus, only 10 percent showed changes in the sciatic nerves also. This finding would clearly indicate that the common autopsy practice of examining the sciatic trunks only is inadequate. Gross lesions often occurred which were unilateral; an examination can not be regarded as complete, therefore, without inspection of both sides. Another interesting point in the findings was the large size and turgidity of the thymus lobes in about SO percent of the positive cases, as compared with non-paralytic birds of the same age. Although retarded involution of the thymus is not regarded as a specific lesion, a parallel may exist between this and the status thymicolymphaticus of human beings as reported by Young and Tumbull (1931) In all lots of four birds or more which had a typical clinical history of fowl paralysis as to age, symptoms, season, and blindness, the gross lesions could be demonstrated in one or more birds. The extreme changes illustrated and described in the literature were found very rarely and are not likely to be expected if the specimens are submitted by an alert clientele of a highly developed poultry industry.
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on April 5, 2015
No. 3
MAY,
188
POULTRY
SUMMARY
In view of the complex etiology of paralytic conditions in birds, the recognition of the underlying disease factors is of utmost importance. According to a number of authorities there is a definite entity known as true fowl paralysis, range paralysis, or neurolymphomatosis gallinarum. The disease is probably not contagious in nature, but certain evidence points toward a transmission of the inciting factor through the egg. With this possibility in mind, the diagnosis of true fowl paralysis plays an important part in any contemplated program of eradication. Since the etiological factor is unknown, the only possible way of diagnosis is the examination of the nervous system by pathological and histopathological methods. Of the two methods the microscopic study is preferable if it can be carried out, but the gross examination of the sciatic trunk and brachial plexus is serviceable in routine diagnostic work and should be an established procedure. The gross examination should be conducted on at least four birds from each suspected lot. Nerve lesions consisting of changes in
size and consistency of the nerve tissue are most apt to be found in the dorsal root ganglia of one or the other side of the brachial plexus. A simple method of gross examination of the nerves is described which requires only a limited number of tools and is applicable in the field as well as the laboratory. REFERENCES
Baum, H., 1930. Das Lymphgefass System d. Huhnes. Berlin, J. Springer: 6. Bayon, H. P., 1930. Vet. Rec, 10:1129. , 1932. 12:457-467. Beach, J. R., and D. E. Davis, 1925. Cal. Agr. Exp. Sta. Circ. 300. Brandly, C. A., 1930. Kan. Agr. Exp. Sta., Bi. Rpt. for 1928-1930:123. Doyle, L. P., 1926, J.A.V.M.A. 68:622. , 1928. J.A.V.M.A. 72:585-587. •, 1929. Poul. Sci. 8 :159-160. , 1931. Poul. Sci. 10:393. Eijkman, C , 1890, 1893, 1896. Geneesk. Tijdschr. v. Ned. Ind. 30, 33, 36. Emoto O., and K. Miyamoto, 1930. J. Jap. Soc. Vet. Sci. 9 :309. Galloway, I. A., 1929. Proc. Roy. Soc. Med., 22 (Part 1 ) : 1167. Johnson, E. P., 1932. Va. Agr. Exp. Sta. Tech. Bui. 44. Kaupp, B. F., 1921. J. Am. Assoc. Instr. and Invest. in Poul. Husb. 7:25. Lee, A. M., 1931. J.A.V.M.A. 78:204-216. McGaughey, C. A., and H. W. Downie, 1930. J. Comp. Path, and Therap. 43 :63-76. McGaughey, C. A., 1930. Vet. Rec. 10:1143-1144. Marek, J., 1907. Deut. Tierarzt. Wochnschr. 15:417. Pappenheimer, A.M., L. C. Dunn, and V. Cone, 1926. Storrs Agr. Exp. Bui. 143. , 1929. J. Exp. Med. 49 :63-86. Seifried, O., 1930. Arch. Wiss. Tierh., 62:208-222. Stafseth, H. J., 1931 a. J.A.V.M.A. 78:423-429. , 1931 b. 78:793-809. Thomas, E. F., 1930. Fla. Agr. Exp. Sta. Rpt. 54. Van der Walle and Winkler-Junius, 1924. Tijd. V. Vergel. Geneesk. Enz. 10:34. Warrack, G. H., and T. Dalling, 1932. Vet. J., 88: 28-43. Young, M. and H. W. Turnbull, 1931. J. Path, and Bact. 34:213-258.
Downloaded from http://ps.oxfordjournals.org/ at Michigan State University on April 5, 2015
Since a thorough histological diagnosis of neurolymphomatosis would require the preparation of serial sections of practically the entire central nervous system, the gross examination was used as a working basis in routine diagnostic work. Whenever intestinal parasitoses occurred in association with nerve lesions the owner was informed of both findings; when only parasitoses were revealed the report was made accordingly. Practical experience seemed to justify this procedure in that losses from paralysis associated with parasitoses could be more easily stopped by remedial measures when no gross lesions in the nerves were found.
SCIENCE