Brief Communicatioins and Case Reports
Vet Pathol29(4). 1992
uted to infection of bone marrow stem cells.4 In contrast, previous studies suggest that infection of stem cells in bone marrow is not responsible for infection of erythrocytes in BTV-infected ~ a t t l e .The ~ present study demonstrated a mechanism whereby erythrocytes can become camers of BTV without undergoing any productive infection.
Acknowledgements We gratefully acknowledge Ms. T. Hanington and Ms. V. Wong for their superb technical assistance. These studies were supported by USDA Special Research Grant 89-34 1 164447 and funds provided by the Livestock Diseases Research Laboratory and the USDA under the Animal Health Act, 1977, Public Law 95-113.
References 1 Du Toit RM: The role played by bovines in the transmission of bluetongue in sheep. J S Afr Vet Med Assoc 33:483-490, 1984 2 Eaton BT, Crameri GS: The site of bluetongue virus attachment to glycophorins from a number of animal erythrocytes. J Gen Virol 70:3347-3353, 1989 3 Eaton BT, Hyatt AD, Brookes SM: The replication of bluetongue virus. In: Bluetongue Viruses, ed. Roy P and Gorman BM, pp. 89-1 18. Springer-Verlag, Berlin, Germany, 1990 4 Emmons RW, Oshiro LS, Johnson HN, Lennette EH: Intraerythrocytic location of Colorado tick fever virus. J Gen Virol 17:185-195, 1972 5 Heidner HW, MacLachlan NJ, Fuller FJ, Richards RG, Whetter LE: Bluetongue virus genome remains stable throughout prolonged infection of cattle. J Gen Virol69: 2629-2636, 1988 6 Jain N C The erythrocyte: its morphology, metabolism, and survival. In: Veterinary Hematology, 4th ed., pp. 527-562. Lea & Febiger, Philadelphia, PA, 1986 7 Luedke AJ: Distribution of virus in the blood compo-
8
9 10
11
12
13
14
15 16
359
nents during the viremia of bluetongue. Proc Annu Meet US Anim Health Assoc 74:9-21, 1970 MacLachlan NJ, Barratt-Boyes SM, Brewer AW, Stott JL: Bluetongue virus infection of cattle. In: Bluetongue, African Horse Sickness and Related Orbiviruses, ed. Walton TE and Osburn BI. CRC Press, Boca Raton, FL (in press) MacLachlan NJ, Jagels G, Rossitto PV, Moore PF, Heidner HW: The pathogenesis of experimental bluetongue virus infection of calves. Vet Pathol 27:223-229, 1990 Miura Y ,Goto Y ,Kubo M, Kono Y : Pathogenicity of Chuzan virus, a new member of the Palyam subgroup of the genus orbivirus of cattle. Jpn J Vet Sci 50:632637, 1988 Nunamaker RA, Ellis JA, Wigington JG, MacLachlan NJ: The intracellular detection of bluetongue virus particles within ovine erythrocytes. Comp Biochem Physiol 101A:47 1-476, 1992 Ozawa Y , Salama SA, Dardiri AH: Method for recovering African horse sickness virus from horse blood. Proc 3rd Int Conf Equine Infect Dis, pp. 58-68. Karger, Basel, Switzerland, 1972 Parsonson IM: Pathology and pathogenesis of bluetongue infections. In: Bluetongue Viruses, ed. Roy P and Gorman BM, pp. 119-1 4 1. Springer-Verlag, Berlin, Germany, 1990 Richards RG, MacLachlan NJ, Heidner HW, Fuller FJ: Comparison of virologic and serologic responses of lambs and calves infected with bluetongue virus serotype 10. Vet Microbiol 18:233-242, 1988 Spreull J: Malarial catarrhal fever (bluetongue) of sheep in South Africa. J Comp Pathol Ther 18:321-337, 1905 Whetter LE, MacLachlan NJ, Gebhard DH, Heidner HW, Moore PF: Bluetongue virus infection of bovine monocytes. J Gen Virol70:1663-1676, 1989
Request reprints from Dr. N. James MacLachlan, Department of Veterinary Pathology, School of Veterinary Medicine, University of California, Davis, CA 956 16 (USA).
Vet Pathol 29359-361 (1992)
Neurohypophyseal Astrocytoma (Pituicytoma) in a Rhesus Monkey (Mmma mulatta) H. HOGENESCH, J. J. BROERSE, AND C. ZURCHER Key words: Astrocytoma; pituitary; primates; rhesus monkeys. Reports of central nervous system and pituitary tumors in nonhuman primates are rare.'^^,^ Because the overall incidence of tumors markedly increases with age,5 the rarity of tumor reports probably reflects the relatively young age at death of most monkeys in captivity. Tumors of the neurohypophysis are rare in all domestic and laboratory animals and in human beings. This report describes an astrocytoma
arising in the neurohypophysis of an aged, untreated rhesus monkey. A 21-year-old female rhesus monkey (Macaca mulatta) was euthanatized because of its emaciated and moribund condition. The animal had served as a control in a study of the long-term effects of radiation. A complete necropsy revealed pulmonary acariasis with severe bronchopneumonia
360
Brief Communications and Case Reports
Vet Path01 29(4), 1992
Fig. 1. Neurohypophyseal tumor. The tumor consists of interwoven bundles of cells with prominent perivascular arrangement. Hematoxylin-phloxine-saffron. Bar = 100 pm. Fig. 2. Neurohypophyseal tumor. GFAP-positive tumor cells are prominent around blood vessels. Indirect immunoperoxidase, Mayer’s hematoxylin counterstain. Bar = 50 pm. Fig. 3. Neurohypophyseal tumor. Cells around blood vessels and scattered through other parts of the tumor stain positively for vimentin. Indirect immunoperoxidase, Mayer’s hematoxylin counterstain. Bar = 50 pm.
and bronchiectasis. The posterior portion of the pituitary contained a circumscribed 4-mm-diameter white nodule. Tissue specimens were fixed in 10% neutral buffered formalin, embedded in paraffin, and stained with hematoxylinphloxine-saffron,’ Bodian’s silver stain, and phosphotungstic acid-hematoxylin. The pituitary nodule was well demarcated and nonencapsulated and compressed the surrounding neurohypophyseal tissue. It consisted of interwoven bundles and nests of elongate or plump oval cells with a moderate amount of vascular stroma. Blood vessels were frequently surrounded by radiating cells (Fig. 1). The cells had indistinct margins and a variable amount of pale acidophilic cytoplasm. Nuclei were elongate or oval to round, with coarsely granular chromatin and irregular nuclear membranes. Nucleoli were inconspicuous, and mitotic figures were absent from the sections examined. A central area of necrosis was present. The adventitial layer of blood vessels within the tumor was frequently thickened by loosely arranged fibrillar or dense hyaline collagen. Bodian’s silver stain did not reveal any neurofibrils. Few cytoplasmic fibrils were seen in phosphotungstic acid-hematoxylin-stained sections.
Paraffin sections were prepared for immunohistochemical evaluation by deparaffinization and rehydration, followed by inhibition of endogenous peroxidase activity with methanol/ H,O,. Sections were stained with monoclonal mouse antivimentin (1 :5, Dakopatts, Denmark), followed by peroxidase-labeled rabbit anti-mouse (1 : 100, Dakopatts) or with rabbit anti-GFAP (1 :400, Dakopatts) or rabbit anti-Sl00 (1 : 1,000, HSC Research Development Corp., Toronto, Ontario, Canada), followed by peroxidase-labeled swine antirabbit (1 :60, Dakopatts). Positive controls were paraffin sections from multitissue blocks, and negative controls were sections incubated with the second antibody only. Sections treated with anti-GFAP and anti-vimentin antibodies had thick, prominent positive bands in the cytoplasm of a moderate number of tumor cells. Staining was particularly strbng in cells around blood vessels (Figs. 2,3). Anti-S 100antiserum weakly reacted with cells in some areas, whereas in other areas, it remained negative. Anti-S 100 antiserum stained cytoplasm diffusely, in contrast to the cytoplasmic bands that were often seen in reactions treated with anti-GFAP and antivimentin antibodies.
Brief Communications and Case Reports
Vet Pathol 29(4), 1992
Primary tumors in the neurohypophysis should be differentiated both from tumors that occur in adjacent structures and infiltrate into the neurohypophysis and from metastases. The small size of the tumor and its confinement to the neurohypophysis ruled out tumor origination in surrounding tissues. Meningioma was ruled out by positive staining for GFAP and S100. No other tumors were observed in the animal, making a metastatic tumor unlikely. Two varieties of primary neurohypophyseal tumors are recognized: astrocytomas and granular cell tum01-s.~ Astrocytomas arise from pituicytes, the neurohypophyseal glial cells, which are considered astrocytes by most investigator^.^ Astrocytomas from the neurohypophysis are also known as pituicytomas. Granular cell tumors are characterized by plump oval cells with periodic acid-Schiff-positive cytoplasmic granules. These cells may be modified astrocytes, but their exact lineage is still a matter of debate.9 This tumor was diagnosed as an astrocytoma, based on histologic findings and positive staining for GFAP. Positive staining for GFAP, vimentin, and S 100, as seen in this tumor, is commonly seen in human astrocytoma~.~.~ The variation in staining intensity among individual tumor cells indicates differences in the quantity of intermediate filaments and S 100 protein and may reflect the degree of differentiation of the tumor cells. An inverse relationship between the malignancy of glial cell tumors and the level of GFAP expression has been ~uggested.~ Well-documented cases of primary astrocytomas in the neurohypophysis have been reported in human beings,8,10 rats,2 and a Siamese cat." These tumors may cause clinical symptoms by compression or invasion of adjacent tissues. No evidence of clinical disease related to the tumor was observed in this rhesus monkey. This is the first report of such a tumor in a nonhuman primate.
Acknowledgement
36 1
2 Carlton WW, Gries CL: Pituicytoma, neurohypophysis, rat. In: Endocrine System, ed. Jones TC, Mohr U, and Hunt RD, pp. 156-1 60. Springer-Verlag, Berlin, Germany, 1983 3 Herpers MJHM, Ramaekers FCS, Aldeweireldt J, Moesker A, Slooff J: Co-expression of glial fibrillary acidic protein- and vimentin-type intermediate filaments in human astrocytomas. Acta Neuropathol70:333-339, 1986 4 Jacque CM, Kujas M, Poreau A, Raoul M, Collier P, Racadot J, Baumann N: GFA and S 100 protein levels as an index for malignancy in human gliomas and neurinomas. J Natl Cancer Inst 62479-483, 1979 5 Lapin BA: Use of nonhuman primates in cancer research. J Med Primatol 11:327-341, 1982 6 Lowenstine LJ: Neoplasms and proliferative disorders in nonhuman primates. In: Primates: The Road to Selfsustaining Populations, ed. Benirscke K, pp. 78 1-8 14. Springer-Verlag, Berlin, Germany, 1986 7 Luna L, ed.: AFIP Manual of Histologic Staining Methods, 3rd ed., p. 39. Armed Forces Institute of Pathology, Washington, DC, 1968 8 Rossi ML, Bevan JS, Esiri MM, Hughes JT, Adams CBT: Pituicytoma (pilocytic astrocytoma). J Neurosurg 62768772, 1987 9 Russell DS, Rubinstein LJ: Pathology of Tumours of the Nervous System, 5th ed., pp. 376-378. E. Arnold, London, England, 1989 10 Scothorne C: A glioma of the posterior lobe of the pituitary gland. J Pathol Bacteriol 69:109-112, 1955 11 Zaki F, Harris J, Budzilovich G: Cystic pituicytoma of the neurohypophysis in a Siamese cat. J Comp Pathol 85:46747 1, 1975 Request reprints from Dr. H. HogenEsch, Institute for Aging and Vascular Research, PO Box 430, 2300CK Leiden (The Netherlands).
We thank Mr. T. Glaudemans for photographic assistance.
References 1 Beniashvili DS: An overview of the world literature on spontaneous tumors in nonhuman primates. J Med Primatol 1fk423-437, 1989
Vet Pathol29:361-363 (1992)
Eastern Equine Encephalomyelitis in an Adult Cow E. D. MCGEE,C. H. LITTLETON, J. B. ~LIAPP,AND R. J. BROWN Key words: Cow; eastern equine encephalomyelitis; nonsuppurative encephalitis. A 1%-year-old crossbred beef cow submitted alive to the Mississippi Board of Animal Health Veterinary Diagnostic Laboratory had been recumbent for 2 days. The cow could stand with assistance but circled to the left when walking. No other animals from the herd of 125 had been affected,
and there had been no additions to the herd within the previous 8 months. An ante mortem complete blood count revealed a mild inflammatory neutrophilia and a normal total leukocyte count (1 1,700 total leukocytes, 7,020 neutrophils, 468 band neu-
Vet Pathol29(4). 1992
uted to infection of bone marrow stem cells.4 In contrast, previous studies suggest that infection of stem cells in bone marrow is not responsible for infection of erythrocytes in BTV-infected ~ a t t l e .The ~ present study demonstrated a mechanism whereby erythrocytes can become camers of BTV without undergoing any productive infection.
Acknowledgements We gratefully acknowledge Ms. T. Hanington and Ms. V. Wong for their superb technical assistance. These studies were supported by USDA Special Research Grant 89-34 1 164447 and funds provided by the Livestock Diseases Research Laboratory and the USDA under the Animal Health Act, 1977, Public Law 95-113.
References 1 Du Toit RM: The role played by bovines in the transmission of bluetongue in sheep. J S Afr Vet Med Assoc 33:483-490, 1984 2 Eaton BT, Crameri GS: The site of bluetongue virus attachment to glycophorins from a number of animal erythrocytes. J Gen Virol 70:3347-3353, 1989 3 Eaton BT, Hyatt AD, Brookes SM: The replication of bluetongue virus. In: Bluetongue Viruses, ed. Roy P and Gorman BM, pp. 89-1 18. Springer-Verlag, Berlin, Germany, 1990 4 Emmons RW, Oshiro LS, Johnson HN, Lennette EH: Intraerythrocytic location of Colorado tick fever virus. J Gen Virol 17:185-195, 1972 5 Heidner HW, MacLachlan NJ, Fuller FJ, Richards RG, Whetter LE: Bluetongue virus genome remains stable throughout prolonged infection of cattle. J Gen Virol69: 2629-2636, 1988 6 Jain N C The erythrocyte: its morphology, metabolism, and survival. In: Veterinary Hematology, 4th ed., pp. 527-562. Lea & Febiger, Philadelphia, PA, 1986 7 Luedke AJ: Distribution of virus in the blood compo-
8
9 10
11
12
13
14
15 16
359
nents during the viremia of bluetongue. Proc Annu Meet US Anim Health Assoc 74:9-21, 1970 MacLachlan NJ, Barratt-Boyes SM, Brewer AW, Stott JL: Bluetongue virus infection of cattle. In: Bluetongue, African Horse Sickness and Related Orbiviruses, ed. Walton TE and Osburn BI. CRC Press, Boca Raton, FL (in press) MacLachlan NJ, Jagels G, Rossitto PV, Moore PF, Heidner HW: The pathogenesis of experimental bluetongue virus infection of calves. Vet Pathol 27:223-229, 1990 Miura Y ,Goto Y ,Kubo M, Kono Y : Pathogenicity of Chuzan virus, a new member of the Palyam subgroup of the genus orbivirus of cattle. Jpn J Vet Sci 50:632637, 1988 Nunamaker RA, Ellis JA, Wigington JG, MacLachlan NJ: The intracellular detection of bluetongue virus particles within ovine erythrocytes. Comp Biochem Physiol 101A:47 1-476, 1992 Ozawa Y , Salama SA, Dardiri AH: Method for recovering African horse sickness virus from horse blood. Proc 3rd Int Conf Equine Infect Dis, pp. 58-68. Karger, Basel, Switzerland, 1972 Parsonson IM: Pathology and pathogenesis of bluetongue infections. In: Bluetongue Viruses, ed. Roy P and Gorman BM, pp. 119-1 4 1. Springer-Verlag, Berlin, Germany, 1990 Richards RG, MacLachlan NJ, Heidner HW, Fuller FJ: Comparison of virologic and serologic responses of lambs and calves infected with bluetongue virus serotype 10. Vet Microbiol 18:233-242, 1988 Spreull J: Malarial catarrhal fever (bluetongue) of sheep in South Africa. J Comp Pathol Ther 18:321-337, 1905 Whetter LE, MacLachlan NJ, Gebhard DH, Heidner HW, Moore PF: Bluetongue virus infection of bovine monocytes. J Gen Virol70:1663-1676, 1989
Request reprints from Dr. N. James MacLachlan, Department of Veterinary Pathology, School of Veterinary Medicine, University of California, Davis, CA 956 16 (USA).
Vet Pathol 29359-361 (1992)
Neurohypophyseal Astrocytoma (Pituicytoma) in a Rhesus Monkey (Mmma mulatta) H. HOGENESCH, J. J. BROERSE, AND C. ZURCHER Key words: Astrocytoma; pituitary; primates; rhesus monkeys. Reports of central nervous system and pituitary tumors in nonhuman primates are rare.'^^,^ Because the overall incidence of tumors markedly increases with age,5 the rarity of tumor reports probably reflects the relatively young age at death of most monkeys in captivity. Tumors of the neurohypophysis are rare in all domestic and laboratory animals and in human beings. This report describes an astrocytoma
arising in the neurohypophysis of an aged, untreated rhesus monkey. A 21-year-old female rhesus monkey (Macaca mulatta) was euthanatized because of its emaciated and moribund condition. The animal had served as a control in a study of the long-term effects of radiation. A complete necropsy revealed pulmonary acariasis with severe bronchopneumonia
360
Brief Communications and Case Reports
Vet Path01 29(4), 1992
Fig. 1. Neurohypophyseal tumor. The tumor consists of interwoven bundles of cells with prominent perivascular arrangement. Hematoxylin-phloxine-saffron. Bar = 100 pm. Fig. 2. Neurohypophyseal tumor. GFAP-positive tumor cells are prominent around blood vessels. Indirect immunoperoxidase, Mayer’s hematoxylin counterstain. Bar = 50 pm. Fig. 3. Neurohypophyseal tumor. Cells around blood vessels and scattered through other parts of the tumor stain positively for vimentin. Indirect immunoperoxidase, Mayer’s hematoxylin counterstain. Bar = 50 pm.
and bronchiectasis. The posterior portion of the pituitary contained a circumscribed 4-mm-diameter white nodule. Tissue specimens were fixed in 10% neutral buffered formalin, embedded in paraffin, and stained with hematoxylinphloxine-saffron,’ Bodian’s silver stain, and phosphotungstic acid-hematoxylin. The pituitary nodule was well demarcated and nonencapsulated and compressed the surrounding neurohypophyseal tissue. It consisted of interwoven bundles and nests of elongate or plump oval cells with a moderate amount of vascular stroma. Blood vessels were frequently surrounded by radiating cells (Fig. 1). The cells had indistinct margins and a variable amount of pale acidophilic cytoplasm. Nuclei were elongate or oval to round, with coarsely granular chromatin and irregular nuclear membranes. Nucleoli were inconspicuous, and mitotic figures were absent from the sections examined. A central area of necrosis was present. The adventitial layer of blood vessels within the tumor was frequently thickened by loosely arranged fibrillar or dense hyaline collagen. Bodian’s silver stain did not reveal any neurofibrils. Few cytoplasmic fibrils were seen in phosphotungstic acid-hematoxylin-stained sections.
Paraffin sections were prepared for immunohistochemical evaluation by deparaffinization and rehydration, followed by inhibition of endogenous peroxidase activity with methanol/ H,O,. Sections were stained with monoclonal mouse antivimentin (1 :5, Dakopatts, Denmark), followed by peroxidase-labeled rabbit anti-mouse (1 : 100, Dakopatts) or with rabbit anti-GFAP (1 :400, Dakopatts) or rabbit anti-Sl00 (1 : 1,000, HSC Research Development Corp., Toronto, Ontario, Canada), followed by peroxidase-labeled swine antirabbit (1 :60, Dakopatts). Positive controls were paraffin sections from multitissue blocks, and negative controls were sections incubated with the second antibody only. Sections treated with anti-GFAP and anti-vimentin antibodies had thick, prominent positive bands in the cytoplasm of a moderate number of tumor cells. Staining was particularly strbng in cells around blood vessels (Figs. 2,3). Anti-S 100antiserum weakly reacted with cells in some areas, whereas in other areas, it remained negative. Anti-S 100 antiserum stained cytoplasm diffusely, in contrast to the cytoplasmic bands that were often seen in reactions treated with anti-GFAP and antivimentin antibodies.
Brief Communications and Case Reports
Vet Pathol 29(4), 1992
Primary tumors in the neurohypophysis should be differentiated both from tumors that occur in adjacent structures and infiltrate into the neurohypophysis and from metastases. The small size of the tumor and its confinement to the neurohypophysis ruled out tumor origination in surrounding tissues. Meningioma was ruled out by positive staining for GFAP and S100. No other tumors were observed in the animal, making a metastatic tumor unlikely. Two varieties of primary neurohypophyseal tumors are recognized: astrocytomas and granular cell tum01-s.~ Astrocytomas arise from pituicytes, the neurohypophyseal glial cells, which are considered astrocytes by most investigator^.^ Astrocytomas from the neurohypophysis are also known as pituicytomas. Granular cell tumors are characterized by plump oval cells with periodic acid-Schiff-positive cytoplasmic granules. These cells may be modified astrocytes, but their exact lineage is still a matter of debate.9 This tumor was diagnosed as an astrocytoma, based on histologic findings and positive staining for GFAP. Positive staining for GFAP, vimentin, and S 100, as seen in this tumor, is commonly seen in human astrocytoma~.~.~ The variation in staining intensity among individual tumor cells indicates differences in the quantity of intermediate filaments and S 100 protein and may reflect the degree of differentiation of the tumor cells. An inverse relationship between the malignancy of glial cell tumors and the level of GFAP expression has been ~uggested.~ Well-documented cases of primary astrocytomas in the neurohypophysis have been reported in human beings,8,10 rats,2 and a Siamese cat." These tumors may cause clinical symptoms by compression or invasion of adjacent tissues. No evidence of clinical disease related to the tumor was observed in this rhesus monkey. This is the first report of such a tumor in a nonhuman primate.
Acknowledgement
36 1
2 Carlton WW, Gries CL: Pituicytoma, neurohypophysis, rat. In: Endocrine System, ed. Jones TC, Mohr U, and Hunt RD, pp. 156-1 60. Springer-Verlag, Berlin, Germany, 1983 3 Herpers MJHM, Ramaekers FCS, Aldeweireldt J, Moesker A, Slooff J: Co-expression of glial fibrillary acidic protein- and vimentin-type intermediate filaments in human astrocytomas. Acta Neuropathol70:333-339, 1986 4 Jacque CM, Kujas M, Poreau A, Raoul M, Collier P, Racadot J, Baumann N: GFA and S 100 protein levels as an index for malignancy in human gliomas and neurinomas. J Natl Cancer Inst 62479-483, 1979 5 Lapin BA: Use of nonhuman primates in cancer research. J Med Primatol 11:327-341, 1982 6 Lowenstine LJ: Neoplasms and proliferative disorders in nonhuman primates. In: Primates: The Road to Selfsustaining Populations, ed. Benirscke K, pp. 78 1-8 14. Springer-Verlag, Berlin, Germany, 1986 7 Luna L, ed.: AFIP Manual of Histologic Staining Methods, 3rd ed., p. 39. Armed Forces Institute of Pathology, Washington, DC, 1968 8 Rossi ML, Bevan JS, Esiri MM, Hughes JT, Adams CBT: Pituicytoma (pilocytic astrocytoma). J Neurosurg 62768772, 1987 9 Russell DS, Rubinstein LJ: Pathology of Tumours of the Nervous System, 5th ed., pp. 376-378. E. Arnold, London, England, 1989 10 Scothorne C: A glioma of the posterior lobe of the pituitary gland. J Pathol Bacteriol 69:109-112, 1955 11 Zaki F, Harris J, Budzilovich G: Cystic pituicytoma of the neurohypophysis in a Siamese cat. J Comp Pathol 85:46747 1, 1975 Request reprints from Dr. H. HogenEsch, Institute for Aging and Vascular Research, PO Box 430, 2300CK Leiden (The Netherlands).
We thank Mr. T. Glaudemans for photographic assistance.
References 1 Beniashvili DS: An overview of the world literature on spontaneous tumors in nonhuman primates. J Med Primatol 1fk423-437, 1989
Vet Pathol29:361-363 (1992)
Eastern Equine Encephalomyelitis in an Adult Cow E. D. MCGEE,C. H. LITTLETON, J. B. ~LIAPP,AND R. J. BROWN Key words: Cow; eastern equine encephalomyelitis; nonsuppurative encephalitis. A 1%-year-old crossbred beef cow submitted alive to the Mississippi Board of Animal Health Veterinary Diagnostic Laboratory had been recumbent for 2 days. The cow could stand with assistance but circled to the left when walking. No other animals from the herd of 125 had been affected,
and there had been no additions to the herd within the previous 8 months. An ante mortem complete blood count revealed a mild inflammatory neutrophilia and a normal total leukocyte count (1 1,700 total leukocytes, 7,020 neutrophils, 468 band neu-
