Theron G. Snider

Encephalitis, lymphoid tissue depletion and secondary diseases associated with bovine immunodeficiency virus in a dairy herd

Encephalitis, lymphoid tissue depletion and secondary infections occurred over a 5-yr-period in Holstein cows infected with bovine immunodeficiency virus (BIV). There were 59 cattle studied, the majority during 1991, when a severe environmental stress occurred, each with one or more primary causes of death, natural or by euthanasia, and most with several secondary diseases. The encephalitis was characterized by meningeal, perivascular and parenchymal infiltration with lymphocytes, occasional plasma cells and macrophages with perivascular edema in some cows. Affected areas included the cerebrum, cerebellum, and spinal cord with no particular distribution pattern recognized. The lymphoid depletion was primarily an absence of follicular development in nodes draining regions with secondary infections such as chronic mastitis and chronic suppurative pododermatitis. Paucity of lymphocytes in thymic-dependent regions of lymph nodes and the spleen suggested a primary depletion of T cells. Secondary infections were often multiple with each cow having several minor conditions, usually considered short-term and treatable. These included mastitis and pododermatitis, with many cows having non-responding abscesses, cellulitis and myositis attributed to injection site infections. A large number of the cattle had parturition difficulties such as dystocia, obturator paralysis, and metritis. Pulmonary, cardiovascular, and intestinal disease were recognized as both primary and secondary disease conditions. There was a high level of infection with bovine leukemia virus with 4 of the 59 cattle having lymphosarcoma. Under practical conditions, the infection with BIV has a different effect on the host than has been observed under experimental conditions. The presence of BIV combined with the stresses associated with parturition and a modern dairy production system were considered causal for the development of untreatable secondary diseases in immunocompromised cattle. The peak incidence in 1991 was attributed to increased environmental stress during renovation of the barn facility. During this time the cattle were kept on open pasture, exposed to an extremely wet winter, and spring weather conditions. The effect of co-infection with bovine leukemia virus, the influence of immunocompromise on the chronicity of mastitis, the relationship with laminitis and pododermatitis, and several questions related to viral transmission, complementarism with bovine leukemia virus, viral reactivation and immunoprophylaxis all remain as viable avenues for future investigations.

Fish Pasteurellosis of cultured striped bass (Morone saxatilis) in coastal Alabama

Abstract The first reported epizootic of fish pasteurellosis caused by the bacterium Pasteurella piscicida in a cultured population of fish in the United States is described. The epizootic occurred in populations of striped bass ( Morone saxatilis ) cultured in earthen, brackish-water ponds at the Claude Peteet Mariculture Center, Gulf Shores, AL. Losses of approximately 49 000 fingerlings (80% of the existing stock) occurred over a 3-week period. Oxytetracycline was administered via the feed within 48 h of the onset of mortality. Oxytetracycline residues in tissues of fish sampled during the treatment period were quantitated by a fluorometric method. The isolated bacterium was characterized biochemically and serologically. The sensitivity of the bacterium to various antibiotics was determined, and the minimum inhibitory concentration of oxytetracycline was determined to be 0.25 ppm. The salient histopathological features of the disease in striped bass are described.

Histopathology of C57BL/6 mice inoculated orally with Mycobacterium paratuberculosis.

The susceptibility of C57BL/6 mice to oral inoculation with Myobacterium paratuberculosis was evaluated histopathologically. Granulomatous lesions containing acid-fast bacteria developed in the mesenteric lymph nodes in over 50% of the mice by 11 months after inoculation. The results suggest that C57BL/6 mice may be useful for studying infection, pathogenesis, and other aspects of paratuberculosis.

Isolation of an Avian Serovar of Chlamydia Psittaci from a Case of Bovine Abortion

Figure 2. Placenta; the cotyledonary villi are extensively necrotic, with clumps of cellular debris (large arrow) and thrombosis (small arrow). HE, bar 5 50 mm. Figure 1. Marked vasculitis involving the arterioles of the placenta. There are fibrinoid necrosis (arrow) and severe infiltrates of the media, composed of leukocytes, mainly neutrophils. The surrounding placental tissue is necrotic. HE, bar 5 80 mm. Many microbial agents have been incriminated as causes of abortion in cattle. Implication of one of these agents in a given case is often problematic. This report deals with abortion in a university-maintained teaching dairy herd that averages about 100 lactating cows. The herd is split into 3 production groups on concrete lots and is fed a total mixed ration according to production level. During previous Dairy Herd Improvement (DHIA) sampling periods, the herd had an average production per cow of 8,325 kg of milk. Average somatic cell count and body condition score are 180,000 and

Lysis and fractionation of Mycobacterium paratuberculosis and Escherichia coli by matrix solid-phase dispersion

A novel method for the lysis and subsequent fractionation of bacterial constituents from Mycobacterium paratuberculosis strain 19698 (M. paratuberculosis) and Escherichia coli strain DH5 alpha utilizing the technique of matrix solid-phase dispersion (MSPD) is described. Bacteria were blended with octadecylsilyl (C18) derivatized silica to obtain cellular lysis. The blended material was used to prepare a column which was sequentially eluted with solvents of increasing polarity. Fractionation of cellular components was confirmed by analysis of the solvent extracts. The possible applicability of the MSPD technique as a general method for the lysis and fractionation of bacterial components is proposed.

Malignant Schwannoma in a Goat

Peripheral nerve sheath tumors (PNSTs) are tumors that originate from the cells that comprise the sheaths of peripheral nerves. One type of PNST originates from the Schwann cell and is thus termed Schwannoma. Two other types of cells, perineural cells and fibroblasts, are components of peripheral nerve sheaths and may give rise to tumors. Depending upon the cell of origin and the degree of differentiation, PNSTs may exhibit a wide range of histologic patterns of fibroblastic and sarcomatous growth. These tumors (particularly the malignant variety) may closely mimic histologic pattern characteristics of other fusiform tumors, including fibrosarcomas, leiomyosarcomas, and synovial cell sarcomas. Electron microscopic and/or immunohistochemical evaluation is often necessary in establishing the diagnosis of PNSTs. In this report, a malignant Schwannoma (malignant PNST) originating from a thoracic spinal nerve of a goat with metastasis to the liver, lungs, spleen, and vertebral canal is described. Schwannomas occur most frequently in cattle, in which they are usually benign and often multiple. Malignant Schwannomas are uncommon. Neoplastic disease is reportedly rare in the caprine. Abattoir surveys in the USA and South Africa have detected a lower incidence of neoplasia in goats than in other domestic species. Although there is at least 1 reported case of a Schwannoma (neurilemmoma) in the goat, an extensive review of the literature failed to find any report of a malignant Schwannoma in caprines. In this case, the diagnosis of a malignant Schwannoma was made using a combination of light and electron microscopy and immunohistochemical staining. A g-year-old female Alpine goat was evaluated for progressively worsening rear limb ataxia of 2 days duration. The goat was able to stand with assistance. Proprioception and nociception were decreased bilaterally. Cerebrospinal fluid analysis revealed an increased protein (59 mg/dl; normal < 40 mg/dl) and white blood cell (wbc) count (12 wbc/μl; normal < 5 wbc/dl), predominantly lymphocytes. A compressive spinal lesion in the lumbar spine was suspected. To minimize costs, radiographs were not obtained. Prednisolone (2.2 mg/kg orally every 12 hours) was administrated for 5 days. The goat’s condition deteriorated during this time, and when examined again, the animal was unable to rise. Nociception was absent bilaterally in the rear limbs. The goat was euthanized and presented for necropsy. Postmortem examination revealed multiple nodular tumors within several organs, including the liver, lungs, and

Vertebral Lymphosarcoma as the Cause of Hind Limb Paresis in a Horse

A 23-month-old, 400-kg female quarterhorse was referred to the Louisiana State University Veterinary Teaching Hospital for recumbency due to rear limb paresis. Eleven days earlier, the owner had noticed transient abnormal head and neck posture, but no other abnormalities were noted until the animal suddenly became recumbent 3 days prior to referral. On physical examination, the horse was alert. Cranial nerve responses were normal, as were reflexes and cutaneous sensations of the forelimbs. There was paresis of the rear limbs, but patellar and withdrawal reflexes and sensory perception were intact. Tail control and anal muscle tone were normal. A complete blood count (CBC) revealed mature neutrophilia (16,400 white blood cells/μl, 90% segmenters), hyperfibrinogenemia (800 mg/dl), and hyperproteinemia (9.0 g/dl). With the exception of a slight elevation in creatine phosphokinase, the chemistry panel was normal, including calcium levels. Cerebrospinal fluid collected from the lumbosacral space was normal. A thoracolumbar spinal cord lesion was suspected and the horse was treated accordingly. No change in condition was seen in 24 hr and the animal was euthanized. Within the vertebral canal at the level of the first lumbar vertebra was an elongated, tan-white subperiosteal mass measuring 2 x 5 cm (Fig. 1). This mass had a glistening smooth surface (periosteum) and compressed the spinal cord at that point. Cross section of the first lumbar vertebra revealed destruction of the vertebral body and replacement by soft tan-white tissue. This tissue displaced and replaced trabecular bone in the vertebral body and at the base of the dorsal spinous process. Focal destruction of the cortex presumably allowed formation of the subperiosteal mass, which protruded into the vertebral canal. The spleen weighed 22 kg and contained a 30-cm-diameter round mass (Fig. 2). The surface of the splenic mass was smooth and mottled in color from red to tan to dark purple. There were 5 thick, sessile, discoid plaques present on the splenic mass and the adjacent capsule. The plaques were pale tan, 4-8 cm in diameter, flattopped, and elevated 2-4 cm above the capsular surface. Cut section of the mass and plaques revealed multiple coalescing round nodules of moderately soft tan tissue (Fig. 3). Nodules varied in size from 0.5 to 2 cm in diameter and were occasionally separated from one another by hemorrhage, giving the tissue an overall marbled tan and red appearance. Approximately 50% of the center of the mass was necrotic, as characterized by friable yellow-tan tissue and a 9-cm-diameter area of liquification necrosis. Mesenteric lymph nodes were enlarged and many contained multiple discrete cortical nodules up to 1.5 cm in diameter.

Comparison of the Resistance of C57BL6 and C3HHe Mice to infection with Mycobacterium paratuberculosis

Susceptibility of C57BL/6 (Bcgs) and C3H/HeN (Bcgr) mice to an intraperitoneal infection with Mycobacterium paratuberculosis strain 19698 was compared (by histopathology and the number of mycobacteria isolated from the spleen). Mycobacterial counts from the spleen of Bcgr mice progressively decreased over the course of infection but remained unchanged in Bcgs mice. Granulomatous lesions and acid-fast bacteria were consistently present in the liver and lymph nodes of Bcgs mice, whereas lesions were transient or absent in Bcgr mice. These results indicate that Bcgr mice are inherently resistant to M. paratuberculosis, whereas Bcgs mice are inherently susceptible. These differences may prove useful in elucidating the mechanisms of resistance and susceptibility to paratuberculosis and other mycobacterial infections.

Natural bovine lentiviral type 1 infection in Holstein dairy cattle. I. Clinical, serological, and pathological observations

Abstract Clinical, serological, and pathological abnormalities observed in Holstein cows naturally infected with bovine lentivirus 1 bovine immunodeficiency virus (BIV) and other infections were progressive and most commonly associated with weight loss, lymphoid system deficiency, and behavioral changes. Clinical evidence of meningoencephalitis was dullness, stupor, and occasional head or nose pressing postures. The polymerase chain reactions associated the BIV provirus with the lesions in the central nervous system and lymphoid tissues. Multiple concurrent infections developed in retrovirally infected cows undergoing normal stresses associated with parturition and lactation. A major functional correlate of the lymphoreticular alterations was the development of multiple secondary infections which failed to resolve after appropriate antibacterial therapy. The chronic disease syndrome in dairy cows associated with BIV may be useful as a model system for investigation of the pathogenesis of the nervous system lesions and lymphoid organ changes that occur in humans with lentiviral infection.

Differences in the kinetics of T cell accumulations in C3HHeN (Bcg-resistant) and C57BL6 (Bcg-susceptible) mice infected with Mycobacterium paratuberculosis

The accumulation of various T cell subsets in Bcg-susceptible (C57BL/6) and- resistant (C3H/HeN) strains of mice were compared following an intraperitoneal infection with Mycobacterium paratuberculosis. Groups of mice from both strains were killed at 3, 5, 10, 15, 30, and 150 days after infection and lymphocytes were harvested from the peritoneal exudate cells (PEC), spleen, intestinal epithelial lymphocytes (IEL), lamina propria lymphocytes (LPL), Peyers patches, and mesenteric lymph node (MLN) and labelled with monoclonal antibodies to CD3, CD4, CD8, gamma delta TCR, CD25, and CD44 for flow cytometric analysis. Uninfected C3H/HeN mice had higher proportions of CD4+ cells in the spleen, MLN, LPL, IEL, and Peyers patches, while uninfected C57BL/6 mice had higher proportions of CD8+ and/or gamma delta T cells. Significant increases in accumulation of CD8+ and gamma delta T cells were detected in the peritoneum and other tissues in both strains of mice after infection. Higher CD4/CD8 ratios were observed in most lymphoid tissues of C3H/HeN mice, while increased proportions of CD8+ and/or gamma delta T cells were present in C57BL/6 mice. These results indicate that significant differences in T cell profiles exist between these two strains of mice, both inherently and in response to infection with M. paratuberculosis. Innately lower levels of CD4+ cells and/or higher percentages of CD8+ and gamma delta T cells may play a role in the increased suspectibility of C57BL/6 mice to infection with M. paratuberculosis.