Pseudorabies virus infections in explants of porcine nasal mucosa.

The spread of infection and the morphogenesis of three pseudorabies virus strains were studied in explants of porcine nasal mucosa. Virulent NIA-3 virus was compared with a deletion mutant 2.4N3A, and with a non-virulent Bartha virus. All three virus strains infected nasal epithelial cells. NIA-3 virus particles were enveloped mainly at the inner nuclear membrane; the virus rapidly invaded the stroma, causing widespread necrosis. In contrast, 2.4N3A virus particles were enveloped mainly at the endoplasmic reticulum and the infection spread more slowly. Bartha virus particles were enveloped mainly at the endoplasmic reticulum; the infection spread slowly and remained restricted to the epithelial cells. In situ DNA hybridisation showed an accumulation of Bartha virus DNA in the nucleus 24 hours after inoculation. In nasal mucosa viral virulence seemed directly related to the speed of replication and release of virus from infected cells.     

Pathogenesis of digestive tract lesions in duck plague.

White Pekin ducklings were inoculated orally with duck plague virus. Tissues from the digestive tract were collected daily after inoculation and examined by light, electron and fluorescent microscopy. There were necrosis and degeneration of stratified squamous epithelium of the esophagus and cloaca, epithelium of intestinal crypt and esophageal submucosal glands, macrophages in the lamina propria, and submucosal fibrocytes and lymphocytes. Submucosal hemorrhages occurred after degeneration and necrosis of lymphocytes, macrophages, fibrocytes and epithelial cells. Viral antigens were detected in all these cells by use of fluorescein-labeled antibodies. With the electron microscope, nucleocapsids were seen in the nuclei, budding through the inner nuclear membrane; enveloped virions were present in cytoplasmic vacuoles of macrophages, epithelial cells and fibrocytes. In lymphocytes, nucleocapsids were also in the nuclei, but karyorrhexis and cytolysis occurred before viral maturation was completed.     

Pathology of infectious diarrhea of infant rats (IDIR) induced by an antigenically distinct rotavirus

Suckling rats were inoculated with a group B rotavirus to determine the progression of the morphologic changes induced in the intestine by this virus. Several changes were observed by light microscopy 1 day after viral inoculation: shortening of small intestinal villi, villous epithelial necrosis, and villous epithelial syncytia. The lesions were most often present in the distal small intestine, although other small intestinal segments were affected to a lesser degree. By day 3 post-inoculation, epithelial necrosis, and syncytia were no longer present; however, the villous epithelium was disorganized and irregularly vacuolated, and intestinal crypt epithelium was hyperplastic. Alterations in villous height to crypt depth ratios were present in portions of the small intestine for the remainder of the 12-day study period. Epithelial syncytia appeared to form by the breakdown of the lateral interdigitating membranes of the absorptive villous epithelium. Viral particles, abundant in the syncytia, appeared to form from amorphous or reticular arrays of viral precursor material. Group B rotaviral antigens, as detected by indirect immunofluorescence, were present in large amounts in the small intestinal villous epithelium only on the first day after viral inoculation. These studies show that two important diagnostic features of group B rotaviral infections of rats, epithelial syncytia and viral antigen as determined by immunofluorescence, are present only on the first day of disease. These findings should be taken into consideration when attempting to diagnose disease induced by this agent.     

Fatal nonneurological EHV-1 infection in a yearling filly

A case of fatal nonneurological equine herpesvirus 1 (EHV-1) infection in a yearling filly is described. Gross lesions included extensive pulmonary edema, prominent laryngeal lymphoid follicles, and congestion and edema of the dorsal third ventricle choroid plexus. Histologically, there was vasculitis, hemorrhage, and edema in the lungs and dorsal third ventricle choroid plexus as well as mild intestinal crypt necrosis with occasional intranuclear inclusion bodies. The perivascular and vascular inflammatory infiltrates were comprised mainly of T lymphocytes and macrophages. EHV-1 antigen was identified within the nucleus and cytoplasm of endothelial cells, dendritic-like cells of the pharyngeal lymphoid follicles, pharyngeal glandular epithelium, crypt enterocytes, and monocytes. Attempted virus isolation was negative. Weak seroconversion for EHV-1 was observed. Herpesvirus-like particles were identified within pharyngeal endothelial cells by transmission electron microscopy. Polymerase chain reaction amplified 369 and 188 base-pair fragments specific for EHV-1. The scarcity of pathognomonic viral inclusions and lesions in this case suggests that this disease may not be recognized, particularly in situations when ancillary laboratory procedures are limited.     

Experimental infection of calves with bovine viral diarrhea virus genotype II (NY-93).

To ascertain the virulence of bovine viral diarrhea virus (BVDV) genotype II, isolate NY-93 was inoculated intranasally into 3 calves, 2 of which were treated with a synthetic glucocorticoid prior to and after virus inoculation. Anorexia, fever (up to 42 C), dyspnea, and hemorrhagic diarrhea developed 6 days after intranasal inoculation with BVDV NY-93. The condition of all calves deteriorated further until the end of the study on day 14 postinoculation. The most significant postmortem macroscopic changes in all calves were limited to the gastrointestinal tract and consisted of moderate to severe congestion of the mucosa with multifocal hemorrhages. Microscopic lesions found in the gastrointestinal tract were similar to those observed in mucosal disease, including degeneration and necrosis of crypt epithelium and necrosis of lymphoid tissue throughout the ileum, colon, and rectum. The basal stratum of the epithelium of tongue, esophagus, and rumen had scattered individual necrotic cells. Spleen and lymph nodes had lymphocytolysis and severe lymphoid depletion. Severe acute fibrinous bronchopneumonia was present in dexamethasone-treated calves. Abundant viral antigen was detected by immunohistochemistry in the squamous epithelium of tongue, esophagus, and forestomachs. BVDV antigen was prominent in cells of the media of small arteries and endothelial cells. The presence of infectious virus in tissues correlated with an absence of circulating neutralizing antibodies. These findings highlight the potential of BVDV genotype II to cause severe disease in normal and stressed cattle.     

A scanning and transmission electron microscopic study of rotavirus-induced intestinal lesions in neonatal gnotobiotic dogs

Neonatal gnotobiotic dogs orally inoculated with canine rotavirus had ultrastructural changes limited to the jejunal and ileal regions of the small intestine. Early scanning electron microscopic findings consisted of swollen villus epithelial cells, denuded foci on intestinal villi, and slight to moderate villus atrophy. Later changes were slight villus atrophy with no denuded intestinal villi. Transmission electron microscopic changes in villus epithelial cells from 12 to 48 hours post-inoculation included: rotavirus particles associated with intracytoplasmic vacuoles near the terminal web and apical tubules; viral particles in dilated cisternae of rough endoplasmic reticulum; and moderate numbers of necrotic cells having no microvilli, swollen mitochondria, membrane-bound lipid-like material in the cytoplasm, clumped chromatin around the periphery of the nucleus, and disruption of the cytoplasmic membrane. In jejunum and ileum at 72 to 154 hours post-inoculation, there were fewer necrotic villus epithelial cells and fewer virus particles. In addition, the ultrastructural morphology of the majority of the villus epithelial cells was similar to crypt epithelium. These studies showed that rotavirus infected the villus epithelial cells with subsequent propagation of the rotavirus and destruction of villus epithelial cells.     

鸡传染性法氏囊病的病理学研究

人工接种２８日龄非免疫鸡传染性法氏囊病病毒（ＩＢＤＶ）后,对感染鸡的法氏囊、胸腺、脾、盲肠扁桃体、哈德氏腺、肝、肾进行病理组织学检查。感染后４８ｈ,法氏囊淋巴组织最早出现坏死且长久存在。其他淋巴器官的病变出现较迟,程度轻微且恢复较快。ＩＢＤＶ单抗免疫荧光检测,法氏囊及其他淋巴器官中均检测到病毒,接种后１２ｈ法氏囊中即检出病毒,持续时间也最长（攻毒后１２ｄ）,其次是盲肠扁桃体（攻毒后８ｄ）。攻毒１３ｄ以后,上述器官均未检测到病毒。法氏囊粘膜上皮的扫描电镜观察,攻毒后２ｄ,上皮细胞肿胀,微绒毛减少或消失。攻毒后３ｄ,局部上皮细胞坏死、脱落,并向整个粘膜层扩展,攻毒后１０ｄ,上皮层基本修复。     

人工感染IBDV鸡法氏囊的电镜研究

通过透射电镜系统观察了人工感染传染性法氏囊病病毒（ＩＢＤＶ）后鸡法氏囊各类细胞的病理变化。感染后１２￣２４ｈ，病毒粒子主要见于髓质淋巴细胞中，细胞中可见到大量纤维样病毒发生基质及无囊膜包围的大型病毒晶格，细胞核染色质浓缩，核中出现纤维样结构。感染后３６ｈ，淋巴细胞开始大量裂解死亡。无囊膜包围的病毒晶格也出现于髓质网状细胞中，被感染的网状细胞并不裂解，而表现出细胞凋亡的特征：染色质固缩呈颗粒块状，胞     

Lesions of spontaneous canine viral enteritis

Spontaneous enteric disease characterized by hemorrhagic diarrhea and high mortality occurred in puppies from commercial kennels in three midwestern states. Microscopic lesions resembling those of panleukopenia in cats were seen in the intestines. The predominant features were necrosis of crypt epithelium, collapse or dilation of crypt lumina and villous atrophy. Viral particles morphologically resembling parvovirus were found in the feces by direct electron microscopy. The canine virus reacted with antibody to feline panleukopenia virus by immunoelectron microscopy and fluorescent antibody technique. Fluorescent antibody was used to detect virus in the crypt epithelium of affected dogs. Feline kidney cells inoculated with fecal preparations had cytopathic effect and positive fluorescence by fluorescent antibody technique.     

Gut-associated lymphoid tissue in the large intestine of calves. II. Electron microscopy

Scanning electron microscopy of lymphoid tissue in the large intestine of three germfree calves (age 3, 6, and 7 days) revealed two different units: propria nodules and lymphoglandular complexes (LGC). Propria nodules had lymphoid tissue predominantly in lamina propria and were covered by distinct follicle-associated epithelium which lacked goblet cells; nodules were surrounded by wide crypts, which were also lined by follicle-associated epithelium towards the luminal side. Lymphoglandular complexes had lymphoid follicles in the tunica submucosa; epithelial diverticulae extended through the muscularis mucosae branching into the lymphoid nodule. In centers of lymphoglandular complexes, protrusions of lymphoid tissue were covered with distinct follicle-associated epithelium. By transmission electron microscopy cells compatible with M cells in the small intestine of calves and cells with characteristics of both enteroabsorptive and M cells were found. Follicle-associated epithelium of propria nodules and lymphoglandular complexes differed only in the relative frequency of cell types.     

Necrotic colitis in two cats - a description of the lesions

The lesions in two cases of necrotic colitis in old cats are described. Both had gross lesions of a necrotic, hemorrhagic colitis without gross lesions in the small intestine. Histologically the lesions resembled those of feline panleukopenia virus infection, namely: necrosis and loss of crypt epithelium, dilation of crypts and lining of crypts by flattened epithelium, subsequent collapse of the lamina propria and hemorrhage from subepithelial capillaries. Both grossly and histologically these lesions were restricted to the colon without similar involvement of the small intestine.The histories and clinical signs, the virological and hematological studies suggest that feline panleukopenia virus was not the etiological agent in these cases. No other causal agent was identified.     

Cell differentiation in intestinal adenomatosis of pigs studied by histochemistry of laminin and enzymes of epithelial and subepithelial tissue

The distribution of enzymes and laminin was examined in ileal tissue from pigs suffering from intestinal adenomatosis to reveal the nature of the lesion. A disruption of the normal and specific pattern of distribution was found. Thus, the normal ileal epithelium was characterised by brush border enzymes: alkaline phosphatase, magnesium-dependent adenosine triphosphatase (Mg-ATPase), fluoride resistant acid phosphatase and 5'-nucleotidase; enzymes of the basolateral border: Mg-ATPase; and cytoplasmic enzymes: beta-glucuronidase, non-specific esterase and acid phosphatase. Subepithelial fibroblasts seemed to be characterised by 5'-nucleotidase. Laminin was present as a continuous band under the surface and crypt epithelium, somewhat thicker in the former. In contrast, the branching proliferating crypts of intestinal adenomatosis largely lacked enzymes characteristic of both villus and crypt cells. Reactions for the subepithelial components, laminin and fibroblasts were also reduced. The deficient differentiation of the epithelial as well as subepithelial components in porcine intestinal adenomatosis distinguish the condition from crypt hyperplasia and indicate an adenoma-like character.     

The differential localization of IgA,IgM and IgG in the gut of suckled neonatal piglets

The localization of immunoglobulins IgG, IgM and IgA in tissue sections prepared from the ileum of neonatal and adult swine were compared. Eighty percent of the immunoglobulin-containing lymphoid cells in the lamina propria of conventional adult German Landrasse swine were IgA-positive with lower numbers of IgM cells and occasionally an IgG cell. Anti-μ and α-chain reagents also stained the cytoplasm of the crypt epithelial cells. By comparison to these adult control tissues, the ileum of unsuckled neonates contained no immunoglobulins although after the ingestion of colostrum, the entire cytoplasm of the villus epithelial cells stained intensely when tested for IgG with only faint staining for IgM and IgA. On the other hand, IgA and IgM were readily localized on what appears to be only the apical border of the crypt epithelial cells but in contrast to the adult, the cytoplasm of these cells was unlabelled. IgG was absent from the crypt region. We interprete these findings to indicate an important, selective role for the villus epithelium in the absorption into the neonatal circulation of colostral IgG and probably IgA and IgM, and a specialized role for the crypt epithelium in adsorbing colostral IgA and IgM; possibly by complexing with mucin-bound secretory component.     

Pathogenesis of canine parvovirus-2 in dogs: histopathology and antigen identification in tissues

The pathogenesis of canine parvovirus-2 was studied in orally inoculated conventional dogs using histopathological and peroxidase anti-peroxidase staining techniques. Lymphoid necrosis and depletion of lymphocytes from lymphoid tissues were most notable on days 5 and 6 after exposure. Lymphocyte hyperplasia occurred following day 7. Epithelial cell changes in segments of the small intestine were more severe on days 6 to 9 after exposure in areas associated with Peyer's patches and in the upper segments of the small intestine. The lymphocyte was the primary infected cell. Virus infected cryptal epithelial cells were not detected until 24 hours after the identification of infected cells in lymphoid tissues on day 4 after exposure. The majority of virus infected epithelial cells were found in crypts intimately associated with or adjacent to Peyer's patches in the upper segments of the small intestine.     

Experimentally induced porcine proliferative enteritis in specific-pathogen-free pigs

Thirty-three, 10-week-old, specific-pathogen-free pigs were randomly allotted to 3 treatment groups: group 1--intragastrically given homogenized intestinal mucosa (crude inoculum) from pigs with naturally occurring proliferative enteritis; group 2--given cultures of Campylobacter sputorum subsp mucosalis; and group 3--controls. One pig from each group was killed 4, 7, 10, 14, 18, 21, 24, 28, 31, 36, and 38 days after inoculation. The earliest intestinal lesion observed in groups 1 and 2 was leukocytic exudate within crypt lumina and focal inflammation of the surrounding lamina propria. The lesions occurred primarily over ileal aggregated lymphoid nodules (Peyer's patches). These changes were followed by focal proliferation of immature crypt epithelial cells and infiltration of increasing numbers of macrophages into the lamina propria. Campylobacter sp-like organisms were observed within the cytoplasm of affected epithelial cells by light and electron microscopies. Lesions progressed to diffuse crypt cell proliferation, elongation of crypts, and loss of villi. Mucosal necrosis was not a prominent feature.     

Pathological and immunohistochemical study of experimental peste des petits ruminants virus infection in goats

Peste des petits ruminants (PPR) is an emerging, economically important viral disease of goats and sheep in the Indian subcontinent. In the present investigation, 15 hill goats were experimentally infected with 2 ml of 10% splenic suspension of a virulent isolate of PPR virus (PPR/Izatnagar/94) that had caused heavy mortality (>75%) in goats during 1994 outbreaks in northern India. More than 86% (13 of 15) animals died between 9 and 13 days post inoculation at the height of temperature or when temperatures were declining. Necropsy findings included congestion of gastrointestinal tract (GIT), nasal sinuses, consolidation of antero-ventral lobes of lungs, engorged spleen, and occasionally oedematous lymph nodes. Histopathological examination of major organs of GIT revealed degeneration and necrosis of labial mucosa, severe mucosal and submucosal congestion, degeneration and necrosis of intestinal epithelium and lymphoid cell depletion from Peyer's patches along with presence of syncytia at times. Lungs showed broncho-interstitial changes and presence of intracytoplasmic and intranuclear eosinophilic inclusions in alveolar macrophages and syncytial cells. These changes in lungs were frequently complicated with serofibrinous pneumonia (57%, eight of 14). Lymphocytolysis and occasional syncytia formation were evident in the lymphoid tissues. Immunohistochemical (IHC) findings included presence of PPR virus antigen in the labial, intestinal, and bronchiolar epithelial cells, pneumocytes, macrophages and syncytial cells in lungs, and lymphoid (intact and necrotic) and reticular cells in lymphoid organs. The findings of the study indicated the highly virulent nature of the PPR virus isolate (PPR/Izatnagar/94), causing 100% mortality and characteristic pathological changes in the target organs such as lungs, intestines and lymphoid tissues. The results of the IHC study suggested that indirect immunoperoxidase could be an alternative method in the absence of more sophisticated methods of laboratory diagnosis of PPR virus infection in goats.     

Cytologic diagnosis of Lawsonia intracellularis proliferative ileitis in a Japanese snow macaque (Macaca fuscata)

Diffuse ileal thickening and ileocecocolic lymphadenomegaly were observed during exploratory laparotomy in a 2-year-old male Japanese snow macaque (Macaca fuscata) that had flu-like signs and diarrhea. Cytologic examination of ileal biopsy imprints revealed many mature, mildly karyolytic neutrophils and fewer well-differentiated lymphocytes, eosinophils, macrophages, and plasma cells in a background containing amorphous, necrotic material. Tightly cohesive sheets of moderately pleomorphic epithelial cells also were seen. The cytologic diagnosis was chronic, active, mixed inflammation with atypical epithelial cells and necrosis. Histologically, the mucosal and crypt epithelium was moderately hyperplastic with a loss of goblet cells, increased mitoses, and frequent crypt abscesses. Within the lamina propria and extending into the submucosa was a marked neutrophilic infiltrate, with low numbers of lymphocytes, histiocytes, plasma cells, and eosinophils. The histologic diagnosis was chronic, diffuse, marked suppurative and lymphocytic ileitis. Warthin-Starry silver staining of the ileal biopsy and imprint specimens demonstrated numerous pleomorphic, curved bacilli consistent with Lawsonia intracellularis. Polymerase chain reaction (PCR) and immunohistochemistry confirmed the identity of the infectious agent. L intracellularis infection may be underdiagnosed because silver stain is required to visualize the organism with light microscopy and because the pathognomonic crypt hyperplasia may be complicated by secondary pathologic changes. Application of silver stain to cytologic specimens should be considered when distal intestinal lesions associated with hyperplastic epithelium, with or without inflammation, hemorrhage, or necrosis, are identified in animals with clinical signs of enteritis, especially in frequently affected species or in stressed or young animals.     

Histology, immunohistochemistry and ultrastructure of the tonsil of the soft palate of the horse

The tonsil of the soft palate was an oval, flat structure located centro-rostrally on the oral surface of the soft palate. Its stratified squamous non-keratinized epithelium was perforated by holes or small crypts the deeper parts of which were loosely spongiform inter-digitated with lymphoid tissue. These unusual features have not previously been reported in tonsils of any species. Crypts and reticulated epithelium as found in the lingual and palatine tonsils were not observed. Lectins showed varying affinities for specific layers of the epithelium. M cells were not observed. A few Langerhans cells were distributed among surface epithelial cells. Lymphoid tissue was arranged loosely and in isolated lymphoid follicles in the subepithelial lamina propria mucosae. Although IgA+ cells and macrophages were proportionately more numerous the amount of lymphoid tissue was much less than in the lingual and palatine tonsils. Most of the follicular germinal centres lacked a darkly stained corona. CD4 positive were more numerous than CD8+ lymphocytes and were distributed in the parafollicular and inter-follicular areas. Large clusters of mucus acini positive for glycogen, acidic and neutral mucopolysaccharides separated lymphoid tissue from deeply placed striated muscle. Only a few high endothelial venules were observed in the parafollicular and inter-follicular areas. These had relatively few vesiculo vacuolar or other organelles in their high endothelial cells and few lymphocytes attaching to their walls.     

Intestinal trichomonads (Tritrichomonas mobilensis) in the natural host Saimiri sciureus and Saimiri boliviensis

A retrospective study of cecal and colonic tissues from 28 squirrel monkeys (Saimiri sciureus and Saimiri boliviensis) demonstrated enteric trichomonads within luminal crypts. Twenty-one of 28 (75%) had trichomonads in the mucosal epithelium either in cup-like depressions or intraepithelial vacuoles. Organisms were also beneath the superficial luminal mucosal epithelium and between the basement membrane and crypt epithelial cells. Immunoperoxidase staining also identified organisms within the lamina propria and submucosa. Additional histologic changes included mucosal ulceration, multifocal cryptitis, and focal epithelial necrosis. Most areas containing trichomonads did not have an associated inflammatory response.     

Histological studies on the ontogeny of bovine palatine and pharyngeal tonsil: germinal center formation, IgG, and IgA mRNA expression

The development and distribution of lymphocyte subsets in calf palatine and pharyngeal tonsil were examined. During prenatal development, B cells were distributed in the subepithelial area, and T cells and MHC class II⁺ cells were found in the deep layer of B-cell area, respectively, in both tonsils. At neonatal stage, lymphoid follicle containing a few CD4⁺ cells have been formed in both tonsils. IgG⁺ and IgA⁺ cells were found in the parafollicular and epithelial area. At 3 months old, many germinal centers were recognized in both tonsils. CD4⁺ cells and IgG mRNA expression were detected in light zone of germinal centers. Many IgG, and IgA mRNA expressions also could be detected in the parafollicular and subepithelial area of both tonsils. The data suggest that both tonsils have an important role of local immune defense against invading antigen after birth. The comparison of the histological characteristics of tonsil and Peyer's patch during ontogeny is also discussed.