Evaluation of uniformity of morphological injury of the large colon following severe colonic torsion.

This report describes the evaluation of uniformity of morphological injury of the large colon following severe colonic torsion in 17 horses presented to the Veterinary Medical Teaching Hospital. In 16 horses, twist occurred at the colonic base and in 1 at the sternal and diaphragmatic flexure. Eleven of the 17 horses were subjected to euthanasia at surgery and 6 of 17 following surgical correction within 4 days postoperatively. The objective of this study was to determine if the degree of histological changes present at the pelvic flexure were uniformly distributed throughout the regions of the colon involved in cases of severe colonic torsion.

Hepatic sarcocystosis in a horse.

Hepatic sarcocystosis was diagnosed in a horse in association with refractory bacterial osteomyelitis and plasma cell tumor of the maxilla and hepatic salmonellosis. Gross lesions included pleural, pericardial, and peritoneal effusions, hepatomegaly, gastric ulceration, colonic edema, and proliferative tissues filling 2 maxillary dental alveoli. Histologically, liver was characterized by severe suppurative, necrotizing, periportal hepatitis, and severe periacinar necrosis. Hepatocytes frequently contained protozoal schizonts in various stages of development. In mature schizonts, merozoites were often arranged radially around a central residual body, consistent with asexual division by endopolygeny. Ultrastructural features of merozoites included an apical conoid and polar ring, anterior micronemes, central nuclei, and absence of rhoptries. These protozoa did not react to antisera raised against Neospora caninum, Sarcocystis neurona, Toxoplasma gondii, or Hammondia hammondi. The microscopic and ultrastructural characteristics and immunoreactivity of this organism are consistent with a Sarcocystis sp. other than S. neurona. This is the first report of Sarcocystis-associated hepatitis in a horse. The life cycle of this organism and source of infection are unknown.

Pathogenesis of foot-and-mouth disease in swine, studied by in-situ hybridization.

Eight 7-month-old pigs were inoculated intradermally with 10(3) plaque-forming units of foot-and-mouth disease virus, type O, and killed 24, 48, 72, or 96 h later. Numerous tissues from each animal were collected and examined histopathologically and by in-situ hybridization to determine the presence of virus and its correlation with lesion development. The probe for in-situ hybridization was a biotinylated 500-base negative-sense transcription product corresponding to a portion of the gene encoding polymerase. With this technique, virus was shown to be widely disseminated in all epidermal tissues, regardless of histologically apparent cellular disruption.

The accuracy of intraoperative diagnoses based on examination of frozen sections. A prospective comparison with paraffin-embedded sections.

The accuracy of diagnoses based on examination of frozen sections was determined by comparing the results to those obtained by examination of tissues prepared using conventional methods (formalin fixation, paraffin-embedded tissue). One hundred ninety-four specimens were examined using the frozen section technique; 37 were examined to confirm a tentative diagnosis or to document lymph node metastasis and the remainder were examined to diagnose an unknown pathologic process. Of the 194 specimens examined, an accurate, specific diagnosis was obtained in 161 (83%); in 19 (10%), the pathologic process was correctly identified, but a specific diagnosis was not obtained; and in 2 (1%) the diagnosis was deferred. The remaining 12 (6%) were incorrectly diagnosed by the frozen section technique. When the number of specimens in which a specific diagnosis was obtained was combined with the number of specimens in which the pathologic process was correctly identified, the overall accuracy rate of the frozen section technique was 93%. There was no difference in the accuracy of the frozen section technique based on the reason for submission of the sample, source of tissue submitted, or the type of pathologic process (i.e., inflammatory or neoplastic). Of the 12 incorrect diagnoses, 4 (33%) were because of sampling errors and 8 (67%) were caused by interpretation errors.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxalate nephrosis and renal sclerosis after renal transplantation in a cat.

A 10-year-old castrated domestic shorthair cat received two renal allografts, 14 days apart, for the treatment of chronic renal failure. Oxalate nephrosis developed in both allografts, and they became nonfunctional. During the transplantation period, the cat was not exposed to exogenous sources of oxalate, and there was no evidence of primary type 2 hyperoxaluria before surgery. Urologic surgery, in particular renal transplantation, has been identified as a factor that can precipitate renal failure in human patients with decompensated renal function and hyperoxaluria. If hyperoxaluria was present before surgery in this cat, it was most likely caused by increased absorption or decreased metabolism of dietary oxalate.

Ultrastructural mucosal injury after experimental ischemia of the ascending colon in horses.

The ultrastructural injury that develops sequentially in the ascending colon during experimentally induced ischemia was examined in 6 halothane-anesthetized horses. Colonic ischemia was created by 2 types of vascular occlusion 24 cm proximal and distal to the pelvic flexure. In all horses, transmural vascular compression was created. The colonic venous circulation was obstructed in 3 horses, whereas in the other 3 horses, arterial and venous circulation was obstructed. Two additional horses were anesthetized as controls for determination of any morphologic alterations associated with the experimental protocol. Full-thickness colonic biopsy specimens were obtained from the antimesenteric border of the pelvic flexure at 0, 0.25, 0.5, 1, 1.5, 1.75, 2, 2.25, 2.5, 3, 3.5, 4, 4.5, and 5 hours during occlusion, and were studied by light and transmission electron microscopy. Morphologic alterations did not develop in the colon of control horses. Mucosal congestion was observed by light microscopy in the colon of horses with experimentally induced ischemia, but congestion developed early in those with obstructed colonic venous circulation, compared with those having arterial and venous obstruction. Inter- and intracellular vacuolation and loss of staining initially resulted in groups of 3 to 5 superficial luminal epithelial cells. Alterations in the glandular epithelium lagged behind those in the superficial epithelium, but were observed in both groups by 2 hours of obstruction. These changes progressed to 100% sloughing of all epithelium by 4.5 to 5 hours. The initial cellular alterations, which were observed by transmission electron microscopy, developed at 0.25 hour in horses with colonic venous obstruction and was characterized by inter- and intracellular edema.(ABSTRACT TRUNCATED AT 250 WORDS)

A pathogenesis study of highly pathogenic avian influenza virus H5N2 in chickens, using immunohistochemistry.

Eighteen specific pathogen-free chickens (nine hens older than 1 year and nine 15-week-old males) were inoculated with highly pathogenic avian influenza virus A/Chicken/Pennsylvania/1370/1983 (H5N2). Birds were serially killed and tissues collected for histological and immunohistochemical evaluation. In the group of older hens, disease was acute or peracute. By immunohistochemistry, antigen was abundant in capillary endothelium in multiple organs, and staining for antigen in parenchymal cells was marked in brain and heart. In the group of younger male birds, disease was subacute. Immunohistochemical staining of capillary endothelium was less pronounced and viral antigen staining was evident in the parenchymal cells of the heart, brain and kidney.

A pathogenesis study of foot-and-mouth disease in cattle, using in situ hybridization.

Eight calves were exposed in an aerosol chamber to nebulized foot-and-mouth disease virus. Two control animals were exposed in a similar manner to cell culture media only. Animals were euthanized at intervals and various tissues examined by in situ hybridization using a biotinylated RNA probe corresponding to a portion of the viral gene coding for the polymerase enzyme. By this technique large amounts of viral nucleic acid were found in coronary band, interdigital cleft and tongue as early as six hours postexposure, indicating a very rapid delivery from the portal of entry to the predilection sites for lesion development. This occurred well before the onset of viremia which by virus isolation was not detectable until 30 hours postexposure. The in situ hybridization signal in these tissues decreased in intensity and extent with time to focally positive areas, occasionally surrounding a vesicle. Other epidermal sites not normally thought of as sites for foot-and-mouth lesion development, such as carpus and eyelid, also had some viral nucleic acid detectable at various time intervals. In the lung by in situ hybridization, alveolar septa had viral nucleic acid early in infection (6-18 h postexposure) while later (36-96 h postexposure), the in situ hybridization signal was prominent in alveolar macrophages.

Atresia coli in the foal: a review of six cases.

Physical examination and exploratory celiotomy were performed on five neonatal foals presented with signs of acute colic. Atresia coli was confirmed in each foal during surgery. The most consistent finding on physical examination was the absence of meconium staining following repeated enemas. The large, transverse and/or small colon were involved in all foals. One eight month aborted foetus was submitted for necropsy and diagnosed as having atresia coli and congenital hydrocephalus. Atresia coli should be considered for neonatal foals with signs of acute colic.

Persistent experimental Salmonella dublin intramammary infection in dairy cows.

Experimental intramammary infections were induced in five post-parturient Holstein cows by inoculation of low numbers (5000 colony forming units) of virulent Salmonella dublin via the teat canal of mammary gland quarters. Rectal temperature, pulse and respiratory rates, milk yield, and milk quality as assessed by the California Mastitis Test (CMT) and somatic cell counts (SCC) were recorded every 12 hours at milking. Bacteriologic cultures of foremilk quarter samples and feces were obtained daily, as were complete blood counts. ELISA titers for IgG and IgM recognizing S. dublin lipopolysaccharide (LPS) were obtained weekly on serum and quarter milk samples. All cows excreted S. dublin intermittently from infected quarters, but no changes were detected in rectal temperature, appearance of the mammary gland or secretions, CBC, milk yield, and pulse and respiratory rates. Somatic cell counts were modestly increased in infected quarters as compared with uninfected quarters (P = .015, paired t test); however, CMT scores after infection remained low, and were not significantly different from pre-infection scores (P greater than .10, sign test). After infection, administration of dexamethasone resulted in signs of clinical mastitis and increased excretion of S. dublin from mammary quarters (P = .0004, paired t test). One cow had necrotizing mastitis and S. dublin septicemia and was euthanatized. In the four surviving cows, clinical improvement was observed after systemic gentamicin therapy and intramammary infusion with polymyxin B, but all cows continued to excrete S. dublin intermittently from one or more quarters and occasionally from feces for the remaining period of observation. All infected cows demonstrated a rise in IgG and IgM ELISA titers recognizing S. dublin LPS in serum and milk. At necropsy (13-25 weeks postinfection), S. dublin was recovered only from the mammary tissue or supramammary lymph nodes in three of four cows. In one cow, mammary gland and lymph-node samples were negative for S. dublin despite positive milk cultures. In all cows, histopathologic examination revealed multifocal areas of chronic active mastitis. These lesions were similar to histopathologic findings from mammary gland carriers with naturally acquired S. dublin infection.

A preliminary study of the pathogenesis of foot-and-mouth disease virus using in situ hybridization.

Five adult guinea pigs were inoculated intraepithelially in the right hindfoot pad with foot-and-mouth disease virus. Animals were euthanatized with carbon dioxide at 4, 10, 24, 48, and 72 hours post-inoculation. Generalized disease developed in the guinea pigs, as evidenced by depression and inappetance by 24 hours post-inoculation and by the formation of vesicles in the noninoculated hindfoot pad by 48 hours post-inoculation. By in situ hybridization, using a 500 base pair biotinylated RNA probe, viral nucleic acid was detected in the noninoculated fore- and hindfoot pads as early as 10 hours post-inoculation, well before any pathologic changes associated with foot-and-mouth disease virus infection were detected. These tissues remained consistently positive for the presence of viral nucleic acid up to the end of the experiment. At this time, in the forefoot pad, even though virus had first been detected with certainty in that tissue 62 hours previously, there was still no microscopic evidence of foot-and-mouth disease virus-induced damage in the histologic section. Similarly, tongue tissue was positive by in situ hybridization at 4, 48, and 72 hours post-inoculation, yet there was never any microscopic evidence of degeneration or vesicle formation. From this preliminary study, it appears that, in the guinea pig, the virus is widely disseminated to foot pads and tongue, with epidermal lesions resulting only in selected areas.

A comparison of three techniques for closure of pelvic flexure enterotomies in normal equine colon.

Six enterotomies 3 cm long, spaced at 3 cm intervals, were made in the antimesenteric border of the pelvic flexure of the ascending colon in five adult horses. Ten incisions each were sutured with a Utrecht pattern (single layer), a full-thickness simple continuous oversewn with a Cushing pattern (two layer), and a mucosal simple continuous with a seromuscular simple continuous oversewn with a Cushing pattern (three layer). In all horses, chromic gut and polyglactin 910 were each used once for each pattern. On day 6, the pelvic flexure was excised and the colonic vessels were injected with a radio-opaque mass. Sections of each enterotomy were studied by light microscopy and high detail radiography. The single-layer closure led to serosa-to-mucosa healing and a thin bowel wall, and the three-layer closure resulted in distortion of the bowel wall by hematoma formation and submucosal contamination with ingesta. The two-layer closure resulted in good alignment and improved healing. There was less inflammatory reaction with polyglactin 910 than with chromic gut.

An immunohistochemical study of the pneumonia caused by peste des petits ruminants virus.

Ten goats were inoculated with peste des petits ruminants virus, a paramyxovirus closely related to rinderpest virus. All goats developed severe clinical disease, 8/10 having coughing or dyspnea as prominent clinical signs. In addition, all of the goats had stomatitis and diarrhea. Histopathologic and immunohistochemical studies were done only on the respiratory tracts. Pathologic changes ranged from mild multifocal bronchiolitis and bronchitis to severe bronchointerstitial pneumonia. Lesions were more severe in anteroventral than caudal lobes. The histologic nature of the viral process in the goat lungs had many features in common with the processes of pneumonia in dogs, due to canine distemper, or pneumonia in human beings, due to measles virus. Immunohistochemical staining of formalin-fixed, paraffin-embedded respiratory tract tissue was performed using an indirect system with rabbit anti-rinderpest virus serum, biotinylated anti-rabbit antibody, streptavidin-alkaline phosphatase, and nitroblue tetrazolium chromogen. Staining was sensitive, highlighting the presence of viral antigen in both lung and trachea of all goats. Viral antigen was found in both cytoplasm and nucleus of tracheal, bronchial, and bronchiolar epithelial cells, type II pneumocytes, syncytial cells, and alveolar macrophages. In general, the amount of staining correlated directly with the severity of the inflammatory process.

Vascular injury associated with naturally occurring strangulating obstructions of the equine large colon.

Ten horses were euthanatized before, during, or after surgery to correct severe volvulus of the large colon. At surgery, the colonic serosa changed from blue-gray, blue or purple toward a more normal pink in seven horses after the volvulus was corrected. The mucosa consistently remained black or dark red. Results of postmortem colonic microangiography revealed perfusion of the serosa and the circular and longitudinal muscle layers, but mucosal perfusion was limited by thrombosis in the muscularis mucosae and submucosa. There was evidence of thrombosis of the mesenteric colic vessels in six horses. Damage to the colonic vascular system, especially thromboembolism in the submucosa, may be an important limitation to colonic viability after surgical correction of volvulus of the large colon.

Fetal membranes and ancillary structures of llamas (Lama glama).

The placenta of llamas is epitheliochorial, with patchy areas of dense folded papillation serving as the placentome. The amnion of the full-term placenta is closely adhered to either the allantois or the chorion and remains with these structures at the time of parturition. Llamas and alpacas, like dromedaries, have an extra fetal membrane that is derived from the epidermis of the fetus. In association with the watery amniotic fluid of llamas, the epidermal membrane is slippery, facilitating delivery of the fetus.

Microvascular circulation of the ascending colon in horses.

Microvascular circulation of the ascending colon in healthy horses was studied using microangiography, light microscopy, and scanning electron microscopy. The pelvic flexure with 30 cm of ventral and dorsal colon attached was removed from 14 adult horses immediately after horses were euthanatized. The lumen was flushed with warm water, and this section of the ascending colon was placed in a 37-C bath of isotonic NaCl. In sections from 8 horses, colic vessels were perfused with a radio-opaque medium for microangiography. After angiographic evaluation, tissue sections were prepared for light microscopic observation, using standard histologic methods. In sections from 6 horses, injection replicas were made by perfusing the vessels with 2 types of plastics. The results of microangiography, light microscopy, and scanning electron microscopy of vascular replicas were correlated, providing a comprehensive documentation of the microvasculature of the ascending colon at the pelvic flexure. Arteries branched from mesenteric colic vessels approximately every 2 cm toward the colonic tissue. Immediately after branching, arterial vessels formed an anastomotic plexus, the colonic rete. However, each branch from the colic vessel eventually continued into the colonic tissue. A second set of vessels originated from the colonic tissue. A second set of vessels originated from the colonic rete and supplied the mesenteric lymph nodes. Arterial vessels penetrated the tunica muscularis into the submucosa 3 to 4 cm toward the antimesenteric border forming a submucosal vascular network. From the submucosal arterioles, branching took place at right angles to supply the mucosal capillaries. Capillaries surrounded the colonic glands and anastomosed at the luminal surface, forming a superficial luminal honeycomb-appearing vascular plexus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal health research in the Small Ruminant Collaborative Research Support Program.

Disease is a major constraint in small ruminant production systems in lesser-developed countries throughout the world. Animal health projects have been an integral part of the Small Ruminant Collaborative Research Support Program (SR-CRSP) from its inception. At the onset, these projects were oriented toward herd health care and veterinary extension activities. Later, all the projects developed a sharper focus in that they were directed to more basic studies of infectious disease. Diseases currently being investigated include caseous lymphadenitis, contagious caprine pleuropneumonia, caprine arthritis-encephalitis, ovine pulmonary carcinoma, ovine progressive pneumonia and neonatal mortality of alpaca. Continued, sharply focused studies are projected for the future to take advantage of recombinant technology in the development of multivalent vaccines.

Strangulating volvulus of the ascending colon in horses.

Of 57 horses with strangulating volvulus of the ascending colon, 42 were mares (including 21 postparturient mares), 8 were stallions, and 7 were geldings. Volvulus occurred most frequently in the summer (n = 24) and spring (n = 17). Pain was evaluated as severe in 41 horses, moderate in 9, and mild in 4. The abdominal fluid from 30 horses varied from clear yellow in 19 horses, to cloudy yellow in 3 horses, and serosanguineous in 8 horses. Protein content and nucleated cell count in the abdominal fluid were 2.5 +/- 1 g/dl and 1,000 +/- 900 microliters, respectively. Fifty horses had greater than or equal to 360 degrees volvulus and 7 had a 270 degrees volvulus, with 49 occurring in a counterclockwise direction. The site of volvulus in all horses was at the mesenteric attachment of the colon, except for a 360 degrees volvulus at the sternal and diaphragmatic flexures in 1 horse. Survival rates for horses with a greater than or equal to 360 degrees and a 270 degrees volvulus were 36% and 71%, respectively. The difference in survival rates reflected the severe vascular occlusion in the colon of horses with greater than or equal to 360 degrees volvulus. In nonsurvivors, hemorrhage in the submucosa and lamina propria (P less than 0.005) and edema in the submucosa (P less than 0.01) were greater than those in survivors. In nonsurvivors, greater than 97% of the superficial epithelium was lost. In horses that survived, only 60% of the cells were lost or degenerated.(ABSTRACT TRUNCATED AT 250 WORDS)