Histological assessment of ß-amyloid precursor protein immunolabelled rectal biopsies aids diagnosis of equine grass sickness.

BACKGROUND: An accurate, minimally invasive, ante-mortem diagnostic test for equine grass sickness (EGS) is currently lacking. Although histological examination of haematoxylin and eosin-stained rectal biopsies for chromatolytic neurons is insensitive as a diagnostic test for EGS, we hypothesised that its diagnostic accuracy could be improved by immunolabelling for ß-amyloid precursor protein (ß-APP), which has increased expression in cranial cervical ganglia (CCG) neuronal perikarya in EGS. OBJECTIVES: To develop a grading scheme for assessing the distribution and intensity of ß-APP immunoreactivity within individual rectal submucosal neurons and subsequently to determine the value of the distribution of different grades of neurons in EGS diagnosis. STUDY DESIGN: Retrospective case-control diagnostic accuracy study. METHODS: Initially, a standardised grading scheme was developed and ß-APP immunoreactivity in individual neuronal perikarya and axons was compared in sections of CCG and ileum from EGS and control horses. The grading scheme was then refined before being blindly applied to submucosal neurons in rectal biopsies derived from 21 EGS and 23 control horses. RESULTS: ß-APP immunoreactivity was increased in neuronal perikarya and axons in sections of CCG, ileum and rectum from EGS horses compared with controls. For rectal biopsies, a mean immunoreactivity grade exceeding 1.1 was 100% specific and sensitive for EGS, and the presence of at least one neuron with diffuse labelling of the entire cytoplasm (grade 3) was 95% sensitive and 100% specific for EGS. MAIN LIMITATIONS: Although the diagnostic criteria facilitated the discrimination of the EGS and control biopsies evaluated in this study, further prospective validation using a larger sample set is required. CONCLUSIONS: Histological assessment of ß-APP immunolabelled rectal biopsies is more sensitive than conventional histological examination in EGS diagnosis. Further validation is required before this technique can be advocated for use in clinical decision making.

Idiopathic Fibrosis of the Tunica Muscularis of the Large Intestine in Five Horses with Colic.

Histological evidence of fibrosis affecting the outer layer of the large intestinal tunica muscularis was identified in five of 32 horses affected by colic. In three cases, foci of pale eosinophilia and vacuolation of myocytes were observed. These findings are suggestive of a degenerative and fibrotic abnormality in the outer layer of the tunica muscularis of the large intestinal smooth muscle of some horses with colic.

A database survey of equine tumours in the United Kingdom.

REASONS FOR PERFORMING STUDY: Survey data on equine tumours are sparse compared with other species and may have changed over time. OBJECTIVES: To describe the most frequently diagnosed equine tumours recorded by a diagnostic pathology laboratory over 29 years, to identify background factors associated with tumour type, and to identify any changes in the tumours diagnosed or the background of cases submitted during the study period. STUDY DESIGN: Observational; cross-sectional analysis of records of a diagnostic pathology laboratory. METHODS: The records of all neoplastic equine histology submissions to the University of Bristol (January 1982-December 2010) were accessed from a database, and a list of diagnoses compiled. The 6 most commonly diagnosed tumour types were analysed using logistic regression to identify background factors associated with tumour type. The overall population of equine tumour submissions and the relative frequency of diagnosis of the most common tumour types were compared between decades. RESULTS: There were 964 cases included. The most frequently diagnosed tumours were: sarcoid (24% cases), squamous cell carcinoma (SCC) (19%), lymphoma (14%), melanoma (6%), gonadal stromal tumour (6%) and mast cell tumour (MCT) (4%). With sarcoid, Thoroughbred/Thoroughbred cross and gelding as reference categories: increasing age was significantly associated with the odds of each of the other tumour types, mares were at reduced risk of SCC, Arab/Arab cross had a higher risk of MCT, Cob/Cob cross had an increased risk of SCC and MCT, and ponies had an increased risk of melanoma. The mean age of submissions increased in each successive decade and the breed composition became broader. Sarcoids and lymphoma formed a smaller proportion of diagnoses in later decades. CONCLUSIONS: The types of tumours submitted to this laboratory have changed over the last 3 decades. Current data inform clinicians and researchers and further studies are warranted to follow trends.

Gross, computed tomographic and histological findings in mandibular cheek teeth extracted from horses with clinical signs of pulpitis due to apical infection.

REASONS FOR PERFORMING STUDY: The most prevalent type of equine dental pulpitis due to apical infection is not associated with coronal fractures or periodontal disease. The pathogenesis of this type of pulpitis is not fully understood. Computed tomography (CT) is increasingly used to investigate equine dental disorders. However, gross, tomographic and histopathological changes in equine dental pulpitis have not been compared previously. OBJECTIVES: To compare gross, CT and histological appearances of sectioned mandibular cheek teeth extracted from horses with clinical signs of pulpitis without coronal fractures or periodontal disease. To contribute to understanding the pathogenesis of equine dental pulpitis. STUDY DESIGN: Descriptive study using diseased and healthy teeth. METHODS: Mandibular cheek teeth extracted from horses with clinical signs of pulpitis (cases), and from cadavers with no history of dental disease (controls), were compared using CT in the transverse plane at 1 mm intervals. Teeth were then sectioned transversely, photographed and processed for histopathological examination. Tomographs were compared with corresponding gross and histological sections. RESULTS: Cement, dentine and bone had similar ranges of attenuation (550-2000 Hounsfield Units, HU) in tomographs but could be differentiated from pulp (-400 to 500 HU) and enamel (> 2500 HU). Twelve discrete dental lesions were identified grossly, 10 of which were characterised histologically. Reactive and reparative dentinogenesis and extensive pulpar mineralisation, previously undescribed, were identified. Pulpar oedema, neutrophilic inflammation, cement and enamel defects, and reactive cemental deposition were also observed. The CT and pathological findings corresponded well where there was mineralised tissue deposited, defects in mineralised tissue, or food material in the pulpar area. Pulpar and dentinal necrosis and cement destruction, evident grossly and histologically, did not correspond to CT changes. CONCLUSIONS: Computed tomography is useful for identifying deposition and defects of mineralised material but less useful for identifying inflammation and tissue destruction. The equine dentine-pulp complex responds to insult with reactive and reparative changes.

Early lesions following aerosol challenge of rhesus macaques (Macaca mulatta) with Mycobacterium tuberculosis (Erdman strain).

Three rhesus macaques (Macaca mulatta) were challenged with Mycobacterium tuberculosis (Mtb), Erdman strain, as part of studies to investigate lesion development at early time points in tuberculosis (TB) and to assess computed tomography (CT) as a method of monitoring disease progression in vivo. Animals were challenged with either a high, mid or low dose of aerosolized Mtb. The low-dose animal was killed humanely at 24 days post challenge (dpc) and the remaining animals at 25 dpc. Abnormalities in clinical parameters were observed in all animals, but clinical signs relating to respiratory disease were not seen. Pulmonary changes consistent with TB infection were detected by CT at 21 dpc and magnetic resonance imaging (MRI) post mortem. Pulmonary nodule counts obtained from both imaging techniques were directly proportional to the challenge dose and correlated with gross and microscopical lesion counts. On gross and microscopical examination, lesions of similar size and morphology were observed in the lungs of all three animals, with the majority containing necrotic foci. Concomitant gross and microscopical, granulomatous lesions were observed in the tracheobronchial lymph nodes of all animals together with evidence of systemic spread. These findings further contribute to our understanding and knowledge of early lesion formation in the lungs of non-human primates.

Early lesions following aerosol infection of rhesus macaques (Macaca mulatta) with Mycobacterium tuberculosis strain H37RV.

As part of a study to investigate early changes following exposure to aerosols of Mycobacterium tuberculosis (Mtb), 10 rhesus macaques (Macaca mulatta) were infected with high (731 colony forming units [cfu]), medium (70 cfu) or low (7 cfu) doses of Mtb, and tissues were examined at 2 and 3 weeks post infection (wpi). Clinical disease was not observed. Results of advanced imaging and pathological findings were compared with respect to the delivered dose and time post infection. Magnetic resonance imaging revealed lesions in the lungs at these early time points ex vivo immediately prior to detailed post-mortem examination in the absence of clinical disease. In animals exposed to high and medium doses of Mtb that were studied at 2 and 3 wpi, a range of lesions including small foci of mainly mononuclear cells, primarily macrophages (granulomatous lesions), as well as obvious granulomas, were observed microscopically in the lungs, including lymphatics and hilar lymph nodes. In the low-dose group at 3 weeks, small lesions were identified in the lung and hilar lymph nodes of one animal, and the remaining two animals in this group had lesions in either lung or hilar lymph node. Acid fast bacilli were demonstrated in the lung and lymph nodes in all animals that received high and medium doses, and the lymph nodes of two animals at the low dose. A dose-dependent effect was observed with increasing dose and time post infection. Furthermore, early dissemination of bacilli to the draining, hilar lymph nodes with concomitant granulomatous lesion formation was observed. By contributing to the recognition of early lesion development due to aerosol challenge of Mtb in the rhesus macaque, this study forms a basis for further investigation of early lesions and may inform the design of future vaccine and therapeutic studies involving early time points in this species.

The clinical and pathological features of gastric impaction in twelve horses.

REASONS FOR PERFORMING STUDY: Gastric impaction in the horse is poorly described in the veterinary literature. OBJECTIVES: To review the clinical and pathological features of gastric impaction. METHODS: The clinical details of horses presenting with colic over a 7-year period and cases in which gastric impaction was considered to determine the outcome were reviewed. Clinical and clinicopathological data were recorded. RESULTS: Twelve cases of gastric impaction were recorded (1.4% of 857 horses hospitalised for colic). Diagnosis was achieved by ultrasonographic examination, gastroscopy, exploratory celiotomy and/or post mortem examination. Five out of 12 horses were successfully treated, 5/12 were subjected to euthanasia (3 at celiotomy and 2 due to recurrence of impaction) and 2/12 died. Three out of 12 horses had spontaneous gastric rupture despite attempted treatment (one was subjected to euthanasia at celiotomy and 2 died). Post mortem examination (7 horses) revealed gross muscular thickening of the stomach wall in 6/7 horses. Histological examination revealed focal fibrosis of the stomach wall in 4/6 and focal myositis in 1/6 horses. CONCLUSIONS AND PRACTICAL SIGNIFICANCE: Gastric impaction is a rare cause of colic and affected horses can present with acute, chronic or recurrent colic in the presence or absence of other gastrointestinal disease. Spontaneous gastric rupture may occur. A proportion of affected horses have gross thickening of the muscular layers of the stomach wall.

Multiple small intestinal pseudodiverticula associated with lymphoma in three horses.

Three mature horses presented with progressive weight loss, inappetence, ventral abdominal oedema and lethargy. Two of the animals had intermittent signs of low grade abdominal pain. At presentation, all 3 had hypoalbuminaemia; 2 had hyperfibrinogenaemia and the other had neutrophilia. An oral glucose tolerance test was performed in 2 cases, both of which demonstrated impaired glucose absorption. One pony treated with corticosteroids failed to improve and developed peritonitis and was subjected to euthanasia after 2 weeks. One pony had small intestinal biopsies obtained via a standing flank laparotomy, which revealed a mainly mononuclear cell infiltrate of the mucosa. It failed to respond to treatment with antibiotics and corticosteroids and, after 2 months, developed sternal oedema in addition to the ventral abdominal oedema and peritonitis and was subjected to euthanasia. The remaining pony deteriorated despite symptomatic therapy and was subjected to euthanasia after one week. At post mortem examination, all 3 animals had multifocal lesions of small intestinal wall thickening, mucosal ulceration, pseudodiverticula and enlarged mesenteric lymph nodes. One pony also had a multinodular mass at the root of the mesentery, a mediastinal mass and a lung mass. Histological examination confirmed the presence of lymphoma of the intestinal wall at post mortem examination in each case and immunohistochemistry (including retrospective evaluation of the intestinal biopsies obtained from the pony that underwent a flank laparotomy) indicated that the lymphomas were of T cell origin.

Liver lobe torsion in three adult rabbits.

This paper describes three cases of liver lobe torsion in rabbits presenting with anorexia, lethargy, jaundice and abdominal pain. This condition was associated with anaemia and elevation of alanine aminotransferase, aspartate aminotransferase and gamma-glutamyl transferase. Abnormal radiological findings included hepatomegaly, gas-filled intestinal loops consistent with gastrointestinal ileus and ascites. Ultrasonographic findings included heterogeneous liver parenchyma, free abdominal fluid and reduced bowel motility. Diagnosis was confirmed by histopathological examination of the liver in all three cases.

Influence of colostrum deprivation and concurrent Cryptosporidium parvum infection on the colonization and persistence of Escherichia coli O157 : H7 in young lambs.

Escherichia coli O157 : H7 and Cryptosporidium parvum infections of man have been associated with direct contact with small ruminants. Colostrum protects neonates against gastrointestinal pathogens, and orphan lambs, which are common on petting farms, may be deprived of this protection. In a recent study, it was demonstrated that high shedding of E. coli O157 : H7 by an 8-week-old goat kid was associated with coincidental C. parvum infection. Furthermore, both pathogens were co-located in the distal gastrointestinal tract. It was hypothesized that colostrum deprivation and pre-infection with C. parvum predisposed young ruminants to colonization and increased shedding of E. coli O157 : H7. To test this, 21 lambs 5 weeks of age were divided into four groups as follows: (A) colostrum-deprived and inoculated with E. coli O157 : H7, (B) colostrum-deprived and inoculated with C. parvum and then E. coli O157 : H7, (C) conventionally reared and inoculated with E. coli O157 : H7, (D) conventionally reared and inoculated with C. parvum and then E. coli O157 : H7. C. parvum was detected between 8 and 12 days post-inoculation in most of the infected lambs. At 24 h post-inoculation with E. coli O157 : H7, all lambs were shedding between 5 x 10(4) and 5 x 10(7) c.f.u. E. coli O157 : H7 per gram of faeces. E. coli O157 : H7 was shed in higher numbers in the groups pre-inoculated with C. parvum, whether conventionally reared or colostrum-deprived. Interestingly, for the colostrum-deprived lambs on day 3, a significant difference in shedding of E. coli O157 : H7 was observed (P = 0.038), with the lambs inoculated with E. coli alone yielding higher counts than those pre-inoculated with C. parvum. From day 15 onwards, shedding of E. coli O157 : H7 was highest from the colostrum-deprived C. parvum-infected lambs, then (in descending order of shedding) the colostrum-deprived lambs, the conventionally reared lambs infected with C. parvum, and the conventionally reared animals. In total, four animals were euthanized, two at 24 h and two at 96 h post inoculation with E. coli O157 : H7 (two conventionally reared and two colostrum-deprived). All animals euthanized were from groups pre-inoculated with C. parvum prior to challenge with E. coli O157 : H7. On examination of tissues, in three of the four animals examined, multifocal attaching and effacing lesions were observed in the caecum, colon, rectum and at the recto-anal junction, and were confirmed by immunohistochemistry to be associated with E. coli O157 : H7.

Bacterial cholangitis/cholangiohepatitis with or without concurrent cholecystitis in four dogs.

OBJECTIVES: To evaluate the clinical, clinical pathology, diagnostic imaging, microbiological and pathological features of cholangitis/cholangiohepatitis in the dog. METHODS: The study design was a retrospective review of cases of bacterial cholangitis/cholangiohepatitis presented to the University of Bristol during the period 1995 to 2000. The diagnosis was made based on hepatic histopathological findings and positive bile culture results. RESULTS: Four dogs met the inclusion criteria. Common presenting signs included anorexia (n=4), jaundice (n=4), vomiting (n=4) and pyrexia (n=2). All four dogs had a leucocytosis or neutrophilia reported at some time in their history along with serum bilirubin elevation. In addition, serum alkaline phosphatase and alanine transaminase activity was increased in all of the dogs in which it was measured both before and at the time of referral. In general, the diagnostic imaging findings were non-specific. Organisms cultured from bile aspirates were Escherichia coli (n=3), Clostridium species (n=2) and a faecal Streptococcus species (n=1). Two cases resolved with medical treatment alone; two with concurrent cholecystitis required cholecystectomy. Following surgery, both of these cases showed a resolution of clinical signs. CLINICAL SIGNIFICANCE: This report highlights the fact that bacterial cholangitis/cholangiohepatitis with or without concurrent cholecystitis should be considered as a potential differential in dogs presenting with signs referable to biliary tract disease.

Demonstration of Ollulanus tricuspis in the stomach of domestic cats by biopsy.

Ollulanus tricuspis is a small nematode of the family Ollulanidae, found in the stomach of domestic cats and other felids. Of 131 gastric biopsy samples collected at endoscopic examination, four were shown to contain the parasite. Vomiting was the main presenting sign in three cats and weight loss in the fourth. The stomachs were grossly normal on endoscopic examination. Chronic gastritis was observed histologically in two cases, while the remaining cases were microscopically normal. The significance of the parasite remained undetermined. To our knowledge, this is the first report of O. tricuspis infection in domestic cats in which the diagnosis was made by examining routine endoscopic biopsy samples.

Colonization of 8-week-old conventionally reared goats by Escherichia coli O157 : H7 after oral inoculation.

Enterohaemorrhagic Escherichia coli O157 : H7 infections of man have been associated with consumption of unpasteurized goat's milk and direct contact with kid goats on petting farms, yet little is known about colonization of goats with this organism. To assess the contribution of flagella and intimin of E. coli O157 : H7 in colonization of the goat, 8-week-old conventionally reared goats were inoculated orally in separate experiments with 1x10(10) c.f.u. of a non-verotoxigenic strain of E. coli O157 : H7 (strain NCTC 12900 Nal(r)), an aflagellate derivative (DMB1) and an intimin-deficient derivative (DMB2). At 24 h after inoculation, the three E. coli O157 : H7 strains were shed at approximately 5x10(4) c.f.u. (g faeces)(-1) from all animals. Significantly fewer intimin-deficient bacteria were shed only on days 2 (P = 0.003) and 4 (P = 0.014), whereas from day 7 to 29 there were no differences. Tissues from three animals inoculated with wild-type E. coli O157 : H7 strain NCTC 12900 Nal(r) were sampled at 24, 48 and 96 h after inoculation and the organism was cultured from the large intestine of all three animals and from the duodenum and ileum of the animal examined at 96 h. Tissues were examined histologically but attaching-effacing (AE) lesions were not observed at any intestinal site of the animals examined at 24 or 48 h. However, the animal examined at 96 h, which had uniquely shed approximately 1x10(7) E. coli O157 : H7 (g faeces)(-1) for the preceding 3 days, showed a heavy, diffuse infection with cryptosporidia and abundant, multifocal AE lesions in the distal colon, rectum and at the recto-anal junction. These AE lesions were confirmed by immunohistochemistry to be associated with E. coli O157 : H7.

Attaching-effacing lesions associated with Escherichia coli O157:H7 and other bacteria in experimentally infected conventional neonatal goats.

Four conventionally reared goats aged 6 days were inoculated orally with approximately 10(10) colony-forming units (cfu) of a non-verotoxigenic strain of Escherichia coli O157:H7. All remained clinically normal. Tissues were sampled under terminal anaesthesia at 24 (two animals), 48 and 72 h post-inoculation (hpi). E. coli O157:H7 was cultured from the ileum, caecum, colon and rectum of all animals, but the number of bacteria recovered at these sites varied between animals. Attaching-effacing (AE) lesions associated with O157 organisms, as confirmed by immunolabelling, were observed in the ileum of one of the two animals examined at 24 hpi, and in the ileum, caecum and proximal colon of an animal examined at 72 hpi. E. coli O157 organisms were detected at > or =10(5) cfu/g of tissue at these sites. In addition, AE lesions associated with unidentified bacteria were observed at various sites in the large bowel of the same animals. Lesions containing both E. coli O157 and unidentified bacteria (non-O157) were not observed. Non-O157 AE lesions were also observed in the large bowel of one of two uninoculated control animals. This indicated that three (one control and two inoculated) animals were colonized with an unidentified AE organism before the commencement of the experiment. The O157-associated AE lesions were observed only in animals colonized by non-O157 AE organisms and this raises questions about individual host susceptibility to AE lesions and whether non-O157 AE organisms influence colonization by E. coli O157.

Attaching-effacing bacteria in animals.

Enteric bacteria with a demonstrable or potential ability to form attaching-effacing lesions, so-called attaching-effacing (AE) bacteria, have been found in the intestinal tracts of a wide variety of warm-blooded animal species, including man. In some host species, for example cattle, pigs, rabbits and human beings, attaching-effacing Escherichia coli (AEEC) have an established role as enteropathogens. In other host species, AE bacteria are of less certain significance. With continuing advances in the detection and typing of AE strains, the importance of these bacteria for many hosts is likely to become clearer. The pathogenic effects of AE bacteria result from adhesion to the intestinal mucosa by a variety of mechanisms, culminating in the formation of the characteristic intimate adhesion of the AE lesion. The ability to induce AE lesions is mediated by the co-ordinated expression of some 40 bacterial genes organized within a so-called pathogenicity island, known as the "Locus for Enterocyte Effacement". It is also believed that the production of bacterial toxins, principally Vero toxins, is a significant virulence factor for some AEEC strains. Recent areas of research into AE bacteria include: the use of Citrobacter rodentium to model human AEEC disease; quorum-sensing mechanisms used by AEEC to modulate virulence gene expression; and the potential role of adhesion in the persistent colonization of the intestine by AE bacteria. This review of AE bacteria covers their molecular biology, their occurrence in various animal species, and the diagnosis, pathology and clinical aspects of animal diseases with which they are associated. Reference is made to human pathogens where appropriate. The focus is mainly on natural colonization and disease, but complementary experimental data are also included.

Naturally acquired attaching and effacing Escherichia coli in sheep.

In a series of experiments involving the inoculation of sheep with Escherichia coli O157:H7, and subsequent detailed histopathological examination of the intestinal mucosa, attaching-effacing (AE) lesions formed by elements of the natural flora were observed in 18% of animals. These incidental AE lesions typically were small and sparse, and were not associated with clinical disease. It was possible to identify further some of the lesional bacteria, revealing that E. coli O115 had formed lesions in one of the seven affected animals, and similarly E. coli O26 had formed some of the lesions in another. As AE strains, source flocks, housing and feed sources were diverse, a common source of lesion-forming bacteria appears to be unlikely. It is postulated that subclinical AE lesions are a mechanism of persistence of AE bacteria in sheep.