Expression of Platelet-derived Growth Factor-b Receptor and Bovine Papillomavirus E5 and E7 Oncoproteins in Equine Sarcoid. (J. Comp. Path. 2008, Vol. 139, 231e237). A subset of equine sarcoids harbor BPV (Bovine Papilloma Virus) DNA expresses the viral oncoproteins E5 and E7 together with the PDGF-bR.  The oncoproteins expressed by BPV lead to PDGF-bR activation and downstream signaling leading to cellular transformation.

Lymphoproliferative Disease with Features of Lymphoma in the Central Nervous System of a Horse: This report describes an unusual form of lymphoproliferative disease with features of lymphoma restricted to the CNS and with no evidence of a primary lesion elsewhere. IHC examination defined an overwhelming predominance of T lymphocytes with admixed B lymphocytes and activated macrophages. Other DDx considered, were non-suppurative encephalitis, granulomatous meningoencephalitis, neoplastic reticulosis, and lymphomatoid granulomatosis

Quantitative and Qualitative Evaluation of Dermal Elastin of Draught Horses with Chronic Progressive Lymphoedema

J. Comp. Path. 2009, Vol. 140, 132e139 Chronic progressive lymphoedema in horses, a disease of certain draught breeds, is associated with altered elastin metabolism. In all horses the mean elastin concentrations were highest in the superficial dermis, gradually decreasing in the mid-dermis and deep dermis. As compared with horses of a non-susceptible breed, affected horses had increased amounts of dermal elastin in both the distal limb and neck, while nonaffected horses of a susceptible breed had decreased amounts.

Clinical, pathological and immunohistochemical features of a pulmonary blastoma in a horse

the VETERINARY RECORD | February 7, 2009 Pulmonary blastoma is a very rare primary malignant lung tumour affecting human beings, with a mixture of poorly differentiated epithelial and mesenchymal components. Microscopically, all pulmonary tumour masses were solid, non-encapsulated and infiltrative throughout the alveolar septa, causing progressive occlusion of alveoli. These tumour masses were composed of spindle-shaped to pleomorphic mesenchymal neoplastic cells resembling active fibroblasts or blast-like cells, surrounded by an abundant fibrous or myxomatous,mineralised foci. The epithelial component was composed of small nests, linear arrays and irregular tubules lined with cubical, columnar or pleomorphic non-ciliated epithelial cells. Mesenchymal tumour cells showed strong cytoplasmic immunolabelling for vimentin and they were negative for keratins and S-100 protein. Approximately 10 to 15 per cent of neoplastic mesenchymal cells showed weak to moderate cytoplasmic immunoreactivity to the á-smooth muscle actin. Epithelial tumour cells presented strong cytoplasmic immunoreactivity for keratins and were negative for vimentin, á-smooth muscle actin and S-100 protein.

Isolation of Campylobacter fetus subspecies fetus in a two-year-old Quarterhorse with chronic diarrhea of an undetermined etiology.  J Vet Diagn Invest 21:266–269 (2009). Molecular testing revealed the species as Campylobacter fetus subsp. fetus as a possible organism associated with large bowel diseasein this filly.

Equine colitis X associated with infection by Clostridium difficile NAP1/027.  J Vet Diagn Invest 21:377–380 (2009). At necropsy, cecal and colonic mucosae were congested throughout, and there was segmental edema and significant thickening of the intestinal wall. Excessive numbers of mononuclear cells were found in mucosal lamina propria. Submucosal hemorrhage was diffuse and extensive, and Clostridium difficile toxins A and B were detected. Large numbers of C. difficile were isolated, and genetic characterization revealed  them  to  be  North  American  pulsed-field  gel  electrophoresis  type  1,  polymerase  chain  reaction ribotype 027, and toxinotype III. Genes for the binary toxin were present, and toxin negative–regulator tcdC contained  an  18-bp  deletion.  This  genotype  comprises  the  current  human  ‘‘epidemic  strain”.  Clostridium  difficile  causes hemorrhagic,  necrotizing enterocolitis  with  high  mortality  in  foals.

An atypical equine gastrointestinal stromal tumor.  J Vet Diagn Invest 21:387–390 (2009). Histologic  examination demonstrated dense sheets, fascicles,palisades, and interconnecting streams of neoplastic spindle cells with lesser numbers of admixed multinucleated giant cells. Based on morphology alone, this neoplasm might have been  misdiagnosed  as  a  peripheral  nerve  sheath  tumor  because  many  of  the  morphologic  features  were suggestive  of  neural  differentiation.  Neoplastic  cells  expressed  cluster  of  differentiation (CD)117  (c-kit), vimentin,  desmin,  smooth  muscle  actin,  neuron-specific  enolase,  and  S-100  protein  and  did  not  express cytokeratin. Based predominantly on the immunohistochemical profile, especially the CD117 positivity, this neoplasm  was  diagnosed  as   a  gastrointestinal  stromal   tumor  with both  myogenic   and   neurogenic differentiation.

Survey of equine cutaneous neoplasia in the Pacific Northwest. J Vet Diagn Invest 18:123–126 (2006).  Sarcoids (51.4%), Squamous cell arcinoma (18.3%),Ocular squamous cell carcinoma was most common in paints and quarter horses, and penile/preputial squamous cell carcinoma was ost common in appaloosas and quarter horses. Findings suggest that equine sarcoid and squamous cell carcinoma occur more frequently in the Pacific northwest than in the northeastern United States.

Hypertrichosis in a horse with alimentary T-cell lymphoma and pituitary involvement. J Vet Diagn Invest 19:128–132 (2007).  Hyperhidrosis, and abnormal fat distribution in addition to severe diarrhea. A presumptive clinical diagnosis of protein-losing enteropathy and pituitary pars intermedia dysfunction was made. T-cell lymphoma was diagnosed in a rectal biopsy specimen. The pituitary gland was diffusely enlarged. Histologically, neoplastic lymphocytes infiltrated the gastrointestinal mucosa, mesenteric lymph nodes, and the pituitary gland. In addition, there was hyperplasia of the pituitary gland pars intermedia. Pituitary adenoma was not present. Hypertrichosis in this case could have been triggered by a combination of adenomatous hyperplasia of pars intermedia and lymphoma resulting in disruption of the hypothalamic dopaminergic tone or disruption of the hypothalamic thermoregulatory center.

Kernicterus in a neonatal foal. J Vet Diagn Invest 19:209–212 (2007).  Seizure activity and severe icterus. Degeneration and necrosis of cerebral neurons and cerebellar Purkinje cells; severe hepatocellular degeneration and necrosis; and deposition of amorphous golden-yellow material in the cerebellar granular cell layer, pulmonary alveoli, renal tubular epithelium, splenic trabecula, and the lamina propria of the small and large intestine. (bilirubin encephalopathy).

Infections caused by pathogenic free-living amebas (Balamuthia mandrillaris and Acanthamoeba sp.) in horses. J Vet Diagn Invest 19:317–322 (2007). Granulomatous amebic encephalitis caused by Balamuthia mandrillaris and Acanthamoeba culbertsoni and systemic infections caused by Acanthamoeba sp.  The systemic amebic infection was perhaps ‘‘opportunistic’’ considering the visceral involvement by this protozoan in association with Aspergillus sp. and/or Escherichia coli and Pseudomonas sp.

Comparative evaluation of Rose Bengal plate agglutination test, mallein test, and some conventional serological tests for diagnosis of equine glanders. J Vet Diagn Invest 19:362–367 (2007). Glanders is a bacterial disease primarily of equines caused by Burkholderia mallei and is communicable to man and other animal species.

Detection of Leptospira interrogans DNA and antigen in fixed equine eyes affected with end-stage equine recurrent uveitis. J Vet Diagn Invest 19:686–690 (2007) positive immunoreactivity (open arrows) with Leptospira antibody for antigens in the ciliary body of an horse affected with equine recurrent uveitis (ERU). All test samples and controls were negative for Leptospira DNA by realtime PCR analysis.

Lymphangiosarcoma in the nictitating membrane of a horse.  J Vet Diagn Invest 20:108–110 (2008). Immunohistochemically, the neoplastic cells stained positive for vimentin and partially positive for factor VIII–related antigen. Ultrastructural analysis revealed discontinuous endothelial lining vascular channels thatpartially lacked a basal membrane. Based on the histopathologic,  immunohistochemical, and ultrastructural features lymphangiosarcoma was diagnosed.

Fatal pulmonary hemorrhage associated with RTX toxin–producing Actinobacillus equuli subspecies haemolyticus infection in an adult horse.  J Vet Diagn Invest 20:118–121 (2008). severe pulmonary hemorrhage with suppurative bronchopneumonia was found. Actinobacillus equuli subsp. haemolyticus was cultured from a transtracheal wash performed antemortem as well as from the lungs at necropsy. The presence of airway associated hemorrhage in conjunction with bacterial bronchopneumonia suggested endothelial damage caused by a locally elaborated bacterial toxin, possibly produced by the A. equuli strain isolated from the lungs. The objective of this report was to indirectly document the presence of hemolysin repeat in structural toxin (RTX).

Small intestine adenocarcinoma in conjunction with multiple adenomas causing acute colic in a horse.  J Vet Diagn Invest 20:121–124 (2008). Exploratory laparotomy revealed a distal jejunum full-thickness wall induration and multiple small adherent intraluminal masses. Histologic examination revealed an adenocarcinoma and multiple polypoid adenomas. Colic was considered secondary to partial jejunal lumen obstruction by the adenocarcinoma. Adenocarcinoma recurrence or transformation from remaining adenomas into an adenocarcinoma is still a major risk.

Hemolytic-uremic syndrome in a postpartum mare concurrent with encephalopathy in the neonatal foal. J Vet Diagn Invest 20:239–242 (2008). Thrombotic microangiopathy (TMA) is characterized by thrombocytopenia, microangiopathic hemolysis, and organ ischemia resulting from platelet thrombosis within the arterial microvasculature and capillaries.4,8,13 The kidneys and brain are most prominently affected, and acute renal failure and/or neurologic signs are the predominant clinical manifestations. Hemolytic-uremic syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP) are the renal and neurologic forms, respectively, of TMA described in the human literature. Hemolytic-uremic syndrome occurs most commonly in children as a postdiarrheal complication of enteritis caused by Escherichia coli 0157 and other Shiga toxin-producing E. coli (STEC). Thrombotic microangiopathy involving glomeruli was evident on microscopic examination of the mare’s kidneys. Microscopic evidence of brain edema was the principal postmortem finding in the foal. Escherichia coli 0103:H2 was isolated from the mare’s uterus and the gastrointestinal tracts of both animals.

Lymphangiosarcoma in the nictitating membrane of a horse.  J Vet Diagn Invest 20:108–110 (2008). Histologically, the mass consisted of dilated, thin-walled vascular clefts and channels, lined by flattened to cuboidal endothelial cells with moderate cellular pleomorphism. Immunohistochemically, the neoplastic cells stained positive for vimentin and partially positive for factor VIII–related antigen. Ultrastructural analysis revealed discontinuous endothelial lining vascular channels that partially lacked a basal membrane.

Pathologic findings in equine muscle (excluding polysaccharide storage): a necropsy study.  J Vet Diagn Invest 20:572–579 (2008). Chronic myopathic change (excessive fiber size variation and internal nuclei) was evaluated in horses without polysaccharide storage myopathy and was the most common finding (36 animals; 15.7%). Chronic myopathic change was more common in older animals. Generalized muscle atrophy was present in 30 animals (13.1%). Myonecrosis was attributed to endotoxic injury (11 animals; 4.8%), bone fracture (8 animals; 3.5%), bacterial infection (5 animals; 2.2%), muscle rupture (3 animals; 1.3%), selenium deficiency (2 animals; 0.9%), and exertional rhabdomyolysis (1 horse; 0.4%); cause was not determined in 9 animals (3.9%). Intramyofiber protozoa were detected in 19 horses and ponies (8.3%). Denervation atrophy was detected in 14 animals (6.1%). Neoplasia involving muscle occurred in 3 animals (1.3%), injection site reactions were detected in 4 animals (1.7%), and focal lymphocytic infiltrates were found in 6 animals (2.6%). Other findings were ring fibers (2 horses; 0.9%), fiber splitting (2 horses; 0.9%), and fat infiltration (1 horse; 0.4%).

Bronchopneumonia associated with extraintestinal pathogenic Escherichia coli in a horse.  J Vet Diagn Invest 20:661–664 (2008). (ExPEC) strains carrying distinct virulence attributes are known to cause diseases in humans and animals and infect organs other than the gastrointestinal tract.  The strain of E. coli belonged to O2:H21 and carried virulence genes cnf1, sfa, foc, fimA, and papG allele I that are known to be associated with ExPEC strains. The strain was resistant to several antimicrobials including clindamycin, erythromycin, oxacillin, penicillin, and rifampin.

Fat embolism secondary to yellow fat disease in an Appaloosa horse.  J Vet Diagn Invest 20:684–687 (2008). multinodular, hemorrhagic foci in fat tissues with yellow-brown discoloration. The most affected areas were peritoneal fat and perirenal, epicardial, and subcutaneous adipose tissues. Other findings were hepatic lipidosis and multiple 1–1.5 cm hemorrhagic foci scattered in both lungs. Histopathological examination revealed severe degeneration and necrosis of adipose tissue with dystrophic calcification. The necrotic fat was infiltrated by abundant foamy macrophages and multinucleated giant cells. Based on these histopathological changes, yellow fat disease, also called nutritional panniculitis, was diagnosed. In addition, the microscopic examination of lung and kidney sections stained with osmium tetroxide and oil red O revealed numerous lipid droplets within glomerular and alveolar septal capillaries.

Isolation of Arcanobacterium hippocoleae from a case of placentitis and stillbirth in a mare.  J Vet Diagn Invest 20:688–691 (2008). necrosuppurative placentitis and stillbirth in an American Quarterhorse mare. Numerous colonies of irregular, Gram-positive, rod-shaped bacteria were observed by histological examination within fibrin lattice associated with placental lesions. Arcanobacterium hippocoleae was isolated.

Idiopathic arterial medial calcification of the thoracic arteries in an adult horse. J Vet Diagn Invest 20:692–697 (2008). Histologically, the tunica media of the aorta, coronary arteries, and pulmonary arteries were expanded by foci of elastin fiber calcification and extracellular matrix with lacunae formation. The vascular lesions are comparative to what has been described as medial arterial calcification, seen in humans suffering from chronic renal failure or diabetes mellitus.

Equid herpesvirus 2–associated oral and esophageal ulceration in a foal.  J Vet Diagn Invest 20:811–815 (2008). Oral mucosal pustules, and esophageal ulcers, nuclear inclusions suggestive of herpesviruses. Immunohistochemical staining with antibodies specific for EHV-2 was positive for epithelial cells in the vicinity of the ulcer but not in more distant mucosa. Electron microscopic evaluation of the biopsy showed herpesviral particles in epithelial cells. This foal likely had lesions associated with EHV-2 and not EHV-1, -4, or -5.

Fibropapilloma of the glans penis in a horse.  J Vet Diagn Invest 20:816–819 (2008). multiple, smooth, glistening, grayish-pink, variably sized, exophytic, nodular masses circumferentially surrounding the external urethral orifice.  Microscopically, the masses consisted of abundant amounts of loosely arranged fibrovascular stroma with low numbers of spindloid to stellate fibrocytes. The overlying epithelium was mildly to moderately hyperplastic with short anastomosing rete ridges (pseudoepitheliomatous hyperplasia). The lesion was diagnosed as fibropapilloma because of features similar to bovine penile fibropapilloma including anatomical location, gross appearance, and histological characteristics. A sarcoid was considered but negated as the lesion lacked the classical streaming and interlacing spindle cell population, ‘‘picket-fence’’ appearance at the epithelial interface, and long, thin, dissecting rete ridges typical of most equine sarcoids. Polymerase chain reaction for the Bovine papillomavirus-1 and Bovine papillomavirus-2 E5 gene and for Equine herpesvirus 1, 3, and 4 was negative on formalin-fixed tissue specimens.

Herpesvirus-associated neurological disease in a donkey.  J Vet Diagn Invest 20:820–823 (2008). Asinine herpesvirus in DNA extracted from deep pharyngeal swabs.  This sequence had complete identity with short sequences of asinine herpesvirus previously identified in donkeys with interstitial pneumonia. Amino acid analysis of the entire sequence indicated high similarity with Equid herpesvirus 7 Zebra herpesvirus 1 (90%), and Equid herpesvirus 2. subfamily Gammaherpesvirinae.

Abortion in a horse following Neorickettsia risticii infection.  J Vet Diagn Invest 20:827–830 (2008). Potomac horse fever was diagnosed based on polymerase chain reaction (PCR) analysis of whole blood and a high antibody titer to Neorickettsia risticii. The mare made a rapid clinical recovery following antibiotic therapy, but aborted 98 days later. Necropsy on the aborted fetus revealed lymphohistiocytic colitis, lymphadenitis, myocarditis, and hepatitis. The placentawas grossly and histologically normal.

Morphometric Analysis of the Retina from Horses Infected with the Borna Disease Virus.  Vet Pathol 44:57–63 (2007).  BD was diagnosed by detection of pathognomonic Joest-Degen inclusion bodies (intranuclear) in the postmortem brains. Retinae with strongly altered histologic appearance as well as retinae with only minor changes.  BD in horses causes alterations of the retinal histology of a variable degree. A loss of photoreceptors may explain the observed blindness in infected horses.

Mesenchymal Hamartoma of the Liver in a Late-Term Equine Fetus.  Vet Pathol 44:100–102 (2007). normal hepatic parenchyma had been obliterated, replaced, and expanded by abnormal bile ducts surrounded by abundant, myxoid stroma.  Small portions of the liver had bridging septa of fibrosis and proliferations of small-caliber abnormal bile ducts, resembling another congenital biliary abnormality termed congenital hepatic fibrosis.

Verminous Encephalitis in a Horse Produced by Nematodes in the Family Protostrongylidae.  Vet Pathol 44:119–122 (2007). Parasitic granulomatous eosinophilic inflammation was associated with eggs, larvae, and adult nematodes in the cerebellum. Nematodes had histological characteristics of the superfamily Metastrongyloidea. The presence of dorsal-spined larvae in the CNS was further indicative of infection with a nematode in the family Protostrongylidae. Infections were most compatible with Parelaphostrongylus tenuis but specific diagnosis was not possible.

Colonic Ganglioneuromatosis in a Horse.  Vet Pathol 44:207–210 (2007).  fascicles of spindle-shaped cells consistent with Schwann cells, clusters of neurons, supporting enteric glial cells, and thick bands of perineurial collagen. Most of the nodules coincided with the location of the myenteric plexus and extended through the outer layer of the tunica muscularis to the serosal surface.   With Immunohistochemistry neurons were positive for neuron specific enolase (NSE) and S-100 and the Schwann cells and enteric glial cells were positive for S-100 and glial fibrillary acidic protein (GFAP).

Three Equine Cases of Mixed Hepatoblastoma with Teratoid Features.  Vet Pathol 44:211–214 (2007).  sheets and cords of fetal and embryonal epithelial cells that frequently formed sinusoid-like structures. Intermixed with the neoplastic epithelial cells were variable amounts of hemorrhage, necrosis, osteoid, and bone. Immunohistochemically, the epithelial cells stained variably positive for alpha- fetoprotein, frequently positive for vimentin, and occasionally positive for Cytokeratin

Pulmonary Aspergillosis and Ischemic Distal Limb Necrosis Associated with Enteric Salmonellosis in a Foal. Vet Pathol 44:215–217 (2007). Salmonella typhimurium-disseminated pyogranulomas with intralesional fungal hyphae. The morphologic characteristics of fungal hyphae were consistent with Aspergillus spp., and large numbers of A fumigatus were isolated. Thus, limb lesions are consistent with symmetrical peripheral gangrene, a potential complication of sepsis.

Confocal Laser Scanning Analysis of an Equine Oral Mast Cell Tumor with Atypical Expression of Tyrosine Kinase Receptor C-KIT. Cresyl violet-positive mast cells accompanied by numerous eosinophils. Strong, diffuse, intracytoplasmatic immunohistochemical signal for tryptase and a faint membrane-associated and perinuclear signal for tyrosine kinase receptor KIT. Confocal laser scanning microscopy confirmed an aberrant spatial colocalization of KIT in the Golgi apparatus, which may be the result of a defective protein processing within the tumor cells.

Equine Osteosarcoma: A Series of 8 Cases. Vet Pathol 44:247–249 (2007). mandible of young horses.. fibroblastic osteosarcoma with fewer osteoblastic type tumors.

Infection of Internal Umbilical Remnant in Foals by Clostridium sordellii. Vet Pathol 44:269–275 (2007). All foals had acute peritonitis, and the internal umbilical remnant was thickened by edema, hemorrhage, and fibrosis. A moderate amount of serosanguinous fluid with fibrin strands was present in the pericardial sac and pleural cavity. Histopathologically, the urachus and umbilical arterial walls were thickened by edema and exhibited hemorrhage, fibrin, and leukocytic infiltration. Gram-positive bacterial rods were observed in subepithelial areas of the urachus, the adventicia of umbilical arteries, and interstitium of the internal umbilical remnant. In foals, the most important causes of omphalitis are Escherichia coli and Streptococcus zooepidemicus.

Ovarian and Intestinal Angiomatosis in a Horse.  Vet Pathol 44:386–388 (2007). Raised nodules on the serosal surface of the small intestine and the right and left ovaries were composed of numerous, variably sized, redundant vascular profiles filled with red blood cells and fibrin thrombi. Based on the presence of multiple nodules composed of benign vascular channels scattered within the small intestine and ovary, a diagnosis of angiomatosis is proposed.

Multiple Masses in a Horse’s Tongue Resulting from an Atypical Perineurial Cell Proliferative Disorder.  Vet Pathol 44:398–402 (2007). Microscopically, the bases for these masses were slender, fusiform, mesenchymal cells that formed compact whorls around myelinated and unmyelinated nerves. These cells were labeled by antibodies directed against vimentin but not by S-100. Ultrastructurally, multiple, concentrically arranged, long, slender cell processes, with discontinuous external laminae and many pinocytotic vesicles, helped to accurately phenotype the proliferative element .

Dental Benign Cementomas in Three Horses. Vet Pathol 44:533–536 (2007). multiple bony enlargements of the upper and lower jaw extending into the oral cavity.  Histopathologically, the tumors consisted of excessive deposition of cementum-like tissue. Cells, resembling cementoblasts, lined irregularly shaped lacunae, which were present in the tumor tissue, and showed minimal cellular pleomorphism. Mitotic figures were not present.

Omental Leiomyoma in a Male Adult Horse. Vet Pathol 44:722–726 (2007). Multiple white-to-yellow lobules. Histologically, the mass consisted of slightly pleomorphic spindloid-shaped cells arranged in interlacing bundles containing elongated nuclei with blunt ends. The majority of tumor cells revealed a positive immunoreaction for a-smooth muscle actin, vimentin, and neuron-specific enolase and were negative for S-100, factor VIII–related antigen, and glial fibrillary acidic protein.

Equine Multinodular Pulmonary Fibrosis: A Newly Recognized Herpesvirus-Associated Fibrotic Lung Disease. Vet Pathol 44:849–862 (2007). Gross lesions consisted of multiple nodules of fibrosis throughout the lungs. Histologically, there was marked interstitial fibrosis, often with preservation of an ‘‘alveolarlike’’ architecture, lined by cuboidal epithelial cells. The airways contained primarily neutrophils and macrophages. Rare macrophages contained large eosinophilic intranuclear viral inclusion bodies. Caused by γ-herpesvirus, EHV-5.

A Soluble Secreted Glycoprotein (eCLCA1) is Overexpressed Due to Goblet Cell Hyperplasia and Metaplasia in Horses with Recurrent Airway Obstruction. Vet Pathol 44:901–911 (2007).  Horses affected by RAO had strong goblet cell metaplasia in bronchioles and goblet cell hyperplasia in bronchi and the trachea. Expression of the eCLCA1 protein was tightly linked to all airway goblet cells in both groups.  SO, eCLCA1 is a secreted glycoprotein and not an integral membrane protein. Taken together, the results suggest that eCLCA1 mediates its effect as a soluble constituent of airway mucins that is overexpressed in RAO airways because of goblet cell hyperplasia and metaplasia, not transcriptional upregulation.

Quantitative and Qualitative Evaluation of Dermal Elastin of Draught Horses with Chronic Progressive Lymphoedema: Chronic progressive lymphoedema (CPL) is a recently recognized disease of the lymphatic system in Shires, Clydesdales and Belgian draught horses, characterized by progressiveswelling, hyperkeratosis and fibrosis of distal limbs and is associated with altered elastin metabolism. The characteristic lesions are seen in the skin of the distal limbs. As compared with horses of a non-susceptible breed, affected horses had increased amounts of dermal elastin. CPL of horses is a generalized disease. Reduced efficiency of the elastic network in supporting the dermal lymphatics may explain the development of CPL.

Correlation of Pituitary Histomorphometry with Adrenocorticotrophic Hormone Response to Domperidone Administration in the Diagnosis of Equine Pituitary Pars Intermedia (PI) Dysfunction Vet Path 2008 Jan: PI is regulated by dopaminergic tone from hypothalamic neurons. Loss of dopaminergic inhibition is hypothesized to cause the PI hypertrophy and hyperplasia that result in the clinical manifestations of PI dysfunction (PID). Domperidone, a dopamine receptor antagonist, should exacerbate the loss of dopaminergic inhibition in horses with PPID and increase the release of endogenous adrenocorticotrophic hormone by PI melanotrophs. The results suggest that this test could be particularly important in horses with PI lesions but without having developed hirsutism.

Polysaccharide Storage Myopathy in Cob Normand Draft Horses: Vet Path 2008 Mar Gluteus medius muscle was sampled from 53 Cob Normand horsesfor histologic evaluation. Twenty horses (38%) exhibited amylase-resistant (therefore not glycogen) material in myocytes consistent with polysaccharide storagemyopathy. Diameter of affected type II fibers was increased. Amylase resistant material was also present in smooth muscle and macrophages.

Regional Pulmonary Veno-occlusion Vet Path 2008 May: A Newly Identified Lesion of Equine Exercise-induced Pulmonary Hemorrhage: Grossly, both right and left lungs had numerous dark brown to blue–black foci along the caudodorsal visceral pleura.  (Dorsocaudal lung fields) Only 14% had severe vascular remodeling,  fibrosis,  and  hemosiderin  accumulation,  hypertrophy  of  vessels within the pleura, and interlobular septa and bronchial neovascularization. We propose that regional veno-occlusive remodeling contributes to the pathogenesis of  EIPH, with  the  venous  remodeling  leading to  regional  vascular  congestion  and  hemorrhage, hemosiderin accumulation, fibrosis, and bronchial angiogenesis.

Arterial Calcification in Race Horses.  Vet Pathol 45:617–625 (2008). On microscopic examination, elastic fibers within the tunica media were thinned, fragmented, and calcified, and surrounded by dense collagen matrix. Elemental analysis showed distinct peaks for calcium and phosphorus, consistent withhydroxyapatite mineral. The frequent occurrence of calcification in the tunica media of large pulmonary arteries of young racing horses indicates the need to investigate its pathogenesis and potential clinical implications

REVIEW Paper: Mare Reproductive Loss Syndrome.  Vet Pathol 45:710–722 (2008). An epidemic of early fetal loss (EFL), late fetal loss (LFL), fibrinous pericarditis, and unilateral uveitis. Nonhemolytic Streptococcus spp. and Actinobacillus spp. accounted for 65% of the organisms isolated from fetuses submitted.  The pathologic findings in fetoplacental units of LFL included bronchopneumonia and funisitis, and there were no findings in EFL.  Currently, 2 hypotheses are proposed for MRLS. One hypothesis proposes that an ETC-related toxin with secondary opportunistic bacterial invasion of the fetus leads to MRLS. The second hypothesis suggests that a breach of gastrointestinal mucosal integrity by hairs of ETC leads to a bacteremia and results in MRLS.

Cyclooxygenase-2 Expression in Equine Tumors.  Vet Pathol 45:825–828 (2008). COX-2 was expressed in 2 of 14 sarcoids, 7 of 11 melanomas, and 32 of 37 SCC, 56% of which demonstrated moderate-to-strong immunoreactivity. There were no differences in expression between anatomic sites. In conclusion, most equine SCC and many melanomas appear to express COX-2 and thus could respond to COX-2 inhibitor therapy

Hypoxic/ischemic Encephalopathy Associated with Placental Insufficiency in a Cloned Foal: Grossly; flattened cerebral gyri, shallow sulci, yellowish cortical (green autofluorescence with UV), Micro: laminar cortical necrosis, rarefaction and gemistocytes; microcotyledons were markedly attenuated with absence of chorionic villi; Neonatal maladjustment syndrome: newborn foal show behavioral and neurologic symp (barkers, wanderes, dummies), proposed cause is fetal hypoxia, ischemia, could be due to fetal malformation, meconium aspiration, placental insufficiency, premature placental separation.

Neuropathology of Naturally Occurring Trypanosoma evansi Infection of Horses: Grossly: asymmetric leukoencephalomalacia with yellowish discoloration of white matter and flattening of the gyri, spleenomegaly, lymphadenomegaly, hindlimb muscle atrophy. Histo: necrotizing encephalitis (most severe in the white matter), with edema, demyelination, and lymphoplasmacytic perivascular cuffs. Mild to moderate meningitis or meningomyelitis.

Identification of Bartonella henselae in an Aborted Equine Fetus: Multifocal areas of necrosis present in fetal liver, kidney, lung and adrenal gland. Vasculitiswas present in all the organs with necrosis and in placenta.

Diagnostic Exercise: Intraosseous Epidermoid Cysts in the Third Phalanx of a Dressage Mare: Intraosseous epidermoid cysts are rare pseudoneoplastic lesions formed by the proliferation of epidermal cells within osseous tissue. Grossly, odorless, nonsuppurative, cream-colored, compacted, laminated-to-concentric,cyst-like intraosseous structures observed by sagittal sections through the affected phalanx of horses. characterized histologically by the accumulation of laminated keratin demarcated by an external layer of squamous epithelium. DDx is keratoma but it is not intraosseous

Pleomorphic Corneal Sarcoma Resembling Malignant Peripheral Nerve Sheath Tumor in a Horse: Squamous cell carcinoma is the most common equine ocular tumor; it commonly arises at the limbus and originates from conjunctival or corneal epithelium, other tumor can be angio and hemangiosarcoma. This tumor was composed of spindloid cells and was positive by IHC with vimentin, S100 and NSE indicating peripheral nerve sheath tumor.

Lymphoproliferative Disease with Features of Lymphoma in the Central Nervous System of a Horse: This report describes an unusual form of lymphoproliferative disease with features of lymphoma restricted to the CNS and with no evidence of a primary lesion elsewhere. IHC examination defined an overwhelming predominance of T lymphocytes with admixed B lymphocytes and activated macrophages. Other DDx considered, were non-suppurative encephalitis, granulomatous meningoencephalitis, neoplastic reticulosis, and lymphomatoid granulomatosis

Activated Platelet-Derived Growth Factor b Receptor Expression, PI3K-AKT Pathway Molecular Analysis, and Transforming Signals in Equine Sarcoids.  Vet Pathol 46:589–597 (2009). Bovine papillomavirus (BPV) types 1 and 2 are associated with sarcoids, in which the expression of the major transforming oncoprotein (E5) is often recorded. The transformation activity of the virus is due to the binding of the E5 to the platelet-derived growth factor b receptor (PDGFb-r). The PI3K–AKT–cyclin D3 molecular pathway downstream to the activation of the PDGFb-r is shown to be expressed.  phospho-JNK and phospho-JUN are more expressed in sarcoids than in normal skin.

Clara Cell Secretory Protein Is Reduced in Equine Recurrent Airway Obstruction.  Vet Pathol 46:604–613 (2009). Chronically  affected  animals  have  lung  remodeling  characterized  by smooth  muscle  hyperplasia, collagen  deposition,  lymphoid  hyperplasia,  and  impaired  aerobic  performance.  Clara cell  secretory protein (CCSP) counters inflammation in the lung.  CCSP lung gene expression was significantly higher in healthy animals than in animals with chronic RAO.

Characterization of the cDNA encoding αIIb & β3 in normal horses & 2 horses w/Glanzmann thrombasthenia (GT). pp78-82. Jan 2006

–  GT =  Inherited, intrinsic platelet defect characterized by quantitative or qualitative change in platelet glycoprotein complex IIb-IIIa (integrin αIIbβ3)Cant bind to fibrinogen

–  subunits encoded by separate genes, & both must be expressed to get stable complex; so defect in either gene = GT

–  these 2 horses had nml coag tests, normal platelet numbers, nml vWF Ag levels; marked impairment of clot retraction & plt aggregation responses

–  cDNA: single guanine -> cytosine base change (proline replaces arginine); 1 horse hetero, 1 horse homozygous

2 cases of equine abortion caused by Rhodococcus equi. pp208-11. March 2006  JTP

–  ubiquitous soil bacterium; infects horses, pigs, sheep, goats, cattle, llamas, cats, humans

–  usu. foal (2-6 months old) lesions: pyogranulomatous pneumonia, lymphadenitis, polyarthritis, ulcerative enteritis

–  Abortions at 7 & 8 months of gestation; cultured from aborted equine fetuses before, but rare cause (JVDI 2002)

FETUS: diffuse pyogranulomatous pneumonia w/numerous Gm+ coccobacilli w/in cytoplasm of macs, MNGC (Langhans), less commonly neutrophils; similar lesions to those observed in foals

–  enhanced EMH w/megakaryocytosis in liver & spleen

–  isolated from lung, liver, spleen, & stomach contents

VapA antigen = virulence factor of R. equi; present in virulent strains

Severe pulmonary disease due to multisystemic eosinophilic epitheliotropic disease (MEED) in a horse. pp189-93. March 2006  JTP

–  MEED usu. in young horses; eosinophilic & L-P infiltrates w/formation of eosinophilic granulomas in multiple organs (pancreas, salivary glands, GIT, biliary & bronchiolar epithelium, skin); poor prognosis

–  skin lesions (& wgt loss) common: generalized chronic progressive exfoliative dermatitis; eosinophilic, lymphoplasmacytic; marked acanthosis & hyperkeratosis

–  this case w/only respiratory signs & wgt loss – lungs poorly collapsed & nodular; pulmonary parenchyma w/innumerable discrete spherical nodules in military pattern – similar nodules scattered in liver & renal LN

–  histo: fibrosing eosinophilic granulomas, often w/central mineralization; also bronchiolitis fibrosa obliterans (bronchiolar lumens filled w/fibrous tissue & inflamm. cells)

Comparison of histopathologic criteria & skeletal muscle fixation techniques for the dx of polysaccharide storage myopathy (PSSM) in horses. pp257-69. May 2006  NW

Polysaccharide storage myopathy (PSSM) is most accurately diagnosed in muscle biopsy specimens on the basis of appearance of amylase-resistant, abnormal polysaccharide, NOT amylase-sensitive glycogen, regardless of fixation technique.

In general, frozen sections appeared to be better suited for studying myopathies because many histopathologic features of skeletal muscle were obscured by formalin fixation.

Ubiquitin expression in muscle from horses w/polysaccharide storage myopathy (PSSM). pp270-75. May 2006  JTP

–  Metabolic myopathy characterized by abnormal aggregates of PAS+, amylase-sensitive glycogen, & PAS+, amylase resistant polysaccharide w/in myofibers; common in many horse breeds

–  No defect in glycolytic or glycogenolytic pathways – cause of PSSM unknown

–  Ubiquitin: highly conserved ptn – covalently binds to other proteins to mark them for degradation as part of the ubiquitin-proteasome pathway

–  Ubiquitin expression in all but 1 PSSM-affected horse; was not detected in non-PSSM-affected horses

–  Glycogen aggregates develop & are ubiquitinated prior to development of amylase-resistant inclusions

Ubiquitin immunostaining no more sensitive than PAS staining for dx of PSSM EXCEPT amylase sensitive glycogen aggregates. (Ubiqutination occurs before amylase resistance develops. Ubiqutin picks up amylase resistant glycogen better, vice versa for PAS).

Serial transverse sections of skeletal muscle; horse with polysaccharide storage myopathy (EPSSM):

Subsarcolemmal (arrowheads) and multiple intracytoplasmic (arrows) aggregates of periodic acid-Schiff (PAS)-positive and amylase-sensitive glycogen, all of which express ubiquitin.

Plasma fibrinogen indicator of physeal or epiphyseal osteomyelitis in foals: JAVMA. Serum fibrinogen > 900 mg/dl à Physeal or epiphyseal osteomyelitis or Rhodococcus pneumonia.

Ivermectin Toxicosis in Three Adult Horses: JAVMA: Ataxia, depression, lip drooping, muscle fasciculations. Cranial nerve defects. . Normal ivermectin levels detected. Ivermectin à ↑ GABA recptors. Picrotoxin is a GABA receptor antagonist that blocks chloride channels. Collies with mutant mdr1 gene have faulty P-glycoprotein in BBB à Ivermectin sneaks through.

Systemic AL Amyloidosis Associated with Multiple Myeloma in a Horse: Grossly, diffuse GI hemorrhage, markedly thickened jejunal mucosa, andsplenomegaly were present. Histo: diffuse severe amyloid deposits present in the lamina propria of glandular stomach, duodenum, and jejunum. Much of the spleen and sternal bone marrow was replaced by neoplastic round cells, and multiple foci of amyloid were also present in the spleen and BM. Most equine cases are localized, AA amyloidoses associated with chronic inflammation such as severe strongyle infection, tuberculosis, neoplasia such as lymphoma and adrenal cortical adenoma.

Funisitis Associated with Leptospiral Abortion in an Equine Placenta: The umbilical cord had diffuse superficial yellow discoloration along its entire length. Microscopic evaluation showed an exudate of neutrophils admixed with fibrin on the surface. Warthin–Starry stain showed spirochetes in the Wharton’s jelly (gelatinous sub made up of mucopolysaccharides) of the umbilical cord. A locally extensive, severe placentitis not involving the star and allantoic cystic hyperplasiawere the other lesions observed in the allantochorion.

Incidence of Polysaccharide Storage Myopathy: Necropsy Study of 225 Horses: 101 horses and ponies with lesions of PSSM were identified. Incidence of PSSM on breed; Thoroughbreds had the lowest (27%) and draft-related horses had the highest (86%) incidence. Chronic myopathic changes (excessive fiber size variation, increase in number of internal nuclei) were more severe in PSSM-affected horses than in nonaffected horses.

Immunodeficiency/anaemia syndrome in a Dales pony Veterinary Record (2009) 165, 289-290

FELL:  Disease manifests at two to six weeks of age; weakness, dyspnea, nasal discharge, poor growth, reduced appetite, diarrhea and pale gums. Low PCV, lymphopenia (B cells), neutrophilia, low Ig.

Foal becoming progressively weaker due to systemic infections. No effective treatment.

GROSS: Thrush, colitis, pneumonia, inactive or aplastic bone marrow, and hypoplastic thymus/ lymph nodes. Heritability pattern consistent with autosomal recessive.

DALES: GROSS: Severe atelectasis of cranioventral lung lobes. The thymus was not identifiable.

HISTO: Airways filled with necrotic debris, squamous cells and occasional rod-shaped bacteria. Adenoviral inclusions in respiratory epithelium. Candida infection of tongue. Small intestinal cryptosporidia. Loss of villi, fibrosis, and severe mononuclear and neutrophilic infiltration and crypt dilation, occasionally forming crypt abscesses.

Splenic follicles atrophic, lymph nodes had poor architecture and no follicular development. Bone marrow hypoplasia.

IMMUNOHISTOLOGY: Low number CD3+ lymphocytes in the bone marrow. Poor B cell immunostaining in lymph node follicles. There was expression of CD79A in the bone marrow, but primarily by immature cells.

Two cases of equine pregnancy loss associated with Leptospira infection in England: Infection with Leptospira can cause abortions and stillbirths in domestic cattle, sheep and pigs, as well as in wild animals. Reported as a cause of abortions in mares in several countries, including the USA, Canada, South America, New Zealand, Australia and some European countries. In both cases there was mild mononuclear infiltration in liver, adrenal gland. Neutrophilic funisitis was seen in one case.

Extrapulmonary disorders associated with Rhodococcus equi infection in foals:

150 cases (1987–2007).  JAVMA, Vol 235, No. 7, October 1, 2009.

Abdominal  manifestations  of  R equi  infection  include mesenteric  lymphadenopathy, ulcerative  enterotyphlocolitis, peritonitis,  and  large intra-abdominal  abscesses. Nonseptic polysynovitis characterized  by  synovial  effusion  without  lameness has been identified for a multitude of foals with R equi pneumonia. Septic  arthritis and osteomyelitis. the  admitting  complaint  for  all these foals was marked lameness. Septic pleuritis, mediastinal lymphadenopathy, uveitis and hypopyon, pyogranulomatous hepatitis, intracranial  abscesses,  and  cellulitis  and  subcutaneous abscesses.

Comparative Skeletal Muscle Histopathologic and Ultrastructural Features in Two Forms of Polysaccharide Storage Myopathy in Horses. Vet Pathol46:1281–1291 (2009). A dominant mutation in the glycogen synthase 1 gene (GYS1) accounts for a substantial proportion of PSSM cases in at least 17 breeds, including Quarter Horses, but some horses diagnosed with PSSM by muscle histopathologic analysis are negative for the mutation. Abnormal polysaccharide was fine granular or homogenous in appearance (49/53; 92%), often amylase-sensitive (28/53; 53%), more commonly located under the sarcolemma, and consisting of b glycogen particles in GYS1-negative horses. However, in GYS1-positive horses, abnormal polysaccharide was usually coarse granular (50/52; 96%), amylase-resistant (51/52; 98%), more commonly cytoplasmic, and consisting of b glycogen particles or, in some myofibers, filamentous material surrounded by b glycogen particles. We concluded that 2 forms of PSSM exist and often have distinctive abnormal polysaccharide. However, because evaluation of the histologic appearance of polysaccharide can be subjective and affected by age, the gold standard for diagnosis of PSSM at present would appear to be testing for the GYS1 mutation followed by evaluating muscle biopsy for characteristic abnormal polysaccharide in those horses that are negative for the mutation.

Colic caused by Panicum maximum toxicosis in equidae in northern Brazil. J Vet Diagn Invest 21:882–888 (2009). severe  colic  and  death  in  horses  and  mules. serum urea nitrogen and creatinine concentrations were occasionally elevated.  The  stomach,  small  intestine,  and  large  intestine  had  severe hemorrhages and occasional mucosal erosions and ulcerations. Ulceration and hemorrhage of the urinary bladder were rarely observed.  Histologic  examination  revealed  diffuse  lymphoplasmacytic  gastritis  and  enteritis  with  severe congestion,  hemorrhage,  and  occasional  epithelial  necrosis  and  ulceration. Degeneration  and  occasional  necrosis  of bile  duct  epithelial  cells  and  degeneration  of  hepatocytes were observed in the liver. Toxin unknown- not saponins.

Atypical Dermatophilus congolensis infection in a three-year-old pony. J Vet Diagn Invest 22:141–143 (2010). A 3-year-old pony filly was examined for enlarging mandibular lymph nodes during the preceding 10 months. Biopsy of the node revealed mixed and granulomatous inflammation and thick, filamentous Gram-positive bacteria. Dermatophilus congolensis, confirmed by biochemical testing and sequencing of the ribosomal RNA gene, was cultured from a sample aspirated from the infected site.

An outbreak of orthopoxvirus-associated disease in horses in southern Brazil. J Vet Diagn Invest 22:143–147 (2010). papules, and vesicles progressing to proliferative and exudative lesions on the muzzle, external nares, and external and internal lips. The vesicles eroded, and the proliferative lesions eventually bled and progressed to moist crusts and scars. Direct electron microscopy of skin biopsies revealed brick-shaped, 250–300-nm virus particles with orthopoxvirus

morphology. Histological examination of the lesions revealed vacuolar degeneration of the cells of the

stratum spinosum and the presence of large intracytoplasmic, eosinophilic inclusion bodies. Polymerase chain reaction amplification of poxvirus A-type inclusion body gene confirmed the presence of orthopoxvirus DNA in horse tissues.

Ivermectin toxicosis in three adult horses.  JAVMA, Vol 235, No. 5, September 1, 2009.  Clinical Signs- depression, forelimb and hind limb ataxia, drooping of the superior and inferior lips, and muscle fasciculations. Bilateral mydriasis, decreased pupillary light reflexes, and absent menace reflexes were evidentOne horse was euthanized, and a high concentration of ivermectin was detected in its brain tissue at postmortem examination. Analysis of the ivermectin concentration in the paste product revealed that the concentration was approximately that indicated on the packaging.  Clinical Relevance—Ivermectin toxicosis is an uncommonly reported condition in equids that  should  be  considered  when  acute  neurologic  impairment  develops  after  ivermectin  administration. Recovery is possible with supportive care and time. Toxic concentrations of ivermectin have been reported for several  animal  species,  including  dogs,  cats,  pigs, cattle, horses, chelonians, and frogs.  The  mechanism  of  action  of  ivermectin  involves potentiating  the  release  of  the  inhibitory  neurotransmitter  GABA,  causing  an influx  of  chloride  ions  and hyperpolarization  of  neuronal  membranes. This sequence of events inhibits neuromuscular transmission and leads to flaccid paralysis of invertebrates, in which GABA receptors are located in the peripheral nervous system. In mammals, GABA receptors are located only in the CNS and an intact blood-brain barrier protects from the neurologic effects of ivermectin.  Picrotoxin is recommended as a reversal  agent for ivermectin toxicosis in dogs, and it functions as a GABA-receptor antagonist by blocking the chloride ion channels.  Neuronal excitability caused by picrotoxin  administration  may  lead  to  seizures;  therefore, the  agent  has  a  narrow  margin  of  safety.  For example, Collies have a multidrug-resistance gene  (mdr1)  that  encodes  for  P-glycoprotein,  which  is  an  integral  part  of the blood-brain barrier that functions to keep ivermectin from entering the CNS. Dogs possessing a deletion mutation  of  the  mdr1  gene  are  unable  to  synthesize P-glycoprotein appropriately and have a high sensitivity  to  ivermectin.

Outbreak of rhinitis caused by equine herpesvirus type 3 M. Barrandeguy, N. Ulloa, K. Bok, F. Fernández

Veterinary Record (2010) 166, 178. Outbreak of unilateral rhinitis associated with EHV-3, most likely spread by a contaminated endoscope. Forty horses showed exudative lesions of the transitional epithelium at the mucocutaneous junctions of only the right nostril, and one horse showed these lesions in both nostrils. The lesions were characterized by epidermal sloughing of the necrotic domes of pustules, giving rise to shallow, raw or encrusted erosions and ulcers. EHV-3 via VI and PCR.

The horses’ records showed that they had been examined endoscopically by a veterinarian, using the same flexible endoscope, to evaluate their respiratory tract function in the week before the onset of the lesions. The development of lesions in the mouth and nostrils of mares and foals naturally infected with EHV-3 has been reported before, as has foamite transmission.

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