Unusual Patterns of Serum Antibodies to Streptococcus Equi in Two Horses with Purpura Hemorrhagica

An enzyme-linked immunosorbent assay (ELISA) was developed for use in horses to determine serum titers of antibodies of the immunoglobulin classes IgA, IgG, and IgM to Streptococcus equi M-like protein and culture supernatant protein antigens. Serum antibodies were determined in 28 adult horses, including 9 horses with recent S. equi infections, 17 horses without known exposure to S. equi, but without a history of respiratory disease in the preceding 4 months, and 2 horses with clinical purpura hemorrhagica. Serum IgA titers to culture supernatant protein antigen were highest in recently infected horses (P less than 0.001). Serial determinations of antibody titers in the horses with purpura showed that IgG antibodies to both S. equi M-like protein and culture supernatant protein antigens were undetectable initially, but later rose coincidental with clinical recovery from the disease. Possible mechanisms for these findings are discussed.     

Effects of exercise on the hemostatic system of thoroughbred horses displaying post-exercise epistaxis

Hemostatic parameters in 5 Thoroughbreds which had recently displayed post-exercise epistaxis, and 4 normal horses, were assessed using blood samples taken when the animals were at rest, immediately before exercise, and 5 minutes after galloping 1.2. km at maximum speed. Exercise resulted in marked depression in the adenosine diphosphate (ADP)-induced aggregation response of platelets from both groups of horses. No significant differences were detected when comparing the results from each group. However, there was a tendency for the platelets from the bleeder group to be less responsive to ADP. Because not all aspects of platelet function were studied the possible role of platelet abnormalities in the pathogenesis of exercise-induced pulmonary hemorrhage could not be completely discounted.     

Pharmacology of Furosemide in the Horse: A Review

Furosemide, a diuretic, is frequently administered to horses for the prophylaxis of exercise-induced pulmonary hemorrhage and the treatment of a number of clinical conditions, including acute renal failure and congestive heart failure. Furosemide increases the rate of urinary sodium, chloride, and hydrogen ion excretion. Plasma potassium concentration decreases after furosemide administration but urinary potassium excretion in horses is minimally affected. Renal blood flow increases after furosemide administration. Systemically, furosemide increases venous compliance and decreases right atrial pressure, pulmonary artery pressure, pulmonary artery wedge pressure, and pulmonary blood volume. The systemic hemodynamic effects of furosemide are only manifest in the presence of a functional kidney, but can occur in the absence of diuresis, emphasizing the importance of the renal-dependent extra-renal effects of furosemide. The renal and systemic hemodynamic effects of furosemide are modified by prior administration of nonsteroidal anti-inflammatory drugs. Furosemide administration attenuates exercise-induced increases in right atrial, aortic, and pulmonary artery pressures in ponies. Furosemide prevents exercise and allergen-induced bronchoconstriction in humans and decreases total pulmonary resistance in ponies with recurrent obstructive airway disease. These pharmacologic effects are frequently used to rationalize its questionable efficacy in the prevention of exercise-induced pulmonary hemorrhage. Neither the effect of furosemide on athletic performance nor its efficacy in the prevention of exercise-induced pulmonary hemorrhage has been convincingly demonstrated.     

SONOGRAPHIC FEATURES OF HISTIOCYTIC NEOPLASMS IN THE CANINE ABDOMEN

The purpose of this retrospective study was to describe the ultrasonographic features of malignant histiocytosis (MH), malignant fibrous histiocytoma, and histiocytic sarcoma in abdominal organs of dogs. The medical records of 18 dogs that had undergone abdominal sonography and had a histopathologic diagnosis of abdominal MH, malignant fibrous histiocytoma, and histiocytic sarcoma were reviewed. The organ most commonly affected was the spleen. MH was the most common followed by histiocytic sarcoma and malignant fibrous histiocytoma. In the spleen there were often multiple hypoechoic nodules with well-defined borders. In one dog, without focal lesions, the spleen was enlarged and hypoechoic. The liver was the second most commonly affected organ. MH was most common followed by histiocytic sarcomas and malignant fibrous histiocytoma. The most common sonographic feature in the liver was the presence of multiple hypoechoic nodules with well-defined borders. One dog without hepatic nodules had a liver that was ultrasonographically enlarged and hypoechoic. MH in the abdominal lymph nodes resulted in hypoechoic lymphadenopathy. Malignant fibrous histiocytoma was the only neoplastic type in the kidneys appearing as a single heteroechoic renal mass with well-defined borders. MH was observed in the stomach of one dog. Sonographically there was a single well circumscribed hypoechoic mass with well-defined borders and abnormal stomach layers. In this study it was not possible to differentiate between MH, malignant fibrous histiocytoma, and histiocytic sarcoma using sonography.     

B-MODE AND DOPPLER ULTRASOUND IMAGING OF THE SPLEEN WITH CANINE SPLENIC TORSION: A RETROSPECTIVE EVALUATION

The ultrasonographic appearance of splenic torsion has been described; the splenic parenchyma can be normal, hypoechoic or anechoic with interspersed linear echoes (coarse/"lacy" appearance). The ultrasonographic parenchymal appearance of 15 dogs in this report with splenic torsion varied: mottled hypoechoic regions (n=2), diffusely hypoechoic (n=11) and normal (n=2). Because splenic torsion causes vascular congestion due to splenic vein compression and eventual thrombosis, visible splenic vein intraluminal echogenicities compatible with thrombi were seen in 13 dogs using B-mode. Using spectral Doppler and color Doppler imaging of the splenic veins, no measurable flow velocities were detected in any of the 15 dogs. The varied B-mode ultrasonographic appearance of the splenic veins for intraluminal echoes and spectral or color Doppler evaluation for absent velocity flow.     

Effect of Platelet-Activating Factor Antagonist L-691,880 on Low-Flow Ischemia-Reperfusion Injury of the Large Colon in Horses

Objective—To determine the effect of platelet-activating factor (PAF) antagonist L-691,880 on low-flow ischemia and reperfusion (I-R) of the large colon in horses. Animals —12 adult horses. Experimental Design—Horses were anesthetized, and the large colon was exteriorized through a ventral median celiotomy and instrumented. Colonic arterial blood flow was reduced to 20% of baseline (BL) and maintained for 3 hours; flow was then restored, and the colon was reperfused for 3 hours. One of two solutions was administered intravenously 30 minutes before reperfusion: group 1, 10 mL/kg 0.9% NaCl; and group 2, 5 mg/kg PAF antagonist L-691,880 in 0.9% NaCl. Hemodynamic variables were monitored and recorded at 30-minute intervals. Systemic arterial and colonic venous blood were collected for measurement of blood gas tensions, oximetry analyses, packed cell volume, and total plasma protein concentrations. Colonic venous blood was collected for determination of lactate, 6-keto prostaglandin F_1α (6-kPG), prostaglandin E₂ (PGE₂), and thromboxane B₂ (TXB₂) concentrations. Full-thickness biopsy specimens were harvested from the left ventral colon for histological evaluation. Results—There were no significant differences between the two groups for any hemodynamic or metabolic variables. Colonic venous pH decreased, and carbon dioxide tension and lactate concentration increased during ischemia but returned to BL values during reperfusion. Colonic venous 6-kPG concentration was significantly increased above BL value at 2 hours and remained increased through 6 hours in horses of both groups. Colonic venous PGE₂ concentration was significantly greater in group 2 compared with group 1 throughout the study. Colonic venous PGE₂ concentration was increased above BL value from 3 to 6 hours in horses of both groups. Colonic venous TXB₂ concentration was not different between groups but was significantly increased above the BL value for the first hour of reperfusion. Low-flow I-R of the large colon caused significant mucosal necrosis, hemorrhage, edema, and neutrophil infiltration; however, there were no differences in histological variables between vehicle-control and PAF antagonist-treated horses. Conclusion—No protective effects of PAF antagonist L-691,880 were observed on colonic mucosa associated with low-flow I-R. Additionally, deleterious drug-induced effects on hemodynamic and metabolic variables and colonic mucosal injury were not observed.     

Isolation, culture and ultrastructure of a xylem-limited bacterium associated with Sumatra disease of cloves

A xylem-limited bacterium (XLB) previously shown to be associated with Sumatra disease of clove trees was consistently isolated from diseased but not from healthy trees. Isolation of the XLB was most successful using freshly expressed bacterial ooze obtained from root and branch tissues with low to moderate levels of xylem vessel invasion in trees at early stages of disease. XLB were commonly isolated from trees with the rapid form of disease but infrequently from those with slow decline. Bacterial colonies grew slowly on nutrient agar, reaching a maximum diameter of 1 mm in 5-7 days at 28^oC. Cells of the bacterium were 0.5-0.6 μm in width and 1.0-1.5 μm in length and did not possess flagella. The bacterial envelope was strongly rippled and Gram negative.     

Sumatra disease in cloves induced by a xylem-limited bacterium following mechanical inoculation

Suspensions of a Gram negative, non motile nutritionally fastidious bacterium, cultured from clove trees affected by Sumatra disease and inoculated by needle puncture into the xylem of seedling cloves and young trees, caused the death of over 60% of the plants withing 2 year. Bacteria, confined to zylem vesssels, occurred throughout the vascular systems of dying plants and were also still active in some of the plants which survived for 3 years after inoculation. Bactria resembling those used as inoculum were readily reisolated form dying plants but not from any water-treated controls. Symptoms in experimental plants and the appearance and distribution of vessels occluded by bacteria were indistinguishable from those resulting from natural infection. All clove types tested were susceptible, including progeny from trees which had survived past disease attack. Result suggest the importance of using vigorously growing plants and providing protection against full sunlight during incubation for the successful establishment of beacterial infection in juvenile clove plants follwing mechanical inoculation.