Coagulation profiles in 27 horses with large colon volvulus

Objective: The objective of this study was to evaluate coagulation profiles in horses with surgical treatment of large colon volvulus (LCV), and determine if an association exists between hemostatic dysfunction and outcome. Design: Prospective clinical investigation from February to December 2000. Setting: Large animal intensive care unit in a veterinary teaching hospital. Interventions: Blood was collected from horses intra‐operatively, 24, and 48 hours following surgical treatment for LCV. Measurements: Coagulation profiles, thrombin–antithrombin (TAT) levels, and D‐dimer concentrations were determined for each time point. The number of tests abnormal in the standard coagulation profile, defined as the degree of hemostatic dysfunction, was determined for each horse for the duration of the study period. The association between each test and outcome, as well as the degree of hemostatic dysfunction for each horse and outcome, was determined using univariate analysis and logistic regression. TAT levels and D‐dimer concentrations were compared to the results of the standard coagulation profile and to patient outcome using univariate analysis and logistic regression. Main results: Seventy percent of horses evaluated with surgical treatment of LCV had evidence of hemostatic dysfunction (3/6 tests abnormal). Only 18% of those patients had clinical signs recognized by the attending clinician as a coagulopathy. There was an association between the development of a coagulopathy and outcome, with horses with 4/6 tests abnormal being more likely to be euthanized, and those with 3/6 tests abnormal having a prolonged hospital stay. Platelet count, prothrombin time, and TAT levels may be helpful in predicting outcome in horses with LCV. Conclusions: Hemostatic function should be evaluated in horses with surgical treatment of LCV to detect subclinical coagulopathies and direct subsequent intervention.     

Disseminated Intravascular Coagulation Associated with Colic in 23 Horses (1984–1989)

Disseminated intravascular coagulation (DIC) secondary to colic was diagnosed in 23 horses. Each horse was categorized retrospectively as to the cause of the colic based on surgical and/or necropsy findings: group 1 consisted of 14 horses with compromised intestine that required resection and anastomosis; group 2 consisted of 3 horses with nonstrangulating intestinal displacement and/or impactions; and group 3 consisted of 6 horses with colic associated with enteritis and/or colitis. Horses were considered to be affected with DIC if at least three of five hemostatic parameters were significantly abnormal: decreased antithrombin III (AT III) values, increased level of fibrin degradation products (FDP), thrombocytopenia, prolonged activated partial thromboplastin time, and prolonged prothrombin time. The most consistent hemostatic abnormalities were decreased AT III activity, increased FDP titers, and thrombocytopenia. Clotting times were more variable and did not always correlate with the presence of excessive hemorrhage. Excessive hemorrhage was present during surgery in seven horses and occurred within 1 to 12 hours after surgery in nine other horses. In addition to treatment of the primary disease, 19 horses received treatment for DIC consisting of heparin and/or plasma or fresh whole blood transfusions. Heparin alone was used in 12 horses. Heparin, in addition to fresh whole blood transfusions or fresh plasma, was administered to four horses. Three horses were treated with plasma alone. Four other horses were not treated specifically for the DIC. Eight horses (34%) survived the acute coagulopathy. Although a greater proportion of the surviving horses received heparin therapy (87.5%; 7/8) than did those that died (60%; 9/15), the difference was not statistically significant (P = 0.345).(ABSTRACT TRUNCATED AT 250 WORDS)     

Association of admission plasma D-dimer concentration with diagnosis and outcome in horses with colic

Background: Coagulopathies detected in horses with gastrointestinal problems seem to be associated with poor outcome. Plasma D‐Dimer concentration is a sensitive test for assessing coagulopathies. Hypothesis: Plasma D‐Dimer concentration tested on admission is related to diagnosis and outcome in horses with colic. Animals: Four hundred and ninety three horses referred for evaluation of abdominal pain. Methods: Prospective observational clinical study. Horses were grouped according to diagnosis (medical and surgical intestinal obstructions, ischemic disorders with and without intestinal resection, enteritis, peritonitis), outcome (survivors, nonsurvivors), and number of coagulopathies (normal profile, 1 or 2 coagulopathies, subclinical disseminated intravascular coagulation [DIC]). Blood samples were collected on admission and plasma D‐Dimer concentration, clotting times (PT and aPTT), and antithrombin activity were determined. Positive likelihood ratios (LR+) were calculated for evaluation of D‐Dimer cut‐off values, which were later tested in a logistic regression model. Results: Horses with enteritis or peritonitis had significantly (P < .001) higher plasma D‐Dimer concentrations and more severe coagulopathies on admission than horses with other diagnoses. Nonsurvivors also had significantly (P < .001) higher plasma D‐Dimer concentrations at presentation than did survivors, and those horses with subclinical DIC on presentation had an odds ratio (OR) 8.6 (95% confidence interval [CI], 3.3–22.5, P < .001) for nonsurvival. Finally, D‐Dimer concentrations >4,000 ng/mL had a LR+ of 5.9 and an OR 8.8 (95% CI, 4.5–17.1, P < .001) for nonsurvival. Conclusion and Clinical Importance: Plasma D‐Dimer concentration measured on admission can be used to facilitate diagnosis and outcome prediction in horses with colic. A potential cut‐off value for nonsurvival was found at approximately 4,000 ng/mL.     

Putative intestinal hyperammonaemia in horses: 36 cases

Reasons for performing the study: Intestinal hyperammonaemia (HA) has been infrequently reported in individual horses; however, there have been no studies describing clinical and laboratory data as well as short‐ and long‐term outcome in a larger number of cases. Objectives: To describe clinical and laboratory data and short‐ and long‐term outcome in a large group of horses with intestinal HA. Methods: Multi‐centred, retrospective study; case records of horses with HA were reviewed and any horse with a clinical or post mortem diagnosis of intestinal HA was included. Hyperammonaemia was defined as a blood ammonium (NH₄⁺) concentration ≥60 µmol/l and horses with a diagnosis of primary hepatic disease were excluded. Relevant data were recorded and, if appropriate, data from survivors were compared to nonsurvivors to identify potential prognostic indicators. Results: Thirty‐six cases, 26 mature horses and 10 foals with intestinal HA were identified. Case histories included diarrhoea, colic and neurological signs and the most common clinical diagnosis was colitis and/or enteritis. The most common clinical and laboratory abnormalities included tachycardia, increased packed cell volume, hyperlactataemia and hyperglycaemia. Fourteen horses (39%) survived to discharge; NH₄⁺ concentration on admission was the only parameter significantly associated with survival. All surviving horses and foals for which follow‐up information was available recovered completely and returned to their intended use without further complications. Conclusions and potential relevance: Intestinal HA occurs in mature horses and foals and can be associated with severe clinical and laboratory abnormalities; further studies are required to investigate predisposing factors and delineate possible differences in aetiologies.     

The association of erythromycin ethylsuccinate with acute colitis in horses in Sweden

In Sweden there are several reports of mares developing acute colitis while their foals were being treated orally for Rhodococcus equi pneumonia with the combination of erythromycin and rifampicin. In this study 6 adult horses were given low oral dosages of these antibiotics, singly or in combination. Within 3 days post administration of erythromycin, in one case in combination with rifampicin, 2 horses developed severe colitis (one fatal). Clostridium difficile was isolated from one of the horses, whereas no specific pathogens were isolated from the other. Both horses had typical changes in blood parameters seen in acute colitis. Clostridium difficile was also isolated from the faeces of a third horse given an even lower dosage of erythromycin in combination with rifampicin. This horse developed very mild clinical symptoms and recovered spontaneously. In the fourth horse given erythromycin only, very high numbers of Clostridium perfringens were isolated. The horses given rifampicin only did not develop any clinical symptoms and there were no major changes in their faecal flora. In conclusion, it has been demonstrated that low dosages of erythromycin ethylsuccinate can induce severe colitis in horses associated with major changes of the intestinal microflora. Clostridium difficile has been demonstrated as a potential aetiological agent in antibiotic-induced acute colitis.     

Ultrasonographic findings in horses with right dorsal colitis: five cases (2000-2001)

OBJECTIVE: To determine whether ultrasonography would be useful in the diagnosis of right dorsal colitis in horses. DESIGN: Retrospective study. ANIMALS: 5 horses with right dorsal colitis and 15 healthy adult horses. PROCEDURE: Mural thickness and appearance of the right dorsal colon were determined from ultrasonographic images obtained at right intercostal spaces 10, 11, 12, 13, and 14. RESULTS: The right dorsal colon could be imaged most consistently at the right 11th, 12th, and 13th intercostal spaces, below the margin of the lung and axial to the liver. Mural thickness measured from ultrasonographic images was significantly greater in horses with right dorsal colitis than in healthy horses. The right dorsal colon in affected horses had a prominent hypoechoic layer associated with submucosal edema and inflammatory infiltrates. Successful treatment of 1 horse with right dorsal colitis was associated with a decrease in mural thickness coincident with an increase in serum albumin and total protein concentrations and weight gain. A decrease in mural thickness was also observed in a second horse treated for right dorsal colitis that was not associated with healing of the right dorsal colon or an increase in serum albumin concentration but rather thinning of a segment of the right dorsal colon that eventually ruptured. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that ultrasonographic measurement of mural thickness and evaluation of the appearance of the right dorsal colon may be useful in the diagnosis of right dorsal colitis in horses.     

Evaluation of high-speed treadmill videoendoscopy for diagnosis of upper respiratory tract dysfunction in horses

OBJECTIVE: To evaluate high-speed treadmill videoendoscopy as a diagnostic technique and document the abnormalities found in Australian horses referred for poor performance associated with abnormal upper respiratory tract noise but where a definitive diagnosis could not be made at rest. DESIGN: A retrospective clinical study using client-owned horses. PROCEDURE: The clinical records and videorecordings of all horses referred to the University of Sydney for poor performance associated with abnormal upper respiratory tract noise during a 13-month period were examined. Only horses with a normal physical examination including absence of lameness, and where a definitive diagnosis of the cause of the abnormal upper respiratory tract noise could not be made from the resting videoendoscopic examination were included in the study. The age, gender, breed of horse and the purpose for which the horse was used were ascertained from the record and videorecordings were reviewed by the authors and any abnormalities noted. RESULTS: There were 37 horses included in the study. An upper airway abnormality was identified during high-speed treadmill videoendoscopy in 73% of horses. One abnormality was identified in 22 horses, 2 abnormalities in 4 horses and 3 abnormalities in 1 horse. Abnormalities identified included laryngeal hemiparesis (n = 15), axial deviation of the aryepiglottic folds (n = 10), pharyngeal collapse (n = 3), dorsal displacement of the soft palate (n = 2), epiglottic collapse (n = 1), axial deviation of the vocal cord (n = 1) and laryngeal collapse (n = 1). CONCLUSIONS: The results of this study are similar to reports from overseas and suggest high-speed treadmill videoendoscopy appears to be a useful technique to diagnose the cause of upper airway dysfunction in Australian horses referred specifically for poor performance associated with abnormal upper respiratory noise. However, a diagnosis will not be made in all horses undergoing this procedure. There were five horses with two or three abnormalities none of which were apparent at rest. This would suggest that in all horses making abnormal upper respiratory noise associated with poor performance, even where an abnormality is identified at rest, high-speed treadmill videoendoscopy should be performed for a complete diagnosis.     

Results of surgical treatment of colic in miniature breed horses: 11 cases

OBJECTIVE: To report on the outcome of surgical treatment of acute abdominal crises in miniature breed horses. DESIGN: Retrospective case series of miniature horses presented to the University Veterinary Centre, Camden with an acute abdominal crisis. METHODS: Hospital records of all miniature horses that underwent ventral midline laparotomy for acute abdominal crisis between 1997 and 2001 were reviewed. The signalment, history, clinical signs, results of ancillary diagnostic procedures, location and type of intestinal lesion, treatment and outcome were retrieved from each case record. Long-term survival was determined by telephone interview of owners. RESULTS: Eleven miniature horses including five females and six males underwent ventral midline laparotomies for acute abdominal crisis during the study period. Ages ranged between 1 month and 19 years. Surgical findings included faecalith obstruction (seven horses), enterolith (one horse), strangulating lipoma of the descending colon (one horse), jejunal infarction (one horse), and caecal infarction (one horse). Long-term survival rate (minimum 12 months post surgery) was 55%. Six of eight horses with simple intraluminal obstructions survived, while the three horses with gastrointestinal lesions associated with vascular compromise were euthanased either at surgery (caecal infarction), or postoperatively, due to complications (strangulating lipoma of the descending colon, jejunal infarction). Postoperative complications in this study included impaction of the descending colon (two horses), diarrhoea (two horses), peritonitis (one horse), hyperlipaemia (two horses), incisional infection (two horses) and abdominal adhesions (one horse). Hyperlipidaemia was present in five of seven horses in which serum triglycerides were measured at presentation. CONCLUSIONS: Simple intraluminal obstructions of the large intestine were frequently encountered during exploratory laparotomy in miniature horses presented for acute abdominal crises, and their surgical treatment was associated with a good prognosis. In contrast, this study suggested that abdominal pain associated with vascular compromise of gastrointestinal tissues in miniature horses was associated with a poorer prognosis, consistent with reports in other horse breeds. Possible contributing factors to faecalith formation, including poor quality roughage, dental disease, and inadequate water consumption, should be recognised and avoided in miniature horses. Serum triglyceride concentrations should be measured in miniature horses presented for acute abdominal pain. If elevated, nutritional supplementation should be provided.     

Medical Management of Right Dorsal Colitis in 5 Horses: A Retrospective Study (1987–1993)

Right dorsal colitis in horses has been associated with administration of phenylbutazone. Although reports of right dorsal colitis in this species have described surgical treatment associated with a poor prognosis, we have had success treating this condition medically. This report describes 5 horses with right dorsal colitis confirmed during celiotomy that were initially managed medically. All horses had a history of intermittent abdominal pain; weight loss was noted in only 1 horse. The doses (2.0 to 4.6 mg/kg PO bid) and duration (5 to 30 days) of administration of phenylbutazone were not unusually high relative to those recommended (4.4 mg/kg PO bid). Hypoproteinemia and hypoalbuminemia were observed in all horses at the time of admission; packed cell volume was low in 4 horses, and hypocalcemia was also observed in 4 horses. Three of 5 horses (60%) appeared to respond to dietary management and discontinuation of administration of nonsteroidal anti-inflammatory drugs. Dietary management consisted of feeding pelleted feed, and restricting or eliminating roughage for a period of at least 3 months. Two horses developed strictures of the right dorsal colon. One horse that developed a colonic stricture, possibly because its owners did not comply with recommendations for management, was subsequently treated surgically. The remaining horse that developed a stricture of the right dorsal colon was euthanized. These data indicate that some horses with right dorsal colitis can be successfully managed with medical treatment.     

Osteomyelitis of the sustentaculum tali in horses: 10 cases (1992-1998)

OBJECTIVE: To determine outcome of horses with osteomyelitis of the sustentaculum tali (ST), with or without associated tarsal sheath tenosynovitis, following surgical debridement and lavage. DESIGN: Retrospective study. ANIMALS: 10 horses in which a diagnosis of osteomyelitis of the ST had been made on the basis of history, physical examination findings, and results of radiography. PROCEDURE: Information on results of diagnostic testing, surgical findings, postoperative treatment, and short-term outcome was obtained from the medical records. Long-term follow-up information was obtained through reevaluation of horses at the teaching hospital and telephone conversations with referring veterinarians, owners, and trainers. RESULTS: Treatment consisted of surgical debridement, intra- and postoperative lavage, and long-term antimicrobial and anti-inflammatory treatment. Eight horses had evidence of involvement of the tarsal sheath. One horse was euthanatized after surgery because of a lack of response to treatment; the other 9 were discharged from the hospital. Severity of lameness had improved, but all still had grade-1 or -2 lameness at the time of discharge. One horse was euthanatized after discharge because of contralateral hind limb laminitis, and another horse was lost to follow-up. Of the remaining 7 horses, 6 returned to their previous use, and 1 was sound but retired for breeding for unrelated reasons. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that horses with osteomyelitis of the ST, with or without concomitant tarsal sheath tenosynovitis, can have an excellent to good outcome and may return to their previous use after surgical debridement of affected tissues and lavage of the tarsal sheath.     

THE APPLICATION OF TECHNETIUM-99m HEXAMETHYLPROPYLENEAMINE OXIME (99mTc-HMPAO) LABELED WHITE BLOOD CELLS FOR THE DIAGNOSIS OF RIGHT DORSAL ULCERATIVE COLITIS IN TWO HORSES

The application of 99mTc-HMPAO labeled white blood cells to support the diagnosis of right dorsal ulcerative colitis was studied in two horses with a history and clinical signs consistent with phenylbutazone toxicity. These images were compared to a reference horse unaffected by right dorsal ulcerative colitis. Blood was collected aseptically in heparinized syringes from the patients for in vitro white blood cell (WBC) radiolabeling. The buffy coat was separated out and radiolabeled with 99mTc-HMPAO. The radiolabeled blood was re-injected i.v. and four images of the right and left side of the patient's abdomen were acquired at 4 hours and 20 hours post-injection. Results of the nuclear study revealed no abnormal findings in the abdomen at the four-hour post-injection images in any horse. Images obtained 20 hours post-injection revealed a linear uptake of radiolabeled WBCs in the right cranioventral abdomen in the region of the right dorsal colon in both horses with right dorsal ulcerative colitis. The reference horse had no radiopharmaceutical uptake in this region. This nuclear imaging study was a rapid, non-invasive method to identify right dorsal colon inflammation. These findings not only supported the diagnosis of right dorsal ulcerative colitis, but also facilitated appropriate medical management of each horse.     

Bacterial meningitis and brain abscesses secondary to infectious disease processes involving the head in horses: seven cases (1980-2001)

OBJECTIVE: To determine clinical features of horses with bacterial meningitis or brain abscesses secondary to infectious disease processes involving the head. DESIGN: Retrospective study. ANIMALS: 7 adult horses. PROCEDURE: Medical records of Tufts University, the University of Pennsylvania, and the Livestock Disease Diagnostic Center (Lexington, Ky) were reviewed to identify adult (> 12 months old) horses in which a postmortem diagnosis of bacterial meningitis or brain abscess had been made. Horses were included in the study if an intracranial infection was confirmed, the horse had a primary infectious disease process involving the head, and there were no signs of systemic infection. RESULTS: 23 adult horses with bacterial meningitis or a brain abscess were examined during the study period, but only 7 met the criteria for inclusion in the study. Primary sites of infection included the paranasal sinuses, nasal cavity, periocular tissues, and submandibular lymph nodes. Three horses died suddenly prior to hospitalization, and 1 horse was hospitalized but died 7 days after the onset of neurologic abnormalities. The remaining 3 horses were euthanatized because of a rapid deterioration in clinical status. CONCLUSIONS AND CLINICAL RELEVANCE: Although rare, fatal intracranial complications can develop in horses with infectious diseases involving the head.     

Evaluation of latex agglutination kits for detection of fibrin(ogen) degradation products and D-dimer in healthy horses and horses with severe colic

Background: Fibrin(ogen) degradation products (FDPs) and D‐dimer are sensitive indicators of excessive fibrinolysis due to disseminated intravascular coagulation (DIC) in dogs. To the authors' knowledge, latex‐agglutination–based plasma FDP and D‐dimer assays have not been validated for use in horses. Objectives: To determine: 1) sensitivity and specificity of latex‐agglutination serum and plasma FDP and D‐dimer assays for diagnosis of DIC; and 2) their prognostic value in horses with severe colic. Methods: At hospital admission and 24 hours later, blood was collected from 30 healthy horses and 20 horses with severe colic. Horses fulfilling predefined laboratory criteria of DIC were enrolled, and their data were subcategorized by survival for analysis. Platelet counts were determined and coagulation panel testing was performed. Serum and plasma FDP concentrations were measured using separate latex agglutination kits. Plasma D‐dimer concentration was measured using 3 latex agglutination kits and a card immunofiltration test. Test sensitivity and specificity results were determined for healthy horses and those with colic. Median test values were compared between colic survivors and nonsurvivors to evaluate the prognostic usefulness of all tests. Results: Performance characteristics varied among assays and kit suppliers. The FDP assays had low sensitivity (<40%), whereas the most accurate D‐dimer kit had 50% sensitivity and 97% specificity. High D‐dimer concentration was the third most common hemostatic abnormality in horses with colic. Median antithrombin (AT) activity was significantly lower and activated partial thromboplastin time (aPTT) was significantly longer in nonsurvivors than survivors. Conclusions: Commercial latex‐agglutination D‐dimer assays might prove useful as adjunctive tests for the diagnosis of DIC in horses with severe colic; however FDP assays are invalid for this purpose. Low AT activity and prolonged aPTT at admission are associated with a poor prognosis in this patient population.     

Cruciate and collateral ligament failure in the equine stifle: seven cases (1975-1985)

Medical records of 7 adult horses with single or multiple ligament failure of the femorotibial ligaments were reviewed to evaluate signalment, history, diagnostic and treatment methods, outcome, and long-term follow-up information. Acute onset of lameness was recorded for most of the horses. Horses with multiple ligament injury had more severe clinical signs than did horses with single ligament injury. Horses with single ligament injury generally required manipulative tests to localize the lameness to the stifle. In all horses, radiography of the stifle assisted in the diagnosis. Horses either were euthanatized (n = 3) or were treated by stall rest (n = 4) after diagnosis. Of the 4 surviving horses, 2 became successful breeding animals, 1 was awaiting breeding, and 1 was used unsuccessfully as a breeding animal. Necropsy findings in 2 of the 3 horses euthanatized after diagnosis revealed early articular damage in 1 horse 1 day after injury, and degenerative joint disease in the other horse 1 year after injury.     

Serum iron and plasma fibrinogen concentrations as indicators of systemic inflammatory diseases in horses

BACKGROUND: Detection of systemic inflammation, which is important for proper diagnosis and prompt treatment, can be challenging. HYPOTHESIS: Measurement of plasma iron concentration is a sensitive method for detecting systemic inflammation in horses compared with measurements of plasma fibrinogen concentration, a traditional marker for inflammation in the horse. ANIMALS: Ninety-seven horses hospitalized with diseases causing systemic inflammation, 22 horses with localized inflammation, and 12 clinically normal horses were included in this study. METHODS: A retrospective study was made on hospitalized horses that had both plasma iron and fibrinogen concentrations measured on hospital admission. RESULTS: Plasma iron concentration was lower in horses with systemic inflammation (64 +/- 45 microg/dL) than the reference interval minimum (105 microg/dL) and were significantly lower (P = .001) than the value in a group of horses with local inflammation (123 +/- 45 microg/dL) and in healthy transported horses (143 +/- 29 microg/dL). Low plasma iron and high fibrinogen concentrations were both sensitive indicators of systemic inflammation in horses with sensitivity of 90 and 82%, respectively. There was a similar correlation between either continued decreases in iron concentration (Rsp of 0.239) or increases in fibrinogen concentration (Rsp of 0.280) during hospitalization and a worse prognosis. CONCLUSIONS AND CLINICAL IMPORTANCE: Measurement of plasma iron concentration better reflected acute inflammation than did fibrinogen concentration.     

Serum amyloid A in equine health and disease

Serum amyloid A (SAA) is the major acute phase protein in horses. It is produced during the acute phase response (APR), a nonspecific systemic reaction to any type of tissue injury. In the blood of healthy horses, SAA concentration is very low, but it increases dramatically with inflammation. Due to the short half-life of SAA, changes in its concentration in blood closely reflect the onset of inflammation and, therefore, measurement of SAA useful in the diagnosis and monitoring of disease and response to treatment. Increases in SAA concentration have been described in equine digestive, reproductive and respiratory diseases and following surgical procedures. Moreover, SAA has proven useful for detection of some subclinical pathologies that can disturb training and competing in equine athletes. Increasing availability of diagnostic tests for both laboratory and field use adds to SAA's applicability as a reliable indicator of horses’ health status. This review article presents the current information on changes in SAA concentrations in the blood of healthy and diseased horses, focussing on clinical application of this biomarker.     

Validation of a Commercial Enzyme Immunoassay for Detection of Clostridium difficile Toxins in Feces of Horses with Acute Diarrhea

Background: Clostridium difficile infection (CDI) is a recognized cause of colitis in the horse. Identification of its toxins is important for management of individual cases and for prevention of transmission and zoonosis. In humans, CDI diagnosis is performed with enzyme immunoassays, none of which have been validated for horses. Hypothesis/Objectives: (1) Establish which test for CDI diagnosis was more frequently used by diagnostic laboratories, (2) determine the identified test's performance, sensitivity, and specificity, and (3) validate its use in diarrheic horses. Animals: Samples were obtained from 72 horses presented with acute diarrhea and hospitalized at the Ontario Veterinary College, University of Guelph. Methods: A survey was conducted to establish which of the tests for CDI diagnosis in horses is most commonly used throughout North America. A questionnaire was sent to all laboratories registered in the Veterinary Infection Control Society and the American Association of Veterinary Laboratory Diagnosticians. The performance of the test was evaluated by comparison to a cell cytotoxicity assay (CTA), the accepted Gold Standard for C. difficile toxin detection. Results: The Techlab C. difficile Tox A/B II ELISA was the most frequently used test. Compared with the CTA, no significant difference was observed, and a good level of agreement (93%) was obtained. The diagnostic performance of the ELISA test was adequate (84% sensitivity and 96% specificity). Conclusions and Clinical Importance: Results demonstrate that the Techlab C. difficile Tox A/B II ELISA is a reliable, adequate, and practical tool for identification of C. difficile toxins in horse feces.     

Plasma lactate as a predictor of colonic viability and survival after 360 degrees volvulus of the ascending colon in horses

Objectives— To determine the relationship between plasma lactate concentration and colonic viability and survival in horses with ≥360° volvulus of the ascending colon.
Study Design— Retrospective study.
Animals— Horses (n=73) with ≥360° volvulus of the ascending colon.
Methods— Medical records (January 2000–November 2005) of all horses examined for colic at Michigan State University Veterinary Teaching Hospital were reviewed. Horses were included only if plasma lactate concentration was measured preoperatively and a diagnosis of ≥360° volvulus of the ascending colon was confirmed by surgery or necropsy. Non-survivors were only included if the ascending colon was evaluated histopathologically. Logistic regression analysis was used to model the relationship between lactate, colonic viability, and survival.
Results— Of 73 horses, 61 were discharged. Mean (±SD) plasma lactate concentration was significantly lower in survivors (2.98±2.53 mmol/L) compared with non-survivors (9.48±5.22 mmol/L; odds ratio [OR]=1.628, 95% confidence limit [CI]=1.259–2.105). Plasma lactate concentration was significantly lower in horses with a viable colon (3.30±2.85 mmol/L) compared with horses with a non-viable colon (9.1±6.09 mmol/L; OR=1.472, 95% CI=1.173–1.846). Plasma lactate concentration <6.0 mmol/L had a sensitivity of 84% and a specificity 83% for predicting horse survival.
Conclusions— Our results demonstrate a strong association between plasma lactate concentration at the time of hospital admission and outcome in horses with ≥360° volvulus of the ascending colon.
Clinical Relevance— Plasma lactate concentration may help predict colonic viability and horse survival after ascending colon volvulus in horses.     

Detection of fibrin deposits in horse tissues by immunohistochemistry

BACKGROUND: Histochemical and immunohistochemical techniques have been used to detect fibrin deposits in different tissues in humans and experimental animal models with disseminated intravascular coagulation (DIC). Fibrin deposits also have been observed in horses with severe ischemic and inflammatory disorders by histochemical stainings (phosphotungstic acid hematoxylin [PTAH]). HYPOTHESIS: Immunohistochemical (IHC) methods can be used to accurately detect fibrin deposits in horses at risk of DIC. ANIMALS: Tissue-organ samples collected on postmortem examination from 87 horses with severe inflammatory and ischemic gastrointestinal disorders. In addition, tissue samples from 13 horses with colic and colonic obstructions or displacements and from 13 slaughter horses were used as controls. METHODS: Tissue samples (kidney, lung, and liver) were stained with PTAH and IHC for blinded histologic examination and comparison. A fibrin score (grades 0 to 4) was established for each tissue sample and for each horse for both techniques. RESULTS: When the IHC method was used, fibrin deposition was observed in 47.1% of the horses with colic with a poor prognosis, compared with 41.4% with PTAH. An agreement of 70% was achieved when both methods were compared, and the lung was confirmed as the most affected organ. Almost none of the colic and slaughter control horses had fibrin deposits in their tissues. CONCLUSIONS AND CLINICAL IMPORTANCE: IHC technique for fibrin antigens was very effective in the detection and identification of fibrin deposits in equine tissues and may be a reliable technique for the postmortem diagnosis of DIC.     

A screening test for subclinical liver disease in horses affected by pyrrolizidine alkaloid toxicosis

Objective: To evaluate various biochemical tests as indicators of subclinical liver disease in horses exposed to pyrrolizidine alkaloid toxicosis.
Design: A clinical pathology field study.
Animals: Twenty-two clinically normal horses from four properties in the Kimberley region of Western Australia.
Procedure: Serum samples from each horse were assayed for gamma glutamyltransferase, alkaline phosphatase and aspartate aminotransferase activities, and for serum bile acid concentration, albumin and total protein. Serum protein electrophoresis was performed and their amino acid profiles determined. Bromosulphophihalein halfclearance times were measured. Horses were then subjected to a single liver biopsy. Results were analysed by, variance of group means, the Fisher-Irwin exact test, and by sensitivity and specificity calculation.
Results: Horses were classified into 2 groups, of 10 unaffected and 12 subclinically affected, on the basis of liver histology. Significant differences between the unaffected and subclinical groups were observed for gamma glutamyltransferase and alkaline phosphatase activities (P < 0.01). Gamma glutamyltransferase had sufficient sensitivity (75%) and specificity (90%) to function as a primary screening test for subclinical liver disease in horses exposed to pyrrolizidine alkaloids. Alkaline phosphatase was useful, but with lower sensitivity (58%).
Conclusion: Serum gamma glutamyltransferase activity is a useful screening test for detecting subclinical liver disease in horses exposed to pyrrolizidine alkaloids under field conditions in northern Australia.