Laurence Lefère

Identification of methylenecyclopropyl acetic acid in serum of European horses with atypical myopathy

REASONS FOR PERFORMING STUDY It is hypothesised that European atypical myopathy (AM) has a similar basis as seasonal pasture myopathy in North America, which is now known to be caused by ingestion of hypoglycin A contained in seeds from the tree Acer negundo. Serum from horses with seasonal pasture myopathy contained the conjugated toxic metabolite of hypoglycin A, methylenecyclopropyl acetic acid (MCPA). STUDY DESIGN Retrospective study on archived samples. OBJECTIVES 1) To determine whether MCPA-carnitine was present in serum of European horses confirmed to have AM; 2) to determine whether Acer negundo or related Acer species were present on AM pastures in Europe. METHODS Concentrations of MCPA-carnitine were analysed in banked serum samples of 17 AM horses from Europe and 3 diseased controls (tetanus, neoplasia and exertional rhabdomyolysis) using tandem mass spectrometry. Atypical myopathy was diagnosed by characteristic serum acylcarnitine profiles. Pastures of 12 AM farms were visited by experienced botanists and plant species were documented. RESULTS Methylenecyclopropyl acetic acid-carnitine at high concentrations (20.39 ± 17.24 nmol/l; range 0.95-57.63 nmol/l; reference: <0.01 nmol/l) was identified in serum of AM but not disease controls (0.00 ± 0.00 nmol/l). Acer pseudoplatanus but not Acer negundo was present on all AM farms. CONCLUSIONS Atypical myopathy in Europe, like seasonal pasture myopathy in North America, is highly associated with the toxic metabolite of hypoglycin A, MCPA-carnitine. This finding coupled with the presence of a tree of which seeds are known to also contain hypoglycin A indicates that ingestion of Acer pseudoplatanus is the probable cause of AM. This finding has major implications for the prevention of AM.

European outbreaks of atypical myopathy in grazing equids (2006-2009). Spatiotemporal distribution, history and clinical features

REASONS FOR PERFORMING STUDY Improved understanding of the epidemiology of atypical myopathy (AM) will help to define the environmental factors that permit or support the causal agent(s) to exert toxicity. OBJECTIVES This European survey of AM aimed to describe spatiotemporal distribution, survival, clinical signs, circumstances in which AM develops and its different expressions between countries and over time. METHODS The spatiotemporal distribution, history and clinical features of AM cases reported to the Atypical Myopathy Alert Group from 2006 to 2009 were described. Comparisons of data from the most severely affected countries and from the large outbreaks were made with Fishers exact and Welchs tests with Bonferroni correction. RESULTS Of 600 suspected cases, 354 met the diagnostic criteria for confirmed or highly probable AM. The largest outbreaks occurred during the autumns of 2006 and 2009 in Belgium, France and Germany. For the first time, donkeys, zebras and old horses were affected, and clinical signs such as gastrointestinal impaction, diarrhoea, penile prolapse, buccal ulceration and renal dysfunction were observed. Affected horses spent >6 h/day on pastures that almost always contained or were surrounded by trees. The latency period was estimated at up to 4 days. Overall survival rate was 26%. Although differences between countries in affected breeds, body condition, horse management and pasture characteristics were recognised, the common presenting clinical signs and mortality were similar between countries. CONCLUSIONS AND POTENTIAL RELEVANCE This study describes new data on case details, history and clinical course of AM that is of preventive, diagnostic and therapeutic value. However, the true impact of the findings of this study on the development of or severity of AM should be tested with case-control studies.

European outbreaks of atypical myopathy in grazing horses (2006–2009): determination of indicators for risk and prognostic factors

REASONS FOR PERFORMING STUDY Appropriate management of atypical myopathy (AM) requires the establishment of an accurate diagnosis and prognosis. Furthermore, preventive measures to avoid AM need to be refined. OBJECTIVES The aims of the study were as follows: 1) to improve the diagnosis of AM; 2) to identify prognostic predictors; and 3) to refine recommended preventive measures based on indicators of risk factors. METHODS An exploratory analysis of cases in Europe between 2006 and 2009 reported to the Atypical Myopathy Alert Group was conducted. Based on clinical data, reported cases were allocated into 2 groups: confirmed or highly probable AM (AM group; further divided into survivors and nonsurvivors); and cases with a low probability of having AM or with another final diagnosis (non-AM group). Using Welchs test and odds ratios corrected for multiple comparisons, the AM vs. non-AM groups were compared to identify indicators for diagnosis and risk factors, and survivors vs. nonsurvivors in the AM group were compared to identify prognostic factors. Sensitivity, specificity and positive and negative predictive values were calculated for specific clinical signs related to final diagnosis and outcome. RESULTS From 600 reported cases, 354 AM cases (survival rate of 26%) and 69 non-AM cases were identified, while there were insufficient data to categorise the remainder. Variables valuable for diagnosing AM compared with similar diseases were as follows: presence of dead leaves and wood and/or trees on pastures; sloping pastures; full-time pasture access; no food supplementation; normal body condition; pigmenturia; normothermia; and congested mucous membranes. Nonsurvival was associated with recumbency, sweating, anorexia, dyspnoea, tachypnoea and/or tachycardia. Survival was associated with remaining standing most of the time, normothermia, normal mucous membranes, defaecation and vitamin and antioxidant therapy. CONCLUSIONS AND POTENTIAL RELEVANCE This study refines the list of risk factors for AM. Clinical signs valuable for diagnosis and prognosis have been identified, enabling clinicians to improve management of AM cases.

Lawsonia intracellularis infection in a 12-month-old colt in Belgium

P. Deprez, DVM, PhD, L. Lefere, DVM, K. Vanschandevijl, DVM, G. van Loon, DVM, PhD, Department of Large Animal Internal Medicine, K. Chiers, DVM, PhD, R. Ducatelle, DVM, PhD, Department of Pathology, Bacteriology and Poultry Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium C. J. Gebhart, DVM, PhD, Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, 1971 Commonwealth Avenue, St Paul, MN 55108, USA Lawsonia intracellularis infection in a 12-monthold colt in Belgium

Ultrasound-guided biopsy as a diagnostic aid in three horses with a cranial mediastinal lymphosarcoma.

An ultrasound examination of the thorax of three horses which were performing poorly or had mild signs of colic showed that they had a cranial mediastinal mass and a pleural effusion. A cytological examination of the pleural fluid showed that it did not contain neoplastic cells. A histological examination of an ultrasound-guided core biopsy of the cranial mediastinal mass showed that in each of the three horses it was a lymphosarcoma.

European outbreak of atypical myopathy in the autumn 2009.

BACKGROUND Atypical myopathy is an acute, severe rhabdomyolysis occurring in grazing horses. In the beginning of October 2009, a new outbreak occurred in several European countries. Geographic, demographic and clinical data of the reported cases in the month October 2009 are described. KEY FINDINGS The survival rate in this outbreak was 25%. The most frequently observed clinical signs were congested mucous membranes, dyspnea, tachycardia, depression, weakness, stiffness, recumbency, trembling, sweating, and myoglobinuria. Nonsurvivors were significantly more likely to be recumbent than survivors. Prognostic factors, symptomatic treatment, and preventive measures are discussed. SIGNIFICANCE Differences were encountered during the described outbreak of atypical myopathy in October 2009 compared with previous outbreaks reported. Equine practitioners should be aware that previous epidemiological studies have shown that after a high prevalence in the autumn, new cases are likely to occur in the following spring.

Determination of the source of increased serotonin (5-HT) concentrations in blood and peritoneal fluid of colic horses with compromised bowel.

REASONS FOR PERFORMING STUDY Increased plasma (5-HT) concentrations are reported in horses predisposed to develop laminitis and after i.v. infusion of endotoxins. In the equine jejunum contractile 5-HT1A-like receptors show tachyphylaxia upon prolonged activation with 5-HT. Therefore, increased systemic 5-HT release in colic horses could play a possible role in the pathophysiology of ileus. OBJECTIVE To investigate possible increased systemic release of 5-HT in colic horses with compromised bowel and to identify the source of 5-HT overload. METHODS Concentrations of 5-HT were determined in plasma and peritoneal fluid (PF) of healthy horses (n = 10), strangulating small intestinal colic horses (n = 18), nonsurgical colic horses (n = 10) and cryptorchid stallions (n = 6). It was attempted to identify the source of 5-HT overload by comparing the blood and PF 5-HT concentrations within horses and by assessing the in vivo platelet activation through determination of the beta-thromboglobulin (beta-TG)/platelet factor 4 (PF4) ratio. RESULTS All horses in the strangulating small intestinal colic group had plasma (P = 0.006) and PF (P = 0.01) 5-HT concentrations above those found in the control group. Plasma beta-TG/PF4 ratio in these horses exceeded 2 in all cases, indicating in vivo platelet activation. Concentrations of 5-HT in PF of colic horses with compromised bowel were significantly lower than the corresponding plasma concentrations (P = 0.005). POTENTIAL RELEVANCE In horses with compromised bowel, significant amounts of 5-HT can be released into the systemic circulation, through massive release of platelet-stored 5-HT. 5-HT is a very potent proinflammatory, vasoconstrictive and immunomodulatory agent. In view of the rapid and prolonged tachyphylaxia, shown for the jejunal 5-HT1A-like receptors, this increased systemic 5-HT release could play a role in the pathophysiology of ileus in horses.

Traditional and Quantitative Assessment of Acid-Base and Shock Variables in Horses with Atypical Myopathy

BACKGROUND Descriptions of acid-base disturbances in atypical myopathy (AM) are limited. OBJECTIVES Describe and compare traditional and quantitative acid-base abnormalities and cardiovascular shock status in horses with AM at admission. ANIMALS 34 horses with AM, 15 healthy controls. METHODS Retrospective case-control study. Records were searched for shock variables (packed cell volume [PCV], blood urea nitrogen [BUN], heart and respiratory rate) and acid-base variables (venous blood gas analysis, electrolytes, total protein, lactate) on admission. Base excess (BE) of free water (BEfw), chloride (BEcl), total protein (BEtp), and unidentified anions (BEua), anion gap (AG), measured strong ion difference (SIDm), and concentration of total nonvolatile weak acids ([Atot]) were calculated. Acid-base classifications, using simplified strong ion model and traditional approach, and shock grades were assigned. A 2-sample Wilcoxon rank-sum test and Bonferroni correction compared variables in AM cases versus control horses. Significance was P < .05/16 for acid-base and P < .05/5 for shock variables. RESULTS Tachycardia, tachypnea, and normal to increased PCV and BUN were common in AM cases. Respiratory, metabolic acid-base alterations, or both were mainly caused by respiratory alkalosis, lactic acidosis, and SIDm alkalosis, alone or in combination. Evaluated variables (except pH, potassium concentration, total protein, and related calculations) were significantly different (P < .001) between AM cases and control horses. The strong ion model provided a more accurate assessment than the traditional approach and identified mixed derangements. CONCLUSIONS AND CLINICAL IMPORTANCE Acid-base derangements should be evaluated in horses with AM and this preferably with the strong ion model.

Incarceration of the small intestine in the epiploic foramen of three calves

THE most frequent causes of small intestinal obstruction in cattle are intussusception and partial or complete intestinal volvulus. Strangulation of an intestinal segment by fibroserosal bands or ligaments, and incarceration in internal or external hernias, are cited in the literature as less common causes (Pearson 1973, Smith 1990). Although strangulation of the small intestine in the epiploic foramen is a well-known cause of colic in the horse (Edwards and Proudman 2002), this type of small intestinal obstruction has rarely been reported in cattle (Dirksen and Doll 2002). This short communication describes the incarceration of the small intestine in the epiploic foramen of three calves. Over a period of 15 years (1988 to 2003), approximately 900 cattle were presented at the Faculty of Veterinary Medicine, Ghent University, with clinical signs of intestinal obstruction. The diagnosis of small intestinal incarceration in the epiploic foramen was made in only three cases. All three were female calves of the Belgian blue breed, aged between one-and-a-half and three months. Clinical signs of moderate to severe abdominal pain had been observed for two to three days before admission. Faecal production was reduced to absent, and one calf passed a small amount of bloody mucoid faeces. All calves were slightly to moderately dehydrated and acidotic (Table 1). Transabdominal ultra sonography was performed in calves 2 and 3 from the left and right abdominal wall using a 2·5 MHz sector scanner (Sonos 100; Hewlett Packard). The presence of dilated small intestinal loops and the absence of motility in those loops were indicative of small intestinal obstruction. Because of the history of ileus for several days and the ultrasonographic findings (in calves 2 and 3), an exploratory laparotomy was performed on each calf through a right flank incision, with the animal in left lateral recumbency. Calves 2 and 3 were premedicated with xylazine 2 per cent (Xyl-M; VMD), received sacrococcygeal epidural anaesthesia, with procaine hydrochloride 4 per cent and local infiltration anaesthesia with procaine (Procaine hydrochloride 4 per cent + adrenaline; Eurovet). Calf 1 received only local infiltration anaesthesia with xylocaine (Alfacaine 2 per cent; Pharmalux). Laparotomy revealed a left to right incarceration of a portion of the jejunum through the epiploic foramen in calves 1 and 2, while in calf 3 the incarceration was from right to left. In calf 1, adhesions between the intestines and the surrounding structures made reposition of the incarcerated segment impossible and the calf was euthanased during surgery. At postmortem examination a large portion of the distal jejunum was found to be firmly entrapped through the 4 cm long, cleft-shaped epiploic foramen. Reposition of the incarcerated jejunal segment was achieved in the other two calves, by careful traction combined with pushing in the same direction. In calf 2, viability of the entire small intestine was judged to be very poor after repositioning of the incarcerated segment because of extensive congestion, and no attempt was made to remove the strangulated part of the intestine. Two tears in the greater omentum were closed and the gaseous distention of the jejunum was reduced by aspiration on multiple sites with a 25 G needle and a suction apparatus. After surgery the animal was treated with a balanced polyionic intravenous fluid (Haemofiltration Solution; Baxter), neomycin and procaine penicillin (Neopen; Intervet) and flunixin meglumine (Finadyne; Schering Plough), but it died within an hour. In calf 3, the incarcerated jejunal segment was located inside the omental bursa between the superficial and deep wall of the greater omentum (right to left herniation). After repositioning this segment, oedema of the mesentery and congestion of the intestine were noticed, but shortly after reduction the colour of the intestinal wall turned pink again and peristalsis returned. The caecum and colon were mildly dilated and gas was removed by suction through a 25 G needle. After closure of the abdomen, the calf was treated for two days with lactated Ringer’s perfusion (Haemofiltration Solution; Baxter) and flunixin meglumine and for three days with neomycin and procaine penicillin. The calf was discharged three days after surgery and was doing well three months later. The epiploic foramen (foramen of Winslow or foramen omentale) forms the entrance to the omental bursa. It is located in the right dorsal abdomen and is bordered by the caudate process of the liver, the pancreas, the caudal vena cava and the hepatic portal vein (Constantinescu 2001). Incarceration of a segment of the small intestine in that foramen is a typical form of obstructive colic in the horse, and was reported in 6·9 per cent of horses surgically treated for colic in a survey by Steenhaut and others (2001). This report demonstrates that incarceration of the small intestine in the epiploic foramen of cattle, although rare, should be included in the differential diagnosis of strangulation of the small intestine. Only one brief reference to this type of strangulating small intestinal disorder in ruminants is reported in the veterinary literature (Dirksen and Doll 2002). Because of its location, exteriorisation and visual inspection of the incarceration is not possible when the laparotomy is performed through a right abdominal wall incision. Correction of the incarceration is therefore technically challenging and has to be carried out blindly, similar to the surgical treatment of epiploic foramen strangulation in horses through a ventral midline approach. In horses complications are known to arise during this blind correction of the entrapped intestinal segments: traction on the intestine during reduction may Calf 1 Calf 2 Calf 3

A commercially available immunoglobulin E-based test for food allergy gives inconsistent results in healthy ponies

REASONS FOR PERFORMING STUDY Commercial immunoglobulin E (IgE)-based tests are available for diagnosis of food allergies and are commonly used in equine practice. However, these tests have been proven unreliable as a screening method in man and other species, but not critically evaluated in equids. Therefore, a commercially available IgE-based test for horses was evaluated. OBJECTIVES To evaluate the consistency of the results obtained with a commercially available IgE-based test for food allergy diagnosis in ponies (Phase I) and to subject ponies to a provocation trial with the presumed allergens (Phase II). STUDY DESIGN Allergen screening followed by experimental food provocation trials in healthy ponies. METHODS Blood samples of 17 healthy Shetland ponies were taken at 2 different time points, sent blinded to a commercial laboratory for screening of common food allergens and the results were evaluated for consistency (Phase I). Ponies that were positive for food allergens were consecutively challenged orally with each allergen separately for 14 days (Phase II). A washout period of one week was applied in ponies with multiple positive results. Clinical parameters and serum amyloid A were monitored during the provocation trial. RESULTS Only 7/17 ponies were negative on the IgE-based test at the 2 time points, 3 had positive results twice but only one tested positive twice for the same food allergen. No abnormalities were noted during the provocation trials. CONCLUSIONS This study demonstrated that this IgE-based test is not a reliable screening tool for food allergy in healthy equids.