J.H. van der Kolk

Laboratory diagnosis of equine pituitary pars intermedia adenoma

The objective of the study was to determine the sensitivity with which an adenoma of the pars intermedia of the pituitary gland can be predicted in horses by measuring the basal concentrations of glucose, cortisol, adrenocorticotropin (ACTH), and insulin, the urinary concentration of corticoids, the urinary corticoid:creatinine ratio, and the plasma cortisol concentration after the administration of 25 IU of ACTH intravenously. The records of 24 cases of histologically confirmed equine pituitary pars intermedia adenomas were used. An adenoma of the pars intermedia of the pituitary gland in horses was predicted with a sensitivity of 100, 100, and 92% for basal plasma ACTH (n = 16), the urinary corticoid:creatinine ratio (n = 7), and basal plasma insulin (n = 12), respectively. The sensitivity of the ACTH-stimulation test was 79% (n = 14).

Acquired multiple Acyl-CoA dehydrogenase deficiency in 10 horses with atypical myopathy

The aim of the current study was to assess lipid metabolism in horses with atypical myopathy. Urine samples from 10 cases were subjected to analysis of organic acids, glycine conjugates, and acylcarnitines revealing increased mean excretion of lactic acid, ethylmalonic acid, 2-methylsuccinic acid, butyrylglycine, (iso)valerylglycine, hexanoylglycine, free carnitine, C2-, C3-, C4-, C5-, C6-, C8-, C8:1-, C10:1-, and C10:2-carnitine as compared with 15 control horses (12 healthy and three with acute myopathy due to other causes). Analysis of plasma revealed similar results for these predominantly short-chain acylcarnitines. Furthermore, measurement of dehydrogenase activities in lateral vastus muscle from one horse with atypical myopathy indeed showed deficiencies of short-chain acyl-CoA dehydrogenase (0.66 as compared with 2.27 and 2.48 in two controls), medium-chain acyl-CoA dehydrogenase (0.36 as compared with 4.31 and 4.82 in two controls) and isovaleryl-CoA dehydrogenase (0.74 as compared with 1.43 and 1.61 nmol min(-1) mg(-1) in two controls). A deficiency of several mitochondrial dehydrogenases that utilize flavin adenine dinucleotide as cofactor including the acyl-CoA dehydrogenases of fatty acid beta-oxidation, and enzymes that degrade the CoA-esters of glutaric acid, isovaleric acid, 2-methylbutyric acid, isobutyric acid, and sarcosine was suspected in 10 out of 10 cases as the possible etiology for a highly fatal and prevalent toxic equine muscle disease similar to the combined metabolic derangements seen in human multiple acyl-CoA dehydrogenase deficiency also known as glutaric acidemia type II.

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.

Anaplasma phagocytophilum infection in horses in the Netherlands

EQUINE granulocytic anaplasmosis is a tickborne disease caused by the obligate intracellular bacterium Anaplasma phagocytophilum (previously Ehrlichia equi ), which can elicit febrile disease in animals and human beings ([Dumler and others 2001][1]). The disease has previously been referred to as

Hormonal responses to acute exercise, training and overtraining a review with emphasis on the horse

Summary Overtraining is an imbalance between training and recovery leading to symptoms associated with a neuroendocrine dysbalance called the overtraining syndrome, a disease characterized by behavioral emotional and physical symptoms similar with depression. Although the prevalence of overtraining is high in human and equine athletes, at present no sensitive and specific test is available to prevent or diagnose overtraining. Nowadays, it is believed that combination of different (hormonal) parameters appear to be the best indicators of overtraining. Therefore, this review provides a summary of previous literature examining the response of the hypothalamic‐pituitary‐adrenal (HPA) axis and the growth hormone‐insulin‐like growth factor‐I (GH‐IGF‐I) axis to acute and chronic exercise as well as overtraining in humans and horses. The exercise induced hormonal responses seem to be equal for the equine as well as the human athlete, which makes comparisons possible. Repeated bouts of exercise are suggested to provide a way to detect subtle changes in hormonal responses in the individual athlete, which may make them an important tool in detecting early overtraining. This should be combined with corticotropin releasing hormone (CRH) stimulation tests and basal ACTH and GH pulsatility determination. Further research is needed to establish the correct training intensity and rest period for the exercise test in equines.

Borrelia burgdorferi infections with special reference to horses. A review

Summary This review discusses the literature on B. burgdorferi infections in view of the rising incidence of this infection in general and the increasing concerns of horse owners and equine practitioners. Lyme disease, the clinical expression of Borrelia infections in man is an important health problem. The geographic distribution of B. burgdorferi infections in equidae should resemble that of human cases because the vector tick involved, Ixodes ricinus, feeds on both species and, indeed, the infection has been established many times in horses. However, a definite diagnosis of the disease “Lyme borreliosis” in human beings as well as in horses and other animals is often difficult to accomplish. Although a broad spectrum of clinical signs has been attributed to B. burgdorferi infections in horses, indisputable cases of equine Lyme borreliosis are extremely rare so far, if they exist at all.

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.

Effect of head and neck position on outcome of quantitative neuromuscular diagnostic techniques in Warmblood riding horses directly following moderate exercise.

REASONS FOR PERFORMING STUDY There has been growing interest in training techniques with respect to the head and neck position (HNP) of the equine athlete. Little is known about the influence of HNP on neuromuscular transmission in neck muscles. OBJECTIVE To test the hypothesis that different HNPs have effect on single fibre (SF), quantitative electromyographic (QEMG) examination and muscle enzyme activity directly after moderate exercise. METHODS Seven Warmblood horses were studied using a standard exercise protocol in 5 HNPs: HNP1: unrestrained; HNP2: neck raised; bridge of nose around the vertical; HNP4: neck lowered and considerably flexed, bridge of nose pointing towards the chest; HNP5: neck raised and considerably extended; bridge of nose in front of the vertical; HNP7: neck lowered and flexed; bridge of nose pointing towards the carpus. Mean consecutive difference (MCD) of single muscle fibre potentials and motor unit action potential (MUP) variables (amplitude, duration, area, turns and phases) were recorded in each fixed position directly after exercise at rest using commercial EMG equipment. Muscle enzyme activity was measured before and 4, 6 and 24 h after exercise. RESULTS Mean consecutive difference in all HNPs was higher than in HNP1 (22 µs, P < 0.001) of which HNP4 was highest with 39 µs compared to 30 µs in HNP2 (P = 0.04); MCD in HNP 5,7 was with 25 µs lower than in HNP 2 and 4 (P < 0.001). Odds ratio for MCD suggestive for conduction delay or block was 13.6 in HNP4 compared to HNP1 (P < 0.001). Motion unit action potential variables followed the same pattern as MCD. Lactate dehydrogenase (LDH) activity increased in HNP4 at 4 h (P = 0.014), 6 h (P = 0.017) and 24 h (P = 0.038) post exercise and in HNP5 and HNP7 at 4 h (P = 0.037; 0.029). CONCLUSIONS AND CLINICAL RELEVANCE HNP4 in particular leads to a higher rise in LDH activity, MCD and MUP variables, indicating that HNPs have effect on variables characterising neuromuscular functionality.

Equine acquired multiple acyl-CoA dehydrogenase deficiency (MADD) in 14 horses associated with ingestion of Maple leaves (Acer pseudoplatanus) covered with European tar spot (Rhytisma acerinum)

This case-series describes fourteen horses suspected of equine acquired multiple acyl-CoA dehydrogenase deficiency (MADD) also known as atypical myopathy of which seven cases were confirmed biochemically with all horses having had access to leaves of the Maple tree (Acer pseudoplatanus) covered with European tar spot (Rhytisma acerinum). Assessment of organic acids, glycine conjugates, and acylcarnitines in urine was regarded as gold standard in the biochemical diagnosis of equine acquired multiple acyl-CoA dehydrogenase deficiency.

Basal glucose metabolism and peripheral insulin sensitivity in equine pituitary pars intermedia dysfunction

Background: Glucocorticoids are suggested to precipitate laminitis and induce insulin resistance in horses. Hypothesis/Objectives: To assess insulin sensitivity and the basal amount of glucose metabolized in equine pituitary pars intermedia dysfunction (PPID). Animals and methods: The euglycaemic hyperinsulinaemic clamp (EHC) technique was performed in seven horses with a diagnosis of PPID based on the presence of hypertrichosis and positive dexamethasone suppression-test results comprising one gelding and six mares with a mean age of 21.1 ± 5.8 (SD; range 15–34) years. Results were compared with those from five negative (healthy) controls comprising two geldings and two mares with a mean age of 10.0 ± 2.5 (range 7–13) years and six positive (diseased) controls comprising two geldings and four mares with a mean age of 12.5 ± 4.5 (range 8–21) years examined during the same period. Differences were assessed by means of the Mann–Whitney U test. Results: Mean basal rate of glucose metabolism (9.0 ± 4.2 versus 16.0 ± 5.2 µmol/kg BW/min; p = 0.030) and mean glucose metabolism rate-to-plasma insulin concentration ratio (2.9 ± 1.6 versus 6.2 ± 2.7 × 10−6; p = 0.048) were significantly lower in PPID horses than in negative controls, respectively. No differences were found between both control groups. Conclusions and clinical importance: In horses suffering from PPID it seems important to reduce the insulin resistance, thereby potentially decreasing the risk of laminitis as being a major complication of equine PPID. Plasma glucose concentration following fasting might be considered in the screening of horses for PPID.