Abstract: Although conventional therapies prevent organophosphate (OP) lethality, laboratory animals exposed to such treatments typically display behavioral incapacitation. Pretreatment with purified exogenous human or equine serum butyrylcholinesterase (Eq-BuChE), conversely, has effectively prevented OP lethality in rats and rhesus monkeys, without producing the adverse side effects associated with conventional treatments. In monkeys, however, using a commercial preparation of Eq-BuChE has been reported to incapacitate responding. In the present study, repeated administration of commercially prepared Eq-BuChE had no systematic effect on behavior in rhesus monkeys as measured by a six-item serial probe recognition task, despite 7- to 18-fold increases in baseline BuChE levels in blood. Antibody production induced by the enzyme was slight after the first injection and more pronounced following the second injection. The lack of behavioral effects, the relatively long in vivo half-life, and the previously demonstrated efficacy of BuChE as a biological scavenger for highly toxic OPs make BuChE potentially more effective than current treatment regimens for OP toxicity.

Abstract: The objective of this study was to compare the stress response of horses suffering from laminitis after short- and long-term treatment with the intent to evaluate power spectral analysis of heart rate variability (HRV) for pain monitoring. Data were collected from 19 horses with acute or chronic exacerbating laminitis without known primary disease before and after treatment with non-steroidal anti-inflammatory drugs (NSAID). Recordings were carried out the day after admission to the equine hospital. Measurements were repeated on day 7 of the treatment. The recorded parameters included a clinical orthopaedic index (OLPI: Obel-grade plus hoof tester score), frequency of weight-shifting between contralateral limbs, mean beat-to-beat interval (R-R) duration, standard deviation of continuous R-R intervals, low- (LF) and high-frequency (HF) components of HRV, sympatho-vagal balance (LF/HF), and plasma concentration of cortisol, adrenalin and noradrenalin. The LF represents mainly sympathetic influences on the heart whereas HF is mediated by the parasympathetic tone. Weight-shifting and OLPI decreased significantly with treatment. The LF normalized units (n.u.) decreased after NSAID from 60.41 +/- 21.42 to 51.12 +/- 19.81 and was 49.33 +/- 22.64 on day 7, whereas HF n.u. increased from 35.07 +/- 20.02 to 43.14 +/- 18.30 and was 45.98 +/- 23.00 on day 7. Hormone levels showed no tendency to change with treatment. The OLPI was only correlated with LF/HF, LF and HF (R = 0.57, 0.55 and -0.54 respectively). Significant negative correlations existed between HFn.u. and weight-shifting frequency (R = -0.37), HFn.u. and adrenalin (R = -0.47), and HFn.u. and noradrenalin (R = 0.33). The LFn.u. only correlated positively with adrenalin. Cortisol levels were poorly associated with the other parameters. Determination of the sympatho-vagal influences on cardiac function may offer complementary information for reliable assessment of pain and may represent a valuable alternative method to catecholamine measurements.

Abstract: OBJECTIVE: To determine signalment, history, clinical signs, duration, seasonality, and response to various treatments reported by owners for headshaking in horses. DESIGN: Owner survey. ANIMALS: 109 horses with headshaking. PROCEDURE: Owners of affected horses completed a survey questionnaire. RESULTS: 78 affected horses were geldings, 29 were mares, and 2 were stallions. Mean age of onset was 9 years. Headshaking in 64 horses had a seasonal component, and for most horses, headshaking began in spring and ceased in late summer or fall. The most common clinical signs were shaking the head in a vertical plane, acting like an insect was flying up the nostril, snorting excessively, rubbing the muzzle on objects, having an anxious expression while headshaking, worsening of clinical signs with exposure to sunlight, and improvement of clinical signs at night. Treatment with antihistamines, nonsteroidal anti-inflammatory drugs, corticosteroids, antimicrobials, fly control, chiropractic, and acupuncture had limited success. Sixty-one horses had been treated with cyproheptadine; 43 had moderate to substantial improvement. CONCLUSIONS AND CLINICAL RELEVANCE: Headshaking may have many causes. A large subset of horses have similar clinical signs including shaking the head in a vertical plane, acting as if an insect were flying up the nostrils, and rubbing the muzzle on objects. Seasonality and worsening of clinical signs with exposure to light are also common features of this syndrome. Geldings and Thoroughbreds appear to be overrepresented. Cyproheptadine treatment was beneficial in more than two thirds of treated horses.