Black soil blindness: A new mycotoxicosis of cattle grazing Corallocytostroma-infected Mitchell grass (Astrebla spp)

A new, fatal mycotoxicosis of cattle has been recognised in north-western Australia. A feeding trial confirmed the toxicity of a previously unknown species of Corallocytostroma that grows on Mitchell grass (Astrebla spp). The disease has been colloquially named ‘black soil blindness’ because its most prominent features are its confinement to pastures on black soil, and blindness and death of affected animals. Over 500 cattle have died and considerable subclinical disease is present. Above average wet season rainfall and extended growing seasons may explain the emergence of the fungus. The disease is important because cattle production in large areas of Australia utilise Mitchell grass pastures.     

Increasing halothane concentration abolishes anesthesia-associated arrhythmias in cats and dogs

Fifteen cats and 6 dogs developed ventricular arrhythmias during halothane anesthesia. Halothane was administered by precision vaporizer, using a semiclosed anesthetic system. Cardiac arrhythmias were diagnosed within 5 to 10 minutes after a surgical plane of anesthesia was achieved. Arrhythmias in 9 of 15 cats and 3 of 6 dogs were converted to sinus rhythm by increasing the inspired halothane concentration. Conversion to sinus rhythm occurred within 4 minutes. Cardiac arrhythmias were reestablished in 8 of 9 cats and 2 of 3 dogs, after decreasing the inspired halothane concentration to its original value. Increasing the inspired halothane concentration can convert anesthetic-associated ventricular arrhythmias to sinus rhythm in dogs and cats.     

Inotropic mechanisms of dopexamine hydrochloride in horses.

Mechanisms responsible for the positive inotropic effects of dopexamine were investigated in 8 halothane-anesthetized horses. The hemodynamic effects of increasing infusions of dopexamine (5, 10, 15 micrograms/kg of body weight/min) were determined before and after sequential administration of specific antagonists. Using glycopyrrolate and chlorisondamine, and atenolol and ICI 118,551, muscarinic and nicotinic ganglionic, and beta 1, and beta 2-adrenergic receptor blockade, respectively, was induced. Dopexamine infusions induced increase in heart rate, cardiac output, systolic and mean arterial blood pressure, and maximal rate of left ventricular pressure development (+dP/dtmax). Right atrial pressure and systemic vascular resistance decreased. Parasympathetic and ganglionic blockade attenuated cardiac output, systolic and mean aortic blood pressures, and +dP/dtmax responses to dopexamine infusion. Dopexamine-induced increase in heart rate was potentiated by parasympathetic and ganglionic blockade. beta 1-Adrenergic receptor blockade decreased heart rate, cardiac output, arterial blood pressure, and +dP/dtmax from baseline values and markedly reduced the response to dopexamine infusion. beta 2-Adrenergic receptor blockade induced further decrease in hemodynamic variables from baseline values and completely abolished the cardiostimulatory effects of dopexamine on +dP/dtmax. These data indicate that baroreflex activity, beta 1- and beta 2-adrenergic receptor stimulation may be an important cause of dopexamine's positive inotropic effects in horses.     

Barbiturate anesthesia in greyhound and mixed-breed dogs: comparative cardiopulmonary effects, anesthetic effects, and recovery rates

The cardiovascular effects, anesthetic effects, and recovery rates were evaluated in racing Greyhounds under barbiturate anesthesia. Greyhounds and mixed-breed dogs of similar body weights were given (by IV route) thiopental (15 mg/kg), thiamylal (15 mg/kg), methohexital (10 mg/kg), and pentobarbital (20 mg/kg). The anesthesia lasted longer in Greyhound than in non-Greyhound mixed-breed dogs given thiopental, thiamylal, and methohexital. The mean times from recumbency to standing were 3 to 4 times longer for Greyhounds anesthetized with thiobarbiturates than for non-Greyhound mixed-breed dogs anesthetized with the same drugs, with recovery times for some Greyhounds lasting more than 8 hours. With thiobarbiturate anesthesia, Greyhounds had long periods of respiratory depression, struggled, and relapsed into sleep, whereas in the other dogs, the recovery was quiet. Respiratory depression related to the stage of anesthesia was produced by all barbiturates, but did not result in significant changes in blood gas values. Rectal temperature decreased in all dogs, but did not result in significant hypothermia. Cardiovascular variables and acid-base estimations in Greyhounds were not significantly different from those in mixed-breed dogs before and during barbiturate anesthesia. Packed cell volumes in Greyhounds were significantly higher than those in non-Greyhound mixed-breed dogs after the thiobarbiturates and methohexital were administered. Total plasma protein concentrations were significantly lower in Greyhounds, compared with those in the other dogs before and during barbiturate anesthesia. Methohexital is a useful alternative to thiobarbiturates for short-duration barbiturate anesthesia in Greyhounds.     

Immunisation of chickens to reduce intestinal colonisation with Campylobacter jejuni

1. Systemic and intestinal antibody titres were measured in chickens following subcutaneous, intraperitoneal (IP), oral (po) and combined IP/po administration of antigen, in soluble, emulsified or microparticulate form. Antigens tested included keyhole limpet haemocyanin (KLH), killed Campylobacter jejuni whole cells and purified campylobacter flagellin protein.

2. The effect of immunisation with purified flagellin protein or with killed C. jejuni whole cells in reducing intestinal colonisation was assessed. The ability of newly‐hatched chicks to respond to immunisation was limited, possibly because of the immaturity of the immune system rather than maternal suppression of an immune response. Only 5 of 13 birds that were first immunised when 1‐d‐old with KLH showed a systemic response, even after 4 immunisations, whereas 10 of 11 birds that were first immunised at 24 d‐old responded systemically.

3. In an immunisation and challenge experiment, birds that were immunised twice intraperitoneally, at 16 and 29 d‐old, with killed C. jejuni whole cells, had fewer C. jejuni, in the caecal contents than unimmunised control birds. This reduction in intestinal colonisation, to less than 2% of bacterial numbers in control birds, was associated with an increase in specific IgG in intestinal secretions. There was no significant increase in specific IgA or IgM in intestinal secretions following immunisation and challenge.

4. These results indicate that immunisation can reduce the level of intestinal infection with C. jejuni. The protection may be enhanced by developing improved methods of immunisation that stimulate production of increased titres of specific antibody in intestinal secretions, particularly specific IgA antibody.     

Rethinking equine anaesthetic risk: Development of a novel Combined Horse Anaesthetic Risk Identification and Optimisation tool (CHARIOT)

The most widely used method of assessing the physical status of humans presented for anaesthesia is the American Society of Anaesthesiologists Physical Status Classification System (ASA-PS). The ASA-PS has been applied to animals including horses, but its use is problematic. The authors virtually convened a group of internationally recognised equine veterinary anaesthesiologists with the goal of developing a risk assessment tool for the evaluation of healthy and diseased horses presented for anaesthesia. With this survey and analysis, the authors aim to develop a simple rubric system to assess equine anaesthetic risk that augments the ASA-PS system. The goal is to identify both diseased and healthy horses at increased anaesthetic risk prior to induction of anaesthesia so that measures might be implemented to potentially reduce morbidity and mortality.     

The cardiorespiratory and anesthetic effects of clinical and supraclinical doses of alfaxalone in cats

ObjectiveTo determine the cardiorespiratory and anesthetic effects of 0, 5, 15, and 50 mg kg^?1 intravenous (IV) alfaxalone in hydroxypropyl beta cyclodextrin (Alfaxan; Jurox Pty Ltd, Rutherford, NSW, Australia) in cats.Study designFour treatments of alfaxalone were administered in sequential order.AnimalsEight healthy adult cats (four male; four female) weighing between 3.71 and 5.91 kg.MethodsCats were instrumented for hemodynamic measurements. Four (0, 5, 15, and 50 mg kg^?1) IV doses of alfaxalone were administered over one minute, with a 3-hour washout period between doses 0, 5, and 15 mg kg^?1 on Day 0. The 50 mg kg^?1 treatment was administered 24 hours later. Measurements of heart rate, aortic systolic, mean, and diastolic blood pressures, pulmonary arterial and right atrial mean pressures, cardiac output, respiratory rate, tidal and minute volumes, and arterial blood pH and blood gases (PaO₂, PaCO₂) were performed at pre-determined intervals. Systemic vascular resistance and rate pressure product were calculated. The quality of induction, maintenance, and recovery from anesthesia and the response to noxious stimulation were categorically scored.ResultsAlfaxalone administration resulted in dose-dependent cardiorespiratory depression. Decreases in arterial blood pressure and increases in heart rate occurred at higher doses. Most variables returned to baseline by 15-30 minutes. Respiratory rate, minute volume, and PaO₂ decreased. Apnea was the most common side effect. Induction and maintenance quality were judged to be good to excellent at all doses and quality of recovery good to excellent at all but the 50 mg kg^?1 dose. The duration of anesthesia and unresponsiveness to noxious stimulation increased with dose. The administration of the 50 mg kg^?1 dose produced marked cardiorespiratory depression and apnea.Conclusions and clinical relevanceAlfaxalone produced dose-dependent anesthesia, cardiorespiratory depression and unresponsiveness to noxious stimulation in unpremedicated cats. Hypoventilation and apnea were the most common side effects.