In this edition (2006)

The first two Australian Veterinary Journal– AVA Vet Ed quizzes follow this month's ‘From the editors’. AVA members can score AVA Vet Ed Continuing Education points by completing the quizzes, which are based on two of the articles in this month's issue. Instructions on how to submit answers are provided below the second quiz. The first paper in this issue is an edited transcript of the Plenary Address, given by Richard Whittington, Professor and Chair of Farm Animal Health at The University of Sydney, to the 2006 Annual AVA Conference in Hobart on 21st May. In this thought-provoking address, ‘Global veterinary defence – where to from here veterinary science?’, Professor Whittington examined the future of the veterinary profession in a world that undervalues their contribution to both human and animal health. He illustrated the need for veterinary involvement in a range of public health issues with three case studies. The editors are delighted that he agreed to provide this transcript for the benefit of the wider veterinary profession. Corynetoxin poisoning is caused by the ingestion of certain plants colonised by a nematode and a bacterium. Poisoning can also occur following ingestion of toxic hay and grain. The toxin produces neurological signs in both sheep and cattle of all ages, and is frequently fatal. Toxicity is due to inhibition of protein glycosolation. Glycoproteins are involved in the formation of specific synaptic connections between neurons, and the majority of transmitter receptors are glycoproteins. Neurological signs and mortalities usually cease about a week after removal from toxic pasture. This review presents the gross and histological findings associated with the disease, and discusses the mechanisms of the interactions between the nematode, the bacterium and the pasture that result in production of the toxin. Corynetoxicosis should be considered when there is high mortality in sheep and cattle following neurological disturbance of uncertain aetiology. This is an excellent example of how much the veterinary profession has to offer in unravelling the complexities of animal disease, as highlighted in Professor Whittington's address. Hydrops fetalis is a condition of gross oedema, usually accompanied by ascities, of the subcutaneous tissue of a fetus. It is sometimes associated with Dexter chondrodysplasia or ‘bulldog’ calf, an inherited disorder reported widely in the Dexter breed of cattle. This paper describes three cases of hydrops fetalis in Dexter calves that all involved diffuse anasarca of the head and body, and the complete absence of, or presence of only rudimentary, lung tissue. The calves were 3rd, 4th or 5th generation inbred descendants of one Dexter dam. While these cases superficially resembled Dexter chrondrodysplasia, DNA testing was negative for both known mutations for the disorder. This Dexter hydrops may be the homozygous state for an autosomally recessive defective gene, but more cases are required to confirm this, and advice of further cases is requested by the authors. This short study sought to determine if monensin has any advantageous effects on energy metabolism in dairy cows in early lactation. Forty Friesian cows in the late stages of pregnancy were divided randomly into two equal groups. Three weeks prior to the expected calving date, one group was given a slow release capsule containing monensin; the other group was given a placebo. Concentrations of serum beta-hydroxybutyrate (BHBA), glucose, total cholesterol and triglycerides were measured 1, 2, 4, 6, and 8 weeks after calving. Serum BHBA and non-esterified fatty acid levels were significantly lower in the monensin treated group than in the control group, and the decline in glucose levels over the test period was more severe in the placebo group. Monensin controlled release capsules administered 3 weeks prior to calving appeared to give some protection against subclinical ketosis in early lactating dairy cows in this study. This study from Melbourne and Murdoch Universities reports the history, clinicopathological findings and results of treatment of 17 cases of canine primary hypoparathyroidism seen over a 14 year period. Dogs with persistent hypocalcaemia, clinical signs suggestive of hypocalcaemia and low serum calcium were included in the investigation. Seizures, muscle tremors or fasciculations, and a stiff gait with muscle tetany or cramping were the most common clinical signs. Over half of the dogs also showed behavioural changes such as lethargy, aggression and anxiety. Hyperventilation, hyperthermia and vomiting were seen in fewer than 50% of dogs. Mean serum calcium was around half the normal level. The duration of clinical signs prior to diagnosis (mean 33 days) did not correlate with the presence of any clinical sign. Serum parathyroid hormone was below reference levels in most dogs in which it was measured. Treatments included parenteral calcium gluconate, anticonvulsants and oral vitamin D. All dogs were discharged from hospital alive, and twelve were still alive at the end of the follow up period, a mean of 14.5 months. The parathyroid gland was histologically normal in two dogs that were necropsied after being euthanased for unrelated causes. Although it is a rare condition in dogs and of unknown aetiology, primary hypoparathyroidism is an important differential diagnosis in dogs with signs of hypocalcaemia. Two 9-week-old Chihuahua pups were attacked and bitten by a male Whistling spider, a type of tarantula. Both pups died within 2 hours of being bitten. Whilst a bite from these spiders has a very low risk of causing adverse reactions in humans, the potential risks to dogs and cats should be recognised, because these spiders are increasingly being kept as pets. Bilateral arytenoid dysfunction is uncommon and in the horse may result from various toxicities or from respiratory infections. When a young Thoroughbred horse developed left laryngeal hemiplegia about 12 months after surgical correction of the same disorder on its right side, an alternative treatment was sought. Insertion of a long term tracheal cannula enabled the horse to resume its racing career in New Zealand, as the current rules of racing prevent these horses from racing in Australia. Questions remain as to whether placement of a long term tracheal cannula confers a competitive athletic advantage, and whether it affects the horse's welfare. Chronic guttural pouch empyema following Streptococcus equi equi infection may result in the formation of chondroids, which are concretions of inspissated pus. This report describes the surgical removal of over 200 chondroids from the guttural pouch of a Warmblood horse that presented with a chronic purulent nasal discharge. The large number of chondroids was not anticipated pre-surgically, because there was no externally apparent retropharyngeal swelling. Although other methods of treatment are reported, surgical removal is the treatment of choice in horses with large numbers of chondroids. The horse was normal on physical examination 3 years after surgery.