In this issue – July 2012

Abstract

The authors of the first paper this month recommend that equine practitioners should perform serial tracheal aspiration (TA) and bronchoalveolar lavage (BAL) sampling no less than 24 h apart in clinical situations and should be aware that the effects on cytology of repeated sampling may be different in horses with diseased lungs.1. TA and BAL are commonly used for evaluation of respiratory tract disorders, and before and after treadmill investigations for poor performance, but it is unclear what effects multiple sampling has on cytology. In this study, serial TA and BAL was performed at 24-h intervals over days 1–5, a single sample on day 12 and three samples taken on day 17 at 2.5- and 4-h intervals. Serial TA and BAL fluid samples could be collected at 24-h intervals without affecting the cytology of subsequent samples in clinically normal horses. Performing a second TA 2.5 h after the first significantly increased the percentage of neutrophils, which the authors suggest may have been related to a local inflammatory response to the use of lignocaine. Two limitations of the study were the possibility of accidental sampling an ipsilateral lung and the use of a blind-field BAL technique to mimic clinical practice instead of an endoscopic-guided BAL technique. The authors suggest that clinicians need to be cautious when interpreting cytological changes in subsequent BAL samples when using this technique in the field. A case report presents an atypical case of Murray Valley encephalitis virus (MVEV) infection in an apparently healthy Thoroughbred mare that developed acute abdominal pain within just 30 min of being assessed as normal.2. MVEV was implicated in a number of the 273 cases of suspected arboviral infections in horses in Victoria between December 2010 and June 2011. Clinical signs can include ataxia, hyperaesthesia, pyrexia and depression, but definitive diagnosis is difficult because of the low clinical significance of seroconversion. In the horse in question, an exploratory laparotomy revealed volvulus of the left dorsal and ventral colon and some moderate small intestinal distension, but no evidence of bowel compromise. Ataxia and weakness were noticed after recovery from general anaesthesia, but assessment was complicated by the effect of multiple therapeutic interventions. The mare was euthanased 36 h after presentation because of intractable pain. MVEV infection was confirmed on necropsy. The initial presentation of severe pain and rapid disease progression in this case is in contrast to the numerous recent cases of suspected MVEV. The use of hinged circular fixator constructs for the correction of acquired frontal and sagittal plane crural deformities in three skeletally immature dogs is described in a case study.3. This technique involves a pair of hinges and an angular motor, and most information comes from antebrachial deformities. In this study, angular distraction was carried out at a rate of 1–2 mm/day for a total of 10–38 mm distraction in three cases of crural deformities. At long-term follow-up very mild intermittent lameness was observed in two dogs, but not the third. The hinged circular external skeletal fixation and distraction osteogenesis technique allowed for progressive correction of the skeletal deformities and possible compensatory lengthening of the tibial bone, which is not possible with acute correction techniques. A case report documents the use of a combination of neoadjuvant megavoltage radiotherapy and neoadjuvant and adjuvant chemotherapy to decrease the size of a gingival maxilliary squamous cell carcinoma enough to be surgically resectable.4. Carboplatin and doxorubicin were administered pre- and post-radiotherapy, which was delivered to a total dose of 60 Gy, after which surgical resection with clear macroscopic margins was undertaken. This case report includes good images of the mass, as well as CT identification and the computerised imaging of the radiation plan. Multimodality cancer treatment approaches are the gold standard in human medicine and applied in this case resulted in good quality of life for the dog for the 14 months following surgery before the owners opted for euthanasia for recurrent squamous cell carcinoma. A study in south-west Victoria is the first to document scarlet pimpernel poisoning in Australian cattle.5. Poisoning with scarlet pimpernel, also known as red chickweed, causing gastrointestinal toxicity has been reported in sheep in South Africa and cattle in Uruguay. The Australian cattle were believed to be pregnant, but did not grow as well as expected before becoming depressed, lethargic and mildly ataxic. Pregnancy testing found six animals to be aborting and in total 14 animals died or were destroyed because of their condition. Renal failure was detected in all four necropsied animals. Although scarlet pimpernel is not thought to be highly palatable to cattle compared to sheep, recent rainfall and proliferation of this weed in the absence of other palatable feed may have made it more attractive. In a second paper on poisonings, the author suggests that molybdenum (Mo) deficiency may predispose purine-salvaging species, such as sheep, to a variety of chronic, irreversible neuromodulation disorders.6. Cases of Tribulus terrestris motor neurone disease (Tribulus MND), also known as Tribulus staggers, have occurred in sheep for more than 70 years, even though cattle and horses frequently graze the same Tribulus pastures without developing toxicity. This study investigated the role of Mo-deficient diets in the development of Tribulus MND. Eight sheep were fed 25 mg xanthosine/kg body weight per day for 18 weeks mixed into Mo-deficient chaff and monitored for 42 months for the development of MND signs. Two developed chronic, irreversible and progressive limb weakness that was characterised by decreased muscle tone, neurogenic muscular atrophy and reduced ability to bear weight, causing difficulties with standing and walking, both cases occurring within 31 months. The author suggests that in sheep, elevated blood concentrations of xanthosine result in its excessive accumulation in the CNS, leading to astrocyte degeneration and abnormal neuromodulation. Ureaplasma diversum has been associated with various forms of reproductive failure in cattle, even though it has been considered a normal microfloral inhabitant of the lower reproductive tract of females. As U. diversum has not been previously detected in Australia, there has been little research conducted on its effect on cattle reproduction. In this study, samples were taken from 91 males and females, with and without reproductive lesions, from herds in the Upper Murray and Riverina regions of New South Wales.7. Of these, 32 animals were PCR-positive for U. diversum, most of which were female and did not have reproductive lesions, suggesting it may be a non-pathogenic strain of the organism.7. Although the implications of this study are unclear, the authors note that an organism with unknown pathogenicity and epidemiological context has now been detected in Australia. A case report describes a rare fatal case of acute necrotising ventriculitis in a 4-year-old eclectus parrot.8. Two days before presentation, the normally aggressive bird had become unusually friendly and lost her appetite. The bird was initially treated for suspected acute heavy metal poisoning, based on the presence of yellow to brown vomitus and bright green droppings, but it died within 12 h. Necropsy found marked infiltration of branching septate fungal hyphae, including rhizoids, in the ventriculus, and the authors include clear light micrographs. Swabs produced heavy growths of Candida krusei and Rhizopus microspores var. chinensis. The authors conclude that this case expands the potential fungal aetiological diagnoses that should be considered in cases of gastric dysfunction in companion birds. AE Jackson Editor in Chief N Metzl Editorial Officer