Search

Lagovirus europaeus GI.2, also commonly known as rabbit haemorrhagic disease virus 2, was first detected at two long-term monitoring sites for European rabbits, Oryctolagus cuniculus , in South Australia, in mid-2016. Numbers of rabbits in the following 12-18 months were reduced to approximately 20 per cent of average numbers in the preceding 10 years. The impact recorded at the two South Australian sites, if widespread in Australia and persistent for several years, is likely to be of enormous economic and environmental benefit., Competing Interests: Competing interests: None declared., (© British Veterinary Association (unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

We tested the hypothesis that intracranial pressures and cerebral perfusion pressure in the newborn are more seriously affected by increasing airway pressure during high-frequency oscillatory ventilation (HFOV) than during conventional mechanical ventilation (CMV). Mean airway pressure was acutely elevated in stepwise fashion to 25 cm H2O in six anesthetized, paralyzed newborn lambs. Pressure (mean +/- SE) increased similarly during HFOV and CMV in the jugular vein (7 +/- 1 and 8 +/- 1 cm H2O, respectively), the sagittal sinus (6 +/- 1 and 7 +/- 1 cm H2O), and the cerebrospinal fluid of the lateral ventricle (4 +/- 1 and 6 +/- 1 cm H2O). Decreases in arterial blood pressure (-13 +/- 2 and -10 +/- 2 cm H2O) and cerebral perfusion pressure (-17 +/- 2 and -16 +/- 2 cm H2O) were also similar during HFOV and CMV. Intracranial pressure-volume curves were generated by incrementing cerebrospinal fluid volume in eight lambs. Curves generated during HFOV and CMV were similar, reflecting a similar intracranial compliance during the two ventilatory modes. These data indicate that intracranial compliance and the effects of increasing airway pressure upon intracranial pressures are not significantly different between HFOV and CMV.

Cardio-respiratory physiology in sleep was examined in eight preterm lambs born at 133-135 (134 +/- 1, mean SEM) days of gestation after 3-5 days of pulsatile ACTH/TRH infusion, and contrasted with eight lambs born at term (147 +/- 1 days). Lambs were instrumented with electrodes for recording electrocorticogram, electro-oculogram and nuchal electromyogram to define behavioural states, as well as carotid arterial catheters for determination of arterial pressure, heart rate and arterial blood gases. Compared to full-term lambs, the preterm lambs exhibited extended active sleep times, elevated PaCO2 and faster heart rate in all behavioural states than full-term lambs; with increasing postnatal age, sleep times and heart rate declined. As similar differences are found in preterm human infants, the preterm lamb will be a useful model to study the underlying physiology of these cardio-respiratory alterations.

We aimed to determine the effects of the electrocortical (ECoG) cycle on fetal heart rate and its autonomic control under normoxaemic and hypoxaemic conditions. Heart rate was measured and selective pharmacological blockade was used to quantify sympathetic and parasympathetic tone in low voltage (LV) and high voltage (HV) ECoG. We studied 3 groups of fetal lambs: 6 normal-sized, normoxaemic fetuses (control); 5 growth-retarded, normoxaemic carunclectomy fetuses (carunclectomy-normoxaemic); and 5 growth-retarded, hypoxaemic carunclectomy fetuses (carunclectomy-hypoxaemic). We found slower heart rate in LV compared to HV ECoG in all groups. This was explained by greater parasympathetic tone in LV in all groups, and by a complementary change of sympathetic tone in control fetuses. Hypoxaemic fetuses had slower heart rate than normoxaemic fetuses in both ECoG states. This was due to augmented parasympathetic tone (in LV ECoG) and reduced sympathetic tone (in LV and HV ECoG). We conclude that complementary changes of autonomic tone underly the normal variation of fetal heart rate with the ECoG cycle, with the parasympathetic arm dominant in LV and the sympathetic arm dominant in HV ECoG. In chronic hypoxaemia, complementary changes of autonomic tone contribute to slowing of fetal heart rate. Increased parasympathetic tone and decreased sympathetic tone may enhance cardiac efficiency when the oxygen supply is chronically reduced.