Bluetongue and Douglas virus activity in New South Wales in 1989: further evidence for long-distance dispersal of the biting midge Culicoides brevitarsis

SUMMARY: Infection of cattle with bluetongue and Douglas viruses was detected on the central and southern coast of New South Wales from January to April 1989. Bluetongue virus infection was found well south of areas of expected occurrence. Evidence is presented to support wind-borne dispersal of infected vectors, Culicoides brevitarsis , southwards from the Hunter Valley.     

An epizootic of bovine ephemeral fever in New South Wales in 2008 associated with long-distance dispersal of vectors

Objective To report the rapid transmission of bovine ephemeral fever ( BEF) virus from north-western New South Wales south to the Victorian border in January 2008 and to present data that suggests an uncommon meteorological event caused this rapid southward dispersal of vectors. Procedure The locations of reported clinical cases, data from sentinel herds and results from a survey of cattle in the southern affected area were examined to delineate the distribution of virus transmission. Synoptic weather charts for January 2008 were examined for meteorological conditions that may have favoured movement of vectors in a southerly direction. Results Cases of BEF and exposure to BEF virus in NSW were confirmed west of the Great Dividing Range, extending from the Queensland border to Finley, on the far North Coast and around the Hunter Valley. A low-pressure system moved south across the state on 18–19 January 2008, preceding the first cases of BEF in the south of NSW by 1–2 days. Conclusion Heavy rainfall in December 2007 provided a suitable environment for vector breeding, resulting in the initiation of and support for continuing BEF virus transmission in north-western NSW. The movement of a low-pressure system south across central western NSW in mid-January 2008 after the commencement of BEF virus transmission in the north-west of the state provided a vehicle for rapid southward movement of infected vectors.     

Evaluation of Factors Influencing the Generation of Ammonia in Different Bedding Materials Used for Horse Keeping

Bedding material is an important factor in determining stable air quality in terms of ammonia formation. The objective of this study was to analyze different bedding materials used for horse stables under standardized conditions, to determine which material is best suited for improving the climate of a stable. The particular concern was a reduction in gaseous ammonia concentrations. Therefore, the following materials were examined: wheat straw, wood shavings, hemp shives, linen shives, wheat straw pellets, and paper cuttings. Twelve containers were constructed in an environmentally controlled room, and the same material was placed into two containers, with the amount of material used being determined by its carbon content. A defined ratio of horse manure/urine mixture was added daily to each container over a period of 14 days. The concentrations of gaseous ammonia, carbon dioxide, nitrous oxide, and water vapor were measured continuously above the bedding within the containers. Means of gaseous ammonia were found to be 178.0 mg/m³ for wheat straw, 155.2 mg/m³ for wood shavings, 144.6 mg/m³ for hemp, 133.7 mg/m³ for linen, 60.3 mg/m³ for straw pellets, and 162.6 mg/m³ for paper cuttings. In conclusion, the results of this study have shown that straw pellets are suitable for horse stables, not only to improve air quality but also, first and foremost, in relation to ammonia binding and ammonia transformation within the bedding material, respectively. However, straw pellets may also have disadvantages. The high substrate temperatures that were measured in straw pellets could favor the growth of pathologic germs that can adversely affect animals' health.     

Identification of toxigenic Pasteurella multocida in atrophic rhinitis of pigs by in vitro characterisation

Toxigenic strains of Pasteurella multocida were readily differentiated from non-toxigenic strains by an agarose overlay method using bovine turbinate cells or bovine lung cells. Cells which were young and densely confluent were best suited to this assay. The incubation period required to distinguish toxigenic strains was dependent on the confluence of the monolayers, which was affected by the seeding rate, cell passage level and growth time prior to overlay. The agarose overlay method correctly identified 11 of 11 reference strains of Pasteurella multocida, and visible cytotoxic changes were present in the monolayers after 48 to 65 h. Outbreaks of the enzootic form of atrophic rhinitis in 2 New South Wales piggeries were associated with the isolation of toxigenic type D strains of P. multocida.     

Influence of elevated CO2 and mycorrhizae on nitrogen acquisition: contrasting responses in Pinus taeda and Liquidambar styraciflua

An understanding of root system capacity to acquire nitrogen (N) is critical in assessing the long-term growth impact of rising atmospheric CO2 concentration ([CO2]) on trees and forest ecosystems. We examined the effects of mycorrhizal inoculation and elevated [CO2] on root ammonium (NH4+) and nitrate (NO3-) uptake capacity in sweetgum (Liquidambar styraciflua L.) and loblolly pine (Pinus taeda L.). Mycorrhizal treatments included inoculation of seedlings with the arbuscular mycorrhizal (AM) fungus Glomus intraradices Schenck & Smith in sweetgum and the ectomycorrhizal (EM) fungus Laccaria bicolor (Maire) Orton in loblolly pine. These plants were then equally divided between ambient and elevated [CO2] treatments. After 6 months of treatment, root systems of both species exhibited a greater uptake capacity for NH4+ than for NO3-. In both species, mycorrhizal inoculation significantly increased uptake capacity for NO3-, but not for NH4+. In sweetgum, the mycorrhizal effect on NO3- and NH4+ uptake capacity depended on growth [C02]. Similarly, in loblolly pine, the mycorrhizal effect on NO3- uptake capacity depended on growth [CO2], but the effect on NH4+ uptake capacity did not. Mycorrhizal inoculation significantly enhanced root nitrate reductase activity (NRA) in both species, but elevated [CO2] increased root NRA only in sweetgum. Leaf NRA in sweetgum did not change significantly with mycorrhizal inoculation, but increased in response to [CO2]. Leaf NRA in loblolly pine was unaffected by either treatment. The results indicate that the mycorrhizal effect on specific root N uptake in these species depends on both the form of inorganic N and the mycorrhizal type. However, our data show that in addressing N status of plants under high [CO2], reliable prediction is possible only when information about other root system adjustments (e.g., biomass allocation to fine roots) is simultaneously considered.     

A study of cardiovascular function under controlled and spontaneous ventilation in isoflurane–medetomidine anaesthetized horses

Objective To determine, in mildly hypercapnic horses under isoflurane–medetomidine balanced anaesthesia, whether there is a difference in cardiovascular function between spontaneous ventilation (SV) and intermittent positive pressure ventilation (IPPV). Study design Prospective randomized clinical study. Animals Sixty horses, undergoing elective surgical procedures under general anaesthesia: ASA classification I or II. Methods Horses were sedated with medetomidine and anaesthesia was induced with ketamine and diazepam. Anaesthesia was maintained with isoflurane and a constant rate infusion of medetomidine. Horses were assigned to either SV or IPPV for the duration of anaesthesia. Horses in group IPPV were maintained mildly hypercapnic (arterial partial pressure of carbon dioxide (PaCO₂) 50–60 mmHg, 6.7–8 kPa). Mean arterial blood pressure (MAP) was maintained above 70 mmHg by an infusion of dobutamine administered to effect. Heart rate (HR), respiratory rate (f_R), arterial blood pressure and inspiratory and expiratory gases were monitored continuously. A bolus of ketamine was administered when horses showed nystagmus. Cardiac output was measured using lithium dilution. Arterial blood‐gas analysis was performed regularly. Recovery time was noted and recovery quality scored. Results There were no differences between groups concerning age, weight, body position during anaesthesia and anaesthetic duration. Respiratory rate was significantly higher in group IPPV. Significantly more horses in group IPPV received supplemental ketamine. There were no other significant differences between groups. All horses recovered from anaesthesia without complications. Conclusions There was no difference in cardiovascular function in horses undergoing elective surgery during isoflurane–medetomidine anaesthesia with SV in comparison with IPPV, provided the horses are maintained slightly hypercapnic. Clinical relevance In horses with health status ASA I and II, cardiovascular function under general anaesthesia is equal with or without IPPV if the PaCO₂ is maintained at 50–60 mmHg.     

Sequence of cardiovascular changes leading to pulmonary edema in swine fed culture material containing fumonisin

OBJECTIVES: To determine the sequence of cardiovascular and blood gas changes induced by ingestion of fumonisin-containing culture material in swine and to examine the temporal relationship of these changes to plasma sphinganine and sphingosine concentrations. ANIMALS: 12 healthy castrated pigs (38 to 50 kg). PROCEDURE: Pigs were instrumented to permit cardiovascular monitoring and collection of blood samples. Baseline values were obtained, and pigs were randomly assigned to 1 of 2 groups. Control pigs (n = 6) were fed a standard grower diet, whereas culture material that contained 20 mg of fumonisin B1/kg of body weight was added to the feed of treated pigs (n = 6) each day. Hemodynamic data, results of arterial and mixed venous blood gas analyses, and plasma sphinganine and sphingosine concentrations were recorded every 12 hours until treated pigs were euthanatized because of impending death from pulmonary edema. RESULTS: Sphinganine and sphingosine concentrations were increased in plasma of treated pigs within 24 hours of initial fumonisin exposure and continued to increase dramatically until euthanasia. Fumonisin-treated pigs had increased respiratory rate, mean pulmonary artery pressure, and pulmonary artery wedge pressure, along with decreased heart rate and cardiac output in the 12-hour period before euthanasia. Fumonisin-treated pigs also had systemic arterial hypotension, arterial and mixed venous hypoxemia, metabolic acidosis, decreased oxygen delivery, and increased oxygen consumption immediately before euthanasia. CONCLUSIONS AND CLINICAL RELEVANCE: Fumonisin-induced pulmonary edema in swine is probably caused by acute left-sided heart failure. Onset of hemodynamic changes was associated with plasma sphinganine concentration > or = 2.2 microM/L and plasma sphingosine concentration > or = 1 microM/L.