A review of African horse sickness and its implications for Ireland

ABSTRACT: African horse sickness is an economically highly important non-contagious but infectious Orbivirus disease that is transmitted by various species of Culicoides midges. The equids most severely affected by the virus are horses, ponies, and European donkeys; mules are somewhat less susceptible, and African donkeys and zebra are refractory to the devastating consequences of infection. In recent years, Bluetongue virus, an Orbivirus similar to African horse sickness, which also utilises Culicoides spp. as its vector, has drastically increased its range into previously unaffected regions in northern Europe, utilising indigenous vector species, and causing widespread economic damage to the agricultural sector. Considering these events, the current review outlines the history of African horse sickness, including information concerning virus structure, transmission, viraemia, overwintering ability, and the potential implications that an outbreak would have for Ireland. While the current risk for the introduction of African horse sickness to Ireland is considered at worst 'very low', it is important to note that prior to the 2006 outbreak of Bluetongue in northern Europe, both diseases were considered to be of equal risk to the United Kingdom ('medium-risk'). It is therefore likely that any outbreak of this disease would have serious socio-economic consequences for Ireland due to the high density of vulnerable equids and the prevalence of Culicoides species, potentially capable of vectoring the virus.     

A retrospective and prospective study of megaesophagus in the parma wallaby (Macropus parma) at the San Diego Zoo, California, USA

At the San Diego Zoo (California, USA), 22 cases of megaesophagus were diagnosed in the parma wallaby (Macropus parma), yielding a prevalence of 21.1%. Parma wallabies often have no clinical signs until severe and chronic dilation of the esophagus is present. Clinical signs of advanced disease include weight loss, swelling of the cervical region, regurgitation without reswallowing of ingesta, short flight distance, depression, collapse, dyspnea, and sudden death. Retrospective and prospective studies at the San Diego Zoo and a multi-institutional survey in the United States were used to try to determine the cause of megaesophagus. The retrospective study did not identify an etiology. The prospective study revealed megaesophagus and severely delayed esophageal transit time in eight of eight animals. Myasthenia gravis, lead toxicosis, toxoplasmosis, and thyroid disease were eliminated as possible causes. Of 286 living and dead parma wallabies surveyed at other institutions, three cases of esophageal diverticulum and one case of megaesophagus were reported. The cause of megaesophagus in parma wallabies was not determined.     

Climate Change Impacts Due to Biogenic Carbon: Addressing the Issue of Attribution Using Two Metrics With Very Different Outcomes

Although not without its critics, considerable recognition has been given to the climate cooling benefits provided by storing carbon from biomass in various storage pools. However, it has recently been found that depending on the storage pool/period and source of biomass, the associated climate impacts may be a burden or a benefit. It is important that carbon accounting schemes and life cycle assessment practitioners take these carbon/CO₂ flux dynamics and the climate impacts that they create into consideration. In this work we illustrate these climate impacts with a Norwegian case study using a material flow analysis of the biogenic carbon in harvested wood products derived from a 2006 harvest year. We illustrate the dynamic carbon balance over time and show how the climate impacts can diverge greatly between two well-known climate impact metrics: global warming potential (GWP) and global temperature potential (GTP). We also show how these climate impacts can be attributed to contributing parties with an example of a glue laminated beam value chain which is stored in a long-lived building. We discuss the associated attribution issues that will inevitably arise and we offer recommendations on how best to minimize them.     

Short-term carbon and nitrogen dynamics in soil,litterfall and canopy of a suburban native forest subjected to prescribed burning in subtropical Australia

Purpose

This study aimed to understand the mechanisms of the variations in carbon (C) and nitrogen (N) pools and examine the possibility of differentiating the burning effects from seasonal and pre-existed N limitations in a native suburban forest ecosystem influenced by prescribed burning in subtropical Australia.

Materials and methods

Soil and litterfall samples were collected from two study sites from 1 to 23 months since last burnt. Soil labile C and N pools, soil C and N isotopic compositions (δ¹³C and δ¹⁵N), litterfall mass production (LM), and litterfall total C, total N, δ¹³C and δ¹⁵N were analysed. In-situ gas exchange measurements were also conducted during dry and wet seasons for Eucalyptus baileyana and E. planchoniana.

Results and discussion

The results indicated that labile C and N pools increased within the first few months after burning, with no correlations with climatic factors. Therefore, it was possible that the increase was due to the burning-induced factors such as the incorporation of ashes into the soil. The highest values of soil and litterfall δ¹⁵N, observed when the study was commenced at the experimental sites, and their high correlations with climatic factors were indicative of long-term N and water limitation. The ¹³C signals showed that soil N concentrations and climatic factors were also two of the main factors controlling litterfall and foliage properties mainly through the changes in photosynthetic capacity and stomatal conductance.

Conclusions

Long-term soil N availabilities and climatic factors were the two of the main driving factors of C and N cycling in the studied forest sites. Further studies are needed to compare soil and litterfall properties before and after burning to profoundly understand the effects of prescribed burning on soil labile C and N variations.