Authors: Horton D., Lawson B., Egbetade A., Jeffries C., Cunningham A. A., Fooks A. R.
Veterinary Record. DOI10.1136/vr.101275
Abstract
To compare the effect of a single epidural injection of either lignocaine or tramadol on behavioural changes, anaesthetic indices, leucocyte parameters, erythrocyte sedimentation rates and concentration of cortisol in plasma in goats subjected to castration by high tension band. The geographical range of many arboviruses is expanding, with viruses of the genus Flavivirus comprising some of the most widely reported examples. Most concerning is the ability of these viruses to evolve rapidly to exploit new ecological niches, leading to large-scale disease outbreaks (Vazquez and others 2011).
Usutu virus (USUV) is a mosquito-borne flavivirus that illustrates this changing threat. When USUV was first isolated from mosquitoes (Culex univittatus) in South Africa in 1959 it was not associated with disease in animals or humans (Vazquez and others 2011). However, when USUV emerged in Austria in 2001 it caused seasonal epidemic mortality of blackbirds (Turdus merula) that continued into the summers of 2002 and 2003 (Chvala and others 2007). Subsequent spread of USUV associated with wild and captive bird mortality, has occurred in continental Europe, with a northward-range expansion to southwest Germany in 2011 (reviewed by Becker and others 2012). USUV has also been associated with human disease, confirming its zoonotic potential (reviewed by Vazquez and others 2011). This rapid spread, combined with the public and animal health implications, highlights the need for vigilance for this virus.
Mosquito species involved in USUV outbreaks in Europe are present in the UK (Medlock and others 2005) but minimal surveillance for USUV has been undertaken. Serological evidence for exposure to USUV in British birds was reported in 2001–2002 (Buckley and others 2003), but no virus was isolated and no associated bird mortality was reported. In a random sample of 160 bird brains collected in 2001–2009, and tested using a pan-flavivirus RT-PCR assay, no USUV was detected (Johnson and others 2010). Although UK government-funded surveillance schemes for avian influenza and West Nile virus are designed to detect and investigate wild bird mortality (Brugman and others 2012), they do not currently include surveillance for USUV. Here, we have undertaken retrospective targeted surveillance for USUV in England and Wales.
A total of 1623 birds were examined postmortem between 2005 and 2011, submitted from a total of 956 sites with a widespread distribution across England and Wales. A subset of birds was selected for USUV testing, using the following risk criteria from USUV epizootics in continental Europe. Birds that died between 1st March and 30th November 2005-2011 (to include the period of peak vector abundance) and were (1) species known to be susceptible to USUV infection, including residents and summer migrants; (2) birds of other species submitted with either splenomegaly or hepatomegaly or (3) birds of other species with traumatic injuries (due to the possibility of neurological disease precipitating trauma). A further random sample of birds (n = 51) of a variety of species was selected, particularly from southeast England and East Anglia due to their geographical proximity to continental Europe.
Tissue samples of one or more of brain, spleen, liver and kidney (3–5 mg) were pooled for each bird and homogenised. RNA was extracted from clarified lysates either manually (RNeasy Protect Mini procedure, Qiagen) or automatically (RNeasy Mini QIAcube kit, Qiagen), following the manufacturer’s protocols. Extracted RNA was quantified and stored at −70°C. All samples were tested in duplicate for the presence of USUV RNA using a Sybr-based pan-flavivirus PCR assay, as previously described (Johnson and others 2010).
A total of 201 cases were selected for USUV testing (Table 1). Hepatomegaly and/or splenomegaly were present in 12 per cent (24/201) of cases, and trauma was considered to be the cause of death in 38 per cent (76/201) of cases. Pooled tissue samples from all 201 birds tested were negative for USUV using RT-PCR (Johnson and others 2010). All positive controls showed unambiguous amplification plots and dissociation curves.