Atypical knemidokoptosis in two Dunnocks (Prunella modularis) in southern England

Avian knemidokoptosis, caused by knemidokoptid mites (Knemidokoptinae: Epidermoptidae), has been reported in wild and domestic birds globally. We report two cases of severe knemidokoptosis in Dunnocks (Prunella modularis) from separate sites in Great Britain, where the disease has previously been reported predominantly in finches and, less frequently, in corvids

Detection of Usutu virus infection in wild birds in the United Kingdom, 2020

In August 2020, as part of a long-term disease surveillance programme, Usutu virus was detected in five Eurasian blackbirds (Turdus merula) and one house sparrow (Passer domesticus) from Greater London, England. This was initially detected by reverse transcription-PCR and was confirmed by virus isolation and by immunohistochemical detection of flavivirus in tissues. Phylogenetic analysis identified Usutu virus African 3.2 lineage, which is prevalent in the Netherlands and Belgium, suggesting a potential incursion from mainland Europe

Characterisation, prevalence and severity of skin lesions caused by ophidiomycosis in a population of wild snakes

Ophidiomycosis is an emerging infectious disease affecting wild snakes in the Northern Hemisphere. Recently confirmed in Great Britain, the prevalence, severity and significance of ophidiomycosis has yet to be characterised in free-living snakes at a population level in Europe. Therefore, a population of barred grass snakes (Natrix helvetica) in eastern England was monitored for three seasons (May 2019 to October 2021), to investigate the prevalence (25.5%; 191/750 snakes) and severity of skin lesions and their aetiology. The most frequently observed skin lesion characteristics were changes in scale colour, crusting, and scale margin erosion. The majority of such lesions (96.9%; 185/191 snakes) was observed on the ventral surface along the length of the body. The severity of skin lesions was considered mild in more than half of the cases (53.1%; 98/191 snakes). Predominantly, skin lesions were observed in adult snakes (72.8%; 139/191 snakes). Combined histological examinations and qPCR tests of skin lesions from N. helvetica sloughs and/or carcasses confirmed a diagnosis of ophidiomycosis. Further targeted surveillance, supported by molecular and histological examinations to confirm skin lesion aetiology, is required to determine the extent to which our findings reflect the occurrence of ophidiomycosis in populations within wider landscapes

Evidence for overwintering and autochthonous transmission of Usutu virus to wild birds following its redetection in the United Kingdom

Usutu virus (USUV) is an emerging zoonotic arbovirus in Europe, where it primarily impacts Eurasian blackbirds (Turdus merula). For mosquito-borne viruses to persist in temperate areas, transovarial transmission in vectors or overwintering in either hosts or diapausing vectors must occur to facilitate autochthonous transmission. We undertook surveillance of hosts and vectors in 2021 to elucidate whether USUV had overwintered in the United Kingdom (UK) following its initial detection there in 2020. From 175 dead bird submissions, we detected 1 case of USUV infection, in a blackbird, from which a full USUV genome was derived. Using a molecular clock analysis, we demonstrate that the 2021 detection shared a most recent common ancestor with the 2020 Greater London, UK, USUV sequence. In addition, we identified USUV-specific neutralizing antibodies in 10 out of 86 serum samples taken from captive birds at the index site, demonstrating in situ cryptic infection and potential sustained transmission. However, from 4966 mosquitoes, we detected no USUV RNA suggesting that prevalence in the vector community was absent or low during sampling. Combined, these results suggest that USUV overwintered in the UK, thus providing empirical evidence for the continued northward expansion of this vector-borne viral disease. Currently, our detection indicates geographically restricted virus persistence. Further detections over time will be required to demonstrate long-term establishment. It remains unclear whether the UK, and by extension other high-latitude regions, can support endemic USUV infection

Combining host and vector data informs emergence and potential impact of an Usutu virus outbreak in UK wild birds

Following the first detection in the United Kingdom of Usutu virus (USUV) in wild birds in 2020, we undertook a multidisciplinary investigation that combined screening host and vector populations with interrogation of national citizen science monitoring datasets to assess the potential for population impacts on avian hosts. Pathological findings from six USUV-positive wild passerines were non-specific, highlighting the need for molecular and immunohistochemical examinations to confirm infection. Mosquito surveillance at the index site identified USUV RNA in Culex pipiens s.l. following the outbreak. Although the Eurasian blackbird (Turdus merula) is most frequently impacted by USUV in Europe, national syndromic surveillance failed to detect any increase in occurrence of clinical signs consistent with USUV infection in this species. Furthermore, there was no increase in recoveries of dead blackbirds marked by the national ringing scheme. However, there was regional clustering of blackbird disease incident reports centred near the index site in 2020 and a contemporaneous marked reduction in the frequency with which blackbirds were recorded in gardens in this area, consistent with a hypothesis of disease-mediated population decline. Combining results from multidisciplinary schemes, as we have done, in real-time offers a model for the detection and impact assessment of future disease emergence events

Distribution and load of elephant endotheliotropic herpesviruses in tissues from associated fatalities of Asian elephants

Elephant Endotheliotropic Herpesviruses (EEHVs) are the cause of a highly fatal haemorrhagic disease in elephants primarily affecting young Asian elephants (Elephas maximus) in both captivity and in the wild. The viruses have emerged as a significant threat to Asian elephant conservation, critically affecting overall sustainability of their population. So far insight into the pathogenesis of EEHV infections has been restricted to examination of EEHV-infected tissues. However, little is known about distribution and burden of the viruses within the organs of fatal cases, crucial elements in the understanding of the virus pathogenesis. This study was therefore undertaken to assess the extent of organ and cell involvement in fatal cases of EEHV-1A, 1B and 5 using a quantitative real-time PCR. EEHV-1 and 5 DNA were detectable in all the tissues examined, albeit with substantial differences in the viral DNA load. The highest EEHV-1A DNA load was observed in the liver, followed by the heart, thymus and tongue. EEHV-1B and 5 showed the highest DNA load in the heart, followed by tongue and liver. This study provides new insights into EEHV pathogenicity and has implications in choice of sample type for disease investigation and virus isolation

Distribution and load of elephant endotheliotropic herpesviruses in tissues from associated fatalities of Asian elephants

Elephant Endotheliotropic Herpesviruses (EEHVs) are the cause of a highly fatal haemorrhagic disease in elephants primarily affecting young Asian elephants (Elephas maximus) in both captivity and in the wild. The viruses have emerged as a significant threat to Asian elephant conservation, critically affecting overall sustainability of their population. So far insight into the pathogenesis of EEHV infections has been restricted to examination of EEHV-infected tissues. However, little is known about distribution and burden of the viruses within the organs of fatal cases, crucial elements in the understanding of the virus pathogenesis. This study was therefore undertaken to assess the extent of organ and cell involvement in fatal cases of EEHV-1A, 1B and 5 using a quantitative real-time PCR. EEHV-1 and 5 DNA were detectable in all the tissues examined, albeit with substantial differences in the viral DNA load. The highest EEHV-1A DNA load was observed in the liver, followed by the heart, thymus and tongue. EEHV-1B and 5 showed the highest DNA load in the heart, followed by tongue and liver. This study provides new insights into EEHV pathogenicity and has implications in choice of sample type for disease investigation and virus isolation

Analysis of viral microRNA expression by elephant endotheliotropic herpesvirus 1.

Elephant endotheliotropic herpesvirus 1 (EEHV1), a member of the Betaherpesvirinae subfamily, has recently emerged as an important viral pathogen of Asian elephants that can cause a severe, often fatal, hemorrhagic disease. EEHV1 does not replicate in culture and little is currently known about the molecular biology of this emerging pathogen, with the notable exception of its genomic DNA sequence. Here, we have used small RNA deep sequencing to determine whether EEHV1, like other human and murine betaherpesviruses, expresses viral microRNAs in infected tissues in vivo. Our data provide evidence supporting the existence of at least three novel viral microRNAs encoded by EEHV1 and one of these, miR-E3-5p, is shown to repress target mRNA expression. Moreover, miR-E3-5p expression was readily detectable in tissue samples derived from two infected elephants, including in whole blood. These data shed new light on the biology of EEHV1 and identify small RNAs that have the potential to be useful in the diagnosis of sub-clinical infections in captive Asian and African elephants

Surviving and fatal Elephant Endotheliotropic Herpesvirus-1A infections in juvenile Asian elephants – lessons learned and recommendations on antiherpesviral therapy

Background: Elephant Endotheliotropic Herpesviruses (EEHVs) can cause acute haemorrhagic disease in young Asian elephants (Elephas maximus) and clinical EEHV infections account for the majority of their fatalities. The antiherpesviral drug famciclovir (FCV) has been used routinely to treat viraemic at-risk elephants, but thus far without proven efficacy. This paper presents clinical and virological investigations of two EEHV-1A infected elephants treated with FCV, and discusses anti-herpesvirus therapies of viraemic elephants. Cases presentations: Two 1.5 year old male Asian elephants at a zoological collection in the UK developed clinical EEHV-1A infections. Case 1 showed signs of myalgia for the duration of 24 hours before returning back to normal. EEHV-1A DNAemia was confirmed on the day of clinical signs and continued to be present for 18 days in total. Trunk shedding of the virus commenced 10 days after detection of initial DNAemia. Case 2 tested positive for EEHV-1A DNAemia in a routine blood screening sample in the absence of clinical signs. The blood viral load increased exponentially leading up to fatal clinical disease seven days after initial detection of DNAemia. Both calves were treated with 15 mg/kg FCV per rectum on detection of DNAemia and penciclovir, the FCV metabolite, could be detected in the blood at assumed therapeutic levels. The early indicators for clinical disease were a marked absolute and relative drop in white blood cells, particularly monocytes prior to the detection of viraemia. The most prognostic haematological parameter at later stages of the disease was the platelet count showing a continuous sharp decline throughout, followed by a dramatic drop at the time of death. Conclusions: The EEHV-1A viraemic animals investigated here further highlight the ongoing threat posed by these viruses to juvenile Asian elephants. The findings call into question the efficacy of rectal FCV in clinical cases and direct towards the use of alternative anti-herpesvirus drugs and complementary treatments such as plasma infusions if no improvement in either viral load or the above-mentioned blood parameters are observed in the initial days of viraemia despite anti-herpesvirus therapy