E. Gayo

Lambs are Susceptible to Experimental Challenge with Spanish Goat Encephalitis Virus

Spanish goat encephalitis virus (SGEV) is a member of the genus Flavivirus, family Flaviviridae, and causes encephalomyelitis in goats. The aim of this study was to determine whether sheep are susceptible to experimental challenge with SGEV by two different routes. The results show that SGEV can infect sheep by both the subcutaneous and intravenous routes, resulting in neurological clinical disease with extensive and severe histological lesions in the central nervous system. Lambs challenged subcutaneously developed more severe lesions on the ipsilateral side of the brain, but the lesion morphology was similar irrespective of the route of challenge. The clinical presentation, pathogenesis, lesion morphology and distribution shows that SGEV is very similar to louping ill virus (LIV) and therefore any disease control plan must take into account any host species and SGEV vectors as potential reservoirs. Furthermore, discriminatory diagnostics need to be applied to any sheep or goat suspected of disease due to any flavivirus in areas where SGEV and LIV co-exist.

Inflammatory Lesion Patterns in Target Organs of Visna/Maedi in Sheep and their Significance in the Pathogenesis and Diagnosis of the Infection

Ovine visna/maedi (VM) infection is characterized by the development of chronic inflammatory lesions in different organs, mainly in the lung, mammary gland and central nervous system (CNS), with either histiocytic or lymphocytic pattern predominance being described in the CNS. To help to understand the role of host immune response in the development of these patterns, 50 naturally-infected sheep and eight non-infected sheep from intensive milk-producing flocks were studied. The histological lesion patterns in the three main target organs in each sheep were characterized. Lesion severity was determined, including minimal lesions. A histiocytic pattern was observed in 23 sheep (46%), a lymphocytic inflammatory pattern in 19 sheep (38%) and a mixed inflammatory pattern in eight sheep (16%). Forty animals showed moderate or severe lesions (80%), while 10 had minimal lesions (20%). Moderate or severe lesions affected only one target organ in 20 sheep (50%), two organs in 14 sheep (35%) and all three target organs in six sheep (15%). Infection was confirmed by immunohistochemistry (IHC) using an antibody specific for p28 of VM virus/caprine arthritis and encephalitis virus and by polymerase chain reaction (PCR) in all sheep. Minimal inflammatory lesions associated with positive IHC and PCR were observed. The results suggest that the development of a predominant inflammatory pattern in different organs within the same animal may be related to the host immune response. Minimal and focal lesions, not considered previously, should be taken into account when formulating a differential diagnosis in affected sheep.

Genetic Characterization and Phylogenetic Analysis of Small Ruminant Lentiviruses Detected in Spanish Assaf Sheep with Different Mammary Lesions

Small Ruminant Lentiviruses (SRLVs) are widespread in many countries and cause economically relevant, slow, and persistent diseases in sheep and goats. Monitoring the genetic diversity of SRLVs is useful to improve the diagnostic tools used in the eradication programs. In this study, SRLVs detected in Spanish Assaf sheep with different grades of lymphoproliferative mastitis were sequenced. Genetic characterization showed that most samples belonged to type A and were closer to Spanish SRLV isolates previously classified as A2/A3. Four samples belonged to subtype B2 and showed higher homology with Italian B2 strains than with Spanish B2 isolates. Amino acid sequences of immuno-dominant epitopes in the gag region were very conserved while more alterations were found in the LTR sequences. No significant correlations were found between grades of mastitis and alterations in the sequences although samples with similar histological features were phylogenetically closer to each other. Broader genetic characterization surveys in samples with different grades of SRLV-lesions are required for evaluating potential correlations between SRLV sequences and the severity of diseases.

Canine adenovirus type 1 (CAdV-1) in free-ranging European brown bear (Ursus arctos arctos): A threat for Cantabrian population?

Canine adenovirus type 1 (CAdV-1) is responsible for infectious canine hepatitis. The disease has been described in captive American black bear (Ursus americanus) and European brown bear (Ursus arctos arctos), with just one recently reported case in a cub of a free-ranging brown bear (Ursus arctos horribilis) from Alaska. The aim of this work is to summarize findings related to presence and associated mortality of CAdV-1 in 21 free-ranging Cantabrian brown bears (Ursus arctos arctos) submitted to necropsy in Asturias and Castilla y León (northwestern Spain) from 1998 to 2018. On the basis of the anatomopathological findings and laboratory results three free-ranging brown bears died due to infectious canine hepatitis, which is to our knowledge the first description of death due to this disease in free-ranging bears in Europe. Gross lesions consisted of petechial haemorrhages and congestion in different internal organs, haemorrhagic fluid in internal cavities, friable and yellowish liver and thickening of gall bladder. Microscopic lesions were observed mainly in liver, kidney and brain and consisted of multifocal necrosis of cells with presence of basophilic intranuclear inclusions. Immunohistochemical (IHC) and real-time polymerase chain reaction (qPCR) techniques were used to assess the presence of CAdV-1 in paraffin-embedded liver samples. Viral antigens were detected by IHC labelling within hepatocytes and Küppfer cells in the three animals. The presence of viral DNA was confirmed by qPCR in one of them. In order to evaluate the circulation of CAdV-1 in brown bears, a retrospective study was performed using both IHC and qPCR techniques in 11 and 12 additional brown bears, respectively. An extra brown bear was found positive by IHC. This study shows that CAdV-1 surveillance of brown bears and sympatric carnivores should be considered as major concern for the monitoring the population evolution throughout time in this endangered species.