Experimental infection of specific pathogen-free lambs with ovine adenovirus type 4

Ovine adenoviruses infecting sheep and goats in Türkiye: detection and molecular characterization of three different types

Adenoviruses (AdVs) have been detected in a wide variety of animals. To date, eight types of AdVs in sheep and two types in goats have been identified, which belong to two distinct genera, Mastadenovirus and Atadenovirus. Typically, the term pneumo-enteritis is used to describe adenovirus-induced disease in small ruminants, which has been associated with both enteric and respiratory symptoms of varying severity. The aim of this study was to detect and identify AdVs of small ruminants belonging to the genera Mastadenovirus and Atadenovirus. For this purpose, diagnostic samples (47 lung, 27 intestine, and two pooled tissue samples including intestine and lung) from 49 small ruminants (39 sheep and 10 goats) were used. Following the viral DNA extraction, PCR was carried out by using the primers targeting the hexon gene in order to detect both mast- and atadenoviruses. Sequencing the amplified fragments revealed the presence of three types of ovine adenovirus (OAdV): OAdV-3, OAdV-4, and OAdV-8. Specifically, OAdV-3 was detected in two sheep and a goat while OAdV-4 and OAdV-8 were found in only one sheep each. There is still limited data on the interaction between the viruses in different adenovirus genera and the detected disease, as well as the genetic diversity of adenoviruses, especially in small ruminants. In conclusion, the detection of AdVs in lung and intestinal tissues of small ruminants in this study suggests that these viruses may have contributed to the disease and/or predisposed to other agents.

Pulmonary lesions in lambs experimentally infected with ovine adenovirus 5 strain RTS-42

Twelve lambs were inoculated transtracheally and intranasally with Mastadenovirus ovi 5 strain RTS-42 and killed sequentially. Pulmonary lesions were studied by light and electron microscopy. Four lambs served as sham inoculated controls. Pulmonary lesions consisted of multifocal areas of bronchiolitis and alveolitis associated with necrosis and sloughing of isolated type I and type II alveolar epithelial cells and nonciliated bronchiolar epithelial cells. This was followed rapidly by hyperplasia of the remaining epithelium and repair of the damage. A cellular infiltrate of neutrophils and macrophages began at 2 days after inoculation, peaked at 4 days after inoculation, gradually diminished until minimal at 12 days after inoculation, and was resolved at 21 days after inoculation. Surfactant was abundant and, along with debris, was removed from the alveoli by macrophages. Clinical disease was not seen, but lesions were believed to be sufficient to allow bacteria to colonize the lungs and cause severe disease.

Sequential pathological study of experimental porcine adenovirus enteritis

The sequential enteric lesions of experimental porcine adenovirus strain 6618 infection were studied in 18 hysterotomy-derived, colostrum-deprived piglets, by histology, transmission electron microscopy, and an immunoperoxidase technique. Viral particles could be seen in altered epithelial cells of the lower small intestine from 24 hours until 16 days after inoculation. With the immunoperoxidase technique, viral antigen could be found in epithelial cells at 45 days after challenge. Destruction of epithelial cells and shortening of villi could be related directly to the presence of the virus. Histology of the lower jejunum and ileum, which demonstrates intranuclear inclusion bodies, is proposed as a useful diagnostic technique.

Pathology of ovine adenovirus type 4 infection in SPF lambs: pulmonary and hepatic lesions

Seven lambs were challenged with an aerosol of OA4 virus. Four developed mild pulmonary oedema and a sparse accumulation of mononuclear cells around blood vessels similar to results reported previously. In addition, three had focal hepatic necrosis and one of these three had a non-suppurative occlusive cholangitis and portal tract lymphangitis and thrombosis. Basophilic intranuclear IB's were identified in many necrotic hepatocytes, in lymphatic endothelial cells involved in thrombi but in only one bile duct epithelial cell. Ultrastructurally, virions with the characteristics of adenovirus were seen in hepatocytes. Although only one IB was seen in the affected biliary system there was no evidence that it was caused by an agent other than OA4. Virus was considered to infect the respiratory system directly, be swallowed to infect the alimentary system and carried, possibly within cells, via a haematogeneous and/or lymphogenous route to the liver. The effect of naturally acquired virus on sheep is unknown but it is possible that it may predispose the host to more serious infections.