Isolation of a pathogenic strain of ovine adenovirus type 5 and a comparison of its pathogenicity with that of another strain of the same serotype

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.

Experimental infection of weaned calves and lambs with two strains of bovine adenovirus type 2

The pathogenicity of two genetically different strains of bovine adenovirus type 2 (BAV-2) was tested in a double cross experimental infection of weaned lambs and calves. One of the virus strains was isolated from cattle and represented BAV-2 subgroup "A", while the other was isolated from sheep and belonged to subgroup "B" (Belák et al., 1983). The two virus strains caused infection both in lambs and calves; the viruses were repeatedly reisolated and definite seroconversion was found in all four groups. However, remarkable differences were observed in the pathogenicity: the most intensive virus multiplication and shedding, the most severe clinical symptoms and histopathological lesions were observed in the lamb group infected with the ovine isolate.

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.

Vaccination against ovine pneumonia: a progress report

The results of three field trials of a live, cold-adapted, parainfluenza virus type 3 vaccine supported the hypothesis that infection with this virus initiates some ovine pneumonias. The serological response following vaccination was poor and only 22-44% of vaccinates developed a serum antibody response by two weeks after vaccination. Nevertheless, the prevalence of pneumonia was lower in vaccinated lambs in all three trials at the time that natural infection with PI3 was detected in the non-vaccinated lambs hut the differences were significant in only one trial. In some of the trials the number of deaths and the number of carcases downgraded or condemned because of severe pleural lesions were also lower and growth rates were higher in vaccinated lambs. The vaccine was specific for PI3; thus there was little effect on the prevalence of pneumonias occurring at other times in the absence of new PI3 infections. Nevertheless, this is the first direct evidence that any virus has a role in naturally occurring ovine pneumonias and the first indication that the prevalence of the naturally occurring disease may be reduced by vaccination.