A New Adenovirus from Sheep

Serologic and hexon phylogenetic analysis of ruminant adenoviruses

The objectives of this study were to determine the antigenic relationship among ruminant adenoviruses and determine their phylogenetic relationship based on the deduced hexon gene amino acid sequence. Results of reciprocal cross-neutralization tests demonstrated antigenic relationships in either one or both directions among bovine adenovirus type 6 (BAdV-6), BAdV-7, ovine adenovirus type 7 (OAdV-7), caprine adenovirus type 1 (GAdV-1), and deer adenovirus (Odocoileus adenovirus 1, OdAdV-1). No antigenic cross-reactivity was observed among BAdV-1 through -5, and -8 and the other putative ruminant adenoviruses. Two PCR primer sets, one for mastadenovirus and atadenovirus that amplified an approximately 2,700-bp region in the hexon genes were used for comparative studies. Phylogenetic analysis of the deduced hexon amino acid sequences clustered the ruminant adenoviruses on the Mastadenovirus and Atadenovirus genus branches of the Adenoviridae tree. The recent classification of BAdV-6, and -7 as members of the genus Atadenovirus was supported by phylogenetic distance matrix analysis of their deduced hexon amino acid sequences. Further, we propose that BAdV-6 and -7 be recognized as members of new Atadenovirus species, Bovine adenovirus E and Bovine adenovirus F, respectively. Phylogenetic analysis of OdAdV-1 places this virus in the genus Atadenovirus with a proposed new species Odocoileus adenovirus A. OAdV-6 and GAdV-2 are proposed as members of new Mastadenovirus species Ovine adenovirus C and Goat adenovirus A, respectively.

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.

A sixth species of ovine adenovirus isolated from lambs in New Zealand

Two adenoviruses (WV419/75 and WV757/75), isolated from lambs in New Zealand were compared using neutralisation tests with the five recognised ovine adenovirus species, NINE bovine and four porcine adenoviruses. WV419/75 did not cross-react with any of the viruses tested and represents a new ovine adenovirus species (OAV-6). WV757/75 cross-reacted with bovine adenovirus type 7 (BAV-7) with a homologous to heterologous titre ratio of 16 in one direction only, and also showed a substantial one-way cross reaction in haemagglutination-inhibition tests (WV757 antiserum inhibiting haemagglutination by BAV-7). There was therefore insufficient distinction from BAV-7 virus to allow designation as a separate species. Fluorescent antibody studies with WV419 and WV757 demonstrated virus inclusions in the nuclei of infected cells. These were stained by antiserum to OAV-4 indicating presence of the mammalian group antigen. Thin section electron microscope studies showed typical adenovirus particles and associated inclusions in cell nuclei. The similarity of the two viruses to the bovine subgroup 2 adenoviruses in several of their properties is discussed.

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.

Comparative serological studies with mammalian adenoviruses

Nine serotypes of bovine adenovirus, five serotypes of ovine adenovirus, and four serotypes of porcine adenovirus were compared in reciprocal cross-neutralisation tests, to determine if viruses isolated from different species were indeed distinct serotypes. In addition, the above serotypes were tested for possible antigenic relationships with 28 of 32 human adenoviruses, by one-way cross neutralisation tests with human adenovirus antisera. The results indicated that all viruses tested were distinct serotypes. Ovine adenovirus types 4 and 5, until now not compared by neutralisation tests, were confirmed as separate serotypes.