P. B. Spradbrow

Skin cancer and papillomaviruses in cattle

We examined proliferative lesions on the sun-exposed, unpigmented skin of 13 cattle. Ages of animals at first examination ranged from 4 to 15 years, and 4 were observed for from one to 3 years, during which time progression to malignancy occurred in 2 of them. Early lesions consisted of keratin scales and horns; histology showed underlying acanthosis and hyperkeratosis. Advanced lesions were either squamous cell carcinomas or basaloid tumours with sebaceous and/or squamous differentiation; some were locally invasive but no metastases were found in the 6 animals that were available for necropsy. All 3 types of lesion could occur on the same animal. In early lesions from 11 of 12 animals, there was evidence for the presence of papillomavirus, either virions or viral DNA, the latter detected by gel electrophoresis and/or molecular hybridization. Viral DNA was also detected in 3 basaloid tumours and 2 squamous cell carcinomas from 4 animals. The DNA bound to a probe of bovine papillomavirus type 1 DNA under conditions of low stringency. We suggest that both infection with papillomavirus and exposure to sunlight, possibly in conjunction with other factors such as a period of photosensitization, are involved in the production of this spectrum of proliferative lesions, which bear some resemblance to human skin cancer.

The effect of mycoplasmas and acholeplasmas of equine origin on organ cultures of chicken-embryo trachea

Chicken-embryo tracheal organ cultures were inoculated with equine strains of Mycoplasma arginini, M. equigenitalium, 2 strains of M. subdolum, Acholeplasma laidlawii and 3 strains of A. oculi. All strains established and multiplied in the explant cultures, but only M. subdolum and A. oculi produced a cytopathic effect on ciliated epithelial cells, causing sloughing of cells and cilia after 6 days. There was a correlation between ciliostasis and increase in titre of both M. subdolum and A. oculi and this relationship was not observed with M. equigenitalium and A. laidlawii. All the strains of acholeplasma multiplied to some extent in organ culture media, but reached higher titres in the presence of explants. Cells infected with the M. subdolum strain showed sloughing of cilia, vacuolization, and increase in size of mitochondria, followed by disorganization of epithelium and marked destruction of subcellular organelles. Mycoplasmas were closely attached to the epithelial surface of the tracheal explant 8 days after infection.

Demonstration of vascular permeability changes in cattle infected with bovine ephemeral fever virus

Five cattle infected with bovine ephemeral fever virus were necropsied on the day after onset of clinical disease, when clinical signs of lameness were most severe. Gross lesions observed included a serofibrinous polyserositis involving the synovial, pericardial, thoracic and abdominal cavities. The associated histological changes consisted primarily of oedema and an influx of neutrophils into affected tissues and fluids. In a further eight infected cattle, increases in permeability of vessels associated with serosal surfaces were demonstrated by labelling with either colloidal carbon or Evans blue. Intravenous injections of carbon provided both macroscopic and histological labelling of affected vessels. Evans blue appeared to be more sensitive than carbon but did not provide a histological marker of vascular permeability and provided labelling of tissues rather than individual vessels. The main sites of increased permeability were synovial, pericardial, thoracic and abdominal serosae.

Establishment of a chicken lymphoblastoid cell line infected with reticuloendotheliosis virus

A lymphoblastoid cell line derived from the spleen of a chicken infected with an Australian strain of reticuloendotheliosis virus (REV) and designated RE-LB was established in suspension culture. The presence of REV antigen in the cells was demonstrated by the indirect fluorescent antibody test, while ultrathin sections of the RE-LB line cells revealed C-type particles. Infection of day-old-chickens with the cellular and cell-free culture fluid of the line produced 100 per cent and 50 per cent mortality, repectively. The line is probably transformed because the cells were agglutinated by concanavalin A and grew in soft agar.