Bluetongue virus serotype 20 infections in cattle of breeding age.

Ten cattle (6 heifers and 4 bulls) were inoculated with bluetongue virus (BTV) type 20. Clinical signs, antibody responses, and capabilities of these animals to replicate and maintain virus were assessed. The cattle showed no clinical signs of disease, although they did develop antibodies to BTV which showed long-term increasing titers. Virus was intermittently isolated from samples of blood, but not beyond day 21. Virus was not detected in the semen of the bulls, nor isolated from the tissues of the cattle at necropsy except from the genital tract of the 2 bulls which had been killed within 30 days after their inoculation. Gross and microscopic pathologic changes were not seen in any tissues that were attributable to BTV infection. There was no evidence of damage to the reproductive organs or of the development of a latent carrier state in either the heifers or the bulls.