A General Introduction has been added to each disease chapter in an attempt to give a brief updated overview of the taxonomic, biological and other characteristics of the virus family or group of bacteria /protozoa that cause disease in livestock and, where relevant, involve wildlife. As the text of the three-volume book Infectious Diseases of Livestock is currently under revision the Editors are aware that there are inconsistencies between the updated introductions to chapters and the content of the chapters themselves. Once the chapters have been updated – a process that is currently underway – these inconsistencies will be removed.

The bacteria in this group of bacteria are diverse: all are Gram-positive, but they have few other characteristics in common. They vary in their oxygen requirements, with some being aerobic, while others are facultatively anaerobic or anaerobic. Other variable features include their reaction to the catalase test, whether or not they contain cytochromes, differences in their major fermentation products, and the nature of their peptidoglycan and cell wall components. The isolates of veterinary importance, discussed here, are all in the phylum Firmicutes, together with bacteria such as Bacillus, Clostridium, Mycoplasma and Listeria.1

The aerobic genera contain Micrococcus species, which are commonly found on the skin and in the environment and are not known to be pathogenic. The other aerobic genera are soil and marine inhabitants.

The facultatively anaerobic genera include Staphylococcus and Streptococcus, which are of veterinary importance. Their taxonomic status, growth characteristics and the diseases they cause are discussed in the introductory sections to the relevant chapters.

Other genera in this group are Enterococcus, which are discussed under Streptococcus, Gemella, which is found on mucous membranes and can act as an opportunist, Melissococcus, the cause of European foulbrood of bees, and Vagococcus, which has been associated with disease in salmonid fish. The other facultatively anaerobic genera are found in the environment, and are not associated with disease, 1  except as opportunists. Gram positive anaerobic cocci belong to the phylum Actinobacteria, which also includes actinomycetes and bacteria such as Dermatophilus. Only Peptococcus and Peptostreptococcus are of veterinary importance. They occur normally in the intestine, and act as opportunists. The other genera are environmental and intestinal inhabitants.1


  1. HOLT, J.G., KRIEK, N.R., SNEATH, P.H.A., STALEY, J.T. & WILLIAMS, S.T., 2000. Bergey’s Manual of Determinative Bacteriology. 9th edn. Philadelphia, Baltimore: Williams & Wilkins.
  2. SCHLIEFER, K.H., 1986. Gram-positive cocci. in: SNEATH, P.H.A., MAIR, N.S., SHARPE, M.E. & HOLT, J.G., (eds). Bergey’s Manual of Systematic Bacteriology. Vol. II. Baltimore: Williams & Wilkins.
  3. MAGEE, J.G. & WARD, A.C., 2012. Mycobacterium. In: Goodfellow, M. Kampher, P., Busse, H-J., Trujillo, M. E., Suzuki, K-I., Ludwig, W. & Whitman, W. B., (eds). Bergey’s Manual of Systematic Bacteriology Secom Nd Edition, Volume 5 Part A. New York, Dordrecht, Heidelberg, London: Springer.