a group of infectious diseases in mammals and birds. The causative agents are microorganisms of the group that causes ornithosis, lymphogranulomas, and trachomas. This group occupies an intermediate position between the rickettsiae and viruses with respect to size, antigenic properties, structure, and development. Neorickettsioses have been recorded in almost all countries and have been studied most thoroughly in Europe and North America.
These diseases present a serious problem in the raising of livestock. Neorickettsioses cause infertility and numerous abortions in farm animals; they can also kill many young animals and give rise to atypical forms of pneumonias. These diseases are mostly latent or chronic and can be diagnosed by laboratory methods.