Actinomycosis, Nocardiosis, and Mycobacterial Infections

This chapter discusses the pathophysiology, epidemiology, clinical signs, diagnosis, therapy, prognosis, and public health implications of actinomycosis, nocardiosis, and mycobacteriosis. In both dogs and cats actinomycosis is most commonly associated with subcutaneous and soft tissue abscesses and intrathoracic disease. A presumptive diagnosis of nocardiosis may be made based upon macroscopic and microscopic examination of clinical specimens. Nocardiosis is typically classified as subcutaneous, pulmonary and systemic, or disseminated. Treatment of nocardiosis relies upon debridement and drainage of the lesion and prolonged antimicrobial therapy. Mycobacterial infections are recognized increasingly in companion animals because of improved diagnostic techniques and increased use of immunosuppressive medications. The saprophytic mycobacteria are the most common causes of mycobacteriosis in cats and dogs. Younger animals tend to be more commonly affected by mycobacteriosis, particularly cutaneous forms of the disease. © 2020 by John Wiley & Sons, Inc.