Bilateral granulomatous guttural pouch infection due to Mycobacterium avium complex in a horse

Nontuberculous Mycobacteria in Horses: A Narrative Review

Nontuberculous mycobacteria (NTM) infections are increasing in human and veterinary medicine. Although horses were initially thought to be resistant to NTM infection, reports of horses suffering from gastrointestinal, respiratory, and reproductive diseases associated with NTM have increased in the last few decades. The aim of this literature review is to summarize the mycobacteria species found in horses, describe clinical manifestations, diagnostic and treatment approaches, and public health concerns of NTM infection in horses. Clinical manifestations of NTM in horses include pulmonary disease, lymphadenitis, soft tissue, bone infections, and disseminated disease. NTM are also linked to granulomatous enteritis, placentitis, and abortions. Currently, diagnostic methods for NTM are limited and include acid-fast microscopy, bacterial cultures, species-specific PCR assays, and gene sequencing. In humans, NTM treatment guidelines are available, but their application appears inadequate and inconsistent. In horses, treatment guidelines for NTM infections are not available. NTM are a serious public health threat as 70% of people with untreated acquired immunodeficiency syndrome (AIDS) have a chronic pulmonary disease caused by NTM. Thus, it is essential that we gain a better understanding of NTM infections in horses and their zoonotic potential.

Granulomatous Rhinitis in a Horse due to Mycobacterium intracellulare Infection

Mycobacterial infections in horses are uncommon, but are caused most frequently by Mycobacterium bovis of the Mycobacterium tuberculosis complex or Mycobacterium avium of the M. avium complex. Disease caused by Mycobacterium intracellulare, the second most common species within the M. avium complex, has not been reported in horses to date. Mycobacteriosis in horses most often presents as enteric, pulmonary or, rarely, systemic disease. Here we report a case of M. intracellulare infection in a horse presenting as a granulomatous nasal mass.