Multiple granulomas in three squirrel monkeys (Saimiri sciureus) caused by Mycobacterium microti

Area of Science:

• Veterinary Pathology
• Mycobacterial Infections
• Primate Health

Background:

• Mycobacterium microti, part of the Mycobacterium tuberculosis complex, is known to cause tuberculosis in rodents and can infect other mammals.
• Squirrel monkeys are susceptible to various infectious diseases, requiring careful monitoring in captive environments.

Observation:

• Three adult male squirrel monkeys presented with clinical signs including lethargy, weakness, stridor, and hind leg paralysis.
• Necropsy revealed disseminated granulomatous lesions in multiple organs (mesentery, lymph nodes, lung, liver, kidneys, spleen) and spinal cord in affected animals.
• Histopathology confirmed tuberculous granulomas with central necrosis and acid-fast bacilli.

Findings:

• Mycobacterium microti was identified as the causative agent in all three squirrel monkeys through microbiological and molecular analyses.
• Lesions varied from localized lung granulomas to disseminated disease and severe spinal cord involvement secondary to vertebral fracture and abscess.

Implications:

• This case report underscores the potential for Mycobacterium microti to cause severe, disseminated tuberculosis in non-human primates.
• Findings highlight the importance of diagnostic vigilance for M. microti in primates, especially those with neurological or systemic signs suggestive of tuberculosis.
• Understanding M. microti's pathogenicity in diverse hosts is crucial for disease control and public health, given its zoonotic implications.