Systemic spironucleosis in 2 immunodeficient rhesus macaques (Macaca mulatta)

Area of Science:

• Veterinary Parasitology
• Primate Immunology
• Infectious Diseases

Background:

• Spironucleus species are known fish and terrestrial vertebrate parasites, rarely causing extraintestinal disease.
• Rhesus macaques (Macaca mulatta) are valuable models for studying simian immunodeficiency virus (SIV) infection and acquired immune deficiency syndrome (AIDS).
• Opportunistic infections are common in SIV-infected macaques progressing to AIDS.

Observation:

• Two SIV-inoculated rhesus macaques developed simian AIDS within one year.
• Both macaques presented with systemic protozoal infections alongside common opportunistic viral infections.
• Protozoa were associated with severe gastrointestinal and lymph node pathology in one macaque, and extensive pneumonia in the other.

Findings:

• Ultrastructural, molecular, and phylogenetic analyses identified the protozoan as a Spironucleus species.
• The identified Spironucleus species is closely related to Spironucleus meleagridis, a turkey parasite.
• This is the first documented case of extraintestinal Spironucleus infection in higher mammals.

Implications:

• This study expands the spectrum of opportunistic infections recognized in immunocompromised rhesus macaques.
• It highlights the potential for Spironucleus to cause severe systemic disease in immunocompromised hosts.
• Findings suggest a need for increased awareness of Spironucleus as a potential pathogen in veterinary and comparative medicine contexts.