Systemic Spironucleosis In Two Immunodeficient Rhesus Macaques (Macaca mulatta)

Spironucleus spp. are parasites of fish and terrestrial vertebrates including mice and turkeys that rarely cause extraintestinal disease. Two rhesus macaques (Macaca mulatta) were experimentally inoculated with simian immunodeficiency virus mac251 (SIVmac251). Both progressed to simian acquired immune deficiency syndrome (SAIDS) within one year of inoculation and, in addition to common opportunistic infections including rhesus cytomegalovirus, rhesus lymphocryptovirus, and rhesus adenovirus, developed systemic protozoal infections. In the first case, the protozoa were associated with colitis, multifocal abdominal abscessation, and lymphadenitis. In the second case they one of a number of organisms associated with extensive pyogranulomatous pneumonia and colitis. Ultrastructural, molecular, and phylogenetic analysis revealed the causative organism to be a species of Spironucleus closely related to Spironucleus meleagridis of turkeys. This is the first report of extraintestinal infection with Spironucleus sp. in higher mammals and further expands the list of opportunistic infections found in immunocompromised rhesus macaques.