A 5-year-old female rhesus macaque (Macaca mulatta) was euthanatized due to declining health resulting from experimental infection with simian immunodeficiency virus (SIV). Histopathologic examination of tissues collected at necropsy revealed severe, regionally extensive, granulomatous enterocolitis with intracellular acid-fast bacilli consistent with Mycobacterium species in the colon, ileo-cecal junction, and ileum. The mesenteric lymph nodes also contained intracellular acid-fast bacilli. The diagnosis of mycobacterial disease in this macaque led to a series of actions: all animals previously housed with this macaque were quarantined, and all procedures except for medical treatment were suspended to prevent the spread of a mycobacterial pathogen. Extensive personal protection measures were implemented for humans who had contact with macaques that were exposed to the sick animal. While the location of lesions suggested M. avium complex (MAC) pathogens, infection with M. tuberculosis, M. bovis, or with an atypical Mycobacterium was also considered.1-7
All 60 potentially exposed macaques were tested intradermally for tuberculosis (TB). Feces from the 16 animals for which exposure was deemed the most substantial were examined and cultured for Mycobacterium species. Acid-fast bacilli were seen in large numbers on the direct fecal smear of three of the exposed macaques. Four of 16 fecal samples submitted for culture were positive for MAC. These positive fecal cultures included both SIV-infected and non-infected macaques that had lived in the same room as the presenting macaque. One macaque was euthanatized because it reacted to the intradermal TB test and had a positive fecal culture. Fresh tissue and feces were submitted for culture to the Johne’s Testing Center at the University of Wisconsin’s School of Veterinary Medicine and Wisconsin State Laboratory of Hygiene.
Tissue from the intestine of the presenting 5-year-old female SIV-infected macaque that had been fixed in formalin and embedded in paraffin blocks was submitted to multiple laboratories to identify the pathogen using polymerase chain reaction (PCR). PCR primers specific for Mycobacterium tuberculosis complex species, Mycobacterium avium species, and Mycobacterium avium subspecies paratuberculosis could not identify the numerous acid-fast organisms found on histopathologic examination of the specimen of macaque intestine.
The authors would like to acknowledge the following individuals and institutions for their contribution: Johne’s Testing Center at the University of Wisconsin’s School of Veterinary Medicine, the Wisconsin State Laboratory of Hygiene, the National Veterinary Services Pathobiology Laboratory, Ms. Deb Werner-Keln, Ms. Jill Bodden, Mr. Jacque Mitchen, Ms. Stacy Walz, and Ms. Amanda Trainor.
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