Generalized amyloidosis in rhesus monkeys.

Area of Science:

• Veterinary Pathology
• Primate Medicine
• Comparative Pathology

Background:

• Amyloidosis is a complex disease characterized by extracellular deposition of misfolded proteins.
• Rhesus monkeys are susceptible to various systemic diseases, including amyloidosis, impacting their health and research utility.

Purpose of the Study:

• To characterize the clinicopathological features of generalized amyloidosis in rhesus monkeys.
• To identify the distribution and severity of amyloid deposition in affected organs.
• To investigate potential contributing factors and co-occurring conditions.

Main Methods:

• Retrospective review of necropsy materials from 57 rhesus monkeys with generalized amyloidosis.
• Gross and histopathological examination of tissues to assess amyloid deposition and other lesions.
• Microbiological isolation of Shigella sp. from fecal samples.

Main Results:

• Clinical signs included cachexia, muscle wasting, diarrhea, and arthritis.
• Gross lesions: hepatomegaly, splenomegaly, colitis, cecocolic strictures, osteoarthritis, muscle atrophy.
• Histologic findings: amyloid deposition in small intestine (100%), spleen (93%), large intestine (67%), liver (40%), lymph nodes (71%), stomach/adrenal gland (32%).
• Spleen, liver, and small intestine showed the most significant amyloid accumulation.
• Shigella sp. isolated in 23% of cases; 84% had histologic colitis.
• 100% had lung mites; 25% had cecocolic strictures; 40% had osteoarthritis.
• Age distribution: 60% >10 years, 30% 10 months-5 years, 10% 6-10 years.

Conclusions:

• Generalized amyloidosis in rhesus monkeys presents with significant multi-organ involvement, particularly affecting the gastrointestinal tract and spleen.
• Co-infection with Shigella sp. and pre-existing conditions like colitis and osteoarthritis are common.
• The disease predominantly affects older animals, suggesting age-related factors may play a role.