A review of background findings in cynomolgus monkeys (Macaca fascicularis) from three different geographical origins

Abstract

This review was performed to assess variations in background observations in cynomolgus macaques (Macaca fascicularis) originating from three breeding centres located in Mauritius, The Philippines and Vietnam. The data and tissue samples from 90 cynomolgus monkeys (approximately evenly distributed between the three sources) comprising the control groups from 11 regulatory toxicology studies were used for this investigation. Clinical data--age, body weight, organ weights, haematology and serum biochemistry--were analyzed. Samples of stomach, colon, kidney, heart, liver, spleen and lung were examined microscopically and graded to characterize the degree of lymphoplasmacytic cell infiltration. The main microscopic origin-related variations concerned the digestive tract, where the lymphoplasmacytic cell infiltration grade was significantly lower (p0.001) in cynomolgus monkeys from Mauritius when compared with those from Asia. Generally, only the antral mucosa of the stomach was infiltrated in cynomolgus monkeys from The Philippines, whereas both the fundic and antral regions were infiltrated in those from Vietnam. The digestive tract infiltration grade was strongly correlated with the mean white blood cell count in monkeys from all three sources. Spiral-shaped bacteria were observed in the stomach of monkeys from all three sources, but their presence did not correlate with the severity of the gastric infiltrate. Helicobacter heilmannii-type bacteria were almost always seen in the fundus, Helicobacter pylori-type bacteria were only occasionally seen in the antral region. The incidences of other microscopic findings, such as urothelial cytoplasmic inclusions or Balantidium coli in the caecum, also varied according to the source of the monkeys. Some variations in relative organ weights, haematology and serum biochemistry were also related to the origin of the monkeys, but these did not correlate with the microscopic findings.