Fatal fasting syndrome of obese macaques

A retrospective study of clinical and pathological data showed that 42 generally obese macaques died after losing approximately 30% of body weight. The mean duration of illness for 29 monkeys whose clinical histories were known was 17 days. All animals had severe fatty change of livers and proximal convoluted renal epithelium. Some also had partial or complete renal tubular atrophy. Other common lesions were pancreatic ectasia, pancreatitis, or focal pancreatic necrosis often with fat necrosis. These lesions constitute fatal fasting syndrome and were the only ones present in 10 cases. Twenty additional fatal lesions were present in six cases; nonfatal ones were present in 14 cases. The most common of the latter were fecal impaction and traumatic lesions from fighting after being recaged in new social groups. Of 15 animals studied clinically, 13 were azotemic. Other clinico-pathologic findings were not contributory. One of 10 rhesus monkeys followed prospectively after being transferred from a single cage to a gang cage, died 74 days later with no lesions apart from those constituting the syndrome. A biopsy survey of 31 clinically normal obese macaques showed that only three had mildly fatty livers. These data suggested that obese macaques becoming anorexic for any reason die from this syndrome when body weight loss is approximately 0.1 kg/day.