Congenital malformations and twinning in a breeding colony of Old World monkeys.

Clinical and necropsy records of malformations in Old World monkeys were compiled. The numbers of malformations and birth incidence rate for each species were: Rhesus macaque (Macaca mulatta) 3 (1.02%); Cynomolgus macaque (Macaca fascicularis) 11 (1.62%); Stumptail macaque (Macaca arctoides) 3 (1.55%); African green monkey (Cercopithecus aethiops) 4 (1.5%). There was one pair of rhesus twins (twinning rate: 0.34%). Cardiovascular and central nervous system lesions accounted for 55% of all malformations. Only two of the malformations were in inbred infants. Nine of twenty-one colony-born malformed infants lived 24 hours or more.