Background Upper respiratory tract disease (URTD) is a significant cause of morbidity in captive orangutans (Pongo abelii, Pongo pygmaeus), and the pathogenesis is often unknown.
Methods The prevalence of respiratory disease in captive European orangutans (201 animals; 20 zoos) and possible predisposing factors were investigated.
Results Bornean orangutans (P. pygmaeus) showed chronic respiratory signs significantly more often (13.8%) than Sumatran (P. abelii; 3.6%), and males (15.8%) were more often afflicted than females (3.9%). Hand-reared animals (21%) developed air sacculitis more often than parent-reared animals (5%). Diseased animals were more often genetically related to animals with respiratory diseases (93%) than to healthy animals (54%). None of the environmental conditions investigated had a significant effect on disease prevalence.
Conclusion Results suggest a higher importance of individual factors for the development of URTD than environmental conditions. Bornean, male and hand-reared orangutans and animals related to diseased animals need increased medical surveillance for early detection of respiratory disease.