Stress-effects in Microcebus murinus.

Histological investigations were made over a 10-year period on 164 lesser mouse lemurs that died spontaneously in captivity. The principal lesions found were chronic nephrosis with nephritis which affects 90% of the animals, myocardial necrosis, respiratory insufficiency induced by interstitial pneumonia, fatty changes in the liver, and splenic and gastric lesions. The following are associated with these pathologies: progressive hypothyroidism, stable hypercorticism, slight medulloadrenal hyperactivity, and sexual disorders such as testicular atrophy in males and estrous cycle disturbance or uterine tumor in females. All these data were treated by correspondence analysis; this showed that, except for some rare cases of death which can be attributed to massive parasitic infestation or generalized cancer, the whole captive population of lesser mouse lemurs is suffering from a syndrome that leads to renal insufficiency and death. Most of the observed pathologies are considered as being associated with aging in mammals. But captive Microcebus murinus died between 3 and 4 years of age, whereas their potential life survival is 13 years. Our hypothesis is that these pathologies arise due to an overload of cortico- and medulloadrenal secretions. The above-mentioned hormonal imbalance could be induced by stress factors occurring in captivity, the most important of which would be social stress.