Alopecia: possible causes and treatments, particularly in captive nonhuman primates

Abstract

Alopecia (hair loss) occurs in some nonhuman primates housed in captivity and is of concern to colony managers and veterinarians. Here we review the characteristics, potential causes, and treatments for this condition. Although we focus on nonhuman primates, relevant research on other mammalian species is discussed also, due to the relative paucity of studies on alopecia in the primate literature. We first discuss the cycle of hair growth and explain how this cycle can be disrupted to produce alopecia. Numerous factors may be related to hair loss and range from naturally occurring processes (for example, seasonality, aging) to various biologic dysfunctions, including vitamin and mineral imbalances, endocrine disorders, immunologic diseases, and genetic mutations. We also address bacterial and fungal infections, infestation by parasites, and atopic dermatitis as possible causes of alopecia. Finally, we examine the role of psychogenic factors, such as stress. Depending on the presumed cause of the hair loss, various treatment strategies can be pursued. Alopecia in nonhuman primates is a multifaceted disorder with many potential sources. For this reason, appropriate testing for various disease conditions should be completed before alopecia is considered to be related to stress.

Figure 1.

The left arms of 2 female rhesus monkeys, a 24-y-old (left) and a 9-y-old (right). Neither monkey has conspicuous bald spots on its torso. However, the aged monkey has thinner and shorter hair, which is particularly noticeable on her arms. The areas of skin seen on the 9-y-old monkey's arm are not due to alopecia but instead represent a normal parting of the hair produced by hair growing over the arm in one direction and under the arm in the other direction. This part, which varies in width, has been present in all rhesus monkey arms that we have photographed to date.

Figure 2.

Depicted is the change in hair condition in a female rhesus monkey over the course of her pregnancy. The top and bottom photos, in which the hair condition is normal, were taken at the time of conception and 2 mo after parturition, respectively. The middle photo, showing total-body alopecia, was taken during the month when parturition occurred. These photographs are courtesy of E Davis (NIH Animal Center, National Institute of Child Health and Human Development, Poolesville, MD).