RECTAL PROLAPSE IN THE SULAWESI CRESTED BLACK MACAQUE (MACACA NIGRA): MORBIDITY, MORTALITY, AND RISK FACTORS

Empirical data suggest that rectal prolapse (RP) is common in captive Sulawesi crested black macaques (Macaca nigra) in Europe, resulting in the euthanasia of animals that experience repeat occurrences. However, the prevalence, etiology, and risk factors of RP remain unidentified. The aims of this retrospective study were to assess the morbidity and mortality of RP, to provide an overview of management practices, and to identify risk factors for RP in this species. A questionnaire was sent to all European Ex situ Programme institutions that housed M. nigra between 01 January 2014 and 31 December 2020. Zoological Information Management System medical records and the studbook were used to obtain additional information. The questionnaire had a response rate of 65%, accounting for 204 animals. Of these animals, 25 (12.3%) suffered from at least one RP event during the study period and recurrence was noted in 72%. The majority of prolapses reverted naturally, but 28% of afflicted animals were euthanized for this ailment. Institutions with M. nigra with high frequencies of diarrhea (P= 0.035), those that provided diets of ≥90% vegetables and high-fiber pellet (P < 0.001), and those with more male than female M. nigra (P < 0.001) had increased odds of RP. Institutions that provided fruits daily (P < 0.002) had reduced odds of having RP cases. Although correlation of RP with diet was identified, confounding cannot be excluded, and a detailed dietary analysis needs to take place before altering feeding practices. Acute stressors and detection of protozoa in fecal samples were common findings before an RP event. Demographic analysis indicated that aged females, young males, and subordinate individuals were most affected by this condition. Where tested during an RP intervention, animals had low serum levels of vitamin D. Pedigree analysis hinted at genetic predisposition in this species and requires further investigation.