Comparing Mortalities Across Family Lines: A Retrospective Analysis of Mortalities in the Families Macroscelididae and Tupaiidae at the Smithsonian National Zoological Park
Elephant shrews and tree shrews each belong to singular family orders with unique position in mammalian evolution. Elephant shrews (family Macroscelididae) and tree shrews (family Tupaiidae) both have been kept in captivity for the better part of the last century, with three species from each family currently kept in zoos across North America.1 Only a limited amount of information is known about the health of these animals in the wild or in captivity,2-5 but their lifespan and populations in captivity allow for a unique opportunity to study the morbidities and mortalities of a large population over time. This study reviewed the pathology reports for all individuals that lived at the Smithsonian National Zoological Park from 1976 until October of 2008, for greater than 30 days in the families Macroscelididae (n=118) and Tupaiidae (n=89). Causes of mortality were sorted according to etiology and body system to identify important disease processes in either family and to examine trends across species and families. Infectious disease processes were the most important causes of death in both families, causing 28.8% of elephant shrew mortalities (n=34) and 33.7% of tree shrew mortalities (n=30), with bacterial agents causing roughly half of those. Cryptococcosis was the single most prevalent disease process in both families, with 6.8% and 13.5% mortalities in elephant and tree shrews, respectively. The similarities largely end there, with inflammatory causes (n=23), mostly in the respiratory (n=9) and gastrointestinal tract (n=7), causing the second most deaths in the family Macroscelididae, and iatrogenic causes of death third-most common (n=16). Traumatic causes of death were the second-most common in the family Tupaiidae (n=25), and nutritional causes, mainly inanition, were a distant third (n=11), indicating that these animals were extremely susceptible to mortalities due to social stressors. Additional lesions in both families included changes related to age, stress and immunosuppression, such as cataracts, gastric ulcers, metabolic changes in the liver, and candidiasis of the tongue. In the family Macroscelididae, lesions included ringtail or distal extremity necrosis syndrome (n=9) and a mineralization complex manifested as arteriosclerosis, medial calcification or metastatic mineralization (n=23). In the family Tupaiidae, parasitism was far more common, especially by the spiruid nematode Gongylonema (n=11). These differences highlight the variations in husbandry and medical needs of each family, and the need for further investigation into the diseases of these families.
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