Placentitis and abortion caused by canine distemper virus in a Linnaeus's two-toed sloth

Canine distemper virus (CDV; family Paramyxoviridae, taxon species Morbillivirus canis) causes systemic disease in a broad range of mammalian hosts. CDV commonly targets epithelial, lymphoid, and nervous tissues. Reproductive disease is reported less frequently. Here, we describe CDV-associated placentitis and abortion in a 4-y-old, female Linnaeus's two-toed sloth (Choloepus didactylus) from a private collection. The animal developed respiratory and gastrointestinal illness, aborted a midgestational fetus, and subsequently died. Gross examination revealed necrotizing placentitis. Histologically, the uterus and placenta had vasculitis with thrombosis, endothelial syncytia, and intracytoplasmic and intranuclear viral inclusions within endothelial cells. Additional maternal lesions included bronchointerstitial pneumonia, lymphoid depletion, hepatic necrosis, multisystemic intracytoplasmic and intranuclear viral inclusions, and secondary fungal infection. CDV antigen was abundant within endothelial cells, vessel walls, and perivascular stroma in the uterus and placenta by immunohistochemistry. Real-time PCR detected CDV in the maternal uterus, lung, and placenta. The hemagglutinin gene shared 98.3% nucleotide sequence identity with a CDV previously detected in a raccoon in the United States. Our case documents CDV-associated reproductive failure and endothelial tropism in a sloth, highlighting the potential for severe disease in captive nontraditional hosts.