Citation: Stancu, A.C.; Voia, O.S.; Boldura, O.M.; Pasca, S.A.; Luca, I.; Hulea, A.S.; Ivan, O.R.; Dragoescu, A.A.; Lungu, B.C.; Hutu, I. Unusual Canine Distemper Virus Infection in Captive Raccoons (Procyon lotor). Viruses 2023, 15, 1536. https:// doi.org/10.3390/v15071536 Academic Editors: HuaJi Qiu and Norbert Nowotny Received: 30 May 2023 Revised: 6 July 2023 Accepted: 10 July 2023 Published: 12 July 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). viruses Case Report Unusual Canine Distemper Virus Infection in Captive Raccoons (Procyon lotor ) Adrian Constantin Stancu 1 , Octavian Sorin Voia 2, *, Oana Maria Boldura 1 , Sorin Aurelian Pasca 3 , Iasmina Luca 1 , Anca Sofiana Hulea 1 , Oana Roxana Ivan 4 , Alina Andreea Dragoescu 5 , Bianca Cornelia Lungu 1, * and Ioan Hutu 1 1 Faculty of Veterinary Medicine, Horia Cernescu Research Unit, University of Life Sciences “King Michael I”, 300645 Timisoara, Romania; adrianstancu@usab-tm.ro (A.C.S.); oanaboldura@usab-tm.ro (O.M.B.); anca.hulea@usab-tm.ro (A.S.H.); ioan.hutu@fmvt.ro (I.H.) 2 Faculty of Animal Resources Bioengineering, University of Life Sciences “King Michael I”, 300645 Timisoara, Romania 3 Faculty of Veterinary Medicine, University of Life Sciences, 700506 Iasi, Romania; spasca@uaiasi.ro 4 Faculty of Letters, West University, 300223 Timisoara, Romania; oana.ivan@e-uvt.ro 5 Faculty of Agriculture, University of Life Sciences “King Michael I”, 300645 Timisoara, Romania; alina.urlica@usvt.ro * Correspondence: voia@animalsci-tm.ro (O.S.V.); bianca.lungu@fmvt.ro (B.C.L.) Abstract: Canine morbillivirus, also known as canine distemper virus (CDV), is the causative agent of canine distemper (CD), which is a serious contagious disease of canines, large felids, and, oc- casionally, raccoons. This study included seven raccoons from the Timisoara Zoological Garden, Romania. CDV was detected using RT-qPCR on blood samples, but several other exams were also performed—clinical, bacteriological, immunohistochemistry (IHC) and histopathology, toxicological screening, and necropsy—which confirmed CDV infection. Severe digestive disorders (diarrhea and frequent hematemesis) were observed. The necropsy findings included pseudo membranous gastroenteritis, congestion, and pulmonary edema in two raccoons. Immunohistochemistry showed immunolabeled CDV antigenantibodies on the viral nucleocapsid. Histopathology revealed lym- phocyte depletion in mesenteric lymphnodes and intranuclear and intracytoplasmic inclusions in the enterocytes of the small intestine. Based on the RT-qPCR assay, laboratory tests, and the lesions observed, it was established that the raccoons were infected with CDV, which was the cause of death in two cases. The results from the necropsy, histology, and immunohistochemistry in the raccoons are comparable with reported CDV lesions in dogs. In conclusion, several exams may be performed to establish the etiology of possible interspecific viral infection, but only very specific exams can identify aCDV infection. Laboratory analyses must be completed by RT-qPCR assay or IHC to establish infection with uncommon viruses in raccoons with high accuracy. Keywords: raccoons; canine distemper; Canine morbillivirus; RT-qPCR detection; immunohistochemistry; histopathology 1. Introduction Raccoons belong to the family Procyonidae, which includes 18 species. Procyon lotor lives in a large part of North America, from southern Canada to most of continental North and Central America [1]. In the United States, regular outbreaks occur in free-ranging raccoons (Procyon lotor), a species that might play a role in the epidemiology of Morbillivirus canis, known as canine distemper virus (CDV) in domestic dogs [2]. In Europe, raccoons are considered neozoa (invasive species), while being used in fur coat production (in German farms). In Romania, raccoons are wild animals sometimes found in zoological parks, but keeping them as pets, albeit illegal, is becoming a new trend. Viruses 2023, 15, 1536. https://doi.org/10.3390/v15071536 https://www.mdpi.com/journal/viruses