Paratuberculosis in Captive Scimitar-Horned Oryxes (Oryx dammah)

SIMPLE SUMMARY: Paratuberculosis is a bacterial infection occurring globally in ruminants, with an impact on animal health and welfare. The chronic nature of the disease, the variability in infection progression, and immune response can make diagnosis difficult. The disease can have severe consequences in zoological parks where threatened animal species are hosted. In the present study, we investigated paratuberculosis in a group of scimitar-horned oryx, an endangered ruminant species, hosted in a Northern Italy zoological park. The animals were derived from a flock imported from Slovakia. We report the results of different diagnostic techniques and underline the contribution of each to reach a complete diagnosis. Moreover, bacterial genomic investigation yielded an epidemiological contribution, suggesting an Italian origin of the infection, because the bacteria isolates were more similar to strains endemic in Italian cattle livestock than East European isolates. We emphasize the importance of molecular analyses to trace the origin of infections in terms of both geographical and cross-species tracing. We highlight that paratuberculosis has to be taken into account when dealing with endangered ruminant species, because even the death of a single animal can reduce genetic variability. ABSTRACT: Paratuberculosis, a chronic disease caused by Mycobacterium avium subsp. paratuberculosis (MAP), in ten scimitar-horned oryxes (SHOs) hosted in an Italian zoological park and originating from a Slovakian flock, was documented by pathology, molecular, cultural, and serological testing. The infection origin in this threatened species was also investigated by genomic analyses. Following the death of six of the 10 SHOs, serial investigations of dead and alive animals were performed. Necropsy, carried out on five out of six animals, identified intestinal thickening and mesenteric lymphadenomegaly in one of the animals. Histopathology (5/6) revealed lepromatous (2/5) and tuberculoid (2/5) intestinal forms or lack of lesions (1/5). Ziehl-Neelsen and immunohistochemistry stains identified two multibacillary, two paucibacillary forms, and one negative case. MAP was identified by quantitative PCR (qPCR) in tissue samples in five out of five SHOs and was microbiologically isolated from two of the three animals whose fresh tissue samples were available. Fecal samples were collected in four of the six dead animals: all four resulted positive to qPCR and in MAP was isolated in three. ELISA identified MAP-specific antibodies in three of the five dead animals whose serum was available. qPCR identified MAP in the freshly deposited feces of two out of the four alive animals. From the feces of these two animals, MAP was microbiologically isolated in one case. All isolates were classified as MAP type C and profiled as INMV2 and MVS27 by molecular analysis. Genomic analysis of a field isolate revealed clusterization with a European clade but was more similar to Italian than East European isolates. Our findings underline that paratuberculosis should always be considered in zoological parks in which endangered species are hosted. Infection can be subclinical, and multiple combined testing techniques may be necessary.