Searching for animal models and potential target species for emerging pathogens: Experience gained from Middle East respiratory syndrome (MERS) coronavirus

Vergara-Alert, Júlia; Vidal, Enric; Bensaid, Albert; Segalés, Joaquim

Besides coronaviruses, highly pathogenic viruses belonging to other families represent a threat to either human or animal health, or both. One of the most recent examples is the outbreak of Ebola virus (Filoviridae) in West Africa, which started in December of 2013 in Guinea and evolved as the largest Ebola outbreak recorded with more than 28,600 cases [8] . Furthermore, during recent years, outbreaks caused by other emerging viral pathogens from Arenaviridae, Bunyaviridae, and Flaviviridae families among others, disturbed public and private health, social networks and the economies of the affected countries [9, 10] . Prevention and control of emerging and reemerging viral diseases is efficient when several actions are combined: i.e. creating diagnostic networks and surveillance programs, training medical and veterinary staff, informing the population about sanitary measures, and also promoting research on prophylaxis, treatments and on the causative agent pathogenesis. Regarding the last point, animal models are crucial to study the viral and host factors contributing to the disease as well as transmission outcomes of virus infection and to allow pre-clinical testing of antiviral drugs and vaccines. Non-human primates (NHP) are the preferred models for pathogenesis studies, and potential vaccine and treatment testing, as they better translate to humans [11] . However, working with NHP is costly, with limited availability, and raises ethical problems. Therefore small-animal models are usually the first choice for drug screening. The United States Food and Drug Administration's (FDA) Animal Rule provides guidelines concerning the appropriateness of animal models for licensing purposes [12] . Additionally, by controlling the disease in animal reservoirs and/or in intermediate hosts, virus transmission to humans can be significantly reduced [13, 14] . This is particularly true for domestic or feral animals for which efficient vaccines and vaccination strategies can be implemented [15] . Therefore, in cases of new pathogenic virus outbreaks, the search for natural hosts or potential target animals (as opposed to laboratory animals) seems to be relevant not only to implement prophylactic solutions but also to improve the preparedness for an eventual global extension of diseases. Nowadays, this task is rendered possible by the availability of improved biosafety levels 3 and 4 (BSL3 and 4) animal facilities, which can accommodate large animal experimentation with such highly virulent pathogens [16] .