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

As described in the previous section, a number of animal species have been described as either natural reservoir (dromedary camel) or potential intermediate hosts of MERS-CoV, each one with its benefits and limitations (Table 3 ) when used as experimental infection models. Camelids (dromedary camels, alpacas and llamas), non-camelid domestic species (pigs and rabbits), and NHP (rhesus macaques and common marmosets) have been experimentally demonstrated to be susceptible to MERS-CoV infection, but with differences among them [21] [22] [23] [24] [47] [48] [49] [50] 53, 54] . Experiments with dromedary camels, the natural MERS-CoV host, and probably the first target for controlling MERS through vaccination [53] , are costly and represent a high security risk for animal caretakers because of the difficulty in handling these animals under appropriate biosafety conditions. The main advantages of using the llama or alpaca models are that both belong to the family Camelidae, have smaller size, more gentle behavior, and are more available at a commercial level than dromedary camels; importantly, specific reagents for immune monitoring have been developed for new world camelids [57] . Therefore, they may be useful surrogates for dromedaries under experimental conditions. However, both models are also quite expensive and require large and complex BSL3 facilities. In contrast to camelids, other domestic species such as pigs and rabbits are readily available, with lower cost and easier handling. Additionally, an extensive panel of specific-immunological reagents is available for these species. When compared to camelids, however, lower MERS-CoV titers were detected in nasal cavities and tissue samples of pigs and rabbits during the infection. Furthermore their usefulness as animal models for transmission studies has not yet been addressed.