In wildlife, the natural reservoir host for most animal viruses, overt clinical infections are generally absent. In this paper it is hypothesized that for hundreds of millions of years viruses co-evolved with arthropods, fishes, amphibians, reptiles, birds, and mammals, in a friendly manner, by minimizing virus replication costs and host damage. This virushost mutualism hypothesis may be viewed as diametrically opposite to the virulence-transmission hypothesis. Building on previous work, the transmission ecologies of 36 of the world main livestock viruses are examined in more detail. Viruses and organ systems are aligned on ecological grounds, in an outer- to inner-body fashion. The virus-host interplay changes from acute to persistent infection to ever more virus-host intimacy. From outer- to inner-body virushost mutualism is on the increase. Virus-host antagonism increases from inner- to outer-body. Also explored is the role of the host domain in mutualism-antagonism evolution. For this, the virus evolution trajectory upon a host shift from wildlife to humans or livestock is examined.
Published Date: 2021-09-13;