Patterns of infection, origins and transmission of ranaviruses among the
ectothermic vertebrates of Asia
Abstract
Ranaviral infections, a malady of ectothermic vertebrates, are becoming
frequent, severe, and widespread, causing mortality among both native
and cultured species, raising odds of species extinctions and economic
losses. This turn of events is possibly due to the broad host range of
ranaviruses and the transmission of these pathogens through regional and
international trade in Asia, where outbreaks have been increasingly
reported over the past decade. Here we focus attention on the origins,
means of transmission, and patterns of spread of this infection within
the region. Infections have been recorded in both cultured and wild
populations in at least twelve countries/administrative regions,
together with mass die-offs in some regions. Despite the imminent
seriousness of the disease in Asia, surveillance efforts are still
incipient. Some of the infections transmitted within Asia may transmit
across host-taxon barriers, posing a significant risk to native species.
Factors such as rising temperatures due to global climate change seem to
exacerbate ranaviral activity, as most known outbreaks have been
recorded during summer; however, data are still inadequate to verify
this for Asia. Import risk analysis, using protocols such as Pandora+,
pre-border pathogen screening, and effective biosecurity measures, can
be used to mitigate introduction to uninfected areas and curb
transmission within Asia. Comprehensive surveillance using molecular
diagnostic tools for ranavirus species and variants will help in
understanding the prevalence and disease burden in the region. This is
an important step towards conserving native biodiversity and
safeguarding the aquaculture industry.