maxbiostat
commented
9 years ago This is a really nice comment, full of useful information. Let us discuss it in the face of new analyses with more data.
Closed maxbiostat closed 4 years ago
maxbiostat
commented
9 years ago This is a really nice comment, full of useful information. Let us discuss it in the face of new analyses with more data.
All the results discussed on the spatial diffusion of FMDV in the whole South America continent should be treated with cautions (potentially providing you incorrect data), considering that you have: missing information from missing sequences; a sampling bias in your data according to time and country. It is well known that FMDV was introduced (as you pointed out in the introduction) by human migration from Europe in the end of the 19th Century with early reports in Argentina between 1860 and 1870, and 1895 in Brazil. There were at least two distinct introductions in the North and one in the South but, before the 1922, it is really difficult to say which serotype was (i.e. before the FMDV typing was performed). However, it is clear that the early spread of FMD was coming from the South. Argentina at the time was one of the main export hubs of livestock to the continent and even the Mexico outbreak in 1922 has been attributed by the introduction of infected cattle from Argentina. This holds true for: Chile, 1920 outbreak (decline of cattle industry during 1912 in Chile with large introduction from Argentina); official report in Venezuela 1950 (potential from importation of Argentinian meats/livestock back to the 1947). It might worth to know that the Andes acted as a barrier for taking FMD out of Chile and the western part of South America, until when the regional animal movements and trade primarily caused the spread. The countries of the Rio de la Plata, which were sharing the Pampas ecosystem, experienced an early wave of disease spread and by the 1920 FMD was in Uruguay, Paraguay and Brazil. Historical data suggest that type O was introduced most likely from the South (maybe Argentina) and type A introduced from Europe. From your analysis the initial historical FMD wave has not been characterised (in the years before 1994 for type A; very limited and potentially biased before 1965 for type O). The only part which might be more realistic is the FMD transboundary movements within the ‘countries triangle’ of Colombia, Ecuador and Venezuela, that could sounds more like from Argentina-Venezuela-Colombia-Ecuador, even though you have the effect of sampling bias that needs to be discussed.