With no other snakes in a collection, it really isn't necessary to rule out nido or IBD arenavirus. Nothing can be done to treat them beyond symptomatic support/treatment anyway (which a person would do with any condition regardless if there's a viral component). Diagnosing either would be merely academic.
Published studies and comments by researchers suggest that there are possibly double-digit percentages of aymptomatic (or only intermittently symptomatic) carriers of either virus in captive animals. At some point the hobby is going to have to come to terms with this fact, and accept that anyone with any substantial number of snakes has carriers in their collection (and anyone with one or a couple snakes has a statistical likelihood).
The way forward in light of this fact is, I think, to ensure good biosafety/disinfection protocols to avoid spread of any undetected pathogens (absolute zero tolerance policy on mites, no cohabitation/unnecessary contact between animals, handwashing/sanitizer between animals, full QT process for all new animals), and provide a level of care that helps avoid a reduction in immune response so as to avoid symptoms/secondary infections.
There's lots of good reading and listening out there for a person who wants to learn more.
https://onlinelibrary.wiley.com/doi/...1111/avj.12792
https://journals.plos.org/plosone/ar...l.pone.0229667 (both these suggest that pythons can indeed carry arenavirus asymptomatically long term)
There are many more articles on Google Scholar; those are just the top two hits for 'IBD python asymptomatic'.
A good study on nido: https://www.frontiersin.org/articles...019.00338/full
And a podcast that has been linked here before: https://soundcloud.com/theherpetocul...dr-porcher-dvm