I have a thread in the Emergencies / Diseases / Injuries and Cures fourm and decided to cross it over here to get some more duck inclined people on it.
https://www.backyardchickens.com/threads/muscovy-duck-swollen-belly-new-breathing-issues.1295813/
https://www.backyardchickens.com/threads/muscovy-duck-swollen-belly-new-breathing-issues.1295813/