Needle guns were an early attempt at cartridge firearms, and used a paper cartridge. They were quickly obsoleted by metallic cartridges and magazine repeater after the late 1860s. The German Empire dropped the Dreyse very soon after adopting it in favor of a cartridge rifle (Mauser Gewehr 1871), the Kingdom of Italy replaced the Carcano needle gun with cartridge Vetterli rifles in 1870, and the Swiss Republic did so in 1869.
Many old military firearms were sold off to indigenous peoples of frontier areas (Africa, South America, SE Asia, and North America) when they became obsolete. It is entirely likely that the firearms in the accounts you are reading are one of the needle gun types you mentioned that had become available from military surplus sources.