Originally used by the Encari, this type of ship was appropriated by the Romulan Imperial Fleet to carry a mutagenic virus, being classed as a biogenic transport. Meanwhile, Romulan cargo ships served as biogenic disseminators. (ST video game: Legacy)
A transport of Encari design was observed surveying the planets in the unaligned Epsilon Theta star system. Soon after, an outbreak of a mutagenic virus occured on the inhabited planets of Epsilon Theta. After the system was cured by Earth Starfleet medical ships, the First Minister of Epsilon Theta Prime provided Starfleet with a holographic image, leading to an investigation of Encaria's star system by a task force of Earth Starfleet vessels led by the NX-class Enterprise NX-01, commanded by Captain Jonathan Archer.
Upon reaching Encaria, Starfleet discovered that all life on the planet had been wiped out by the bio-agent and detected a transport which was found to be an unmanned drone carrying a large concentration of the toxin. Following the transport, the Starfleet task force saw it enter a Romulan starbase, which carried a large amount of the toxin in liquid form. Observing the base to be a processing facility, Archer determined that the Romulans were synthesizing the toxin from there and distributing it to Starfleet sectors. Starfleet found that numerous other biogenic transports were harvesting the toxin from five other planets in the system then taking them to harvesting stations in orbit. Ultimately, all five harvesting stations were destroyed along with the starbase by Starfleet. (ST video game: Legacy)