The Loque'eque were a species that originated in the Delphic Expanse. Several centuries prior to 2153, they lost the ability to reproduce and their species began to die out. In an attempt to save their race from total extinction, the Loque'eque engineered a mutagenic virus which transformed the DNA of other species into their own.
The virus also contained genetic memory. Aliens who were infected with the virus communicated in the Loque'eque language, experienced hallucinations and an extremely powerful urge to seek the Loque'eque's home city, Urquat. The Loque'eque civilization was lost but the virus was successful and as of 2093, alien Commander Tret's people had lost tens of millions to the Loque'eque virus.
When an away team from the Enterprise NX-01 beamed down to the Loque'eque homeworld in 2153, three of the four officers were infected with the virus. Fortunately, Doctor Phlox was successful in synthesizing an antidote, returning Captain Jonathan Archer, Lieutenant Malcolm Reed and Ensign Hoshi Sato to their Human forms. Tret's people were still fighting the virus in 2153, using starships patrolling the system and away teams on the Loque'eque homeworld, literally incinerating any host of the virus. (ENT: "Extinction")
In the final draft script of "Extinction", the Loque'eque make-up was described as including bladders which could swell on either side of the neck.
According to Reed actor Dominic Keating, it was challenging for himself, Archer actor Scott Bakula and Linda Park to act as Loque'eque. "Me, Scott and Linda were in full prosthetic make-up. It's gruelling, being in that stuff for 14 hours. I've got sensitive Irish skin," Keating said, with a laugh, "and the glue and the alcohol to release the glue just burns it off [....] It was an interesting acting challenge, to very quickly and succinctly come up with a physicality [and] speech patterns for this race. There were a lot of quick chats in the couple of days before [shooting], we started talking on set about what we thought we might do, but really, it came together the day that we had the make-up on and [...] shot the first scene [....] You just do it and you watch what the other person did and you go, 'I can incorporate that into what I'm doing' [....] It was tough being in the gear, but I really enjoyed it." Keating's performance was influenced by the portrayal which Linda Park, a dancer in reality, delivered for her own Loque'eque persona. "She was terrific to watch and to glean from," stated Keating, "in her physicality of the creature." (Star Trek Monthly issue 109, p. 49)
Linda Park herself described the Loque'eque as a "primitive, sort of super-strength alien lizard." She found wearing the make-up was painful. (Star Trek Monthly issue 110, p. 16)