Oh my, this is Season Three's version of "Space" (the worst episode of Season One, perhaps the worst episode of X-Files ever). This episode is easily the worst of Season Three. It is a total mess, funny at times, but not necessarily intended to be a spoof like the brilliant "Coprophages."
The episode opens with all these men wearing goofy looking knit caps, you know, because we are in Ecuador, get it? A decidely unscary "artifact" is unearthed and a scientist is attacked by a scary looking jaguar in his tent.
Now, if they had used the jaguar for the rest of the killings in the US, the episode might have been attained "average" status. Instead, they use cats (I think) or was it the rats? I laughed out loud when all the little feral kitties jumped out of their boxes in the sewer. It was very, very stupid, but kinda cool in a surreal way.
Anyway, the problem here is that it makes no sense for cats (or rats, or dogs, or whatever) to have dragged off all the victims so abruptly. It just seemed like a cheat from the writers, who probably didn't know what killed the victims either.
The only saving grace in this episode are some of the hilarious one-liners by Mulder and the stunned, disgusted looks given by Scully, especially as Mulder goes to lift the toilet lids and when he starts to descend into the sewer.