Serrata is a notorious toxin created by the Nayabaru, which has been in use for several centuries and remains effective even now.
It has no perceptible effect on the metabolism of mammals, to which it is fed and who absorb it into their bodies, retaining it for up about three approximate weeks (five approximate yeno). These creatures are then released into the wild in the hope that kavkema might catch and eat them, which happens often enough.
Mechanism and Symptoms
Once in the body of a kavkem (or any other saurian or bird), Serrata accumulates preferentially in the lungs and eyes, blocking some neural feedback and enhancing other types. A Serrata poisoning causes visual hallucinations the kavkema describe as 'blotching' that ends in temporary (several hours of) darkness or visual noise and an intense pain in the chest area, said to force the affected kavkem to howl (although it's certainly possible for kavkema to stay silent for the hours Serrata affects them, but the alternative is often self-mutilation).
While not inherent to the toxin itself, tactile and audio hallucinations can occur simply from the brain desperately trying to fill in the blanks of the disappearing surroundings. The blotched, missing visual stimulus may sometimes either directly be interpreted into shapes, or filled with wholly imagined stimuli - in either case, often making the sufferers believe they are seeing kiikama, or shadows thereof.
No one has questioned the Nayabaru on the intended purpose of Serrata, but it's fairly clear it was designed to both incapacitate kavkema and to make them easier to find: Both blindness and pain reduces their mobility and the intense pain indeed often makes them betray their location. Serrata itself does not kill, although kavkema have been known to kill themselves in a desperate attempt to escape the effects, assuming the pain did not prevent them from moving or clawing at their own hypersensitive throat.
There is currently no antidote known to the kavkema - or at least none they could fashion given their circumstances. The Nayabaru themselves of course have an antidote; while they run no risk of ingesting Serrata themselves, they usually have no patience to wait for a kavkem to come out the other end of the symptoms before they can reasonably question the kavkem or keep it quiet.
It's difficult to completely eliminate mammals from a kavkem diet, but some religious fringe groups of kavkema have tried to completely outlaw eating mammals. This is the only reliable protection from Serrata - but obviously not any other Nayabaru technology.
Kavkema known to be poisoned with Serrata are often temporarily abandoned by their group mates, after being hidden as well as possible. The hope is that the kavkem can stay quiet - but in case the victim cannot stay quiet, the distance their companions keep to them will prevent them from being captured as well.
In some areas, instead of hiding the afflicted kavkem, it is assumed the kavkem will not be able to stay quiet, and the victim is simply killed to prevent them from betraying their location and being captured into a life of misery. While this may seem barbaric to human observers, kavkema consider this qasai and as a society typically react positively to such decisive action.