Ganados from Resident Evil 4 are like zombies but more intelligent, vicious, faster and stronger. They can use weapons like chainsaws, dynamite, catapults and arrows, stun rods, rocket launcher and Gatling gun. They are created when a human is infected with las plagas. But a child cannot be made into a Ganado they just die and there is a chance that an adult would die rather than transform into a human but that’s a low chance. They may also use traps to stop an enemy like pushing down a boulder, using lasers, they can also drive cars and trucks to run over there enemy. Unlike zombies they are controlled by the queen las plagas or controlled plagas. Animals may also be use as a weapon by infecting them like dogs. They also performed B.O.W. experiments. They can also speak but only in their native tongue. They can carry out normal everyday tasks like cooking and eating and sleeping and taking care of their pets. They also bond with each other. Hygiene and cleanliness is beyond them. They also use their back as a way to store some of their weapons. They also may be if someone injured them enough that a las plagas will reveal itself.
Las Plagas forms there are several forms of Las Plagas that appear in the game. Some may be different stages of the same organism; others are very clearly different 'species'.
- Blade Plagas- These Plagas are the first form of Las Plagas Leon will encounter. These Plagas are most commonly found in villagers and also Saddler's militia. These Plagas wield a scythe like blade on the end of a long tentacle which they will use to slash at the player at some range. They are however the weakest of the Plagas. They control the weaker Armadura suits.
- Tentacle Plagas- This form of plagas can be found in Colmillos. As with the Blade Plagas, if the host receives enough damage, the plagas will erupt from the spine of the dog, as a swarm of tentacles that can whip Leon possibly to death.
- Centipede Plagas- These Plagas are the second form of Las Plagas Leon will encounter infesting human hosts. These Plagas are often found inside the lower ranking zealots, and are the second type which control Armaduras. These Plagas are short ranged but can cause instant death by biting the players head off at close range. Due to graphic resource issues related to the GameCube version coming on two discs, they are never seen after Salazar's castle is finished.
- Crab Plagas- This form of The Plagas only appears within Garradors. Since they cannot attack and are visible at all times, they serve as the Garradors weak spot. This is one of the few Plagas that do not possess a form of self-defence.
- Spider Plagas- These Plagas (which somewhat resemble 'Face huggers' from the Alien franchise) mostly inhabit the higher ranking zealots and militia. They are the most durable, can spit acid over some distance and detach themselves from their host following death. They are roughly equal to Blade Plagas in terms of threat while attached, and are relatively weak when detached. While detached, they have a leaping grapple which lacks an animation for attacking from the side or rear, much like the Colmillos, meaning they can only use it when directly in front of Leon. Curiously, several are encountered in the game without hosts at all. When without a host, a Spider Plaga will eventually die even if it has taken no damage whatsoever. As they can't climb ladders, simply moving outside their immediate area is an effective means of defeating them.
- Queen Plagas- These are more complex types of Plagas, also known as Master Plagas. They give control over the average Plaga-Infected and have powerful and varied mutation forms; seemingly, no two are alike. In Resident Evil 4, there were only three people infected with the Queen Plagas: Bitores Mendez, Ramon Salazar and Jack Krauser. Notably this type of Plagas can create extremely powerful individuals, while having almost no detrimental effect on the host's mental capacity; something Umbrella's viruses tried to do, but failed. The prime example is Mendez, as he exhibited characteristics of a Tyrant whilst retaining his loyalty and intelligence even after transforming.
- King Plagas- There is only two samples of the Master Plagas, and one is already injected into Saddler's Body. This Plagas gives control over all those who are infected with Las Plagas, with the possible exception of those with Queen Plagas. This occurs regardless of whether the egg has hatched or not, though it is possible to resist this control if the parasite has yet to take full control of the host. Saddler described the Second King Plagas Sample as "our life blood". Los Illuminados were planning to inject the second King Plagas into Ashley when they captured her. The King Plagas has no form on its own, but gives a very powerful mutation due to the power it controls; it also allows for partial transformations, as with the rather infamous trouser-tentacle Saddler uses to kill Luis, also sporting a huge yellow eye inside his throat and super-human strength, speed and resistance to firearms.