do you have any idea what the cause of the wound is???
You say psoriasis, has this been a diagnosis or a guess?
so much depends on what exactly this is can be caused by many things....but yes if it is widespread than it does sound as if its contagious.
A Vet would need to do a culture on it to give an exact diagnosis.
I personally agree with opus88, anyways no its not contageous in anyway , cats are territorial animals they fight with other cats to protect their territory or to acquire more territory. As a result, bite wounds are common in cats, especially when cats are allowed outside. These wounds frequently result in an infection that can be quite debilitating, especially if left untreated. Bite wounds are more common in male cats than in females.
However, when a cat bites another cat, his teeth go through the skin, and then he releases quickly. This results in small puncture wounds in the skin, with holes about the same diameter as the cat's teeth. These holes seal within hours, trapping bacteria from the cat's mouth under the skin of the victim. Within 24 hours, the holes in the skin are almost impossible to find.
The bacteria which are trapped under the skin can multiply for several days before any signs of infection become evident. Swelling and pain at the puncture site are the most common signs of infection. Many times, the first noticeable sign will be the appearance of draining pus or blood. Frequently the cat will also run a fever and stop eating.
If loose skin is present around the puncture sites, a pocket of pus will form an abscess. If the skin is not loose, such as on a foot or the tail, the infection spreads throughout the tissues and causes swelling and pain; this type of infection is called cellulitis.
so i would recommend you to take the cat to the vet where the vet will place the cat on Antibiotics given within 24 hours will usually stop spread of the infection and development of an abscess.
If you don't have money my home remedy is warm some water put a pinch of salt and clean it with a cotton ball make sure you cut out around the area . then see if you can get a bottle of peroxid and gentian violet solution and put either one on your cat . if you going to use the peroxid make sure it goes in the hold remember do not push swab into the holdes to make it bigger . just do it gently remember the your cat can be in pain . he then get a relieve after you clean it do that until it is heal you will notice the difference .
The wounds themselves are not the contagion, but the cats that cause or receive the wounds could be from rabies, distemper, feline leukemia, FIV, or any number of other causes and the infectious diseases can be spread from cat to cat through transfer of fluids (saliva or blood).
Cats don't get psoriasis. If these cats have a severe rash with hair loss, it is most likely notoednic mange, which is a parasitic infection and can be spread to other cats, dogs, and humans through direct contact