“Lockjaw” is a layman’s term for tetanus. It is said that tetanus is extremely rare in cats. The reason why it is called lockjaw is because one of the symptoms is difficulty in opening the mouth. Other symptoms are spastic contractions, rigid extension of the legs, difficulty swallowing, paralysis and retraction of the lips and eyeballs. Sometimes the tail sticks straight out; muscle spasms occur when the cat is stimulated.
All warm-blooded animals including humans can be infected by the bacterium which causes tetanus. Any cut, bite or puncture such as by a rusty nail, can allow the tetanus bacteria entry into the body.
Tetanus usually inhabits soil contaminated by horse or cow manure; something your cat is unlikely to encounter if you live in the city. However, your cat may well encounter this if he/she lives in rural areas and is allowed to wander. In addition, most species of animal play host to this organism in their intestinal tracts but it usually does not cause any disease.
Tetanus is usually fatal if not treated early by your veterinarian. Treatment includes the use of antibiotics and antitoxin’s, sedatives and intravenous fluids.
Some veterinarians may advise that if you have been bitten by a cat the wound should be cleaned by soaking it with hot water containing an antiseptic and then you should see your doctor if you have not been vaccinated against tetanus within the previous three years.
Source: The American Animal Hospital Association Encyclopedia of Cat Health and Care.