A cat usually loses it meow because of an illness; however, there are some instances of voice loss in cats when a veterinarian cannot make a diagnosis. "Loss or change of voice is one of those vague problems that drive vets crazy," says Arnold Plotnick, DVM in an article on CatChannel.com. Plotnick notes that in most of the cases he sees, there is no attributable cause.
Plotnick notes that a viral upper respiratory infection is most often the culprit. These infections are usually accompanied by runny eyes, snotty nose and sneezing. Oral tumors involving the throat can also cause a cat to lose its voice. Laryngeal paralysis is another common cat illness that results in the loss of voice. It occurs when the nerves that control the vocal cords become damaged, causing the larynx to open and close improperly.
Michelle Ullman, in an article on The Nest, cites growths in the vocal cord area of the throat as an additional reason a cat could lose its voice. This can also cause a change in the voice, such as hoarseness. Ullman also notes that hyperthyroidism can result in a hoarse voice or loss of voice. This condition is usually accompanied by weight loss and can be diagnosed through a blood test.