It's a bit off-putting to most humans, but cats love to stalk, kill and sometimes eat mice. It's perfectly natural, but mouse consumption poses health risks to your feline friend. Because a number of ways exist for your cat to get sick from eating a mouse or other rodent, it's best to discourage the practice.
Cats sometimes acquire the Toxoplasma gondii parasite from eating an infected mouse, thus catching the illness called toxoplasmosis. Most felines come into contact with the parasite at some point -- whether by eating a mouse or encountering it in the environment -- and quickly develop an immunity. However, initial infections typically cause mild diarrhea, loss of appetite and other digestive disturbances. In severe cases, a cat's lungs, liver or nervous system may be affected. Your vet can test for toxoplasmosis, and antibiotics are the primary course of treatment.
Several parasitic worm species migrate to their host's lungs, and as a group these are known as lungworms. Capillaria aerophila and Aelurostrongylus abstrusus are two of the more common species affecting cats. Drinking infected water and consuming an infected mouse or other small animal are the primary routes of transmission. Symptoms usually include coughing, shortness of breath and excess mucus. When left unchecked or with severe infestations, cats can develop fluid buildup in the lungs or pneumonia, as well as emphysema and weight loss. A number of antiparasitic medications treat lungworm infections.
Intestinal parasites are a risk to cats who eat mice, which commonly function as primary or intermediary hosts to many types of intestinal worms. Among the more common threats, cats can acquire tapeworms, whipworms, roundworms, and in rare instances, hookworms from consuming infected prey. Infections present a variety of symptoms, including diarrhea, constipation, vomiting, appetite changes, behavioral changes, a sagging belly, visible worms, larvae or eggs in the stool or around the anus, biting or licking the anus, dragging the rear across the floor, weight loss, anemia and stunted growth in kittens. An appropriate antiparasitic medication is the main treatment.
Mice often carry salmonella, and cats can acquire salmonellosis from them, but it's not particularly common. Cats are more likely to be asymptomatic carriers than to succumb to this bacterial infection. If they do get sick, symptoms may include abdominal pain, diarrhea, vomiting or lethargy. Fluids are important, and the disease can usually be allowed to run its course. Cats may also become sick from consuming a mouse that has been poisoned by a pest control substance. And although not a sickness, per se, mouse bones pose risks to cats who eat them. Shards can cut the mouth or get stuck in the larynx, causing choking. Pawing at the mouth, gagging, retching, neck stretching, rubbing the face against the floor, drooling and fainting can all indicate choking. Try to remove the obstruction; if unsuccessful, perform the feline Heimlich maneuver and seek emergency veterinary treatment if necessary.