Cats and Mice: Potential for Disease and Other Dangers

Cat playing with little gerbil mouse on thetable
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Has your cat ever caught a mouse or rat? Cats love to hunt small prey and will often bring home what they catch. Sometimes they eat their prey while other times they leave it as a "gift" for you. While this is a normal, natural behavior, many owners find it disturbing. 

Why Cats Hunt

As obligate carnivores, cats survive in the wild by hunting small prey. They evolved into ideal hunters with stealth, agility, and keen senses. Despite domestication, most cats still have a strong prey drive and an instinctive desire to hunt. They don't always hunt simply for food either. Often, cats will hunt for the sheer enjoyment of it. You may see that your cat brings home live prey, plays with it, but never actually eats it. 

Because this survival instinct remains, it's important that cats have an outlet for this energy. Toys and games can help your cat fulfill his hunting needs without needing to catch live prey. However, most cats will still stalk and catch live prey if given the opportunity, no matter how well-fed they are at home.

Using Cats to Get Rid of Rodents

Throughout history, people have used cats to keep rodents away. Many farms still have "barn cats" that live on the property and hunt the rodents that would normally invade grain supplies. 

Should you use your cat to catch mice and rats? Although vermin prevention can be a nice perk of owning a cat, it should never be the main reason you get a cat. Additionally, it's not fair to your cat to "loan him out" to a friend for the purpose of removing rodents. Cats are domesticated pets that need safe, stable home environments. The stress of temporarily changing homes can lead to health issues.

There's another reason not to use your cat as a mouser or ratter: Rodents can pose significant health risks to both cats and humans. 

Risks Associated With Mice and Rats

There are several ways your cat can be harmed by exposure to rodents. Mice and rats may carry viruses, bacteria, parasites, and even toxins that can affect you or your cat. 

Toxoplasmosis

Toxoplasmosis is one of the most common parasitic diseases in cats. This infection is caused by the Toxoplasma gondii parasite. Toxoplasmosis can affect many animals, including humans. However, the cat is the ideal host for Toxoplasma gondii because it is the only animal in which this microscopic parasite can complete its life cycle. 

Cats become infected by Toxoplasma gondii by ingesting the cysts of this parasite. Most often, this occurs when cats eat mice or rats infected with the parasite. However, they can also ingest it during grooming after coming in contact with infected soil or feces.

Cats infected with toxoplasmosis will often show no symptoms. In rare cases, cats will develop lethargy, gastrointestinal problems, or even respiratory issues. Many cats will remain silent carriers their whole lives.

Humans can contract toxoplasmosis after eating contaminated meat or otherwise accidentally ingesting the microscopic cysts. This may occur after handling cat litter.

The symptoms of toxoplasmosis in humans include fever, headache, lethargy, and muscle pain. Toxoplasmosis may actually cause no symptoms in humans. However, it can cause serious complications for pregnant women and people with weakened immune systems.

Intestinal Parasites

Many rodents are infected with common intestinal parasites like roundworms. Intestinal parasites can cause diarrhea, vomiting, and weight loss. Some intestinal parasites can be passed on to other pets in the home.

If your cat goes outdoors or is known to catch vermin, routine fecal testing is recommended to check for the presence of intestinal parasites. Your veterinarian can prescribe anti-parasitic medications to deworm your cat. In addition, some monthly heartworm and flea preventive medications will deworm your cat with each dose.

Plague

Some rodents carry plague, an infection caused by the bacteria Yersinia pestis. This is the same bacteria responsible for causing the infamous "black plague" of the middle ages. Plague is often transmitted by fleas, but cats can be infected by eating the meat of infected animals (often small mammals).

Cats infected with Yersinia pestis may experience lethargy, depression, loss of appetite, vomiting, diarrhea, coughing, muscle soreness, and fever. The cat may develop lymph node enlargement, lesions in the mouth, and weight loss. Treatment involves the use of antibiotics and providing supportive care. The sooner treatment can begin, the better the odds of survival.

It is uncommon for humans to contract plague. When they do become infected, it is usually through a flea bite. Symptoms and treatment are relatively similar to those in cats.

Leptospirosis

Some rodents carry a bacterium called Leptospira. Though leptospirosis is rare in cats, humans are quite susceptible to the disease. Your cat may bring in an infected rodent, exposing you or other pets to the disease. Leptospirosis causes flu-like symptoms and can lead to liver disease in dogs and humans.

Hantavirus

Several types of rodents are known to carry hantavirus. Cats can be infected by hantavirus but will show no symptoms, therefore the virus is not dangerous to them. In addition, cats cannot transmit hantavirus to people. However, humans can be exposed through contact with infected rodents. Though serious complications from hantavirus are uncommon in humans, exposure can lead to a serious condition called hantavirus pulmonary syndrome.

Rodenticide Toxicity

If your cat eats all or part of a rodent that has ingested rat poison, your cat may also become poisoned. Rodenticide is highly toxic to cats. There are several types of rat poison, so symptoms and treatments will vary. Rodenticide may cause signs like lethargy, gastrointestinal upset, pale gums, drunkenness, seizures, and much more. If you suspect your cat was exposed to rat poison, seek veterinary treatment immediately. Aggressive treatment is often necessary.

Bites and Scratches

Defensive bites or scratches from rodents can cause wounds to your cat. Though some wounds will heal on their own, others will become infected. Your cat may develop an open sore or an abscess at the time of the bite or scratch. If you notice a wound on your cat, be sure to see your veterinarian. Treatment with antibiotics may be necessary for the wound to heal. In the case of a serious abscess, the wound may need to be drained or even treated surgically. 

How to Protect Your Cat and Yourself

If you see your cat with a dead (or dying) rodent, there is no need to be immediately concerned. However, it is best to remove the rodent to prevent your cat from eating it. Always wear gloves when handling rodents. As an added layer of protection against hantavirus, a mask is also recommended.

After exposure to a rodent, it's important to watch your cat closely for several days. Contact your veterinarian right away if your cat is showing any signs of illness. If your cat is a regular rodent-catcher, you may need to visit the vet more frequently to screen for diseases and parasites. 

All cats should be on year-round flea prevention, but this is even more important if your cat is known to catch prey. Consider tick prevention as well.

Avoid using rodenticides around your home. This can reduce but not eliminate the risk of exposure to rat poison.

One of the best things you can do to minimize exposure is to keep your cat indoors. Yes, rodents can get in your house, but there are more to catch outdoors.

In general, you should contact your vet if your cat seems sick in any way.