Can rats harm dogs and cats? Learn the risks to your pets if they eat or come into contact with rodents, as well as what risks rats and mice pose to humans.

can rats harm dogs

It is instinctive for cats and dogs to pursue small prey, such as rodents and birds. In some cases, pets simply pursue and kill the prey. In other cases, the prey animal is consumed by pets. Since wild animals, such as rodents, may carry a variety of pathogens that cause diseases that can impact pet and public health, pet owners should consider discouraging their pets from catching and eating wild animals.


Rodents, like mice and rats, may become infected with the protozoan parasite, Toxoplasma gondii, which causes toxoplasmosis. This can come from contaminated water or soil. Dogs that eat rodents infected with Toxoplasma protozoans may experience symptoms ranging from diarrhea to nervous system issues. In contrast, if a rodent that is infected with T. gondii is ingested by a healthy cat, it is possible that no symptoms of the infection will be observed in the cat. However, the cat’s digestive tract may become infected with the protozoans, thereby causing the cat to shed these protozoans when defecating. 

Can humans be harmed from contact with infected pets?

More than 1 million human cases of toxoplasmosis are reported in the United States each year. Humans can become infected with Toxoplasma protozoans by eating undercooked meat, unwashed fruits and, raw oysters, among other ways. Humans cleaning the litter boxes for cats that live indoors and outdoors may also become infected with the protozoan.

If a human is infected with Toxoplasma protozoans, the condition called toxoplasmosis may develop. Toxoplasmosis is generally asymptomatic in healthy humans. However, flu-like symptoms may be experienced, and in immunocompromised children and adults, more serious symptoms may occur. Pregnant women infected with Toxoplasma protozoans may experience complications during pregnancy due to toxoplasmosis, hence pregnant women are advised not to handle cat feces. There is currently no vaccine in use against toxoplasmosis in cats and humans (Jones et al. 2014).

More information on toxoplasmosis can be found from the American Veterinary Medicine Association and the Centers for Disease Control and Prevention.

What about roundworms?

Rodents and birds may be infected with roundworms (Toxocara spp.). If a pet eats an infected animal, the pet may also become infected. Roundworms can cause intestinal issues in dogs and cats. Symptoms include diarrhea, distended round belly, etc. Some studies show that dogs and cats are more likely to become infected with roundworms if they are already infected with Toxoplasma protozoans (e.g., Jones et al. 2008). Your veterinarian can be consulted if you suspect your pet has been exposed to roundworms. There are a variety of medications that can be administered (in consultation with your veterinarian) to pets to help prevent and/or treat infections with different types of worms.

Roundworms can be passed to humans. In humans experiencing the disease (toxocariasis) associated with these worms, a variety of symptoms may be observed, including fever, headache, rash, digestive issues, vision loss and others (MacPherson 2013). There are a variety of anti-worm treatments that can be employed by medical and/or veterinary professionals, depending on the specifics of each case.

Exposure of outdoor pets to rodents and potential related pathogens is likely inevitable. However, pest control professionals can help develop surveillance and prevention plans to minimize the occurrence of rodent populations, hence minimizing this rodent-pet interaction.



Jones JL, Kruszon-Moran D, Won K, Wilson M, Schantz PM (2008) Toxoplasma gondii and Toxocara spp. co-infection. American Journal of Tropical Medicine and Hygiene 78: 35-39.

Jones JL, Parise ME, Fiore AE (2014) Neglected parasitic infections in the United States: Toxoplasmosis. American Journal of Tropical Medicine and Hygiene 90: 794-799.

Macpherson CN (2013) The epidemiology and public health importance of toxocariasis: A zoonosis of global importance. International Journal of Parasitology 43: 999-1008.