Escherichia coli (E. coli) is a diverse and common group of bacteria found worldwide in the environment, food, and the intestines of warm-blooded animals, including humans and cats. While most strains are harmless and contribute to a healthy gut microbiome, some types are pathogenic, meaning they can cause serious illness. The concern for pet owners centers on zoonotic transfer—the transmission of a disease from an animal to a human. This article addresses the specific, but relatively low, risk of contracting a pathogenic E. coli infection from a household cat.
Understanding E. coli in Cats and the Risk of Transmission
A cat’s digestive tract naturally contains various strains of E. coli, which are typically non-disease-causing bacteria. However, cats can acquire and shed pathogenic strains, such as Shiga toxin-producing E. coli (STEC), including the O157:H7 strain, even without showing symptoms of illness themselves. These harmful bacteria do not typically cause disease in adult cats but can be shed in their feces, turning the animal into a carrier and a potential source of infection for humans.
Cats often acquire pathogenic E. coli strains through their diet, particularly if they consume contaminated raw or undercooked meat or prey (if they are outdoor cats). Once a cat is carrying the bacteria, the primary mechanism for transmission to a human is the fecal-oral route. This involves the bacteria being shed in the cat’s stool and then accidentally ingested by a person, often after handling the cat or its environment without thorough handwashing.
The risk of transmission is highest when a person comes into direct contact with cat feces or surfaces contaminated by it, like the litter box. While the chance of a cat transmitting the most serious strains of E. coli to a human is considered low, it is a possibility, especially for those who are immunocompromised. The presence of multidrug-resistant E. coli strains in pet cats emphasizes the need for careful hygiene practices to prevent zoonotic transfer.
Recognizing Symptoms of E. coli Infection in Humans
An infection with a pathogenic strain of E. coli, such as O157:H7, can result in severe gastrointestinal illness in humans. Symptoms typically begin two to five days after exposure, though the incubation period can range up to ten days. The initial signs usually include the sudden onset of severe abdominal cramps and watery diarrhea.
The most distinctive symptom is the development of bloody diarrhea, which occurs in roughly half of people infected with the O157:H7 strain, sometimes accompanied by vomiting and a mild fever. The illness usually runs its course within five to ten days for most healthy adults, with supportive care like fluid replacement being the standard treatment. Antibiotics are generally avoided, as they may increase the risk of a severe complication.
Those infected, particularly young children, the elderly, and those with weakened immune systems, may develop Hemolytic Uremic Syndrome (HUS). HUS is a serious complication where the Shiga toxin damages the lining of the blood vessels, leading to the destruction of red blood cells and acute kidney failure. Signs of HUS, which require immediate medical attention, include decreased or absent urination, unexplained bruising, paleness, and extreme fatigue.
Essential Hygiene Practices to Prevent Zoonotic Transfer
Preventing the transfer of E. coli from a cat involves strict hygiene routines, especially since a carrier cat may appear perfectly healthy. Meticulous handwashing is the most effective preventive measure against the fecal-oral transmission of bacteria. Hands should be washed thoroughly with soap and running water for at least 20 seconds after handling your cat, before eating, and after any contact with the cat’s food, toys, or bedding.
Managing the litter box safely is particularly important due to the concentration of fecal matter. It is advisable to wear disposable gloves when scooping the litter box, and the contents should be disposed of promptly. After removing the gloves, you must immediately wash your hands with soap and water. Children under five years old and immunocompromised individuals should avoid handling the litter box entirely.
Food handling also presents a risk, especially if you feed your cat a raw meat diet, as this is a known source of contamination for pathogenic E. coli. To minimize risk, avoid feeding raw meat and ensure that all pet food and water bowls are cleaned and disinfected regularly. If your cat develops diarrhea or any other sign of illness, consulting a veterinarian is prudent, as a sick cat poses a higher risk of shedding bacteria.