Pet owners often wonder if a dog’s stomach upset can be transmitted to a person. A “stomach bug” generally refers to acute gastroenteritis, an inflammation of the gastrointestinal tract causing symptoms like vomiting and diarrhea. This illness is often caused by infectious agents such as bacteria, viruses, or parasites. The potential for these agents to jump from animals to humans falls under the category of zoonotic diseases. While many illnesses are species-specific, some common gastrointestinal pathogens have a broad host range, meaning they can cause illness in both dogs and humans.
Pathogens Dogs and Humans Share
Several types of infectious organisms are zoonotic and can cause comparable gastrointestinal distress in both dogs and humans. These shared culprits include certain bacteria and protozoan parasites that have adapted to infect multiple mammalian species.
Bacteria are a prominent group, with Salmonella and Campylobacter being frequently cited examples. Salmonella infection (salmonellosis) causes fever, abdominal cramps, and diarrhea in people. Dogs may also exhibit diarrhea and vomiting, though many infected dogs remain asymptomatic carriers. Campylobacter is a common cause of bacterial diarrhea globally. Dogs, especially puppies, can shed this organism in their feces, even if they do not show signs of illness themselves.
Parasitic infections represent another significant area of overlap, particularly with protozoa like Giardia and Cryptosporidium. Giardia is a microscopic parasite that lives in the intestines and is a frequent cause of nonbacterial diarrhea in both species. Roundworms, specifically Toxocara canis, are also zoonotic. While they cause intestinal issues in dogs, human infection generally results from accidentally ingesting eggs from contaminated environments, which can lead to a condition called visceral larva migrans. These shared pathogens are capable of infecting both species because their biological mechanisms are not restricted to a single host.
Illnesses That Are Species-Specific
Despite shared pathogens, many gastrointestinal illnesses are highly species-specific. This means a dog cannot transmit its particular infection to a person, and vice versa. This species barrier exists because viruses and bacteria require specific host cell receptors to successfully invade and replicate. If a pathogen cannot effectively bind to the cells of another species, it cannot cause a full infection.
Canine Parvovirus (CPV) is a clear example, causing severe hemorrhagic gastroenteritis in dogs, especially puppies. CPV relies on receptors found on rapidly dividing cells in the canine intestinal lining and bone marrow, making it unable to infect human cells. Similarly, Norovirus, often called the “stomach flu” in humans, is the leading cause of epidemic gastroenteritis worldwide. While dogs can carry their own strains of Norovirus, the human-specific genotypes are not generally transmissible to dogs. Symptoms may look the same across species, but the underlying infectious agent is often biologically distinct.
Preventing Transmission Between Pets and People
Mitigating the risk of sharing zoonotic gastrointestinal illnesses centers on vigilant hygiene, especially regarding the fecal-oral route of transmission. This route, where microscopic amounts of feces are inadvertently ingested, is the primary way bacteria and parasites travel between dogs and humans. Rigorous handwashing is the most effective defense against cross-species infection.
Hands should be thoroughly washed with soap and water immediately after handling dog waste, touching pet food or water bowls, or playing with a dog experiencing diarrhea. Prompt and proper disposal of pet feces is a major preventative action, as parasites like Toxocara require time in the environment to mature into an infective stage. Children should be supervised to ensure they do not touch dog feces or put soiled objects in their mouths. Sandboxes should be kept covered when not in use.
Food handling practices also require attention, especially if a dog is fed a raw food diet, which is associated with an increased risk of shedding pathogens like Salmonella and Campylobacter. Avoiding pet access to human food preparation surfaces, such as kitchen counters, prevents cross-contamination. Regular veterinary care, including appropriate deworming protocols, reduces the chance that a dog will carry and shed intestinal parasites. When a dog or human is ill with diarrhea or vomiting, minimize close contact and ensure frequent cleaning of surfaces the pet may have touched.