Dogs are happy to give some sugars as a way of showing affection. Unfortunately, their wet licks and slobbery kisses deliver saliva filled with various germs and organisms. Zoonotic diseases and parasites, those that can spread from one species to another, such as from dog to human, can transfer through your pooch's loving licks. Many parasites, such as roundworm, tapeworm and hookworm, are zoonotic and can spread through such direct contact with your dog. Worms, however, are not one of the various illnesses spread through saliva.
How Worms Spread
The mode of transmission for most worm infestations in dogs is through ingestion of infected animals or feces. If your dog has worms, the worms reside in the gastrointestinal tract and pass eggs out through feces. Humans acquire worms typically through direct or indirect contact with feces or with feces-contaminated soil or food. Walking barefoot on contaminated soil is enough to cause infection with hookworms. Occasionally, dogs will have eggs on their fur due to licking. Petting your dog can transfer the eggs to your hands. Grabbing something to eat after petting an infected dog, without washing your hands, is enough to ingest roundworm eggs.
Symptoms of Worms
Symptoms of a worm infestation in your dog include diarrhea, vomiting and weight loss. Occasionally blood, mucus or worms are visible in vomit or stool. In humans, roundworm infections can cause swelling of the liver, spleen, heart and lungs; fever; weakness; coughing; abdominal pain; nausea; and vomiting. If the worms migrate to the eye, blindness is possible. Hookworms often cause no symptoms in humans but can lead to anemia.
While worms do not pass through canine saliva, other conditions do. One virus that spreads through dog saliva is rabies. The virus enters through broken skin, such as through a bite. Rabies vaccination programs have reduced the number of cases in dogs and therefore reduced dog-to-human transmission, but transmission remains possible. Canine rabies symptoms include fever, seizures, paralysis, dropped jaw, aggression and excessive salivation. In humans, rabies symptoms include drooling, convulsions, loss of muscle function, muscle spasms, low-grade fever and difficulty swallowing.
Other Diseases Spread Through Saliva
Dog saliva contains various forms of bacteria, most of which are normal. While the bacteria are not harmful in the mouth, a dog could simply lick an open cut on your arm and introduce those bacteria into your body. Common bacteria responsible for infections in people include Pasteurella, Staphylococcus aureus or MRSA, and Capnocytophaga canimorsus. Cases of methicillin-resistant MRSA have been linked to canine saliva from a single lick.