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Zooanthroponosis – Canine Diseases Transmissible to Humans

By Dylan Green
Published on 01/28/2024
Reviewed by Dr. Joseph Howard

Rabies

Rabies is a viral infection that is almost always fatal in dogs and humans. It is transmitted through bite wounds. But even the smallest injuries to the skin and mucous membranes can allow the virus to enter. The incubation period (from infection to the onset of symptoms) is about 3 weeks in dogs and between 4 weeks and 3 months in humans.

Symptoms in dogs are usually hoarse barking, difficulty swallowing resulting in increased salivation, aggressive behavior, and in the late stages of the disease, paralysis. In humans, flu-like symptoms occur. The virus almost always causes encephalitis (inflammation of the brain) or myelitis (inflammation of the spinal cord). Later, swallowing difficulties, paralysis, and the typical fits of rage also occur. The only protection for both dogs and humans is vaccination.

Leptospirosis

Leptospirosis is a bacterial infectious disease. Humans can become infected through the urine or blood of an infected dog. In dogs, the disease manifests itself through symptoms such as loss of appetite, vomiting, fever, and bloody stool. The mortality rate is 10% here. In humans, on the other hand, the infection usually resembles a flu. The disease is treated with antibiotics, both in humans and in dogs. There is a vaccine for dogs, but it does not cover all strains and provides less than a year of protection.

Fox Tapeworm / Dog Tapeworm

The fox tapeworm is a type of tapeworm. As the name suggests, it is mostly found in foxes. However, it can also occur in dogs, as small rodents (mice) serve as intermediate hosts. The transmission to humans is not yet fully understood, but there seems to be an increased risk in agriculture and forestry. However, cases have also been reported through dogs or cats. Many people are resistant to the fox tapeworm, and despite ingesting the eggs, no disease outbreak occurs. In the event of an infection, however, this worm can have devastating consequences.

Due to the development of larvae in various organs, the highly dangerous alveolar echinococcosis (the most dangerous parasitic disease in humans – notifiable) can occur. However, this is extremely rare in the United States. The incubation period can be up to 15 years. However, if the first symptoms appear, the larval tissue in the body has already reached a considerable size. The earlier the disease is detected, the better the chances of recovery. In dogs, symptoms only occur with a heavy worm infestation. Usually, the dog is a definitive host, causing less damage. Regular deworming is therefore essential.

Also worth mentioning is the rarely occurring dog tapeworm, which also belongs to the tapeworms. While mostly harmless in dogs, it can be extremely dangerous in humans and lead to cystic echinococcosis (formation of cysts by the larvae). The larvae settle in various organs of the human body. The cysts can be surgically removed, but this procedure is not without risks, as rupture (bursting) of the cysts leads to seeding in the body.

Toxocariasis

Toxocariasis is transmitted through either dog or cat roundworm. Ingestion occurs through the mouth. Symptoms only develop with a heavy infestation. The infestation can only be detected through an ELISA (antibody-based detection method) because the worm’s life cycle does not fully occur in the human body, and thus no worm eggs, larvae, or adult worms can be detected in the stool.

The incubation period is months to years. Once the infection is recognized, treatment is administered through an anthelmintic (thiabendazole or diethylcarbamazine). In dogs, as with the fox tapeworm, symptoms only appear with a massive worm infestation. Therefore, regular deworming is essential here as well.

Scabies / Mange

Scabies is a mite infestation that can also occasionally transfer to humans (mostly as an incorrect host), where it can trigger a kind of pseudo-scabies. Scabies is a highly contagious disease because the mites do not stay with their host but continue to migrate. Symptoms in dogs can include hair loss and scaling in the eye, forelimb, and mouth corner areas, reddened spots on the skin, bald patches in the fur, as well as sore spots primarily between the toes, on the nose, and above the eyes. The therapy and cure depend on the age of the dog and its general condition.

However, there are very good chances of recovery (often, Demodex mange heals spontaneously without therapy). Except for cleanliness and hygiene, there are no preventive measures. Transmission to humans occurs through skin contact. With intact immune systems and good hygienic conditions, the body’s immune response keeps the mite count relatively low. However, if an infection occurs, the symptoms can be varied. Depending on the type of infestation, there are also different forms of therapy. But here too, there are very good chances of recovery.

Five Points to Minimize the Risk of Transmissible Diseases

Even though there are some serious diseases that dogs or other animals can transmit, one should not be discouraged from owning a pet. Those who observe good hygienic conditions and cleanliness, regularly present their dog to the veterinarian, but also pay attention to good nutrition and care for their dog, minimize the risk of potentially transmissible diseases.

The risk of infection from other humans is much higher. One should keep in mind that animals can also transmit diseases. Likewise, we should also remember that we can infect our pets.

Although health-related topics have been written to the best of knowledge and belief, errors may still occur, or they may represent an outdated scientific status, nor do they replace the advice of qualified veterinarians. The authors accept no responsibility for its correctness; all information is provided without guarantee.