According to the Merriam-Webster dictionary the definition of a zoonotic disease is “a disease communicable from animals to humans under natural conditions”. Although rare, bacterial and fungal infections in horses, can cause a variety of illnesses in people, from minor skin infections to serious illnesses. Besides touching your horse, even our common chores such as cleaning stalls and grooming may also put us at risk.
In our world of horses, there are numerous zoonotic diseases and we should be more cautious when we come across them. We’ll highlight a few below but please check out the references listed for additional zoonotic diseases transmitted by horses. We’ll cover the topic of prevention in another blog.
There are two ways a zoonotic disease can be transmitted, direct and indirect. Ingestion, inhalation, skin contact, contact with mucous membranes or open wounds and bites are examples of a direct transmission. Examples of indirect transmission are insect bites and contact with inanimate objects (e.g., blankets, brushes, hoof picks or other items with fecal contamination, then eating lunch).
Contact with your horse itself is one way that a disease is spread, but other ways include contact with urine, feces, or respiratory secretions of an infected animal, or contact with other items in your horse’s environment ie. blankets, brushes, etc.. Disease can also be spread through scratches or bites by your pet but this is less common with horses. Insects (such as the Lyme-disease tick) can also spread an infection from animals to humans.
According to the Centers for Disease Control and Prevention (CDC) salmonellosis and ringworm are the two most common diseases passed from horses to humans. The less common diseases are rabies (rabies is transmitted from horses to people via saliva, and any small cut or abrasion can serve as an entry point), anthrax, Brucellosis, MRSA (methicillin-resistant staphylococcus aureus), and west nile. You can see a complete list of diseases on the CDC website.
The most common zoonotic disease is Salmonella. Salmonella is a bacteria that spreads to people through contaminated food (eggs and meat) or contact with the stool of certain animals, including horses. Horses infected with Salmonella might show no signs of the disease or could have watery diarrhea, depression, and severe dehydration. People infected with Salmonella might have diarrhea, vomiting, fever, or abdominal cramps. Infants, elderly persons, and those with weakened immune systems are more likely than others to develop severe illness. Exposure results from fecal-oral contact (generally due to ineffective hand washing) or oral contact with contaminated materials. Any horse or foal with diarrhea should be isolated, and proper protective clothing should be worn when handling the animal, with further precautions assessed by a veterinarian.
The second most common zoonotic disease is Ringworm (trichophyton and microsporum). Ringworm is a condition caused by a fungus that can infect the skin, hair, and nails of both humans and animals. Ringworm is spread from animals to humans through direct contact with an infected animal’s skin or hair or through contact with contaminated equipment, such as brushes. Ringworm in horses usually begins as a small raised bump that is hairless. The bump can become thick and scaly and sometimes ringworm infection causes circular, bald, scaly patches with broken hairs. Infection in people can appear on almost any area of the body. These infections are usually itchy. Redness, scaling, cracking of the skin or ring-shaped rash may occur.
Other zoonotic diseases to keep your eye on, because it is so common in horses, are dermatophilosis congolensis (rain rot) and scratches which can be both bacterial and fungal (see https://equinesafetyzone.com/scratches/). Direct contact with an infected animal can lead to infections on the hands and arms.
We agree with the CDC’s recommendations to avoid these contagious diseases:
- Wear gloves when working with an infected animal
- Wash your handsthoroughly with soap and running water after doing common chores with horses—especially after touching horse manure or urine, saliva, or blood.
- Wash your hands before eating, drinking, or smoking after handling horses or any animal.
- Cover any open wounds or cuts when visiting or working around horses.
- Seek routine veterinary care, vaccinations and deworming for your horse.
While it is rare for humans to contract a disease from a horse, it is possible. Usually the only way to know whether you have a specific condition is through a laboratory test ordered by your doctor.
Other helpful references: