Any disease or infection that is naturally transmissible from vertebrate animals to humans and vice-versa is classified as a zoonosis or zoonotic disease according to the Pan American Health Organization publication "Zoonoses and communicable diseases common to man and animals". According to the publication, over 200 zoonoses have been described and known for many centuries.
Transmissable from horse to human and vice versa
Any disease or infection that is naturally transmissible from vertebrate animals to humans and vice-versa is classified as a zoonosis or zoonotic disease.
Zoonoses still represent significant public health threats, but many of them are neglected because they are not prioritized by health systems at national and international levels. They affect hundreds of thousands of people and animals especially in developing countries, although most of them can be prevented.
Zoonotic diseases are caused by a number of agents:
- Bacteria
- Parasites
- Fungi
- Viruses
Some examples of zoonotic diseases, classified according to the type of causative agent:
Bacteria
Every year millions of people get sick because of foodborne zoonoses such as Salmonellosis and Campylobacteriosis which cause fever, diarrhea, abdominal pain, malaise and nausea. Other bacterial zoonoses are anthrax, brucellosis, infection by verotoxigenic Escherichia coli, leptospirosis, plague, Q fever, shigellosis and tularaemia. Many cases of these diseases also occur in horses each year.
For example, transmission through water and feed troughs of E coli is considered a major source of on-farm disease movement between/from cattle. Horses should not drink from cattle troughs. Grassland buffers are an effective method for reducing animal/agricultural inputs of waterborne E. coli into surface waters
Parasites
Cysticercosis/Taeniasis is caused by a parasite which infects swine and can cause seizures, headache and many other symptoms in humans. In Latin America for example, 100 out of 100 000 inhabitants suffer from this disease (estimation). Other parasitic zoonoses are trematodosis, echinococcosis/hydatidosis, toxoplasmosis and trichinellosis. Many of the same parasites that affect humans can also infect horses.
Viruses
Rabies is a disease of carnivores and bats mainly transmissible to humans by bites. Almost all persons infected by rabid animals will die if not treated. An estimated number of 55 000 persons, mainly children, die of this disease in the world every year. Dogs are responsible for most human deaths. Other viral zoonoses are avian influenza, Crimean-Congo hemorrhagic fever, Ebola and Rift Valley fever. These viruses affect horses, many of which die of illnesses that can be passed to humans.
Fungi
Dermatophytoses are superficial mycoses that may be acquired from infected animals including horses and affect the skin, hair and nails of humans, causing itching, redness, scaling and hair loss. Another mycotic infection that can be zoonotic is sporotrichosis.
Unconventional agents
The agent of Bovine Spongiform Encephalopathy is thought to be the cause of variant Creutzfeldt-Jakob Disease (vCJD) which is a degenerative neurological disease different from CJD, at present inevitably lethal in humans.
Outbreaks of diseases where multiple animals become infected usually occur in large barns or vet hospitals where many animals are sheltered together. However, most horses are kept in smaller populated farms and facilities where infections tend to be individual, sporadic, and contained.
Manure is often the source of infection in zoonotic diseases. According to Meyers (1997) most feces from recreational horses are deposited in home paddocks and pastures which limits human exposure to horse feces, making the transition of disease to humans relatively rare.