Laminitis, colic, influenza, cushing's disease, equine protozoal myeloencephalitis, strangles, rabies, ulcers, eastern equine encephalitis, equine herpes, west nile virus and arthtiris are all I can think of @ this time.
Some common equine diseases and conditions are colic, flu, tick bite fever, west nile virus, equine infectious anemia, equine protozoal mennangitis, tetinus, rain rot, thrush, diharea and worms. many of these conditions have vaccines to prevent them and others have treatments while some are incurable like EPM.
Wow, this is a broad topic but the most common that you need to familiar yourself with are laminitus (or whenever the horse its lame) and Collic (where the horse has what we would descibe as a cough/or even the flu) Horses arent that different to us so treat them that way.
Some common equine diseases are colic, navicular disease, rain rot, founder and worms (bots). People often call colic a twisted gut and founder is often caused by feed problems.
Some of the more common equine diseases that can be prevented or have their occurrences reduced with vaccination are tetanus, encephalomyelitis, influenza, rhinopneumonitis, West Nile Disease, herpes, strangles, and Potomac Horse Fever. Horses can also be vaccinated against rabies in at-risk areas. Though not an actual disease, colic (generic reference to belly ache) is quite common in horses.
Equine influenza, rabies, equine encephalitis, equine piroplasmosis, tetanus, west nile, equine herpes virus, strangles, swamp fever, potomac horse fever, cushing's, equine viral arteritis, botulism, lime, equine ehrlichiosis, spotted fever, colorado tick fever, heartwater, tularemia, equine granulocytic anaplasmosis, and many more diseases that are not as common or rare. Though thankfully a good number of these are preventable.
Common equine diseases include such conditions as parasites and eye infections, colics and thrush, influenza (flu) and paralysis, arthritis and botulism, degenerative joint disease and anemia, skin cancer and hypothyroidism, laminitis hoof condition and mare reproductive loss syndrome, moonblindness and rhinovirus, ring bone and strangles, vesicular stomatitis and west Nile virus.
Pick up a Vet manual. Merck is the oldest and most trusted Vet manual company. These books are chocked full of equine diseases and ailments. Just read up and study them and you will know a lot about horses. If something ever happens to your horse you will know how to help fix your horse.
One common equine disease is Navicular which is when the cannon bone rotates causing laminitis. Laminitis is a sort of inflammation or irritation such as abscesses on the hoof area.