If by "possums disease" you mean Equine Protozoal Myeloencephalitis, the answer is a few horses will, but these were the minimally affected horses. Severely affected horses (ie, those that are having difficulty walking or standing) generally do not recover fully and many are euthanized for humane reasons when they become infected.
No, horses do not contract parvo.
yes, Equine Protozal Myelitis is a "bug" that can be passed.
Possums can contract a protozoan parasite called Sarcocystis neurona and then shed an infective life stage in their feces. This parasite, when ingested by horses, can migrate to the central nervous system of the horse where it destroys cells in the brain and/or spinal cord which causes neurological disease.
A veterinarian.
Yes, horses can get Cushing"s disease. I'm not sure if you're asking what happens when they do, but they can get it. A horse of a friend of mine got it.
Humans, dogs, pigs, cows, horses, dolphins, possums, and elephants are all placental mammals but there are others as well.
Opossum.
laminitus is a hoof disease where there is a separation of the laminade in the horses hoof. it can be caused by stress or a high sugar content and/or being too fat. it can be fatal in sevre cases.
Only animals with cloven hooves can contract foot and mouth disease. Horses do not have cloven hooves so therefore they cannot contract the disease
Rickets is a disease in which the horse's legs bow in or bow out. It is classed as a disease of the bone.
Equine Infectious Anemia is a contagious disease of horses that has, since the 1800's, resulted in outbreaks which killed large numbers of horses in many countries. There is no vaccination, so testing and either quarantine or euthanasia of infected horses is the current means of disease control. Horses with EIA can suffer from acute or chronic disease or even be inapparent carriers. The disease affects the horse's immune system and is caused by a virus related to HIV.
Which horses? Most horses live on land. Actually all horses except for seahorses live on land.