New Horse Diseases and Ways to Treat Them

African Horse Sickness

• Originally found in sub-Saharan Africa, African horse sickness is a deadly disease that is spread by the Culicoides, a small fly. There are two forms of the disease, the lung form and the cardiac form. The lung form, which is 90 percent fatal, is characterized by a high fever, frothing at the mouth and sudden death. The cardiac form is typified by swelling of the horse's head and eyes, bleeding from membranes in the mouth and eyes, and an inability to swallow. The cardiac form of African horse sickness has a fatality rate of 50 percent. It is believed that as climate change occurs, the habitat of the type of Culicoides that spreads African horse sickness also will expand, spreading the disease to Europe and North America. Since there is no treatment or cure for this disease, researchers are focusing their efforts on developing vaccinations to inoculate healthy horses.

Contagious Equine Metritis

• Contagious equine metritis is a tropical venereal disease that spreads when an infected horse breeds with a non-infected horse. It also may spread when contaminated fluids or instruments used in artificial insemination or breeding come into contact with a non-infected horse. The disease is caused by the bacterium Taylorella equigenitalis. Although any breed of equine may be susceptible, thoroughbreds seem particularly predisposed to the disease. Because contagious equine metritis may be asymptomatic, it is difficult to determine if a horse is infected. Though the bacterium may be present on the external genitalia for years, stallions may not show any sign of the disease. In mares, a white discharge may be apparent 10 to 14 days after infection. In addition, the disease may cause infertility or spontaneous abortion. Although the occurrence of contagious equine metritis is documented in Europe, the disease has been virtually eradicated in the United States. Still, considering that importing horses from Europe to the United States is such big business, the possibility of the disease resurfacing in the United States is far from remote. Since a widespread outbreak of contagious equine metritis could disrupt horse breeding and cripple the horse industry, all horses imported from Europe should be quarantined for disease. In addition, treatment of infected horses is particularly important. Treatment consists of applying disinfectants and topical antibiotics on external horse genitalia. If the disease has infected a mare's uterus, a veterinarian also may prescribe an oral antibiotic to flush the bacteria out of her system.

Equine Herpes Virus Myeloencephalopathy

• Equine herpes virus myeloencephalopathy is a neurological disease spread by the paralytic form of the equine herpes virus (EHV-1). EHV-1 is a common airborne virus that almost all horses older than 2 years of age have been exposed to. Some forms of EHV-1 are more damaging than others. Once rare, the paralytic form of EHV-1 responsible for equine herpes virus myeloencephalopathy has become more prevalent in recent years. Since 2003, the United States Department of Agriculture has reported a significant number of cases of equine herpes virus myeloencephalopathy. Researchers believe that this increased prevalence is due to a mutation of the EHV-1 virus that makes it more robust. Equine herpes virus myeloencephalopathy is manifested by ataxia, urinary bladder atony, or reduced tail tone. In severe instances, horses suffering from equine herpes virus myeloencehpalopathy are unable to stand. Extreme cases of equine herpes virus myeloencephalopathy are fatal. Milder cases of the disease can be treated by antivirals such as acyclovir but the efficacy of such drugs in horses is yet to be determined. In the interim, researchers are working on developing a vaccination to prevent the EHV-1 virus.