With fall and winter weather conditions, horses with compromised lung functions face setbacks unless an effort is maintained to keep them healthy and in comfortable surroundings that can help minimize the effects of cold, wet, windy weather, which can make it more difficult for horses to breathe, especially if their lungs are compromised.
The formation of excess fibrous connective tissue in a horse's lungs can be devastating to the health of the horse. Horses with progressive fibrotic lung disease show varying degrees of increased respiratory rates, abnormal lung sounds and signs of having to make an effort to breathe such as flared nostrils.
In early stages, the horse's difficulties may go unnoticed, but typically, weight loss, fever, coughing, increased respiratory and heart rate and nasal discharge will get the attention of the horse owner.
Diagnosis can be difficult, but will typically involved blood work, chest S-rays, ultrasound, pulmonary fluid analysis and possibly a lung biopsy.
A number of toxins, infiltrations, infectious agents, and inhaled foreign particles have been recognized as possible causes of pulmonary fibrosis, but now, recent research is showing that a subset of fibrotic lung disease in horses is associated with EHV-5.
A research group at Michigan State University has reported that this subset of fibrotic lung disease in horses commonly affects horses in their mid-teens, and have termed the disease equine multinodular pulmonary fibrosis (EMPF).
EHV-5 and its close cousin EHV-2 are in the gammaherpesvirus family which distinguishes it from the better-known equid alphaherpesviruses such as EHV-1.
It is thought that horses contract the EHV-5 virus during the first six months of life, and up to 80% of horses in California are infected with the virus. EHV-5 has also been identified in horses in New Zealand, Australia and Europe.
Prior to research associating EHV-5 with fibrotic lung disease, it had not been recognized with a disease entity in horses. Although the causal relationship between EHV-5 and EMPF has not been proven, the fact that it is frequently detected in the lung tissue of horses with EMPF as compared with control horses, strongly suggests that EHV-5 plays a role in this disease.
Horses with fibrotic lung disease of any type are usually treated supportively with anti-inflammatory drugs and antibiotics if secondary bacterial infection is suspected.
Dr. Stephany Bell and her colleagues at UC Davis are currently doing research into the possibility of antiviral drugs being developed and used to treat this condition. It is hoped that future discoveries regarding the pathogenesis of the disease will lead to prevention and treatment options.