Equine multinodular pulmonary fibrosis (EMPF) is an emerging sporadic, progressive respiratory disease of adult horses. EMPF was first described in horses in 2007, and has been reported in horses living in the United States and Europe. It is a disease in adult horses characterized by chronic, multifocal, fibrotic lung disease. There is growing evidence that suggests that EMPF may be associated with equine herpesvirus type 5 (EHV-5) and possibly asinine herpesviruses (AHV) 4 and 5. The typical clinical presentation of EMPF includes adult horses with a history of fever, weight loss, and respiratory signs ranging from mild tachypnea (abnormal rapid breathing) to marked dyspnea (difficult or labored breathing). EMPF is thought to be similar to idiopathic pulmonary fibrosis in humans. Horses with EMPF may initially be treated for heaves or infectious broncho pneumonia with little to no improvement and progression of clinical signs prior to receiving a diagnosis of EMPF.
Documented cases of EMPF
- In 2007, 5 horses were diagnosed with EMPF in Germany and Austria. The horses were provided supportive treatment, consisting of a variety of medications including corticosteroids and acyclovir. Of the 5 horses, 2 survived and returned to their previous level of activity and the other 3 were euthanized as a result of the ineffectiveness of the treatment.
- In 2011, a case was presented by Dr. Schwarz at the 50th BEVA Congress in Liverpool, UK about a 22-year-old Warmblood stallion that was diagnosed with EMPF that recovered after one week of treatment with valacyclovir (40 mg/kg bwt per os q. 8h) and found to still be in good health 2 years following treatment.
- In 2012, a 4-year-old standardbred gelding was referred to the equine hospital at the Swedish University of Agricultural Sciences in Uppsala, Sweden with a 10-day history of fever (38.5-40°C), reluctance to move, intermittent abnormal breathing, mild coughing, and lethargy. The horse had been previously treated by the ambulatory veterinarian with procaine penicillin IM and acetylcysteine administered orally, however it had no effect on horse's condition. Upon a physical examination, the horse was found to be in thin body condition, with abnormally rapid breathing. The referral hospital treated the horse with penicillin IV, dexamethasone IV, salbutamol administrated via Aeromask, and supportive care (intranasal oxygen). The horse's condition started deteriorating after 3 days of treatment, and was euthanized.
The gold standard for diagnosis of EMPF in horses is through histopathological results from a lung biopsy in combination with confirmation through a qPCR testing of BALF or a combination of whole blood and nasal secretions, which read positive for the presence of EHV-5.
EMPF has been documented in horses living in the United States, Australia, New Zealand, Sweden, Germany, Austria, Italy, Belgium, and the United Kingdom.
The University of California-Davis is currently conducting clinical trials on horses diagnosed with EMPF, to better understand the effects of valacyclovir, (the drug most commonly used for treatment of horses) on EHV-5 viral kinetics in horses. Here is a link to their website for additional information regarding the clinical trial