Equine Influenza Outbreaks
- Equine influenza is most often caused by two strains of the influenza A virus: subtype A1, or H7N7, and subtype A2, or H3N8. Only H3N8 has been active during the past 30 years, according to Horse.com. The virus replicates in the cells of the respiratory tract and is shed through the cough of infected horses; it can also be transferred from items such as food pails and grooming equipment. The incubation period of equine influenza is three days.
- Horses that are infected with equine influenza will typically exhibit a rapid onset of symptoms. These symptoms include coughing, high fever and clear nasal discharge. There may also be swelling of the lymph nodes around the jaw line. In rare cases, a horse may develop edema in its trunk and lower limbs. A thick, yellow or green nasal discharge indicates that a horse has developed a secondary bacterial infection; this can lead to pneumonia and eventually death if left untreated.
- Equine influenza is often diagnosed based on clinical symptoms, especially after more serious causes of these respiratory symptoms, such as strangles and pneumonia, are ruled out. However, test kits for equine influenza are available and usually involve detecting the virus in nasal swab samples.
- A horse with equine influenza is typically isolated from other horses in order to stop the spread of the virus. Food and water intake will be monitored and encouraged, and non-steroidal anti-inflammatory medications may be given to control fevers. Horses that continue to have a fever after three days, especially when accompanied by a thick nasal discharge, should be treated with antibiotics in an aggressive manner, since this indicates a secondary bacterial infection may have progressed to bacterial pneumonia. In cases of equine influenza that do not develop into something more serious, most horses will fully recover and be able to return to normal exercise in three to four weeks. Horses that develop bacterial pneumonia will need a longer recovery period; in addition, damage to the lung tissue may prevent some horses from returning to their former peak condition.
- Horses that may be at risk for contracting equine influenza should be vaccinated, according to the American Association of Equine Practitioners. This includes horses that are often in contact with other large groups of horses, such as at show events or race tracks. In addition, horses should be quarantined for two weeks at a new barn prior to introducing them to other horses. Any horse exhibiting possible influenza symptoms should be immediately isolated from other horses; avoid sharing any equipment that may have been contaminated.