An epizootic of equine influenza in Upper Egypt in 2000.

This study describes an epizootic of respiratory tract disease caused by influenza virus infection in a large population of equines in Luxor and Aswan, Upper Egypt, during the winter of 2000. The epizootic started in January and the infection rate reached its peak in February before gradually decreasing until the end of April, 2000. Horses, donkeys and mules of all ages and both sexes were affected. Free movement of the infected equines and direct contact between the animals at markets facilitated the rapid spread of the disease. The cause of the epizootic was established by use of serological testing and the identification of the influenza virus in nasal secretions. Egg inoculation and the haemagglutination test were used to detect the influenza virus. Both haemagglutination inhibition (HI) and agar gel precipitation tests were performed to identify the isolated influenza virus using reference antisera against A/Equi-1 (H7N7) and A/Equi-2 (H3N8). Antibodies against the equine influenza virus were demonstrated in 416 (95.6%) out of 435 collected sera using the HI test. High rectal temperature, inappetence, conjunctivitis, redness of nasal mucosa, a serous to mucopurulent nasal discharge and a harsh dry cough were the most common clinical manifestations. Stress factors, such as using equines for heavy transportation and drawing, precipitated the onset of the disease, intensified the clinical syndrome, delayed recovery and facilitated secondary bacterial infection. The present study suggested that the absence of a vaccination programme against equine influenza was one of the principal causes of the spread of infection during this outbreak. In conclusion, the implementation of a national equine influenza vaccination programme, using an effective updated vaccine, is essential in Egypt.