Detection of Avian Influenza Virus H5N1 in Horses at Assiut Governorate, Egypt

The highly pathogenic H5N1 is a major avian pathogen that intensively affects the poultry industry in Egypt, even in spite of the adoption of vaccination strategy. The virus is currently panzootic in Egyptian poultry populations and crosses species barriers to humans and animals. In February 2014, 15 horses at El-Fath center, Assiut, Egypt, started to show mild fever, dullness, restlessness, slight nasal discharge and cough. Two weeks later one of these horses died and another one became recumbent. This was associated with the spread of avian influenza cases in the backyard birds in the same area. Serum samples were collected from the diseased horses and from birds in the same area and examined by haemagglutination inhibition (HI) assay for detection of viral antibodies. At the same time, nasal swabs from horses and tracheal swabs from birds collected and examined by rapid antigen detection and quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) for detection of the virus. Serum samples of horses showed positive titer with HI in 13 out of the 14 diseased horses and the highest titer was 6-log2 in the recumbent one. Meanwhile, the result of HI for birds serum samples (450) were negative for 425 samples, which indicate absence of previous vaccination or infection, while the remaining 25 samples were from balady chickens showing HI titer 6-log2±0. 84 and those birds were previously vaccinated 4 weeks before collecting the serum. Avian influenza H5N1 virus could not be detected by using rapid antigen detection strips in the nasal swabs taken from the diseased horses, but could be detected in birds in 102/150 with antigen capture immune-assay (AC-EIA) common antigen type A, 95/150 with (AC-EIA) H5, 0/150 with (AC-EIA) H7 and 0/150 with (AC-EIA) H9 of examined samples. By qRT-PCR, H5N1 virus could be detected only in the nasal swab of the recumbent horse, and in 138/150 tracheal bird swab. In conclusion, Assiut city in Egypt is a disease endemic area where the probability of intimate contact between infected backyard birds and horses is high. Therefore, the disease may be transmitted to these horses from aerosol exposure of infected birds' droppings or contaminated feeds and water or because of direct contact with infected birds. However, the moderate severity of the H5N1 in equine may be responsible for the recovery of most of the diseased horses without further complications.