Evaluation of different serological tests for the detection of antibodies against highly pathogenic avian influenza in experimentally infected ostriches (Struthio camelus)

In the present study we collected 177 serum samples from ostriches (Struthio camelus) infected experimentally with A/ostrich/South Africa/Middleton/2004 (H5N2) highly pathogenic avian influenza virus. We tested these samples using the haemagglutination inhibition (HI) test, the agar gel immunodiffusion test and three enzyme-linked immunosorbent assay kits. We considered the HI test, with homologous antigen and including pre-treatment of sera with 10% chicken red blood cells, as the gold standard. Detectable specific antibodies appeared on day 7 post-infection and persisted until the termination of the experiment. The relative sensitivity and specificity of the tests under evaluation and Cohen's K value were calculated. The results reported herein could be of assistance to decision-makers in drafting guidelines for the definition of the health status of ostriches and for trade purposes.