Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/1996
Publication Date: N/A
Interpretive Summary: Avian influenza (AI) is a disease in poultry caused by a small virus. This virus produces a variety of clinical problems that can be mild to very severe. Controlling AI is essential for maintaining a viable domestic poultry industry and continuing international trade. Two issues were examined in this study: 1) the type of test samples to take from poultry and the types of tests to be performed to diagnose AI, and 2) determination of the risk mild AI has to become a deadly, severe disease in poultry. Samples from the nasal cavity were the best for isolating the AI virus and making a diagnosis of AI. The presence of specific antibodies in the blood of chickens indicated infection with AI viruses. The agar gel precipitin serologic test was the best for detecting AI infection early after virus exposure. Some of the AI viruses from Mexico changed from producing a mild disease to producing a severe, deadly disease. This information will allow veterinarians to correctly diagnose AI. An accurate diagnosis will permit the poultry industry and U.S. regulatory agencies to detect AI early during an outbreak and begin appropriate disease control strategies.
Technical Abstract: Chickens were inoculated with H5N2 Mexican-origin avian influenza virus (AIV) isolates. During clinical disease, oropharyngeal swabs were superior for isolation of AIV, but cloacal swabs were more successful after disappearance of clinical signs. Agar gel precipitin (AGP) serologic test was superior for detecting AIV infection during the clinical phase, but AGP and hemagglutinin inhibition tests were equally effective after recovery from clinical illness. H5/94, M5/94, and J12/94 AIVs produced sporadic illness and death, and were categorized as mildly pathogenic. Q1/95 AIVs produced illness and death in all inoculated chickens and was categorized as highly pathogenic (HP). P11/94B commonly produced clinical illness, but deaths were infrequent. However, passage of P11/94B parent stock and selected 14-day embryo passed AIVs in adult hens resulted in emergence of some highly lethal AIV derivatives. The hemagglutinin of Q1/95 and P11/94B parent stock and derivative AIVs had an identical proteolytic cleavage site of Pro-Gln-Arg-Lys-Arg-Lys-Thr-Arg-Gly, consistent with HP AIVs. However, no consistent differences were identified in the sequence of the hemagglutinin gene to explain the discrepancy in lethality of the P11/94B AIVs. This suggests that genes other than the hemagglutinin impact the full expression of high lethality of Mexican-origin AIV for chickens.