Serological Diagnosis of Influenza A Subtype H1 on Family Poultry of Belo Horizonte, Minas Gerais and Santa Maria, Rio Grande Do Sul, in Brazil.

ABSTRACT Serum samples (n=687) from Gallus gallus domesticus were collected for the investigation of antibodies to avian influenza virus (AIV-A) in the family poultry of the surrounding counties of Santa Maria/RS and the metropolitan region of Belo Horizonte/MG, totaling twenty different counties. Additional samples of seventeen (n=17) free-flying ducks (C. moschata pure or hybrid with Anas platyrhynchos) were collected in Belo Horizonte. The chosen tests for the survey were performed as described by the World Organization for Animal Health (OIE), including agar gel immunodiffusion (AGID) for antibodies to AIV-A nucleoprotein (N) and haemagglutination- inhibition (HI) for antibodies to subtype H1. Out of the 704 serum tests performed by AGID, eight (8/704) were revealed positive for antibodies to AIV-A N protein, with six (6/704) retested positive for subtype H1. Two sera tested positive by AGID were shown to be non reactive to the H1 subtype, suggesting specificity to another subtype. A low occurrence of antibodies to influenza A (1.13%) was found, and mostly (75%) specific to subtype H1. This represents an approximately 0,85% overall occurrence for subtype H1 antibodies, with an unknown subtype specific antibodies detected in one free-flying anatid. The low occurrence of antibodies in the family poultry may suggest a low AIV-A activity during the period of study, information which remains to be confirmed by virus detection.

摘要：本研究采集了圣玛丽亚/RS周边及贝洛奥里藏特大都市区共计20个县的农户家禽家鸡（Gallus gallus domesticus）血清样本（n=687），用于检测其中的禽流感A型病毒（AIV-A）抗体。另在贝洛奥里藏特采集了17份（n=17）自由飞行鸭样本，该样本来自疣鼻栖鸭（C. moschata）纯种个体或其与绿头鸭（Anas platyrhynchos）的杂交个体。本调查采用的检测方法参照世界动物卫生组织（OIE）的标准方案，包括用于检测AIV-A核蛋白（N）抗体的琼脂凝胶免疫扩散试验（AGID），以及用于检测H1亚型抗体的血凝抑制试验（HI）。在704份经AGID检测的血清样本中，共有8份（8/704）AIV-A核蛋白抗体呈阳性，其中6份（6/704）经H1亚型复检呈阳性。另有2份AGID检测呈阳性的血清样本对H1亚型无反应，提示其针对其他流感亚型具有特异性。本次检测发现A型流感抗体的总体阳性率为1.13%，其中75%的阳性样本针对H1亚型。据此计算，H1亚型抗体的总体阳性率约为0.85%，另有1份自由飞行鸭科鸟类样本检出了未知亚型的特异性抗体。家庭家禽中抗体阳性率较低，提示研究期间AIV-A的传播活性较低，该结论仍需通过病毒检测进一步验证。