Investigations on avian influenza A in meat turkey flocks in GermanyUntersuchungen über aviäre Influenza A in Mastputenherden Deutschlands

In the present investigation 315 commercial meat turkey flocks slaughtered in southern part of Germany in year 2001 were serologically examined for antibodies to avian influenza A viruses. Ten blood samples per flock were collected at the time of slaughter and examined using commercial ELISAs. Samples that reacted positively in ELISA were re-examined in haemagglutination inhibition test (HI) using subtype specific antigens. From the 3150 examined samples only 26 samples obtained from 7 flocks reacted positively in ELISA. Examination of these samples in HI revealed negative results to H1, H5, H7 and H9. On the other hand, all samples reacted positive in HI using H6 antigen. In all flocks neither clinical signs nor unusual increased mortalities were observed. End of December 2001 to January 2002 outbreaks of avian influenza were observed in three turkey flocks reared in the central-west region of Germany. In all cases sudden onset of depression, decrease in feed and water intake, respiratory signs accompanied with high mortality were observed. On necropsy pericarditis, petechial haemorrhages in pericardial fat, fibrinous airsacculitis, lung congestion and pneumonia were found. In addition, enlargement of the spleen and inflammation of pancreas were detected. Virological examinations resulted in isolation of an avian influenza A virus in embryonated chicken eggs. All isolates were identified as subtype H6N2 with an intravenous pathogenicity index (IVPI) of 0.0. The current observations indicate that low pathogenic avian influenza A of subtype 6 still circulated in German turkey flocks and in most of cases accompanied with high economic losses