Avian influenza attributable to serovar H7N1 in light layers in Italy.
In March 1999 a syndrome characterized by depression, anorexia, fever, and respiratory and enteric signs appeared in many flocks of turkeys and, to a lesser extent, chickens in the densely populated poultry-rearing regions of Northeastern Italy. Initially the disease was characterized by sinusitis, tracheitis, peritonitis, and pancreatitis. The responsible agent was identified as low-pathogenicity (LP) avian influenza (AI) of H7N1 subtype. Concerning the light layers, the mortality was variable, from 1.7% to 9.5%, whereas egg production decreased by 10% to 40%. According to the epidemiologic data, chickens seemed to be less sensitive to the virus than were turkeys. Nine months later, the AI virus changed to a highly pathogenic (HP) AI virus and affected, besides turkeys, a great number of pullet and layer flocks, with high mortality (80%-100%) in a few days. However, the course of disease was more prolonged in pullets. Within 3 1/2 mo, over 100 outbreaks were reported. Following the HPAI outbreaks, in late 2000 and early 2001, LPAI reemerged, but only one flock of layers was affected.
Department of Animal Pathology, Veterinary Hygiene and Public Health, Section of Veterinary Microbiology and Immunology, University of Milan, via Celoria 10 20133 Milan, Italy. fatromaclodio@libero.it
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D000818:Animals; D002645:Chickens / Q000821:virology*; D004196:Disease Outbreaks / Q000662:veterinary; D005260:Female; D009980:Influenza A virus / Q000145:classification / Q000302:isolation & purification / Q000472:pathogenicity*; D007558:Italy; D010058:Oviposition; D012128:Respiratory Distress Syndrome / Q000662:veterinary* / Q000821:virology