Evaluation of the efficacy of intervention measures and vaccination for the control of LPAI epidemics in Verona province (Veneto, Italy).
Meat-type turkey farms in Verona province (Veneto, Italy) have been affected by three low-pathogenicity avian influenza (LPAI) epidemics between 2000 and 2004. Control measures implemented ranged from stamping out to controlled marketing in conjunction with restocking bans and movement restriction on live poultry, vehicles, and personnel. These measures were complemented with two emergency vaccination programs (2000-01, 2002-03) started after the beginning of the epidemics, while 2004 outbreaks occurred in vaccinated farms. The three epidemics differed in the number of outbreaks, duration, and economic impact. The aim of the investigation was to estimate the risk of infection and the effect of vaccination on the LPAI epidemics affecting turkey farms in Verona province. Farm probability to avoid infection (Ps) was calculated by Kaplan-Meier for each epidemic. The vaccination effect was evaluated for the 2000-01 and 2002-03 epidemics considering different risk before or after the emergency vaccination. The epidemics and vaccination entered as predictors in a Cox regression model and hazard ratios (HR) were calculated. Ps values at the end of the epidemics were as follows: 2000-01 = 0.66, 2002-03 = 0.51, and 2004 = 0.91. Vaccination reduced dramatically the risk of infection. The measures implemented had different effects on the three epidemics. The lower probability of being infected during the 2004 epidemic was most likely related to the protection level of the vaccinated farms acquired before the beginning of the epidemic, which was also responsible for the reduced spread of infection.
Busani
Luca
L
Centro Regionale per l'Epidemiologia Veterinaria, Istituto Zooprofilattico Sperimentale delle Venezie, Viale dell'Univeristà 10, 35020 Legnaro PD, Italy.
Dalla Pozza
Manuela
M
Bonfanti
Lebana
L
Toson
Marica
M
Marangon
Stefano
S
D000818:Animals; D002645:Chickens / Q000821:virology*; D004196:Disease Outbreaks / Q000517:prevention & control / Q000662:veterinary*; D009980:Influenza A virus / Q000472:pathogenicity*; D007252:Influenza Vaccines / Q000276:immunology*; D005585:Influenza in Birds / Q000517:prevention & control*; D007558:Italy / Q000453:epidemiology; D013997:Time Factors; D014611:Vaccination
D007252:Influenza Vaccines