Effect of negative air ionization on airborne transmission of Newcastle disease virus.

Four-week-old mixed-sex White Rock chickens were used in four experiments to determine the effect of negative air ion enrichment on airborne transmission of the Roakin strain of Newcastle disease virus (NDV). The experiments were conducted in specially constructed airborne disease transmission cabinets in which donor (upwind) chickens cannot contact susceptible (downwind) chickens because of physical separation by a "no man's land." Temperature and humidity were computer-controlled at 26.7 C and 50% relative humidity, and ventilation rates were manually adjusted from 0.34 to 1.36 m3/min (12 to 48 ft3/min). Donor chickens were inoculated with Roakin NDV by eyedrop and intranasal routes and placed in the upwind end of each cabinet. One day later, susceptible chickens were placed in the downwind end. Seroconversion (> or = 1:10 NDV hemagglutination-inhibition titer) was considered evidence of infection from inoculation (upwind) or airborne transmission (downwind). Commercial air ion generators were used either in the ends or in the "no man's land" of the treatment cabinets and operated at power supply voltages ranging from -8kV direct current to -15 kV direct current. The use of negative air ion generators reduced airborne transmission an average of 6.6% to 27.7% compared with the control cabinets. Significant (P < or = 0.05) reductions in transmission were obtained with some treatments. The greatest reduction in transmission was obtained with the higher power supply voltages (13.8% reduction) and when the ionizers were placed in the "no man's land" (27.7% reduction) between the upwind and downwind chickens.