Table 1.

Mortality and infection rate

		Number of deaths										Filter covered box
Type of partition	Number of chicks	day 1	day 2	day 3	day 4	day 5	day 6	Toal number of deaths	Mortality	dead or infected	Infection ratio	Number of box	Number of infected box	Infection rate (%)
(a) Mesh filter	24	0	0	0	0	5	18	23	96%	24	100%	6	6	100
(b) Untreated filter	20	0	1*	0	0	0	7	7	37%	15	79%	5	5	100
(c) Antibody filter	20	0	0	0	0	0	0	0	0%	0	0%	5	0	0
Inoculated chicks	48	0	0	42	6	0	0	48	100%	-	-	-	-	-

(a) polypropylene net with 3.7 mm square mesh-, or (b) untreated nonwoven fabric middle efficiency dust filter-, or (c) antibody impregnated same grade filter as (b), were attached to the three sides of the box cages (12 × 16 × 30 cm). Four male chickens weighing 80 g (10 days of age) were housed with food and water in each box cage covered with net or filter. Other chicks were intranasally inoculated with Highly Pathogenic Influenza virus A/Bogor 2/IPB/H5N1(10⁵TCID₅₀/bird). Three infected chicks were housed with food and water at the central area, closely surrounded by the filter boxes. Most of infected chicks at the central area died at 3 days post viral inoculation. At day 6, the surviving chicks in filter partitioned boxes were counted, and the mortality was calculated. In the histopathological and immunohistockemical analyses, the lungs of chicks were examined, and the box with at least one infected chick was scored as an infected box. * Since one chick in the untreatd filter box died in accidentally, the mortality and infection rate were calculated without this accidental case.

The basic specification of the nonwoven fabric middle efficiency dust filter used in (b) and (c) is as follows; average thickness: 0.8 mm ± 0.1 mm, average arrestance: ≧70% according to JIS Z 8901 gravitational method, initial pressure loss: 25 Pa @LV 0.5 m/s.