The PB2, PA, HA, NP, and NS genes of a highly pathogenic avian influenza virus A/whooper swan/Mongolia/3/2005 (H5N1) are responsible for pathogenicity in ducks

Table 1 Comparison of pathogenicity of HK483 and MON3 in 1-day-, 2-week-, and 4-week-old ducks

Virus	Age of ducks	Mortality^a	MDD^b(range)	Virus titers^c
Virus	Age of ducks	Mortality^a	MDD^b(range)	Brain	Lung
HK483	1 day	0/3	≥ 14	5.4, 2.5, 2.5	5.5, 4.5, 2.5
	2 weeks	0/6	≥ 14	-, -, -^d	4.3, 3.5, 2.5
	4 weeks	0/3	≥ 14	-, -, -	2.5, -, -
MON3	1 day	9/9	2.2 (2–3)	8.0, 7.5	5.7, 5.5
	2 weeks	10/10	4.9 (4–7)	8.8, 7.3, 7.3	8.5, 5.5, 5.3
	4 weeks	1/3	7.0	5.5, 4.5, -	4.5, 2.5, 3.7

^a Number of dead ducks/number of examined ducks.
^b Mean death days post-inoculation.
^c At 3 days post-inoculation, the brains and lungs were collected. Suspension of each tissue sample was inoculated into 10-day-old embryonated eggs for titration. Virus titers in tissues were expressed as log 50% egg infectious dose (EID₅₀)/g. The lower limit of detection was 10^1.5 EID₅₀/g.
^d -: < 1.5 log EID₅₀/g.

ISSN: 1743-422X