Amino acid substitutions in the neuraminidase protein of an H9N2 avian influenza virus affect its airborne transmission in chickens

Table 2 Number of chickens infected by recombinant virus in independent experiments*

Dpi	rSD01			r01/NASS			r01/NAHB			r01/NA381			r01/NASS-381
Dpi	Inoculated	Direct-contact	Aerosol-contact	Inoculated	Direct-contact	Aerosol-contact	Inoculated	Direct-contact	Aerosol-contact	Inoculated	Direct-contact	Aerosol-contact	Inoculated	Direct-contact	Aerosol-contact
2	6/10	2/10	0/10	5/10	0/10	0/10	5/10	2/10	0/10	0/10	0/10	0/10	3/10	0/10	0/10
4	10/10	10/10	6/10	10/10	5/10	0/10	10/10	10/10	3/10	10/10	2/10	0/10	10/10	6/10	2/10
6	10/10	10/10	8/10	10/10	9/10	0/10	10/10	10/10	8/10	10/10	8/10	0/10	10/10	9/10	5/10
8	9/10	9/10	10/10	6/10	6/10	0/10	8/10	7/10	10/10	8/10	4/10	0/10	10/10	10/10	7/10
10	9/10	7/10	9/10	4/10	3/10	0/10	8/10	5/10	7/10	4/10	2/10	0/10	8/10	7/10	6/10
12	7/10	6/10	7/10	2/10	0/10	0/10	4/10	2/10	3/10	1/10	0/10	0/10	6/10	5/10	4/10
14	5/10	3/10	6/10	0/10	0/10	0/10	0/10	0/10	0/10	0/10	0/10	0/10	3/10	2/10	0/10

*In every independent experiment, ten SPF chickens (inoculated) were infected intranasally 10⁷ EID₅₀ of recombinant virus, then another ten animals (direct contact) were introduced into the same isolator 24 h later, while ten animals (aerosol contact) were placed separately in another isolator B. Oropharyngeal and cloacal swab samples of the chickens were collected at 2 day intervals and inoculated in SPF embryonated chicken eggs for observation virus shedding. The result expressed as infected number/total number of chickens. Repeat transmission experiments of r01/NASS and r01/NA381 which could not transmit by aerosols were performed. The results indicate that there was no virus shedding of all aerosol contact animals.

ISSN: 1297-9716