Table 4.

Lethality, seroconversion, and tissues tropism among ducks in an intraspecies study of NDV transmission^a.

Viruses	Manifestations of ducks				Virus replication on 3 DPI (log10EID50/g)d in:
	No. D/S/totalb		No. S.C./totalc
	Infectede	Contactf	Infected	Contact	Thymus	Cecal tonsils	Bursa of Fabricius	Trachea	Lung	Brain	Kidney	Spleen
GM	0/0/3	0/0/3	3/3 (8.0)g	0/3	3.08 ± 0.29	2.58 ± 0.14	1.67 ± 0.14	ND	4.17 ± 0.14	ND	2.50 ± 0.25	2.42 ± 0.29
YF18	0/0/3	0/0/3	3/3 (7.7)	3/3 (5.0)	3.33 ± 0.14	2.67 ± 0.52	2.75 ± 0.43	1.92 ± 0.29	5.00 ± 0.43	ND	3.58 ± 0.14	2.83 ± 0.38
GZ289	0/0/3	0/0/3	3/3 (7.3)	0/3	2.75 ± 0.43	2.08 ± 0.38	1.58 ± 0.14	ND	3.92 ± 0.63	ND	2.83 ± 0.38	2.58 ± 0.58

^aDucks were inoculated with 10⁶ EID₅₀ of the indicated virus in a volume of 200 μL via the intraocular and intranasal routes; Tissues, including thymus, cecal tonsils, bursa of Fabricius, trachea, lung, brain, kidney, and spleen were collected aseptically on three DPI from three ducks when infected with the indicated virus and homogenized for virus titration in eggs.

^bNo. D/S/total shows the number of dead (D) and sick (S) as well as the total number of ducks from the observation period. The ducks that showed clinical signs, such as depression, torticollis, incoordination, and tremors, but recovered at the end of the observation were counted as sick animals.

^cNo. S.C./total shows the number of ducks that seroconverted out of the total number of ducks at the end of the observation period.

^dFor statistical analysis, a value of 1.5 was assigned if the virus was not detected from the undiluted sample in three SPF embryonated chicken eggs (Kang et al., 2015). Virus titers are expressed as means ± standard deviation in log₁₀EID₅₀/g of tissue. ND, Not detected.

^eDucks inoculated with virus.

^fThree uninoculated ducks were co-housed with infected ducks as a contact group 8 h after inoculation.

^gAverage antibody titer of infected ducks (log₂).