Comparative pathogenicity and environmental transmission of recent highly pathogenic avian influenza H5 viruses

Figures & data

Figure 1. Survival of 6-week-old SPF chickens (blue), Pekin ducks (orange) and Eurasian (EA) wigeons (green) after intratracheal/intranasal infection (doses 10^5.3 EID₅₀/bird) with (A) H5N8-2014, (B) H5N8-2016, and (C) H5N6-2017 viruses. Per group 10 birds were monitored for 10 days for clinical symptoms and mortality. The pathogenicity score was calculated based on OIE criteria for IVPI, and ranges from 0.0 (no pathogenicity) to 3.0 (highest pathogenicity). The pathogenicity scores for the viruses are listed in the legend.

Figure 2. Mean virus shedding (log₁₀ EID₅₀/ml) after infection with (A) H5N8-2014, (B) H5N8-2016, and (C) H5N6-2017 viruses. Virus shedding was measured in oropharyngeal (OP) and cloacal (CL) swabs collected from chickens (blue), Pekin ducks (orange), and Eurasian (EA) wigeons (orange) during 10 days after infection. The detection limit of 1.7 log₁₀ EID₅₀/ml is marked by a black line.

Table 1. Virus shedding of HPAI infected birds.

Host	virus	OP swabs		CL swabs
		AUC	Duration	AUC	Duration
		Titer* ± SD	days (LCI-UCI)	Titer ± SD	Days (LCI-UCI)
Chicken	H5N8-2014	5.33 (0.63)^a	1.7 (0.6–2.8)^a	4.06 (0.75)^ab	1.7 (0.7–2.7)^a
	H5N8-2016	5.38 (0.37)^a	1.6 (0.6–2.7)^a	4.41 (1.50)^a	1.4 (0.6–2.2)^ab
	H5N6-2017	4.02 (0.38)^b	1.1 (0.4–1.8)^b	3.66 (0.44)^b	1.1 (0.5–1.8)^b
Pekin Duck	H5N8-2014	5.75 (0.38)^a	6.3 (2.7–9.7)^a	2.73 (1.42)^a	5.0 (1.6–8.9)^a
	H5N8-2016	7.13 (0.42)^b	12.0 (5.2–18.5)^b	6.15 (0.86)^b	9.4 (3.1–16.6)^b
	H5N6-2017	6.70 (0.56)^b	8.4 (3.6–12.9)^ab	5.12 (0.73)^b	8.2 (2.7–14.4)^b
EA wigeon	H5N8-2014	6.24 (0.51)^a	11.1 (4.1–18.4)^a	3.38 (0.44)^a	8.0 (2.7–14.0)^a
	H5N8-2016	6.55 (0.86)^a	9.4 (3.5–15.5)^a	4.96 (0.77)^b	9.0 (3.0–15.7)^a
	H5N6-2017	5.93 (0.38)^a	5.5 (2.0–9.1)^b	4.55 (0.75)^b	5.4 (1.8–9.4)^b

EA, Eurasian; OP, oropharyngeal; CL, cloacal; AUC, area under the curve; SD, standard deviation; LCI, lower confidence interval; UCI, upper confidence interval.

*Titer in log₁₀EID₅₀/ml.

^a,b Statistically significant difference between the groups.

Figure 3. Survival of 6-week-old chickens after exposure to water (blue line) or bedding material (orange line) contaminated by Eurasian wigeons infected with H5N8-2016 virus.

Figure 4. Virus shedding of chickens exposed to contaminated water (w1–w10) for 7 days, measured in (A) oropharyngeal (OP) swabs and (B) cloacal (CL) swabs.

Figure 5. Persistence of virus in water and bedding material in the two control cages. The viability of the virus was tested by inoculation into four embryonated eggs (columns), and the amount of viral RNA was determined by real-time RT-PCR (line graph). Samples of water and bedding material were tested pre-collection (P) in the pen housing the Eurasian wigeons, and at days 0, 1, 2, and 5 of the environmental transmission experiment. Water samples were also tested on day 6. WP: water pre-collection, WC1: water control cage 1, WC2: water control cage 2, BP: bedding pre-collection BC1: bedding control cage 1, BC2: bedding control cage 2.