The combination of attenuated Newcastle disease (ND) vaccine with rHVT-ND vaccine at 1 day old is more protective against ND virus challenge than when combined with inactivated ND vaccine

Figures & data

Table 1. Protection against morbidity and mortality after challenge with the Chimalhuacan vNDV strain of commercial layer chickens vaccinated at 1-day-old with the live ND and the rHVT-ND or the inact ND vaccines, according to different vaccination regimens.

		Protection against
Age of challenge	Group	Morbidity (%)	Mortality (%)
6 weeks	Negative	0	0
	rHVT-ND/live ND	100	100
	rHVT-ND/live ND-Chitosan	100	100
	Inact ND/live ND	100	100
10 weeks	Negative	0	0
	rHVT-ND/live ND	100	100
	rHVT-ND/live ND-Chitosan	100	100
	Inact ND/live ND	70	90

Data represent survival rate and clinical protection 2 weeks after challenge by the oculo-nasal route with Chimalhuacan NDV strain.

Table 2. Shedding after challenge at 6 and 10 weeks of age with the Chimalhuacan vNDV strain on commercial layer chickens vaccinated at 1-day-old with the live ND and rHVT-ND or the inact ND vaccines according to different vaccination regimens.

Age	Group	2 d.p.i.	4 d.p.i.	7 d.p.i.	10 d.p.i.
Oropharyngeal swabs ^a
6 weeks	Negative	3.71 ± 1.69 ^b ^A	6.77 ± 0.23^A	N.D.	N.D.
		8/10 ^c ^A	10/10^A
	rHVT-ND/live ND	1.75 ± 1.21^B	3.03 ± 1.82^B	1.92 ± 1.89^A	1.09 ± 0.27^A
		3/10^AB	6/10^A	3/10^A	0/10^A
	rHVT-ND/live ND-Chitosan	2.19 ± 1.56^AB	3.47 ± 2.06^B	3.04 ± 2.61^A	1.03 ± 0.10^A
		4/10^AB	7/10^A	4/10^A	0/10^A
	Inact ND/live ND	1.48 ± 1.02^B	3.40 ± 2.16^B	2.35 ± 1.70^A	1.23 ± 0.72^A
		2/10^B	6/10^A	4/10^A	1/10^A
10 weeks	Negative	4.34 ± 0.75^A	6.36 ± 0.41^A	N.D.	N.D.
		10/10^A	10/10^A
	rHVT-ND/live ND	2.22 ± 1.65^BC	2.07 ± 1.30^C	1.00 ± 1.00^B	1.00 ± 0.00^A
		4/10^AB	4/10^AB	0/10^B	0/10^A
	rHVT-ND/live ND-Chitosan	1.41 ± 0.87^C	2.05 ± 2.22^C	2.72 ± 2.28^B	1.00 ± 0.00^A
		2/10^B	2/10^B	4/10^AB	0/10^A
	Inact ND/live ND	3.49 ± 1.01^AB	4.25 ± 1.52^B	4.99 ± 2.44^A	1.81 ± 1.65^A
		9/10^AB	9/10^AB	8/9^A	2/9^A
Cloacal swabs
6 weeks	Negative	1.45 ± 0.96^A	6.52 ± 0.65^A	N.D.	N.D.
		1/10^A	10/10^A
	rHVT-ND/live ND	1.18 ± 0.58^A	1.43 ± 1.35^B	2.03 ± 1.54^A	1.78 ± 1.46^A
		1/10^A	1/10^B	3/10^A	3/10^A
	rHVT-ND/live ND-Chitosan	1.00 ± 0.00^A	1.00 ± 0.00^B	2.10 ± 1.97^A	1.93 ± 1.32^A
		0/10^A	0/10^B	3/10^A	2/10^A
	Inact ND/live ND	1.00 ± 0.00^A	1.00 ± 0.00^B	2.74 ± 1.76^A	1.79 ± 1.43^A
		0/10^A	0/10^B	4/10^A	2/10^A
10 weeks	Negative	1.50 ± 1.05^A	6.34 ± 0.46^A	N.D.	N.D.
		2/10^A	10/10^A
	rHVT-ND/live ND	1.00 ± 0.00^A	1.00 ± 0.00^B	1.00 ± 0.00^B	1.00 ± 0.00^A
		0/10^A	0/10^B	0/10^B	0/10^A
	rHVT-ND/live ND-Chitosan	1.00 ± 0.00^A	1.00 ± 0.00^B	1.00 ± 0.00^B	1.00 ± 0.00^A
		0/10^A	0/10^B	0/10^B	0/10^A
	Inact ND/live ND	1.00 ± 0.00^A	1.92 ± 2.65^B	2.89 ± 1.97^A	1.78 ± 2.35^A
		0/10^A	2/10^B	5/9^A	1/9^A

^a Data were determined by QRRT-PCR on 1 ml swabs taken at specified d.p.i. Different uppercase superscript letters indicate a significant difference (P < 0.05) between the groups (per column). The cut-off value of QRRT-PCR specific to the Chimalhuacan NDV strain was determined at 10^2.7 EID₅₀/ml swabs. The total numbers of chickens tested were reduced over time because of specific mortality (see Results section). N.D., not determined, due to specific mortality. ^bData represent mean ± standard deviation of log₁₀ EID₅₀ of NDV in 1 ml swabs. For statistical analysis, samples with data value < 2.7 log₁₀ EID₅₀/ml were considered negative for virus while undetected samples were considered negative and received a value of 1 log₁₀ EID₅₀/ml swabs for statistical purposes. ^cData represent frequency (number positive/total tested chickens) of virus detection in 1 ml swabs.

Figure 2. Serum HI antibody titres after vaccination of 1-day-old commercial layer chickens with the live ND and rHVT-ND or inact ND vaccines according to different vaccination regimens. Data represent mean ± standard deviation of HI antibody titres at specified ages (n = 5), which corresponds to the last dilution showing an inhibition of haemagglutination of 4 haemagglutination units of NDV La Sota strain. The HI geometric mean titres were expressed as reciprocal log₂, and titres > 3 log₂ were considered positive (this cut-off value is indicated by the dotted line). Means ± standard deviations with no common uppercase letters differ significantly (P < 0.05).

Figure 3. NDV-specific IgM measured by ELISA after vaccination of 1-day-old commercial layer chickens with the live ND and the rHVT-ND or inact ND vaccines according to different vaccination regimens. Data represent mean ± standard deviation of absorbance values determined by ELISA at specified time of ages (n = 5). Serum samples were diluted 1:100. Mean ± standard deviation at time points with no common uppercase letters differ significantly (P < 0.05). O.D., optical density.

Figure 4. Duodenal NDV-specific IgG antibody titre of commercial layer chickens vaccinated at 1-day-old with the live ND and the rHVT-ND or inact ND vaccines according to different vaccination regimens. Data represent mean ± standard deviation of absorbance values determined by ELISA at specified ages (n = 5). The immunoglobulin response was measured in 1:2 diluted supernatants of ex vivo duodenal tissues cultures. Means ± standard deviations with no common uppercase letters differ significantly (P < 0.05). O.D., optical density.