A five-year surveillance study of vaccination schedules using viral-vectored vaccines against infectious laryngotracheitis in a high-density layer region

Santos, Willian H.M.; Oliveira, Leticia B. de; Leão, Philipe A.; Hergot, Izabella G.; Wenceslau, Raphael R.; Rocha, Christiane M.B.M. da; Ferreira, Helena L.; Resende, Mauricio; Martins, Nelson R.S.; Spatz, Stephen J.; Ecco, Roselene

doi:10.1590/1678-5150-PVB-7037

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Livestock Diseases • Pesq. Vet. Bras. 42 • 2022 • https://doi.org/10.1590/1678-5150-PVB-7037 copy

A five-year surveillance study of vaccination schedules using viral-vectored vaccines against infectious laryngotracheitis in a high-density layer region

Cinco anos de monitoramento de esquemas vacinais com vacinas virais vetorizadas contra laringotraqueíte infecciosa em uma região altamente povoada por galinhas poedeiras

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT:

The effectiveness of vectored recombinant vaccines to control infectious laryngotracheitis (ILT) in chickens from a region (State of Minas Gerais, Brazil) with ~10 million layers was evaluated under field conditions from 2014-2018. During this period, only recombinant turkey herpesvirus (rHVT) or fowl poxvirus (rFPV) vaccines that express antigens of infectious laryngotracheitis virus (Gallid herpesvirus-1; GaHV-1) were used. Layer chickens (n=1,283), from eight different egg-producing companies, were individually sampled and examined (active surveillance), and in instances when government poultry health veterinarians were notified due to respiratory disease (passive surveillance). Clinical, macroscopic, and histopathology examinations were performed to diagnose ILT as well as molecular techniques for the detection and characterization of the GaHV-1 DNA from the trachea and trigeminal ganglia (TG). The layer hens sampled and examined belonged to flocks and farms that used different vaccination protocols (non-vaccinated, single dose vaccination, and prime/boost vaccination). This is the first long-term field study of the effectiveness of ILT vectored vaccines in a high-density multiple age layer hen region. Using various diagnostic methods, the occurrence of GaHV-1 infection and ILT clinical disease in layer hens vaccinated with vectored recombinant vaccines in one quarantined region of Brazil were investigated. The number of ILTV positive chickens by PCR and ILT clinical disease cases was lower in farms when all chickens were vaccinated with at least one vaccine. However, the difference in the detection rates of GaHV-1 infection was significant only when compared farms with prime/boost and farms using single dose of HTV-LT.

INDEX TERMS:
Vaccination; vectored vaccine; laryngotracheitis; layer chickens; Gallid herpesvirus 1; histopathology; PCR; sequencing

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[1] *Corresponding author: ecco@vet.ufmg.br

Farm	A	B	C	D	E	F	G	H
Vaccination protocol	Non-vaccinated	Prime/boost (HVT-LT and FPV-LT)	FPV-LT	FPV-LT	Prime/boost (HVT-LT and FPV-LT)	HVT-LT	HVT-LT	Non-vaccinated*
Housing capacity	40,000	558,000	200,000	199,000	3,586,000	684,000	370,000	150,000
Number of hens per production unit	1	12	9	5	34	13	17	2
Number of chickens per houses	6	13	16	10	34	24	17	3
Vegetation barrier	Absent	Present	Absent	Present	Partial	Partial	Partial	Present
Distance to the nearest farm	30 m	440 m	500 m	1000 m	30 m	420 m	850 m	1000 m
Distance to the nearest road or urban area	131 m	195 m	100 m	332 m	170 m	435 m	300 m	175 m

Farm	June 2014		February 2015		August 2015		February 2016		August 2016		February 2017		Total
Farm	N	Age/VT*	N	Age/VT	N	Age/VT	N	Age/VT	N	Age/VT	N	Age/VT	Total
A	9	36/NV	9	47/NV	-	-	-	-	-	-	-	-	45
	9	56/ NV	9	107/NV	-	-	-	-	-	-	-	-
	9	116/ NV
B	9	32/HVT-LT	9	25/Both vaccines	9	96/Both vaccines	9	70/Both vaccines	9	38/HVT-LT	9	33/HVT-LT	152
	9	18/Both vaccines	9	68/Both vaccines	9	43/Both vaccines	9	27/HVT-LT	10	54/HVT-LT	9	79/HVT-LT
									15	35/HVT-LT	8	9/Both vaccines
									12	15/HVT-LT	8	13/Both vaccines
C	9	38/FPV-LT	9	35/FPV-LT	9	38/FPV-LT	9	55/FPV-LT	9	30/FPV-LT	9	20/FPV-LT	108
C	9	71/FPV-LT	9	83/FPV-LT	9	82/FPV-LT	9	65/FPV-LT	9	88/FPV-LT	9	73/FPV-LT	108
D	9	36/FPV-LT	9	29/FPV-LT	9	36/FPV-LT	9	46/FPV-LT	9	40/FPV-LT	9	31/FPV-LT	110
	9	58/FPV-LT	9	93/FPV-LT	9	85/FPV-LT	9	96/FPV-LT	9	89/FPV-LT	9	97/FPV-LT
									2	72/FPV-LT
E	18	33/Both vaccines	9	35/Both vaccines	9	45/HVT-LT	9	34/HVT-LT	9	26/HVT-LT	9	38/HVT-LT	176
	18	60/Both vaccines	9	65/Both vaccines	9	65/Both vaccines	9	43/HVT-LT	12	34/HVT-LT	9	25/HVT-LT
			9	89/Both vaccines	9	30/HVT-LT	9	81/HVT-LT	9	84/HVT-LT	9	86/HVT-LT
									2	13/HVT-LT
F	9	41/HVT-LT	9	30/FPV-LT	6	19/HVT-LT	9	28/HVT-LT	9	43/HVT-LT	9	39/HVT-LT	126
	9	88/HVT-LT	9	90/FPV-LT	9	34/HVT-LT	9	88/HVT-LT	9	88/HVT-LT	8	97/HVT-LT
					9	87/HVT-LT	3	21/HVT-LT	6	36/HVT-LT	4	19/Both vaccines
G	9	38/HVT-LT	9	34/HVT-LT	9	34/HVT-LT	9	37/HVT-LT	9	34/HVT-LT	9	38/HVT-LT	108
G	9	85/HVT-LT	9	73/HVT-LT	9	87/HVT-LT	9	81/HVT-LT	9	79/FPV-LT	9	80/HVT-LT	108
H	9	50/NV	9	44/NV	9	40/NV	9	75/NV	13	88/NV	10	109/NV	137
	9	67/NV	9	98/NV	9	70/NV	9	95/NV	14	98/NV	10	20/NV
					9	49/NV	9	66/NV
TOTAL	171		153		150		147		185		156		962

Samples period		Summer 2013 Number	Winter 2014 Number	Summer 2015 Number	Winter 2015 Number	Summer 2016 Number	Winter 2016 Number	Summer 2017 Number	Total
Histopathologic diagnosis
	Infectious laringotracheitis	1	0	0	1	0	3	1	6
	Mycoplasmosis	9	38	12	40	22	29	24	174
	Nonspecific (vaccinal) inflammatory infiltrate	38	112	124	91	77	95	93	630
	No lesions	0	11	8	15	7	16	20	77
	Other respiratory diseases	0	2	2	0	0	10	1	15
TOTAL		48	163	146	147	106	153	139	902

Vaccination protocol	PCR Positive (tested samples) Percentage of positives		ELISA Positive (tested samples) Percentage of positives	Histopathology Positive (tested samples) Percentage of positives
Vaccination protocol	Trachea	TG	ELISA Positive (tested samples) Percentage of positives
Non-vaccinated	(38/182) 20.8%^a	26(168) 15.4%^a	14(37) 37.8%^bc	1(158) 0.6%^a
HVT-LT	84(389) 21.6%^a	42(387) 10.8%^a	134(175) 76.5%^a	4(374) 1.0%^a
FPV-LT	36(245) 14.7%^a	32(245) 13.0%^a	16(79) 20.2%^c	0(224) 0%^a
Both vacines (2 doses)	26(146) 17.8%^a	27(146) 18.4%^a	9(20) 45%^b	1(146) 0.6%^a
TOTAL	184(962) 19.1%^a	127(949) 13.4%^a	173(311) 55.6%	6(902) 0.6%

Vaccination protocol	Chicken number/PCR positive
Vaccination protocol	Winter 2014	Summer 2015	Winter 2015	Summer 2016	Winter 2016	Summer 2017	Total (n%)
Non-vaccinated	45/27^a	36/12^a	27/7^a	27/2^a	27/5^a	20/5^ab	182/58 (31.8%)^a
HVT-LT	45/28^a	18/5^a	60/16^a	75/17^a	111/24^a	80/28^a	389/118 (30.3%)^a
FPV-LT	36/18^a	54/11^a	36/5^a	36/9^a	47/9^a	36/5^ab	245/57 (23.2%)^a
Both vaccines	45/24^a	45/16^a	27/4^a	9/0^a	0/0^a	20/1^b	146/45(30.8%)^a
TOTAL (n/%)	171/97	153/44	150/32	147/28	185/38	156/39	962

	PCR total	PCR trachea	PCR TG	ELISA	Histopathology (active surveillance)	Histopathology (passive surveillance)
Total of chickens	962	962	949	311	902	321
% of positive	28.9%	19.1%	13.4%	55.3%	0.6%	38.6%

Year	Diphtheritic fowlpox	Infectious bronchitis	Infectious coryza	ILT	Mycoplasmosis	Response to vaccination	Chronic tracheitis/ regeneration	Total
2016	13	17	9	53	0	5	5	103
2017	2	8	0	20	45	40	0	115
2018	1	0	0	51*	39	12	0	103
TOTAL	16	25	9	124	84	57	5	321