Evaluation of actions of the official veterinary service to mitigate outbreaks of infectious laryngotracheitis and improve biosecurity on laying hen farms

Hergot, Izabella G.; Rocha, Christiane M.B.M. da; Xavier, Fabiana G.; Santos, Willian H.M.; Oliveira, Leticia B. de; Martins, Nelson R.S.; Ecco, and Roselene

doi:10.1590/1678-5150-PVB-6749

ABSTRACT:

Infectious laryngotracheitis (ILT), caused by an Alphaherpesvirus (Gallid herpesvirus-1; GaHV-1), has been noticed in the region of the Terras Altas da Mantiqueira, Minas Gerais. From 2010 to 2018, the “Serviço Veterinário Oficial” (SVO) of the “Instituto Mineiro Agropecuário” (IMA), implemented measures to prevent spread of the virus to other regions and control the disease in the area. Due to the close proximity and consequent epidemiological link among farms, the region was considered a unique epidemiological unit. To check the efficiency of the ILT control measures, we carried out: (1) a seroepidemiological survey, (2) questionnaires for evaluating biosecurity measures; and (3) an evaluation of the influence of farm population density on the occurrence of ILT. In 2016, 2017, and 2018, ILT was investigated using epidemiological and clinicopathological methods, along with GaHV-1 molecular detection. Serological survey was carried out on 24 farms in the quarantined region and on 13 farms from other regions of the state. In 2010 and 2018, questionnaires were applied to collect data and determine indicators of biosecurity practices in all farms of the quarantined area. The differences were then assessed (Wilcoxon’s p<0.05). The results indicated positive serology throughout the region, although only on four farms (16.6%) the chickens have clinical signs, macroscopic and histological lesions of ILT. The prevalence of viral infection increased from 2016 (27%) to 2017 (50%) and was higher in farms with a high stock density (p=0.033). No disease, virus or antibodies were detected in the farms outside of the quarantined area. Although the biosecurity indicators had improved on all farms in the quarantined area (p<0.05), the virus was active and circulating in the region. The contingency measures have contained the outbreak, but biosecurity practices are paramount in the control of new outbreaks. Official control will be maintained in the region, including surveillance of new cases and biosecurity procedures to mitigate the risk of the virus reaching other regions.

INDEX TERMS:
Official Veterinary Service; outbreaks; laryngotracheitis; biosecurity; hen farms; Minas Gerais; Brazil; surveillance; ILT control; layer hen; epidemiology

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

N	ID*	2016					2017
N	ID*	HTP	PCR	CS	RSL	Diagnosis**	HTP	PCR	CS	RSL	Diagnosis**
1	11	+	+	-	-	ILT	-	+	+	-	ILTV
2	7	+	+	+	-	ILT	-	+	+	-	ILTV
3	20	-	+	+	+	ILTV	+	+	+	+	ILT
4	22	-	-	-	+	ORD	+	+	+	+	ILT
5	2	-	+	-	-	ILTV	-	-	+	-	ORD
6	13	-	+	-	-	ILTV	-	-	+	-	ORD
7	14	-	+	+	+	ILTV	-	+	-	-	ILTV
8	3	-	-	+	+	ORD	-	+	+	+	ILTV
9	18	-	-	+	+	ORD	-	+	-	-	ILTV
10	21	-	-	+	+	ORD	-	+	+	+	ILTV
11	19	-	-	+	+	ORD	-	-	-	-	N
12	15	-	-	-	-	N	-	+	-	-	ILTV
13	16	-	-	-	-	N	-	+	-	-	ILTV
14	17	-	-	-	-	N	-	+	+	-	ILTV
15	5	-	-	-	-	N	-	-	+	+	ORD
16	10	-	-	-	-	N	-	-	-	+	ORD
17	12	-	-	-	-	N	-	-	-	+	ORD
18	1	-	-	-	-	N	-	-	-	-	N
19	4	-	-	-	-	N	-	-	-	-	N
20	6	-	-	-	-	N	-	-	-	-	N
21	8	-	-	-	-	N	-	-	-	-	N
22	9	-	-	-	-	N	-	-	-	-	N
23	23	-	-	-	-	no collection	-	-	-	-	N
24	24	-	-	-	-	no collection	-	-	-	-	N

FARMS	Farm ID	Number of houses	Number of chickens housed	Shortest distance from another farm (meters)	Results	Municipalities
A poultry producer with multiple farms**	14*	-	-	-	ILTV	Itamonte
	21	34	3,394,738	30	ILTV	Itanhandu
	22	18	1,269,968	924	ILT	Passa quatro
A poultry producer with multiple farms**	18	12	396,605	2,000	ILTV	Itanhandu
	19	7	330,947	593	ORD	Itanhandu
	20	14	1,310,990	3,700	ILT	Pouso Alto
A poultry producer with multiple farms**	7	12	304,353	425	ILT	Passa Quatro
	9*	-	-	-	NEG	Itamonte
	10	9	51,084	700	ORD	Itanhandu
	11	9	358,817	400	ILT	Itanhandu
A poultry producer with multiple farms	4	6	69,886	6,500	NEG	Passa Quatro
A poultry producer with multiple farms	13	17	261,906	1,440	ILTV	Itanhandu
A poultry producer with multiple farms	2	8	166,057	593	ILTV	Itanhandu
A poultry producer with multiple farms	3	3	22,100	370	ILTV	Itanhandu
A poultry producer with multiple farms	5	14	271,811	1,200	ORD	Passa Quatro
A poultry producer with multiple farms	12	3	22,416	1,470	ORD	Itanhandu
A poultry producer with multiple farms	8*	-	-	-	NEG	Itanhandu
A poultry producer with multiple farms	17	5	28,748	30	ILTV	Itanhandu
A poultry producer with multiple farms	15	5	128,296	1,000	ILTV	Pouso Alto
A poultry producer with multiple farms	23	8	34,278	1,600	NEG	Itanhandu
A poultry producer with one farm	1	9	104,249	1,440	NEG	Itanhandu
A poultry producer with one farm	6	21	119,906	425	NEG	Pouso Alto
A poultry producer with one farm	16	2	77,853	1000	ILTV	Passa quatro
A poultry producer with one farm	24	4	23,875	3700	NEG	Itanhandu

N	Identification of the farms*	Biosecurity indicator (BI)		Biosecurity increment (BInc)**^b
N	Identification of the farms*	2010^a	2018^a,b	Biosecurity increment (BInc)**^b
1	5	24	51	27**
2	10	31	55	24**
3	20	27	51	24**
4	19	26	50	24**
5	11	31	54	23**
6	7	29	52	23**
7	22	27	50	23**
8	2	26	49	23**
9	1	25	48	23**
10	18	27	49	22**
11	16	26	48	22**
12	6	24	46	22**
13	15	27	48	21**
14	21	34	54	20**
15	3	28	47	19**
16	13	27	45	18**
17	23	27	44	17**
18	4	37	51	14**
19	24	21	33	12
20	17	18	30	12
21	12	26	37	11
Geral	Median Quartile 1 - Quartile 3 Mínimum - Maximum	27A 25.5-28.5 18-37	49B 45.5-51.0 30-55	22C 17.5-23.0 11-27

Classification criteria		Specific criteria	Scores given in each evaluation								Evaluation* 2010-2018
			2010				2018
			0	1	2	3	0	1	2	3
Sanitary control	1	Cleaning and disinfection of sheds after unloading of chickens	18	0	0	3	0	0	0	21	P
	2	Manure composting	20	0	0	1	0	4	1	16	P
	3	Disposal of dead birds	0	0	21	0	0	0	9	12	P
	4	Monitoring chickens for diseases	21	0	0	0	0	0	0	21	P
	5	Cleaning and disinfection of vehicles	17	0	0	4	3	0	8	10	P
	6	Wearing clean clothes prior to entering in the houses	6	15	0	0	4	12	3	2	P
Organization on poultry operation	7	Information about the source of chickens in the form to the SVO	21	0	0	0	0	11	2	8	P
	8	Register of flocks per house	3	0	14	4	0	0	2	19	P
	9	Control of the movement of farmers and non-farmer personnel from entering in the farms	21	0	0	0	4	0	17	0	P
	10	Control or prevention of the movement of unauthorized vehicles entering in the farms	20	0	0	1	3	13	0	5	P
Facilities	11	Perimeter fence to seclude the houses	18	1	1	1	3	1	12	5	P
Facilities	12	Wire on the sheds	20	0	1	0	4	0	13	4	P
Productivity	13	Continuous egg production cycle**	16	0	0	0	6	7	3	0	P
Sanitary control	14	Vaccinal program	0	0	0	21	0	0	0	21	U
	15	Fallow period between flocks	18	1	2	0	19	0	2	0	U
	16	Frequency of manure removal	2	2	16	1	2	2	12	5	U
	17	Control of rodents and insects	0	0	0	21	0	0	0	21	U
	18	Cleaning the outside area	1	0	0	20	1	0	0	20	U
Organization on poultry operation	19	Licensed and accredited poultry veterinarian familiar with that the type of operation	2	0	14	5	2	0	10	9	U
Organization on poultry operation	20	Daily report forms for each flock in the farm	21	0	0	0	21	0	0	0	U
Facilities	21	Distance among farms	2	2	6	11	2	2	6	11	U
Facilities	22	Distance from farms to roads	1	0	1	19	1	0	1	19	U
Productivity	23	Number of flocks inside the shed	0	2	0	19	0	2	8	11	N

Brasil

Brasil

Evaluation of actions of the official veterinary service to mitigate outbreaks of infectious laryngotracheitis and improve biosecurity on laying hen farms

Avaliação de ações do serviço veterinário oficial para bloqueio de foco de laringotraqueite infecciosa e melhoria da biosseguridade em granjas de postura

ABSTRACT: