Teresa V. Dormitorio, Joseph J. Giambrone, and Kenneth S. Macklin

Poultry Science Department Auburn University

Isolation and characterization of ILTV along with sanitation and vaccination helped prevent a recurrence of the disease outbreak

Infectious Laryngotracheitis (ILT)

Contagious respiratory viral diseaseILTV: herpesvirus; DS DNA genome

~155kbSymptoms (mild/severe): coughing

of mucus & blood; conjunctivitis; swollen sinuses; increased mortality.

Losses induced by ILT have an important economic impact on the poultry producer and the US export market.

TransmissionTransmission between houses and farms

can occur by airborne particles or fomites.By contaminated people & equipment

(shoes, clothing, used feeders, cages, waterers, etc.)

Virus is highly resistant outside host, but is susceptible to many disinfectants.

Herpesviruses hallmark: can remain dormant in the animal’s nervous system & latent virus reactivated by stress factors or a compromised immune system.

February 13 – 20-200/day mortalityFebruary 14 – depopulated (4 houses)February 15 – ILTV identified by

diagnostic labFebruary 22 – 1st sampling (house

environment and ill birds)March 7 – 2nd sampling April 11 – 3rd sampling

Case study: ILT outbreak in unvaccinated broilers

“One mile away is an egg laying facility”

Use real time PCR and virus isolation to evaluate viral load in the environment of a commercial broiler farm after an ILTV outbreak.

Determine effects of cleaning, disinfection, composting of the litter, and the use of a recombinant vaccine on persistence of ILTV.

Characterize an ILTV field isolate and comparison with vaccine viruses using PCR-RFLP.

Objectives

1st sampling – 9 days after outbreak

House empty for 8 days; heated; Litter decaked & conditioned

• Nipple drinkers• Walls, curtains• Fan louvers• brooders• Beetles• Loose uncaught

birds

ILTV detection from swab

Figure 1: Real-time PCR results of 1st sampling

ILTV detection from CAM

90% of swabs + for ICP4-ILTV50% of + have Cp = 20-30

50% of CAMs + for ICP4-ILTV5 ILTV + on swab, became - on CAMOn 1 decreased Cp1 swab- became + on CAM

House#- Sample Description PCR on swab (Cp) PCR on CAM (Cp)

3-S1 I Brooder near door >35 >35

3-S4 I Nipple drinker- front, right 34 18.43

3-S8 I Nipple drinker- mid, right 30 >35

3-S10 I Top of water line- mid, right 27 negative

3-B11 I Beetles- mid, right 22 31.78

3-S13 I Brooder- mid, left 28 negative

3-S17 I Fan louvers- back, right 29 >35

3-B19 I Beetles- back, left 34 negative

3-S21 I Trachea- outside bird 20 32.01

4-S22 I Trachea- inside bird 27 negative

O-S23 I Eye – outside bird 24 31

3-B24 I Beetles- front 32 negative

2-S26 I Fan louvers, mid left >35 uncertain

2-S29 I Wall- mid right >35 >35

2-B32 I Beetles – mid right negative No CAM

O3-S33 I Water in puddle-back negative 24.71

O3-S35 I Outside curtain, middle opening >35 32.73

O3-S36 I Outside curtain, middle >35 uncertain

O-S38 I Puddle between 2 & 3 Invalid PCR + but no Cp

O-S40 I Mud outside#3, left front >35 negative

Table 1. ILTV DNA detection results using real-time PCR on swab, beetle & CAM samples from poultry houses after a disease outbreak

- 23 days after outbreak; 2 days before chick placement

- Heating, cleaning, disinfecting

- Curtains replaced- Chicks vaccinated in ovo with

recombinant vaccine

2nd sampling

3rd sampling

8 weeks after outbreak; repacement birds 5 weeks old

Figure 2: MspI digests of the 4.9 kb fragment amplified from the ILTV ICP4 gene fragment

M 1 2 3 4 5 6 M

1000

500

300

100

2000

1000

2000

500

300

100

M) DNA Marker1)LT- Blen (CEO)2)LT-IVAX (TCO)3)Laryngo-Vac

(CEO)4)Trachivax (CEO)5)S21 - field

isolate6)AviPro (CEO)M) DNA Marker

Lanes:

200 200

BP BP

5000 5000

ConclusionsILTV was found in environmental

samples and non-caught ill birds 9 days after an LT outbreak.

ICP4 DNA still detectable after heating, cleaning and disinfecting the house, but live virus was not detected and may have been eliminated.

In ovo vaccination of new flock with a recombinant vaccine and disinfection procedures may have helped prevent recurrence of an LT outbreak on this farm.