When Vaccinal Laryngotracheitis (VLT) breaks into broiler flocks, many issues come into play as poultry companies, growers, and state agencies attempt to suppress the spread of the outbreak. Modification of traffic patterns, flock placement schedules, litter management and vaccination programs all help to contain the disease. Most importantly, working together in a concerted effort towards the same goal is paramount to success.

Litter from broiler flocks that have the disease or have been vaccinated for it becomes seeded with virus that can spread to unaffected, unprotected flocks. Litter management at all levels, therefore, becomes important during an outbreak. The following voluntary guidelines can assist poultry growers and litter haulers with litter management during VLT outbreaks:

When the First Case Breaks

When a case of VLT is diagnosed and before it is determined whether it will be necessary to vaccinate, the positive farm’s biosecurity procedures must be enhanced, including longer downtime, keeping the litter in the house and heating it for 100 hours at 100°F. For this strategy to work, it is critical that all stray birds and remaining mortality be properly disposed of immediately after catching. Houses should be kept closed as much as possible to prevent wild birds and other animals from picking up and spreading the virus.

Creation of a Biosecurity Zone

The farms within 5 miles of the first case are in a “Biosecurity Zone” and are asked to keep the litter in-house. The reason being that the incubation period for VLT is long (7-10 days) and the disease is very contagious. There is a good chance that nearby flocks to the first case flock have been infected with the virus but have yet to show signs of the disease before they are processed. The litter of these flocks has great potential to spread the disease to its neighbors if it is taken out of the house and land applied.

As all Farms are Being Vaccinated

As the disease spreads, it may be determined that broiler vaccination is necessary to control the outbreak. Broiler house clean out must be delayed until at least 6 weeks after vaccination starts within a given zone. Keeping all litter in-house while all birds become vaccinated effectively reduces the number of new cases.

When all Broilers are Vaccinated

Once all broilers are vaccinated within a zone, the litter can be taken out and spread within that zone. Treated litter (composted, deep-stacked for 5 days or more, or heat-treated) can be taken out of the zone into non-poultry producing areas by licensed manure haulers. Deep stacking litter for 21 days will help to decrease the microbial load in the material by denaturing pathogens with heat and microbial activity. Manure haulers must ensure that the hauling equipment is in good repair and that each load is covered with a tight fitting tarp in order to prevent any spillage of material during transport onto public roads. Transport vehicles need to be disinfected, especially the undercarriage, tires and wheel wells after leaving the farm and after off-loading of the litter.

When Vaccination is Discontinued

Once vaccination is discontinued, the same “keep the litter in-house” rule applies for another 6 weeks while all farms return back to a non-vaccinated state. Litter management is especially important when trying to get OUT of an outbreak situation where there are, for a period of time, vaccinated and susceptible birds in the same area.

Following these litter management guidelines during a VLT outbreak will help to reduce the spread and scope of the disease. Cooperation of growers, manure haulers and company personnel on litter management practices during disease outbreak will assist in a more rapid recovery.

Reminder: VLT is not transmissible to humans and does not affect the safety and quality of chicken food products.

June 2007