Outbreaks of highly pathogenic avian influenza (HPAI) serotype H5N2 appear to be slowing in the US, but the potential for new outbreaks as migrating birds move south in autumn is high, reports Eric Gingerich, DVM (Technical Specialist in Poultry, Diamond V).
Higher seasonal temperatures are helping, along with growth of vegetation – corn and soybeans growing in fields around poultry houses – which helps to reduce movement of dust carrying virus particles.
However, during summer, migratory waterfowl flyways intermingle in the Arctic, so with the coming of autumn and the return of infected birds, resurgence in H5N2 outbreaks is likely. It can become a perennial national threat.
The unprecedented losses of Midwestern poultry producers so far this year have been horrendous. The loss of turkeys has amounted to about 3.1 per cent of the US annual production. For layers, the loss has been about 11.2 per cent of the US population of layers as of March 2015. Five Midwestern states have been hit the worst (table).
As HPAI spread, egg production and inventories declined and prices began to rise steeply at the end of April (chart).
Also, according to the UDSA’s monthly turkey hatchery report released last week, turkey eggs in incubators were down 5 per cent and poults were down 8 per cent from last year.
How are officials destroying and disposing of birds on infected premises?
To prevent further spread of the disease, proper disposal of birds from infected premises is necessary.
When an infected premise is confirmed, the flocks surrounding the infected premise within 6.2 miles are surveyed for evidence of the virus as well as any dangerous contacts (feed mill routes, crew activity, and so on).
Flock movement from this area requires several negative tests and permission from the USDA incident commander before issuance of a movement permit. Movement of eggs requires daily testing of mortality from each flock on a premise along with assurance that there are no clinical signs of avian influenza before a permit is given.
On infected farms, depopulation of turkeys is mostly done by using fire-fighting foam. In some cases with older birds, it has been difficult to obtain enough foam to cover the heads of these tall birds, especially if they are able to stand on other dead birds.
For layers or pullets, the modified atmosphere killing (MAK) carts are used as a means of applying the fire-fighting foam in cages, although the technique has not been perfected as yet.
Some delays in depopulation result from a lack of a supply of carbon dioxide that is used for euthanasia in these carts. Also, this process is rather time consuming and cumbersome, which can delay the death of these virus-producing birds. A much quicker method is needed to euthanise these birds and stop them shedding virus.
Disposal of a huge amount of dead birds is a monumental task. All means of disposal are being utilised: burial, incineration, composting, and landfills. The most common means of disposal for turkeys is composting in the house.
For layers, it is not possible to compost birds in cage layer houses without pits. So, producers are using burial, incineration, transport to landfills, and composting on fields.
Re-population of an infected premise cannot take place until the premise has undergone complete cleaning and disinfection, has tested negative for virus, and has passed a 21-day waiting period. In addition, all flocks in the surveillance zone must be eligible for repopulation as well.
How can producers keep avian flu out of their flocks?
Enhanced biosecurity and resistance-building tactics used by producers to keep HPAI out of their flocks include the following practices.
Air, water, feed:
Truck drivers and others:
Innovation for future disease protection
The recent HPAI outbreaks are generating innovative approaches to enhance biosecurity, especially under conditions where the contamination is present just outside the poultry house.
Here are some future biosecurity interventions:
But biosecurity alone is not stopping this beast of a virus.
Vaccination is an option, depending on whether USDA determines that it can help reduce the number of outbreaks, thereby making more efficient use of our eradication resources.
Vaccination is going to mean a different monitoring system than in the past. The new system is likely to be based on sentinel bird use or antigen detection rather than on serology.