Too close to risk

Occurrences of the disease are usually linked to pheasants and migrating waterfowl. Newcastle Disease is notifiable, that is, the State Veterinary Service of the Department for Environment, Food and Rural Affairs (Defra) require by law to be informed of any suspected outbreak.

Over 10,000 pheasant poults, ranging from 8-10 weeks of age that had been imported from France, were affected in this latest outbreak. The disease was confirmed after postmortems and tests had been carried out. Some of the birds had earlier been suffering from diarrhoea, listlessness and star gazing and mortality amongst the flock was increasing. Movement restrictions and biosecurity measures were immediately put in place.

Veterinary inspection of known poultry keeping premises in the Protection Zone was undertaken in the following days but no signs of clinical disease were found. Close surveillance was kept on these birds as Newcastle Disease can take up to 21 days to develop. Several other suspected cases were being investigated but at the time of going to print, no further outbreaks of the disease had been confirmed.

Making a diagnosis

It is initially difficult to determine whether or not a bird actually has Newcastle Disease because many of the symptoms are similar to those of other diseases. Newcastle Disease causes some or all of the following signs:

Respiratory signs: gasping and coughing (could be Infectious Bronchitis, Aspergillosis, Gape Worm, Mycoplasma, Pain- such as in Egg Peritonitis)

Nervous signs: dropping wings, dragging legs, twisting of the head and neck, ataxia or circling, depression, anorexia, complete paralysis (could be Blackhead in turkeys, Mareks Disease, Avian TB, Avian Encephalomyelitis, Stroke or Botulism)

Partial or complete cessation of egg production (could be Infectious Bronchitis, Egg Drop Syndrome, Avian Encephalomyelitis, Moult)

Eggs are misshapen, rough-shelled, thin-shelled and contain watery albumen (could be Egg Drop Syndrome, Marek's Disease, Leukosis, Parasites, Fatty Liver Syndrome, Insecticide poisoning)

Greenish watery diarrhoea (could be Worms)

Swelling of the tissues around the eyes and in the neck (could be Mycoplasma)

The proportion of birds which become ill or die depends on the virulence of the virus strain, degree of vaccine immunity, environmental conditions and the condition of the flock. Turkeys with Newcastle Disease mainly show respiratory and nervous signs. However, in waterfowl, the infection is sub-clinical, that is although the birds may have the disease they do not show any signs of illness.

Confirmation of Newcastle Disease is only via laboratory testing on carcass or/and through blood samples. It cannot be confirmed by visual diagnosis alone, but on any suspicion of such a disease, a veterinary surgeon should always be consulted.

Strict measures have to be taken once Newcastle Disease has been confirmed because the disease can spread very easily. The virus is present in the exhaled air, secretions and faeces of infected birds, both before they show signs of illness and during convalescence. Spread is mainly by movement of birds and manure, but equally important is the passing on of disease via human means, such as on vehicles and clothing.

All movement is stopped

When disease is confirmed restrictions are imposed on the infected premises and biosecurity measures are enforced. All birds that could be affected where the outbreak has occurred are slaughtered. Eggs, including hatching eggs, are also destroyed. A Declaratory Order is made - Diseases of Poultry (England) Order 2003 (S.I.2003/1078) - imposing an Infected Area and establishing a Protection Zone of 3km and a larger Surveillance Zone of 10km to impose movement restrictions to help prevent the spread of disease. Also, used litter and poultry manure is not allowed to be removed.

If a poultry keeper is caught up in a Protection Zone, the birds will be considered at risk for it means that there is an outbreak of infection within 3km. The premises will be inspected by state veterinary officers to see whether or not the birds are showing any sign of disease and they will be kept under strict surveillance. To help protect the birds they should be kept in their living quarters. This could mean housed or enclosed in a pen and therefore isolated. During hot weather it may not be possible to keep the birds housed completely, for welfare conditions must be considered.

The entrance to the pen should have a disinfectant foot dip and appropriate disinfecting facilities should also be at the entrance of the property. Keep visitors off the premises, for in the Protection Zone there is a high risk of disease spread.

Any broiler poultry in the Protection Zone that is not suspected of having the disease may be sent to a designated slaughter house if a licence to do so has been issued by a veterinary inspector. Under licence day-old chicks or ready-to-lay pullets may go to premises within the Surveillance Zone on which there is no other poultry. Hatching eggs may be sent to a hatchery if the eggs and their packing have been disinfected before despatch.

Once all infected birds have been disposed of the area is cleansed and disinfected and once this has been completed, after a further 21 days the Protection Zone downgrades to a Surveillance Zone.

Meantime, in the Surveillance Zone poultry may not be moved from the premises out of the zone except under a licence to a designated slaughterhouse outside the zone. Hatching eggs also require a licence to be transported to a designated hatchery outside the zone. Used litter and poultry manure may not be moved out of the zone and no movement of poultry or eggs in the zone should take place. Fairs, markets, shows or other gatherings of poultry or other birds are not allowed.

If birds are slaughtered because they have Newcastle Disease then no compensation is given. Compensation is only provided if slaughtered birds are not diseased at the time of inspection and slaughter. This scenario is usually only likely to happen if a flock is so close to an outbreak that they constitute a high risk of spread of disease, the flock has not been vaccinated and isolating them is difficult.

Vaccination is an option

There is a vaccine against Newcastle Disease and many commercial poultry units do routinely vaccinate. There are several ways of administering the vaccine, either by the use of spray application, as an eye-drop or an inactive injectable vaccine. Whichever process is used be aware that the birds could show a reaction to the vaccine. Conjunctivitis is the most common reaction with snicking and gasping occasionally being seen. The bird looks as though it has a bad cold about two-three days after the vaccination but it soon recovers.

Vaccination works by giving the birds a weakened virus which is unable to cause disease but able to induce immunity in the vaccinated birds. However, a vaccinated bird can shed the virus into the environment for a period following vaccination. Vaccination is voluntary in the UK and generally speaking, pure breeds and gamebirds are not vaccinated, unless there is a high risk of the disease spreading. Although vaccination against Newcastle Disease may well appear sensible, it is best to discuss the option with your veterinary surgeon because much will depend on how the birds are kept and the amount of risk established. Veterinary surgeons with little poultry experience can take advice from specialist poultry practices or pharmaceutical companies that specialise in poultry vaccines.

Whether you choose to vaccinate or not, it is as well to increase biosecurity where poultry are kept and reduce any risk of possible contamination. Biosecurity is a daunting term but it only means the measures that can be taken to prevent anything from endangering the wellbeing of your birds, such as viruses, bacteria, parasites and rodents. Keeping drinkers, feeders and litter as clean as possible is certainly a good way to start. Suitable housing to contain birds should an outbreak of disease occur also helps and in the event of an outbreak the State Veterinary Service will expect birds to be kept in housing or penning where they are under control and isolated.

It may seem somewhat bizarre but be cautious as to who you allow to visit your poultry as well! Don't invite your neighbours round to see some birds if they have only just returned from a part of the world that is experiencing a Newcastle Disease or Avian Influenza outbreak, at least until clothes etc have been washed. Yes, it may seem highly unlikely that this would happen but by being aware of any possible disease contact you could prevent a problem.

For further details about Newcastle Disease visit the Defra website at: http://www.defra.gov.uk and click on the Newcastle Disease page.

Information on Newcastle Disease vaccine is available from: www.intervet.co.uk or the Helpline: 01908 685 249