The three poultry killers
Written by Sue Clarke. Provided by New Zealand Lifestyle Block, incorporating Growing Today, magazine June 2010 issue.
These three diseases are ones you hope never to see, but all lifestyle block poultry owners should know the signs.
You may be wondering why you need to know about three diseases we don't have in New Zealand.
But if these diseases get here it is most likely they will infect a backyard, free range flock before a big commercial farm. Commercial farmers already take precautions to keep out unwanted visitors and regularly blood test their birds to ensure these diseases are not present.
Our strict import and quarantine regulations in regard to poultry stop us importing fancy breeds that are not present in New Zealand, much to the disappointment of poultry enthusiasts. However, it is those same rules that mean we are fortunate to be free of the three most virulent and damaging diseases which affect poultry in most other countries.
In fact, New Zealand has one of the healthiest poultry populations in the world because we don't have the "big three":
- Newcastle Disease
- Avian Influenza
- Infectious Bursal Disease (also known as IBD or Gumboro)
Two other serious diseases affecting ducks are also not present:
- Duck plague
- Duck viral hepatitis
Our isolation from other countries makes border control easier to monitor as these diseases are only likely to come in via the hand of an unwitting traveller, an importer or a smuggler. In many other countries the transfer is often by migratory birds, something that is impossible to police.
However, the distance between us and other land masses means that the resident population of likely suspects - waterfowl and pigeons - cannot migrate, and those birds which do, should they be affected, would probably die before they reach our shores.
1. Newcastle Disease
What is Newcastle Disease?
Newcastle Disease, previously also known as Fowl Pest, has a number of strains. A very mild, non-disease producing strain has been known to show up in blood testing in New Zealand from time to time.
Newcastle Disease (ND) is the biggest disease threat to avian species worldwide. It is endemic in South America, Africa, Asia, parts of Europe and some Pacific islands.
Where ND is known to be a problem a vaccination programme has to be followed to protect the birds. Vaccination for ND is now compulsory in many Australian states following some serious outbreaks there in 2002.
ND is a highly contagious viral infection affecting many species of domestic and wild birds. Most susceptible are fowls, turkeys, pigeons and parrots while a milder disease is seen in a number of species including ducks, geese, pheasants, quail and guinea fowl.
Symptoms
The disease can result in digestive, respiratory and/or nervous signs, with symptoms ranging from a mild, almost unapparent respiratory disease to a very severe depression, a drop in egg production, increased respiration, profuse diarrhoea followed by collapse, or long-term nervous signs (such as twisted necks) if the birds survive.
Severe forms of the disease have high numbers of fatalities.
How is it spread?
Newcastle Disease is caused by a paramyxovirus (mucous-based virus) that can vary in pathogenicity from mild to highly pathogenic. Spread is usually by direct physical contact with infected or diseased birds, and the virus can be present in manure and be expelled out into the air.
Other sources of infection are contaminated equipment, carcases, water, food and clothing. People can easily carry the virus from one shed or farm to another.
The virus can remain alive in manure for up to two months and in dead carcases for up to 12 months, however it is easily killed by disinfectants, fumigants and direct sunlight.
Newcastle Disease does not affect humans in the same way that it does birds but it can cause conjunctivitis in humans.
2. Avian Influenza
What is Avian Influenza?
Avian Influenza or AI (bird flu) has been in the news in recent years, especially the H5N1 strain which has proved particularly virulent across many countries of the world, and is still causing severe losses in many places.
There have been outbreaks of AI in various states of Australia from time to time, though of the H7 sub-type.
Avian influenza is a highly contagious viral infection which may cause up to 100% mortality in domestic chickens or turkeys and is caused by a virus belonging to the family Orthomyxoviridae. All commercial, domestic and wild bird species are susceptible to infection with AI viruses but disease outbreaks occur more frequently in chickens and turkeys.
Symptoms
The clinical signs of infection with High Pathogenic AI virus are variable and can be affected by the existence of other diseases, the age of the birds, the environment, and the severity of the virus itself. In very severe forms the disease appears suddenly and birds die quickly. Some may appear depressed, egg production falls and soft-shelled eggs are produced. There may be profuse watery diarrhoea, combs and wattles may become blue, and respiration may be laboured.
With less-virulent forms of HPAI the clinical signs may include decreased egg production, depression, respiratory signs suggestive of a cold, swelling of the face, possibly some nervous signs and diarrhoea.
How is it spread?
Low pathogenic avian influenza viruses are traditionally spread by migratory wild birds. Many species of waterfowl, especially geese, ducks and swans, carry the virus but generally show no signs of disease. The recent HPAI outbreak in eastern Asia has seen the H5N1 virus cause disease and high mortality in ducks, geese, swans and other wild birds.
3. Infectious Bursal Disease
What is Infectious Bursal Disease?
Also known as Gumboro or IBD, this is a highly contagious viral disease of poultry found almost worldwide. The severity depends on the age and breed of chicken and the virulence of the virus but white Leghorns are more susceptible than broilers and brown-egg layers.
Symptoms
Signs of the disease can include a rapid drop in feed and water consumption, mucoid (slimy) diarrhoea with soiling of the vent feathers, ruffled feathers, listless chicks with unsteady gait or sitting in hunched position, picking at own vent and sleeping with beak touching the floor.
Early subclinical infections are the most important form of the disease because of economic losses. The disease can cause severe, long-lasting suppression of the immune system. Chickens that are immunosuppressed by early IBD infections are more susceptible to other diseases, including those that don't normally affect healthy birds.
Routine blood testing to detect the presence/absence of IBD is carried out on all registered poultry farms in New Zealand on a regular basis.
How would these diseases affect NZ poultry and native birds?
The impact on our poultry industry and many of our native bird species would be devastating, mostly because they have no immunity so the initial outbreak would result in the deaths of probably thousands, if not millions of birds.
There are no vaccines available in New Zealand so one would have to be imported to protect the survivors and forthcoming generations meaning there would be a time lag before birds which were out of the infected zone could be vaccinated.
It is always a difficult decision to be made by the authorities to actually contain the disease by compulsory slaughter and eradicate it completely, or to allow the use of a live vaccine and live with the disease forever more. Australia has now made Newcastle Disease vaccination compulsory in several states, having managed to contain several ND outbreaks over the years by compulsory slaughter, but they are contending with poultry farmers trying to smuggle/import live Newcastle Disease vaccine. As recently as April 2010 Newcastle Disease was detected in pigeons imported from Europe into Australia but luckily it was detected while the birds were still in quarantine and they were destroyed before release.
What would happen if one of these diseases was found in NZ?
The 'big three' exotic poultry diseases are on the list of notifiable diseases, and are considered to be as serious as Foot and Mouth disease for cloven-hoofed animals. MAF would have to be called and its eradication programme would be actioned. This would entail compulsory slaughter of all birds in a wide area, along with destruction of all possible contacts which may have already been moved out of the area. Think of the daily hatch of thousands of day old chicks which are then trucked or flown all over the country every day, and the distribution of eggs from commercial layer farms to the shops which sell them.
The small flock holder on a lifestyle block would not be immune, as MAF would have legal permission to enter all properties in the vicinity of a disease outbreak and seize/cull all likely species.There would then need to be a complete and supervised clean down of facilities after slaughter, and repopulation would be prevented for some months.
The effect on the poultry industry would be serious, and would probably spell the end for all but the most highly efficient commerical farmers as eggs and fresh poultry from Australia would then be permitted into the country as NZ would no longer have disease-free status. Australian farmers have lower production costs due to cheaper grain and would be able to undercut local producers.
What can we do?
If you have one or 100,000 birds, you should always be vigilant in case of sudden disease and death. Report any suspicions immediately, either to a vet or an experienced poultry stock person who will be able to discern whether it was an unusual disease which needs further investigation. You can also call the MAF Hotline for Exotic Disease Notification on free phone 0800 80 99 66.
- Be suspicious of birds which are 'a new imported breed', or if people make comments in passing about 'bringing in a few eggs from a breeder overseas.'
- Take extra precautions if you travel overseas and visit chickens in homes, farms, parks, aviaries etc.
- Are your shoes perfectly poo-free? Have you had a shower and washed your hair in between seeing a friend's fancy chickens in Sydney or going to a poultry show in Australia and coming home the same day and checking your birds?
Yes, transferring these unwanted viruses can be that easy!
REFERENCES
www.poultryhub.org
Healthy Free Range Hens by Neil Christensen
This article was provided by NZ Lifestyle Block, incorporating Growing Today, magazine.
To subscribe, phone 0800 113 488 or go to www.mags4gifts.co.nz/lifestyleblock
