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New Zealand’s poultry flock has a unique and superior animal health status to that found in any other commercial poultry-producing country in the world. New Zealand's avian flock is free of the three major exotic poultry diseases prevelant worldwide - Highly Pathogenic Avian Influenza (HPAI), Newcastle's Disease (ND) and Infectious Bursal Disease (IBD).
Highly Pathogenic Avian Influenza (HPAI)
One of the most recent and relevant exotic disease outbreaks is that of the Highly Pathogenic Avian Influenza epidemic that is currently affecting the poultry flocks throughout Asia and Europe. However, the risk of New Zealand contracting avian influenza is one of the lowest in the world, as it is located out of the flight paths of migratory birds and does not allow any live bird imports.
Strict import controls into New Zealand are in place to protect the superior health status of the national poultry flock and native birds. Consequently, there are no imports of fresh or frozen poultry meat or table eggs to prevent disease coming into the country.
Infectious Bursal Disease (IBD)
Infectious Bursal Disease (IBD), also known as Gumboro disease, is a highly contagious viral infection of young chickens. The main target of the Infectious Bursal Disease Virus (IBDV) is lymphoid tissue and, in particular, the bursa. IBD causes lymphoid depletion of the bursa, and if this occurs in the first two weeks of life, significant depression of the humoral antibody immune response may result.
The clinical symptoms of the disease, usually observed two to three days after exposure, are not specific, but generally include the tendency for birds to pick at their own vent and reluctance to move. Non-specific symptoms can also include depression, anorexia, ruffled feathers, trembling, watery diarrhoea, and sudden death, usually within four days of the signs of the disease appearing. Birds affected by the disease became dehydrated and in the terminal stages, have a subnormal temperature. Mortality rates of between 20 and 30% were reported by Lukert and Saif (2003) with levels of 30 to 40% being reported by the OIE.
Currently, active surveillance is in place for IBD in New Zealand, and after five years, there has been no evidence of its presence. This is an important strength of the New Zealand poultry industry. However, farmers remain vigilant to ensure that this disease never becomes an issue in New Zealand.
Click here to view the EPF's first IBD information sheet, providing information for producers.
Newcastle's Disease (NCD)
Newcastle's Disease is a highly contagious, viral disease that affects domestic poultry, caged and aviary birds and wild birds.
Clinical symptoms of NCD vary widely depending on the infecting virus. In addition, the age, species' immune status and conditions under which the affected bird(s) are reared and/or housed may affect the observable signs of the disease. Animal Health Australia (2004) further reported that the route of exposure and magnitude of the infecting dose would influence the virulence and tissue tropism of the disease.
Viruses of low virulence may cause no disease or mild respiratory distress for a short time in chickens and turkeys. Birds affected by lentogenic strains of the virus may also show a temporary appetite depression and a drop in egg production.
Birds affected by moderately virulent strains of NCDV exhibit characteristic signs of acute respiratory disease, with coughing accompanied by depression, weight loss, and a drop in egg production that may last one to three weeks. Nervous signs may develop later in the clinical course of the disease, but are not common. Mortality is generally low at about 10%.
Highly virulent strains of the disease may be classified as viscerotropic or neurotropic. In the case of viscerotropic NCD, the disease may appear suddenly with high mortality occurring in the absence of other clinical signs. The first clinical signs are often listlessness, increased respiration and weakness, followed by oedema of the head, particularly around the eyes, 2-3 days after the birds become sick. Profuse, bright green diarrhoea is common in birds that do not die during the early stages of infection. In birds surviving infection with the velogenic viscerotropic strain for two to three weeks, affected birds may exhibit muscle tremors, torticollis, paralysis of the legs and wings and opisthotonos prior to death. Mortality may exceed 90% but frequently reaches 100%.
Chickens affected by the neurotropic strain show a sudden onset of severe respiratory disease followed a day or two later by neurological symptoms. Egg production is dramatically affected but there are no sign of diarrhoea. Although morbidity may reach 100%, mortality rate in adult birds is generally 10-20%, although mortality of 50% has been reported in adult birds, with 90% being reported in young chickens.
New Zealand is one of few countries in the world that has never had an outbreak of Newcastle's Disease. This is another great strength of our poultry industry.
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