(au)Newcastle disease

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Date 22:04 May 29

Subject PRO/AH> Newcastle disease - Australia (Victoria) (04)

 

NEWCASTLE DISEASE - AUSTRALIA (VICTORIA) (04)

*********************************************

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International Society for Infectious Diseases

<http://www.isid.org>

 

[1]

14 May 2002

Dr Gardner Murray, via: Reg Butler <reg.butler

 

 

Newcastle disease A160

----------------------

One new outbreak of Newcastle disease A160 was initially detected in

poultry near the town of Meredith, Victoria on 8 May 2002. The estimated

date of first infection is 18 Mar 2002

 

About 250 000 animals are susceptible and egg production has fallen by up

to 40 per cent in 4 to 6 weeks. Between 500 and 1000 deaths have occurred

over the same period. None of the poultry has been destroyed or slaughtered.

 

The outbreak has occurred in a poultry layer (egg production) enterprise

comprising of 9 atmospheric-controlled sheds, each shed containing between

22 000 and 25 000 birds.

 

The Australian Animal Health Laboratory (AAHL) in Geelong, Victoria made

the diagnosis, using serology, virus isolation, and DNA sequencing;

immunohistochemistry and intracerebral pathogenicity index results pending.

 

The causal agent is virulent Newcastle disease (ND) virus of Australian

origin (amino acid sequence of F cleavage site RRQRRF and a 9 amino acid

extension at the HN gene, indicating that the virus is identical, or almost

identical, to the 1999 Mangrove Mountain isolate of virulent ND virus of

Australian origin).

 

The mode of introduction to to the farm is unknown. Epidemiological

investigations are continuing. There has been no evidence of spread of

Newcastle disease from the infected property.

 

In mid to late March 2002 an enterprise near Meredith, western Victoria,

about 75 km west of Melbourne, experienced a significant decrease in egg

shell quality in 2 of 9 sheds. Over a period of 4 weeks, egg production

declined and 4 other sheds experienced a mild increase in mortality, but

within normal industry limits. Records of routine ND serology of the

enterprise show that there was no recent evidence of infection with any ND

virus before late March 2002. On 8 May 2002, upon suspicion of possible

virulent ND, diagnostic samples were despatched to AAHL, where a virulent

sequence was confirmed on 9 May. The suspect flock was quarantined on 8

May, with subsequent implementation of movement controls and restricted

area (RA or infected zone) of about 3 km and a control area (CA) of about

10 km around the affected property. Both areas are legally defined by the

use of Local Government Area boundaries. There are no other commercial

poultry farms within the RA, and only 5 broiler farms within the CA, all of

which show no evidence of ND.

 

Further epidemiological investigations are under way to attempt to identify

the source of the outbreak. At this time there are only 2 commercial layer

farms known to have had any links to the infected farm. Birds on both of

these farms remain healthy with no clinical or serological evidence of ND,

with results of further laboratory tests pending. At that time 4 very small

non-commercial or 'backyard' layer flocks in Victoria that received birds

from the index farm were placed in quarantine, with precautionary

destruction of all 380 birds in these flocks. The response plan developed

by Victoria and approved by Australia's Consultative Committee on Emergency

Animal Diseases (CCEAD) and the National Management Group on 13 May 2002,

aims to eradicate of virulent ND virus infection associated with this

incident.

 

This will be achieved by a stamping-out policy with the maintenance of

strict quarantine and movement controls to prevent any spread of the

disease, detailed and targeted monitoring and surveillance programs to

determine the presence and distribution of ND viruses, disposal of infected

and contaminated products and materials as necessary, and intensive

clean-up and decontamination of the infected premises.

 

Destruction of birds is scheduled to take 5 days, beginning on 14 May 2002,

with disposal by deep burial on-site. The rest of Victoria and Australia

outside of the CA continues to remain free of ND. No additional quarantine

or movement restrictions have been imposed by other Australian States and

Territories, beyond those imposed by Victorian authorities. The

Commonwealth Government and Victorian Government have created websites to

provide current information on this incident (follow links from:

<http://www.affa.gov.au/> and <http://www.nre.vic.gov.au/>, respectively).

 

 

A summary of Australia's past experience with ND and ND viruses follows.

Virulent ND virus first occurred in Australia in 1930 and 1932. Then, and

in a subsequent outbreak in 1932, the disease was successfully eradicated

by a slaughter-out policy. In 1966, an avirulent strain of ND virus,

designated as V4, was identified. V4 virus and other avirulent strains have

since spread through much of the poultry industry in most states, except

for Western Australia. Some avirulent strains now also occur in some

species of wild birds. During the 1990s, strains of ND virus emerged that

were associated with mild disease. Some strains were found to have gene

sequences (at the fusion gene locus associated with virulence) that were

close to those that occur in virulent ND viruses. In September 1998, a

virulent ND virus emerged on a mixed layer and broiler farm at Deans Park,

western Sydney, New South Wales (NSW).

 

Genetic sequencing showed that this virus had originated from an endemic,

avirulent ND virus of Australian origin, and was distinctly genetically

different from ND viruses that occur overseas. In April 1999, a further

outbreak occurred at Mangrove Mountain on the NSW Central Coast, just north

of Sydney.

 

This outbreak was shown to be caused by an Australian-origin virulent ND

virus similar to the Deans Park virus. During investigations, several other

ND viruses with genetic sequences very close to those of virulent viruses

were also identified for the first time -- these are considered to be

precursor viruses to virulent ND viruses of Australian origin. Each of

these outbreaks was stamped out. In early 2000, further cases of ND due to

virulent ND virus of Australian origin occurred in western Sydney and

Tamworth, NSW. The Tamworth property was depopulated but it was decided

that a survey was needed to help define the distribution and type of ND

viruses circulating in Australia before taking response action on the

properties in western Sydney.

 

A national survey for ND virus was undertaken in the last quarter of 2000.

The survey sampling strategy was designed to ensure comprehensive coverage

of all sectors of the Australian commercial poultry industry. No isolates

of virulent ND virus were detected; no isolates with nucleotide sequence or

deduced cleavage sequences related to the viruses associated with the

outbreaks in NSW were detected; all viruses detected were V4 vaccine virus

or V4-like viruses, genetically remote from virulent ND virus.

Subsequently, birds on 5 remaining premises in Western Sydney from which

virulent ND had previously been isolated were destroyed in early 2001.

 

Six months after this stamping-out response had been completed, Australia

was able to meet international standards for being free of virulent ND, and

this status was regained in October 2001. An ongoing ND vaccination program

is in place in the Sydney and Tamworth areas as a risk management measure.

Until this latest incident in Victoria, there had been no outbreaks of ND

or isolations of virulent ND virus in Australia since February 2000.

 

******

[2]

24 May 02

Dr Gardner Murray via: Reg Butler <reg.butler

 

 

Newcastle disease A160: update

------------------------------

A total of 182 000 poultry at the poultry layer (egg production) enterprise

near the town of Meredith, Victoria have been destroyed. See above for

further details of the enterprise and diagnostic methods used.

 

The causal agent is virulent Newcastle disease (ND) virus of Australian

origin (amino acid sequence of F cleavage site RRQRRF and a 9 amino acid

extension at the HN gene, indicating that the virus is identical, or almost

identical, to the 1999 Mangrove Mountain isolate of virulent ND virus of

Australian origin; ICPI 1.61).

 

The mode of introduction to the farm remains unknown. There has been no

evidence of spread of Newcastle disease from the infected property.

 

Stamping out on the one infected farm is continuing. At close of business

23 May 2002 around 182 000 of an estimated 250 000 birds had been

destroyed, with the balance due to be completed by 25 May 2002. Cleaning

and disinfection operations will then start. All surveillance has been

negative. This includes the small number of poultry flocks within the 10 km

CA (surveillance zone), the few in-contact farms, and other poultry flocks

in Victoria and the rest of Australia. Victorian authorities have begun

issuing permits for voluntary vaccination of Victorian poultry flocks as

part of a risk minimisation strategy for ND. The rest of Victoria and

Australia outside of the CA remains free of ND.

 

No additional quarantine or movement restrictions have been imposed by

other Australian States and Territories, beyond those imposed by Victorian

authorities.

 

--

Dr Gardner Murray

Chief Veterinary Officer and Executive Manager

Product Integrity, Animal and Plant Health

Agriculture, Fisheries and Forestry - Australia

 

Reg Butler

Principal Veterinary Officer

Office of the Chief Veterinary Officer

Product Integrity Animal and Plant Health

Agriculture Fisheries and Forestry - Australia

<reg.butler

<www.affa.gov.au>