ProMED-mail |

Published Date: 2011-04-13 12:58:23
Subject: PRO/AH/EDR> Avian influenza (37): South Africa, ostriches, HPAI H5N2, OIE, RFI
Archive Number: 20110413.1161

AVIAN INFLUENZA (37): SOUTH AFRICA, OSTRICHES, HPAI H5N2, OIE, REQUEST
FOR INFORMATION
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A ProMED-mail post
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International Society for Infectious Diseases
http://www.isid.org

Date: Mon 11 Apr 2011
Source: OIE, WAHID (World Animal Health Information Database), weekly
disease information 2011; 24(15) [edited]
http://web.oie.int/wahis/public.php?page=single_report&pop=1&reportid=10477

Highly pathogenic avian influenza, South Africa
-----------------------------------------------
Information received on 12 Apr 2011 from Dr Bothle Michael Modisane,
chief director Partnerships, Department of Agriculture, Forestry and
Fisheries, Food Safety and Biosecurity, Pretoria, South Africa

Summary
Report type: immediate notification
Start date: 1 Feb 2011
Date of 1st confirmation of the event: 16 Mar 2011
Report date: 11 Apr 2011
Date submitted to OIE: 12 Apr 2011
Reason for notification: reoccurrence of a listed disease
Date of previous occurrence: July 2006
Manifestation of disease: clinical disease
Causal agent: Highly pathogenic avian influenza virus
Serotype H5N2
Nature of diagnosis: laboratory (advanced)
This event pertains to the whole country

New outbreaks
Summary of outbreaks
Total outbreaks: 5
Outbreak location: Western Cape province [see comment]
Total animals affected
Species: birds
Susceptible: 14 913
Cases: 100
Deaths: 100
Destroyed: 0
Slaughtered: 0

Epidemiology
Source of the outbreak(s) or origin of infection: unknown or
inconclusive
Epidemiological comments: commercial ostrich farms. Farms tested
positive on serology during routine surveillance, but tested negative
on PCR and no virus could be found. Diagnosis only confirmed after
several follow-up PCR tests. South Africa only reports outbreaks on
confirmation on PCR tests. Initially no clinical signs or mortalities
were seen.

Control measures
Measures applied: quarantine; screening; vaccination prohibited; no
treatment of affected animals
Measures to be applied: stamping out

Diagnostic test results
Laboratory name and type: Agricultural Research Council -
Onderstepoort Veterinary Institute (ARC-OVI) (national laboratory)
Species: birds
Test: haemagglutination inhibition test (HIT)
Test date: 16 Mar 2011
Result: positive

Species: birds
Test: real-time PCR
Test date: 9 Apr 2011
Result: positive

Species: birds
Test: real-time PCR
Test date: 12 Apr 2011
Result: positive

Future reporting
The event is continuing. Weekly follow-up reports will be submitted.

--
Communicated by:
ProMED-mail
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[This report summarized 5 outbreaks in Western Cape Province: 2 in
Uniondale and 3 in Oudtshoorn, where a farm with 5754 commercial
Ostriches experienced 100 deaths. This OIE WAHID report indicates that
the farm in Oudtshoorn where the deaths occurred is a "Commercial
ostrich farm. Outbreak picked up during routine surveillance.
Mortalities and clinical signs started afterwards. PCR positive for
H5N2."

This case doesn't seem to fit the usual pattern for either highly
pathogenic or low pathogenic avian influenza as it doesn't seem to be
killing many birds and produces low mortality on only one out of the 5
farms. ProMED-mail would appreciate details of this unusual case and
its classification as a highly pathogenic virus.

The difference between highly pathogenic (HPAI) strains and low
pathogenic (LPAI) strains has been summarized by the Iowa State's
Center for Food Safety and Public Health
(http://www.cfsph.iastate.edu/Factsheets/pdfs/highly_pathogenic_avian_influenza.pdf)
as follows:

Avian influenza viruses are classified as either HPAI or LPAI
viruses, based on the genetic features of the virus and the severity
of disease in experimentally infected chickens. Although there are
exceptions (such as, viruses that fit the genetic description of HPAI
viruses but cause mild illness), HPAI viruses usually cause severe
disease in poultry, while LPAI infections are generally much milder.
To date, only subtypes containing H5 or H7 have been highly
pathogenic; subtypes that contained other hemagglutinins have been
found only in the LPAI form. H5 and H7 LPAI viruses also exist, and
these strains can evolve into high pathogenicity strains.

For details of a similar 2006 outbreak in ostriches, see the
ProMED-mail postings listed below.

The location of the 5 outbreaks can be seen on the map included in
the OIE WAHID report referenced above. The HealthMap/ProMED-mail
interactive map of South Africa can be seen at
http://healthmap.org/r/008f. - Mod.PC]

See Also