#12,610
The recent spread of H5N8 into southern Africa - first to Zimbabwe in early June, then into South Africa 3 weeks ago - is HPAI H5's first deep incursion into the southern hemisphere. It remains to be seen how well entrenched the virus will become, and how far it will spread, during its first winter season.
Yesterday the OIE announced 2 more farms affected, and South Africa's DAFF (Department of Agriculture, Forests & Fisheries) released the following statement.First the statement (bolding mine), then I'll return with a bit more on the debate over how the virus arrived in Southern Africa, and how it continues to spread.
MEDIA STATEMENT 11 JULY 2017
UPDATE ON AVIAN INFLUENZA H5N8 OUTBREAK IN SOUTH AFRICA
The HPAI H5N8 virus was confirmed in two further locations in South Africa, bringing the total of affected properties to four. The new locations involved commercial layer chickens on farms in Gauteng and Mpumalanga.
The two farms were immediately placed under quarantine by the state Veterinarian. The quarantine includes, as a minimum, a prohibition of the movement of chickens and chicken products onto and off the farm. The necessary measures have been taken to contain and eliminate the disease as efficiently as possible on both farms.
Forward tracing was done and cull chicken depots were identified, which had received live cull chickens from one of the affected farms in the last 21 days. The records of these cull depots are being followed up to trace as many of these chickens as possible. The new Poultry Disease management Agency (PDMA) system of registration of persons buying and selling live chickens made it possible to trace these culls.
The PDMA registration process of sellers and traders of live chickens has progressed well and a number of initial challenges were ironed out. All role players in the poultry industry involved in the buying and selling of live chickens are strongly encouraged to comply with the registration and other requirements that are designed to allow the trade of live chickens to continue without compromising animal health.
The depopulation of the two poultry sites affected in June is complete. The carcasses, waste material, affected eggs and manure have been contained and will be dealt with to ensure prevention of spread of the disease, as well as to prevent contamination of the environment.
Export of chickens and chicken products from registered HPAI free compartments is continuing to countries that accept guarantees from such compartments. There is good cooperation from registered compartments to increase the testing frequency to monthly testing.
Exports of raw meat, eggs and live birds from South Africa to some trade partners have been disrupted, as one of requirements for the certification is country freedom from Highly Pathogenic Avian Influenza, which cannot be provided since 22 June 2017. The export of products, which had been processed to ensure destruction of the virus, is also continuing, unless the trade partner has raised an objection.
The H5N8 virus does not affect humans, Department of Health through the National Institute of Communicable Diseases tested workers from the affected farms and no human cases have been detected.
The HPAI H5N8 viruses that have been isolated from these outbreaks are similar to the viruses isolated from Zimbabwe in June 2017 and from Egypt in 2016, which makes the likelihood of the involvement of wild birds high. Chicken owners and farmers are encouraged to prevent contact of their chickens with wild birds as much as possible.
Increased surveillance in wild birds, commercial chickens and backyard chickens is continuing. Chicken owners, farmers and the public should remain vigilant and all cases of high mortalities in chickens and other birds should be reported to the nearest State Veterinarian.
The public is advised to avoid any gathering of chickens for shows, auctions and similar activities. However, should such activities continue, the organizers are advised to liaise with the State Veterinary Authorities and the auction houses must also be registered with the PDMA.
Media enquiries
Ms Bomikazi Molapo
0788013711
BomikaziM@daff.go.za
Over the past year the evidence for the long distance carriage and spread of HPAI H5 viruses by migratory and wild birds has grown tremendously, although not everyone agrees, as the following media report from South Africa's News 24 illustrates.
Zimbabwe on wild goose chase for source of bird flu
2017-07-05 13:23
News24 Correspondent
Harare - Last month's outbreak of bird flu in Zimbabwe was likely triggered by domestic chickens or ducks, not wild or migratory water birds, a leading ornithologist says.
Recent studies have shown the prevalence of bird flu to be very low in the wild, while migratory birds left Zimbabwe months ago said Peter Mundy, a professor at Bulawayo's National University of Science and Technology (NUST).
(Continue . . . )
This debate is hardly new, and we've covered it many times (see here, here, and here), with many bird enthusiasts claiming `sick birds don't fly', while others point out the clear pattern of poultry outbreaks occurring along migratory bird flyways.
The truth, as always, is more complicated than just blaming one side or the other (see Bird Flu Spread: The Flyway Or The Highway?).The key phase, often overlooked in this debate, is `long-distance spread'; hundred or even thousands of miles, often spanning oceans or continents. Local, or lateral spread, of bird flu is quite often due to the transport or sale of poultry and poultry products, or the movement of contaminated equipment.
The jump of HPAI H5N8 from the DRC in May to Zimbabwe in early June covered a distance of 1400 air miles, but would require (according to Google Maps) a serpentine road trip of over 2000 miles, taking 50+ hours.When you add in the genetic similarities of clade 2.3.4.4 of the H5N8 virus in Zimbabwe to that circulating last winter in Europe, Uganda, and Egypt, and now South Africa, there are few other plausible explanations beyond its arrival by migratory birds.
Last year's reassortment of H5N8 (see last November's EID Journal: HPAI A(H5Nx) Viruses With Altered H5 Receptor-Binding Specificity) appears to have created a virus with a greatly increased avian host range; one that includes (at last count) 78 species of migratory and wild birds.
These genetic changes may help explain last winter's record setting epizootic in Europe, the rapid spread of the virus across Europe, the Middle East, and Central and Southern Africa, and even its persistence in the environment after local bird migration season has ended.While the evidence continues to mount that wild and migratory birds are contributing to their spread, there is a fair amount of evidence suggesting that HPAI viruses like H5N1, H5N8, and H5N6 likely originated - and are maintained - primarily in poultry.
They are then spread (possibly via peridomestic birds or mammals) to wild and migratory birds, who as `secondary transmitters' - transport them along their migratory routes (see Sci Rpts.: Southward Autumn Migration Of Waterfowl Facilitates Transmission Of HPAI H5N1).As we discussed yesterday in ESA Epidemiological Update: HPAI H5 Clade 2.3.4.4 Viruses In Europe, HPAI H5N8's new found persistence in wild birds adds a new wrinkle to all of this, and the jury is still out on whether this is a temporary blip - while birds generate some immunity to this HPAI H5 clade - or a long-term trend.
The sobering two decade history of HPAI viruses is - just about the time we think we about have them figured out - they up and change on us.Which means we need to be prepared for even more surprises, as these viruses continue along their diverse and unpredictable evolutionary journeys.
