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Concern over HPAI in Asia

  

Dec 23, 2016

    

With a severe outbreak of H5N6 avian influenza raging in South Korea and reports of additional farms being affected with this virus on Kyushu Island, in Japan, producers in China are expressing concern over the possibility of introduction of this infection into their flocks.  An added concern is that China has experienced waves of H7N9 avian influenza infection in humans attributed to intimate contact with infected live chickens on farms and in wet markets. It is a matter of fact that wet markets are an important source of poultry meat in rural as well as urban areas despite the presence of supermarkets and QSRs in cities. 

  

A December 20th report in Reuters by Hallie Gu and Jane Chung indicates the extent of inappropriate responses in China to the imminence of HPAI entering flocks.  A spokesperson for a state-owned farm in Shandong Province noted “we feed chickens health-care products, vitamins and anti-virus medicine.”  He added “previously we fed them once every three months but starting from winter time we feed them once every week.”  The reference to ‘anti-virus medication’ is significant since China has consistently and inappropriately used antiviral drugs such as oseltamivir (Tamiflu®) indiscriminately in poultry as a prophylactic measure to the detriment of efficacy in treating humans with this class of drug. 

Intensifying vaccination is beneficial since various serotypes of avian influenza are endemic in China. Creating an immune population among commercial flocks will limit propagation of virus in the event of infection but will also complicate recognition of affected flocks unless DIVA vaccines are used. Immunized flocks will still excrete virus if infected but flocks may be spared catastrophic mortality. Effectively in China birds from flocks not showing obvious clinical signs will be consigned to market unless appropriate surveillance and quarantine restrictions are imposed as components of control programs.

A regional meeting was held in Beijing during the past week to consider measures to prevent and control avian influenza in East Asia.  Representatives from Japan and South Korea which are both affected reviewed the situation with the host Nation.

A typical reaction by Chinese authorities following outbreaks of controllable infections is to place blanket bans on importation from entire nations. Currently this extends to about sixty countries with respect to avian influenza. China, either through institutional ignorance or by design ignores the World Organization for Animal Health (OIE) principles of regionalization and compartmentalization.  Neglect of the latter provision has reduced the ability of the Nation to import grandparent-level  breeding stock from approved compartments in the EU and the U.S. Currently the country is experiencing shortages of commercial chicks of acceptable genetic potential as a result of bans imposed in 2014 and 2015 which have not been amended or relaxed.

In contrast to smaller-scale commercial producers in China who rely on a combination of traditional witchcraft, misuse of drugs and nominal biosecurity, the major suppliers of parent stock for meat and egg-producing strains have intensified biosecurity in recognition of the epidemiology of avian influenza. They have presumably adopted Western practices relating to both Structural and Operational biosecurity.

Japan has confirmed five outbreaks of H5N6 avian influenza since the end of November requiring depletion of 800,000 chickens in addition to flocks of waterfowl.  The position in South Korea is more serious with close to 20 million poultry, principally egg producing flocks, having been depleted since mid-November.  Events in South Korea are closely following previous recent outbreaks which resulted in destruction of as many as one-third of the poultry population. 

Given the extent of infection and its financial consequences it would appear justified for South Korea to introduce mass vaccination to gain time in controlling the spread of infection and to reduce losses associated with their current attempt at eradication. Even if this goal is achieved by early 2017 the Nation will invariably be faced with re-introduction of H5N6 or some other recombinant strain by migratory birds in 2018 or 2019.

Southeast Asia is moving to a “seasonal endemic status” requiring costly and ineffective attempts at long-term eradication. If re-introduction of H5 and H7 strains of highly pathogenic avian influenza become a semi-annual occurrence the Nations impacted to should review their policies on control.

In place of eradication authorities should consider suppression of clinical infection using live-vector vaccines for priming and for broilers followed by effective homologous inactivated emulsions for breeders and egg-producing flocks.