As in Asia, many of birds are kept in free-range backyard farms as sources of income and food in Africa. (Photo:AFP)

    BEIJING, Feb.10 (Xinhuanet) -- Nigerian authorities yesterday informed world health officials of an outbreak of bird flu at a large commercial farm in the northern state of Kaduna, redflaging the world that the deadly H5N1 strain of bird flu has spread to Africa.

    Tens of thousands of caged birds died on the site. A laboratory in Padova, Italy, has confirmed the presence of the H5N1 strain in a dead bird from the facility.

    Nigerian officials have culled thousands of birds, enacted farm quarantines, and curbed poultry shipping in attempts to check the outbreak.

    "The federal government is doing everything to contain the disease within the three centers that have been located," a Nigerian official said.

::::::	Poultry products from Nigeria, others banned in Ghana
::::::	Nigeria braces against Africa's 1st bird flu
::::::	South Africa conducts bird tests for continent
::::::	3 more farms hit by bird flu in Nigeria

    International experts are also in Nigeria to assess the situation and assist local authorities.

    The Nigerian authorities reported no confirmed cases of human infection at this point.

    Migrating birds or the poultry trade may be to blame, experts say. Experts, however, aren't certain how the virus reached Africa.

    Bird flu has been spreading steadily westward from its East Asian source. In recent weeks it has been responsible for human deaths in Turkey and Iraq.

    Preliminary genetic sequencing information indicates that the strain is of Asian lineage, similar to that which recently spread into Turkey

    Officials were not shocked at the deadly flu's appearance in Africa. In October the FAO announced that the virus would likely reach Africa in the near future, citing migrating birds that would soon be moving from breeding grounds in Asia to their winter habitat in Africa.

    Migrating birds are prime suspects in the African appearance of bird flu, but their role remains uncertain.

    "There are other ways diseases move around the world.It could be that wildlife introduced the virus, but through our own activities of commerce, the disease spread," said Juan Lubroth, a Rome-based senior animal health officer with the UN Food and Agriculture Organization (FAO).

   (Agencies)