Wednesday, February 21, 2024

An update on avian influenza and outbreaks around the world

By Elizabeth Bobenhausen Poultry Times staff ebobenhausen@poultrytimes.com

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GAINESVILLE, Ga. — According to the Centers of Disease Control and Prevention website, there are two categories of avian influenza. One is called Highly Pathogenic Avian Influenza (HPAI). The CDC says, “highly pathogenic avian influenza viruses cause severe disease and high mortality in infected poultry.”

The organization explained, “HPAI A(H5) or A(H7) virus infections can cause disease that affects multiple internal organs with mortality up to 90 percent to 100 percent in chickens, often within 48 hours. However, ducks can be infected without any signs of illness. HPAI A(H5) and A(H7) virus infections in poultry also can spill back into wild birds, resulting in further geographic spread of the virus as those birds migrate.

While some wild bird species can be infected with some HPAI A(H5) or A(H7) virus subtypes without appearing sick, other HPAI A(H5) and A(H7) virus subtypes can cause severe disease and mortality in some infected wild birds as well as in infected poultry.”

The other form of AI is called Low Pathogenic Avian Influenza (LPAI). CDC says, “Low pathogenic avian influenza viruses cause either no signs of disease or mild disease in chickens/poultry (such as ruffled feathers and a drop in egg production). Most avian influenza A viruses are low pathogenic and cause few signs of disease in infected wild birds. In poultry, some low-pathogenic viruses can mutate into highly pathogenic avian influenza viruses.”

The CDC states there are four strains of avian flu called A, B, C and D. Wild aquatic birds and wild waterfowl are deemed to be hosts of the Type A virus. The Type A virus is separated into subtypes based on the protein the virus is attached to. There are two proteins called hemagglutinin (HA) and neuraminidase (NA). In total, there are 18 HA subtypes and 11 NA subtypes. For birds, there are 16 HA subtypes and nine NA subtypes. Many combinations of HA and NA proteins can be made. The CDC gives an example of combinations, “an A(H7N2) virus designates an influenza A virus subtype that has an HA 7 protein and an NA 2 protein. Similarly, an “A(H5N1)” virus has an HA 5 protein and an NA 1 protein.” The subtype of A(H17N10) and A(H18N11) has only been identified in bats.

Avian influenza has seen an increase in some areas around the globe. One of the more exotic regions the virus has seen a spread is in Antarctica. According to Reuters, penguins and seals have never been exposed to HPAI. Professionals are concerned about the effect it might have on the animals. The virus seems to be spreading to Bird Island. Bird Island is merged with the British Overseas Territory of South Georgia and the South Sandwich Islands. The H5 strain of the virus was found on the island and reported to the OFFLU. The OFFLU is part of the World Organization of Animal Health (WOAH) and United Nations Food and Agriculture Organization (FAO). During the same time, the illness was found on the Falkland Islands.

In a report, an OFFLU official said “HPAI H5 virus is likely to spread further among Antarctic wildlife, potentially infecting the 48 species of birds and 26 species of marine mammals which inhabit this region. The negative impact of HPAI H5 on Antarctic wildlife could be immense, because their presence in dense colonies of up to thousands of pinnipeds (seals) and hundreds of thousands of birds facilitates virus transmission and may result in high mortality.” The official went on to say, “elephant seals in South Georgia could have been infected by migrating seals from South America where there was a large die-off of the species. Infected elephant seals could possibly transport the virus to neighboring islands and further south to the Antarctic Peninsula. If HPAI H5 virus completes the above-suggested stage of spread, further virus spread in the Antarctic region is likely given the many avian and mammalian species that probably are susceptible to infection.”

According to the WOAH, South Korea saw 47 birds killed due to H5N6 and an estimated 510,810 birds were culled. The outbreaks began Dec. 5 and lasted until Dec. 11 in the Western parts of South Korea. Along with H5N6, South Korea saw the H5N1 strain which made its way to Japan and Cambodia. Cambodia and Japan never saw cases of the H5N6 strain. H5N6 has only been found in Asian countries, the most recent epidemic was seen on a poultry farm in the Philippians in January 2022.

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