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The biology of bird flu

The biology of bird flu

  • Categories: Disease control
  • Author:
  • Origin:
  • Time of issue:2019-02-26
  • Views: 68

(Summary description) Avian influenza, the full name of avian influenza, is an animal infectious disease caused by a virus, usually only infecting birds, and rarely infecting pigs. Avian influenza viruses are highly species-specific, but in rare cases cross species barriers to infect humans.

The biology of bird flu

(Summary description) Avian influenza, the full name of avian influenza, is an animal infectious disease caused by a virus, usually only infecting birds, and rarely infecting pigs. Avian influenza viruses are highly species-specific, but in rare cases cross species barriers to infect humans.

  • Categories: Disease control
  • Author:
  • Origin:
  • Time of issue:2019-02-26
  • Views: 68
Information

Avian influenza, the full name of avian influenza, is an animal infectious disease caused by a virus, usually only infecting birds, and rarely infecting pigs. Avian influenza viruses are highly species-specific, but in rare cases cross species barriers to infect humans. Since it was discovered in Hong Kong in 1997 that humans can also be infected with avian influenza, this disease has aroused great concern from the whole World Health Organization. Since then, the disease has been sporadic outbreaks in Asia, but in December 2003, avian influenza broke out in many East Asian countries—mainly in Vietnam, South Korea, and Thailand—and killed many patients in Vietnam. Until mid-2005, the epidemic not only showed no signs of subsidence, but continued to spread. There are also cases as far away as Eastern European countries.

Classification of pathogens

According to the antigenic classification of nucleoproteins, avian influenza virus belongs to influenza A virus. Influenza A virus is divided into several subtypes according to the antigenicity of hemagglutinin and neuraminidase located on its mantle. (H) has 16 isoforms; neuraminidase (N) has 9 isoforms. All of these subtypes can infect birds, and in birds the highly pathogenic subtypes belong to the H5 and H7 subtypes. The typical chicken avian influenza virus is H7N7, and it is H5N2 that caused the pandemic in the eastern United States in 1983 and 1984. The current human infection in Southeast Asia is H5N1. The H5N1 strain discovered in 1997 was identified as the source of influenza at that time. In 1999, human infection with H9N2 avian influenza occurred in Hong Kong, in 2003, human infection with H7N7 avian influenza occurred in the Netherlands; in January 2006, H3N2 appeared in the United States. Avian influenza can be divided into low pathogenic forms (LPAI) and high pathogenic forms (HPAI) based on different virulence in poultry populations. Strains of H5 and H7 subtypes are found in both high and low pathotypes, and H9 is only found in low pathotypes. Low pathogenic avian influenza can cause mild respiratory symptoms in birds, reduced food intake, reduced egg production, and sporadic deaths. HPAI is the most severe form, with high morbidity and mortality, often killing all infected flocks.

avian influenza infection

Avian influenza can be transmitted to many species of animals, including birds, pigs, horses, seals, whales and humans. However, wild birds act as asymptomatic carriers, transmitting it to more susceptible poultry. It is mainly transmitted by respiratory and fecal-oral routes among birds, and there is no evidence that the virus can survive in cooked meat. The virus first infects the digestive tract of birds, where it replicates in the epithelial cells of the small intestine and eventually spreads in the feces. Symptoms of bird flu vary widely in animals, but the highly virulent type can kill within days. Symptoms of bird flu infection are similar to other flu symptoms, including fever, cough, sore throat, muscle aches, conjunctivitis, etc. In severe cases, breathing problems and pneumonia may occur, which may be life-threatening. There were also some atypical symptoms, in one case a boy infected with the H5N1 virus developed diarrhoea.

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