🐓🐓🐓 Avian Influenza (AI) 🐓🐓🐓
🐓 Avian Influenza (AI) is a contagious viral infection which can affect all species of birds. Young fattening turkeys and laying hens are usually the most affected species.
🐓 The virus causing avian influenza is an Influenzavirus A virus of the family Orthomyxoviridae.
🐓 Influenza A viruses infecting poultry can also be divided on the basis of their pathogenicity (ability to cause disease).
🐓 The very virulent viruses cause highly pathogenic avian influenza (HPAI) with mortality in poultry as high as 100%.
🐓 Other AI viruses cause a much milder disease (low pathogenic avian influenza, LPAI). Clinical signs are much less evident or even absent and mortality is much lower.
🐓 Sometimes secondary infections or environmental conditions may cause exacerbation of LPAI infections leading to more serious disease. Evidence suggests that certain avian influenza virus subtypes of low pathogenicity may, after circulation for some time in a poultry population, mutate into highly pathogenic virus strains.
🐓🐓 Clinical symptoms 🐓🐓
🐓 The main symptoms of HPAI in poultry are;
🐔 depression
🐔 loss of appetite,
🐔 cessation of egg laying
🐔 nervous signs
swelling
🐔 blue discoloration of combs and wattles due to disturbance of blood
🐔circulation
🐔 coughing
🐔 sneezing
🐔 diarrhoea.
🐔 Sudden death can occur without any previous signs.
🐓 The mortality rate may reach up to 100% depending on the species, their age, the virus type involved and environmental factors like concurrent bacterial infections.
🐓 Clinical signs of LPAI consist primarily of mild respiratory disease, depression and drop in egg production in laying birds.
🐓 The incubation periods for these viruses range from as short as a few hours to 3 days in individual birds and up to 14 days to spread throughout a flock.
🐓🐓 Transmission and spread 🐓🐓
🐓 All the available evidence suggests that the most common primary introduction of AI viruses into an area is by wild birds,
🐓 If contaminated with influenza viruses, surface water used as drinking water may also be a source of infection
🐓 Spread of AI viruses from farm to farm is mainly by mechanical transfer of infective faeces, in which virus may be present at high concentrations and may survive for considerable periods. Shared water or food may also become contaminated.
🐓 However, man is a very important cause of secondary spread of AI for domestic poultry. Caretakers, farmers, workers, trucks and drivers visiting farms, moving birds or delivering food have caused the spread of AI virus both on to and within farms.