Jun 17, 2017
Recent history of the disease
- There has been an increased number of Highly Pathogenic Avian influenza (AI) outbreaks globally in the past 15 years. This increasing number has been due to changes of the virus, the growth of the poultry industry in the world, increases in poultry density as well as a growth of live markets.
- Avian Influenza can be roughly divided into highly pathogenic (HPAI) and low pathogenic (LPAI) strains.
- Low pathogenic avian influenza is a natural infection of waterfowl that may cause minimal to no signs of disease in both wild birds and poultry.
- Highly pathogenic avian influenza rarely causes disease in waterfowl but these birds can transmit it to domestic poultry where it can cause a severe disease with high mortality (death).
- Two types of avian influenza viruses, H5 and H7, are the most common highly pathogenic viruses found in nature. The H5 and H7 avian influenza strains are classified as “Highly Pathogenic Avian Influenza” (HPAI) by the World Organization for Animal Health (OIE) because, to date, HPAI viruses found have always been H5 or H7. It is important to understand, however, that not all H5 and H7 influenza viruses are highly pathogenic. Likewise, other strains that are not H5 or H7 can be considered highly pathogenic in certain circumstances. This being said one must also be aware that LPAI could mutate to HPAI.
- The virus has a short incubation period of 1-3 days, and can spread through direct or indirect contact, with migratory waterfowl being the most likely source of infection for domestic poultry. AI virus can be transmitted among birds through direct contact with secretions from infected birds, especially faeces or through contaminated feed, water, equipment, and human clothing and shoes.
- The virus is readily transmitted from farm to farm by the movement of live birds, people (especially when shoes and other clothing are contaminated), and contaminated vehicles, equipment, feed, and cages. Highly pathogenic viruses can survive for long periods in the environment, especially when temperatures are low. Transmission through the egg is uncommon, although contamination of the shell does occur. Avian influenza virus is highly concentrated in the manure and in nasal and eye discharges.
- Environmental conditions have a marked effect on virus survival outside the bird. Avian influenza virus can survive for at least 35 days at 4°C and for at least 7 days at 20°C in manure and can be isolated from dam water where waterfowl are present. The virus can survive for up to 23 days if refrigerated and for several days in carcasses at ambient temperature.
- Acidification of potentially contaminated drinking water to pH 2.5, chlorination by hypochlorite or oxidation by chlorine dioxide should minimise the spread of virus from infected water sources such as dams. The virus can persist in poultry meat products but is eliminated by cooking.
- Heat, extremely low or high pH, and dryness can inactivate avian influenza viruses. Infectivity of influenza viruses is destroyed by exposure to organic solvents and detergents. Virkon S is a disinfectant frequently used to disinfect premises after an outbreak of avian influenza has occurred.
During the time of an outbreak, strict biosecurity must be adhered to.
- Keep all wild birds away from poultry sites.
- Ensure that there are no wild bird nests in houses, that there are no points of entry for wild birds into the houses such as holes in walls, fencing and roofs.
- Keep control over access to poultry houses by people and equipment.
- Limit all possible outside contact such as unnecessary people, equipment and vehicles.
- Only people essential to the operation of the site must have access to the site and only after showering and disinfecting.
- All vehicles and equipment entering the sites must be dipped and sprayed with disinfectant.
- Maintain sanitation of property, poultry houses and equipment (Gluteraldehyde, QAC’s and Virkon S can be used as disinfectants at the highest concentration recommended by manufacturer).
- Avoid the introduction of birds of unknown disease status into flock.
- Report illness and death of birds immediately to Veterinary Services – Private and State.
- Appropriate disposal of manure and dead poultry (incineration).
- Intensive post mortem examinations must be done on all mortalities followed by incineration of the carcasses.
Signs and symptoms of disease can include:
- Sudden death
- Drop in feed and water consumption
- Cyanosis (turning darkened/blue-purple colour) and edema (swelling) of the skin (combs and wattles)
- Nasal/ocular discharge (sometimes with blood)
- Drop in egg production
- Sometimes paralysis and nervous signs
- Bleeding and necrosis of the internal organs and muscles
- Hemorrhage of the ovary with darkened areas of necrosis
- At the stage vaccination is not permitted in RSA
Any new information that may arise from a meeting held between poultry veterinarians, DAFF and producers – 9th June 2017, will be relayed immediately.