Avian Influenza
Wild birds aid in the spread of avian flu.
Avian influenza, also known as bird flu, has turned into one of the world’s greatest disease threats. The disease not only causes huge economic losses by killing thousands of poultry birds across the world each year but some of the strains, such as H5N1 and H7N9, may also be transmitted to humans. The H5N1 strain was first diagnosed in Hong Kong in 1997, according to the World Organisation for Animal Health, and spread from Asia to Europe and Africa since 2003. The strain infected 468 people and killed 282 people between 2002 and 2009 and infected 233 people and killed 125 people between 2010 and 2014. Infection and mortality rates have declined since then, with the World Health Organisation reporting 145 cases and 42 deaths in 2015, 10 cases and three deaths in 2016 and three cases and one death in 2017. Human infection, so far, is primarily ascribed to direct contact with infected or contaminated environments. There are fears that the disease may evolve to spread more efficiently between humans.
Different strains
More than 15 strains of avian influenza exist that are typically classified into two categories according to the severity of the disease in poultry:
Low pathogenic avian influenza, which is associated with no or hardly any signs of illness.
Highly pathogenic avian influenza, which is associated with severe signs of disease and high mortalities.
The H5N8 strain that broke out in South Africa in 2017 was not transferrable to humans but led to the deaths of close to two hundred thousands birds. Some of the affected producers reported that the birds did not show any signs of illness before, but merely ped dead at a scary rate.
Symptoms
According to Lancet Laboratories and the Department of Agriculture’s Avian Influenza-Veterinary Fact Sheet, the disease in the mild form might be expressed as ruffled feathers, reduced egg production or mild respiratory symptoms, such as sneezing or snickering. In the severe form, it is not only the respiratory tract that it is affected but also other organs and tissues, which can result in internal haemorrhaging.
In the severe form symptoms may include some of the following:
The birds might be quiet, lethargic or seem depressed.
There might be a sudden in egg production, with many eggs being either soft-shelled or shell-less.
The wattles and combs of the birds might become swollen and congested.
The face or skin under the eyes might become swollen and bluish purple.
The birds might develop conjunctivitis (inflammation of the conjunctiva of the eye).
Respiratory symptoms may include coughing, sneezing and gasping.
Nervous symptoms might include tremors, twisted necks or paralyzed wings. Some poultry species might lose their balance and end up lying down while making pedalling movements with their legs.
The birds tend to suffer from diarrhoea.
There might be haemorrhages on the hocks of the birds.
A few deaths may occur over several days, followed by a rapid spread and a mortality rate that can approach 100% in 48 hours.
Avian Influenza Management
Free-range birds are more susceptible to avian influenza.
Highly pathogenic avian influenza is a notifiable disease, so a suspected outbreak must be reported to a state veterinarian as soon as possible. Failure to report such a disease is a criminal offence, because of the associated risks. Samples will be taken for laboratory analysis from suspect live and dead birds to confirm the diagnosis and identify the strain of flu. Early identification is extremely important to prevent the disease from spreading to other birds, farms and, if it is a transferrable strain, humans.
Management
A farm where a suspected outbreak has occurred will be placed under quarantine with movement controls to prevent sick birds from getting into contact with susceptible birds. With no available cure, the majority of countries, including South Africa, try to eradicate the disease through “stamping out.”
This entails the culling of all infected and exposed birds, the correct disposal of carcasses and all animal products, thorough decontamination of infested premises as well as strict quarantine and movement controls of poultry and at-risk vehicles to prevent the disease from spreading.
The process is done under government supervision. Special protective clothing and gear are worn during the process, even if the strain is not transmissible to humans.
Vaccination is used in some countries to protect healthy birds during highly pathogenic outbreaks or where the disease has become endemic. The practice is not allowed in South Africa yet, because of the negative impact vaccination might have on international trade and because vaccination might make it more difficult to identify an outbreak. Some South African role-players, however, feel that vaccination should be allowed if South Africa is unable to compensate producers for losses, as is the practice in most of the first world countries.
Prevention
According to the Department of Agriculture, the virus may easily spread from farm to farm through the movement of domestic live birds, people, especially when shoes and clothing are contaminated, and contaminated vehicles, equipment, feed and cages. Farmers should, therefore, be extra cautious and vigorous to prevent the disease from getting onto their farms during an outbreak.
Producers who keep their birds outside should consider moving the birds to a safer place, as the virus may spread through direct contact with secretions from infected birds – wild or other poultry birds – especially faeces or contaminated feed, water, equipment and clothing. Other species, such as cats and pigs, may also be carriers of some strains.
In many countries, there seems to be a seasonal link, with outbreaks occurring around fall and then dissipating as the climate becomes warmer. South Africa monitors the disease in wild birds and on farms, to take quick steps and alert others of the danger when an outbreak occurs.
