Highly Pathogenic Avian Influenza(HPAI)

Highly pathogenic avian influenza, which was first reported in Italy in the late 19th century, has been occurring in various parts of the world, but in recent years, it began to be a problem in several countries in Asia around 2003, and as of 2006, it has been expanding its activities around the world, including Europe and Africa, and in some countries, it has been causing increasing damage, even threatening human lives. In Korea, three highly pathogenic avian influenza outbreaks occurred in 2003/2004, 2006/2007, and 2008, causing hundreds of billions of won in direct damages. Despite the fact that Korea has successfully eradicated the disease in a short period of time and is considered an exemplary case by international organizations, it continues to occur in neighboring countries such as China, Mongolia, Russia, and various countries in Southeast Asia, and the possibility of reintroduction cannot be ruled out.

Clinical Symptoms

Avian influenza is an infectious disease caused by infection of birds with influenza A viruses. It is highly contagious and can infect many types of birds, including domestic and wild birds such as chickens, turkeys, and quails.

Depending on the virus that is infected, the degree of damage in poultry such as chickens and turkeys varies, and it is divided into Highly Pathogenic Avian Influenza (HPAI), which kills many chickens at a high rate, and LowPathogenic Avian Influenza (LPAI), which causes relatively little damage.

High-pathogenic avian influenza is designated as the first class of legal livestock infectious disease in Korea, and the symptoms of avian influenza in birds such as chickens and quails are diverse, including poor eating and lethargy, respiratory symptoms such as facial swelling and sneezing, diarrhea, a sharp decrease in egg-laying rate, and cyanosis caused by hemorrhage in the head area such as the collar.

The mortality rate of infected chickens varies from 0 to 100% depending on the pathogenicity of the virus, especially in highly pathogenic avian influenza-infected broilers or turkeys, the mortality rate increases rapidly, sometimes reaching 100% in a short period of time, and the symptoms described above often do not appear when the birds die immediately after being infected with highly pathogenic avian influenza.

At first, starting from the entrance of the house or the beginning of the infection, the chickens become depressed and sleepy as the feed intake decreases, and then the number of deaths increases rapidly, and it usually takes about 4-5 days from the beginning of the death to the 50% mortality rate.

Shortly before death, cyanosis appears on the neck and legs, the face is swollen and respiratory symptoms occur, and digestive symptoms such as white or greenish diarrhea are also observed.

In severe cases, there may be no lesions at all.

In laying hens, mortality may precede a decrease in egg production.

In ducks, infection with highly pathogenic avian influenza viruses may not result in high mortality or severe clinical signs, so the virus may continue to multiply and be shed without the birds being aware of the infection and may be a major source of transmission.

In laying ducks, feed intake decreases rapidly and some respiratory symptoms appear first, followed by a sharp decrease in laying rate 1-2 days after the decrease in feed intake, which continues for about a week and then gradually recovers.

In meat ducks, mortality rates of around 10 percent can occur when feed intake is suddenly reduced.

Diagnosis

Avian influenza should be suspected when clinical symptoms consistent with avian influenza occur in a person who has lived in or visited an area at risk of infection.

A diagnosis of avian influenza can be made if avian influenza virus is cultured from a specimen obtained from a suspected infected patient or if DNA or antigens of the virus are detected.

The virus may also be detected in a patient's sputum or stool.

In addition, a blood test may be used to identify increased antibodies to the avian influenza virus.

Prevention and treatment

The H5N1 highly pathogenic avian influenza, which originated in Asia and has been spreading to other regions for several years, is expected to continue to occur and spread for the foreseeable future due to the lack of thorough epidemic prevention measures in each country and the possibility of long-distance transmission by migratory birds.

In particular, the outbreak continues to occur in Korea's neighboring countries, which is not a good sign for all of us.

I believe that the government, producers, and consumers should all work together to ensure a healthy winter.

The government has developed detailed countermeasures against possible transmission routes and factors, and is taking measures such as banning imports from outbreak countries, searching travelers' luggage, inspecting areas, and monitoring wild birds, and is intensifying these activities during the winter months.To prevent damage caused by the outbreak of highly pathogenic avian influenza, it is necessary to strengthen disinfection inside and outside farms and implement quarantine to prevent the virus from being transmitted by vehicles, people, equipment, and animals.

In addition, highly pathogenic avian influenza can also be spread through migratory birds, so there are a few things you can do to prevent this.

First, barns, feedlots, and manure pits should be barricaded to prevent migratory and native birds from entering, including gates, netting, and plastic wrapping.

Second, bird breeding farmers should avoid going to migratory bird arrival sites as much as possible, and if they are forced to go, they should wash and disinfect their shoes.

Third, livestock farmers should refrain from traveling to countries with avian influenza outbreaks, such as China and Southeast Asia, as much as possible.