Porcine Reproductive and Respiratory Syndrome(PRRS)

Porcine reproductive and respiratory syndrome (PRRS) is a disease caused by the porcine reproductive and respiratory syndrome virus (PRRSV). In the late 1980s, a severe swine reproductive disease struck North America and Europe, characterized by late pregnancy abortions, premature births, production of weak and emaciated pigs, and respiratory symptoms at all ages. The disease was formerly known as Swine Infertility and Respiratory Syndrome (SIRS), Porcine Epidemic Abortion and Respiratory Syndrome (PEARS) and a mystery disease in the United States, and Blue Ear in the United Kingdom. It is now referred to internationally as PRRS. In Korea, it is managed as a Class 2 statutory livestock disease. There are two types of PRRS, the American type and the European type, depending on the genotype, and both types have been introduced into pig farms in Korea. Transmission of PRRS is mainly through purchase and airborne transmission of infected pigs, and to maintain a negative herd, negative pigs must be purchased as candidates or herd pigs. It is mainly transmitted through the air to neighboring pigs, but it can also be shed in the snot and manure of infected pigs and by direct nose-to-nose contact.

Clinical Symptoms

When PRRS virus is introduced, the severity of the disease varies from farm to farm. In acute cases, feed refusal usually occurs first in sows or fattening pigs. The refusal to eat is temporary, lasting about four to seven days. Fever ranges from subfebrile to feverish, reaching 41°C. In the first few days, abortions and stillbirths occur and weak pigs are born. Farm growth rates are reduced.

In the United States, the reproductive problems caused by PRRS are more severe than ours, and in March 2003, a farm in Illinois saw its average farrowing rate drop to 73%.

When PRRS infection is a problem on a farm, bacterial respiratory disease, including rhinitis, is also difficult to treat because the PRRS virus kills 40 percent of alveolar phagocytic cells, which are essential for respiratory defense. of alveolar phagocytic cells, which are essential for respiratory defense.

Diagnosis

Diagnosis is based on antigenic tests using genetic testing and antibody tests using the ELISA method.

The antigen test is usually performed on a blood sample, but can also be performed on saliva collected on a towel tied to the pigsty.

PRRS antibody levels obtained by ELISA are used to assess the stability of the herd.

High and uneven antibody levels among individuals in a herd may indicate circulation of the virus to infected herds.

Genetic sequencing can be used to distinguish between European and American strains of PRRS viruses, and differences in the size of gene amplification products have also been utilized.

Prevention and treatment

Efficacy of PRRS vaccine is controversial, even in the U.S.

On a conventional farm, you should first determine whether you are experiencing a lot of respiratory disease losses or stillbirths to determine when and what to vaccinate.

For example, in the case of respiratory disease, serological tests should be conducted to determine which age group has the most virus or which age group is prone to re-infection, so that the vaccination date can be determined to maximize the vaccination effect.

Before using a vaccine, an assessment of the PRRS status on the farm is necessary.

Antibody testing should be done to determine if the herd is stable or unstable and a strategy should be developed.

In addition, the genotype of the virus can affect the suitability of the PRRS vaccine, so it is important to determine whether the herd is infected with the American, European, or mixed strain.

Herd closure is also a popular option.

Herd closure is intended to stabilize the herd and requires time and investment, so it must be well planned.

In nursery operations, PRRS should be eradicated by default.

To achieve this, for example, on farms with multi-site production, create a negative piglet herd by moving piglets to a clean farm before they are infected with PRRS through early weaning (14 days of age or younger) and raising them as candidate pigs to create a negative sow herd.

Only PRRS-negative pigs should be introduced to the farm afterward.

If it is unavoidable to reintroduce a group of infected sows, vaccinate them first, and then reintroduce them after a certain period of time. period of time to prevent the virus from spreading in the farm. to prevent the spread of the vaccine virus in the farm.

When using live attenuated vaccine, it should be recognized that it is difficult to differentiate between vaccine virus and field virus serologically, and that when gilts are inoculated, the virus is shed through semen. shed in the semen.

Vaccinating pregnant pigs may occasionally result in stillbirths or mummies.

With PRRS, as with other diseases, purity is important in candidate pigs.

On the farm When purchasing candidates from a farm, serologic testing is recommended, and if PRRS is already a problem on the farm the candidates should be vaccinated with two doses of PRRS vaccine before being introduced.

It is important to note that It is very important to eradicate the rats that carry the disease, and it is also important to break the chain of transmission through disinfection and all-in-all-out.