PRRS SOWS

Pathology description

PRRS (Porcine Reproductive & Respiratory Syndrome) is caused by a virus from the arteriviridae group. PRRS appears to have to distinct clinical phases: reproductive failure and post weaning respiratory diseases. The virus has a particular affinity for the macrophages particularly those found in the lung. Macrophages are part of the body defences. They ingest and remove invading bacteria and viruses but not in the case of the PRRS virus. Instead, the virus multiplies inside them producing more virus and kills the macrophages.

Once it has entered a herd it tends to remain present and active. Up to 40% of the macrophages are destroyed which removes a major part of the bodies defense mechanism and allows bacteria and other viruses to proliferate and do damage.

Symptoms

Clinical signs in dry sows during the first month of infection

Short periods of inappetence spreading over 7-14 days, 10-15% of sows at any one time.

• The body temperature may be elevated to 39-40°C

• Abortions, often late term, may occur at a 1-6% level. These are often the first signs to be noted.

• Transient discoloration (blueing) of the ears may be seen (2% level. Blue ear disease).

• Some sows farrow slightly early. 10-15% over the first 4 weeks.

• Increased returns occur 21-35 days post-service.

• Prolonged anoestrus and delayed returns to heat post-weaning.

• Coughing and respiratory signs.

 

Clinical signs in farrowing sow in the first month of infection

• Inappetence over the farrowing period, a reluctance to drink.

• No milk (agalactia) and mastitis - significant symptoms.

• Farrowings are often 2-3 days early.

• Discoloration of the skin and pressure sores associated with small vesicles.

• Respiratory signs.

• Mummified piglets. 10-15% may die in the last 3-4 weeks of pregnancy.

• Stillbirth levels increase up to 30%.

• Very weak piglets at birth.

• Cyanosis or blueing of the ears is a variable finding and less than 5% of sows show it. It is transient and may last for only a few hours.

Costs of the disease

• Less and weak piglets

• Decreased fertility