Erysipelas is a disease that can sneak up on your herd. You might not have any problems with it for years. And if you decided to stop vaccinating pigs for erysipelas, your herd will either escape the disease or eventually it will catch up with you – more likely the latter.
What you should know is that the incidence of erysipelas in U.S. swine has increased during the 1990s.
What is erysipelas?
It is a disease caused by bacteria named Erysipelothrix rhusiopathiae. This bacterium is found worldwide and can cause disease in many animals besides pigs. Among the potential candidates are sheep, birds, reptiles, fish and even man.
Hogs are susceptible to at least 15 of the 28 identified E. rhusiopathiae serotypes. In the United States most isolates from sick pigs are serotype 1a, followed by 2, 5, and 1b. Serotypes 1 or 1a are most common in sudden outbreaks, whereas serotype 2 is most common in erysipelas cases that causes chronic problems in a herd.
How do pigs get infected?
The main source of infection for pigs is other pigs.
Pigs can carry E. rhusiopathiae strains that can cause disease, and they can carry strains that never seem to create any problems. Erysipelothrix rhusiopathiae has been isolated from the tonsils, skin, fat and lymph nodes of healthy market hogs at slaughter.
The organism can enter a herd with incoming seedstock, or healthy pigs already in your herd may be carrying it. If healthy carrier pigs get stressed by management procedures, their environment or other diseases, or if you stop vaccinating pigs for erysipelas, bacteria may multiply in the healthy pigs and become sufficient to cause disease. It could then spread to other pigs within your herd.
The bacteria is most likely transmitted by direct snout-to-snout or manure-to-snout contact. A contaminated environment is a less common source. However, E. rhusiopathiae is resistant to adverse environmental conditions. It can survive in soil for up to 35 days.
Feral and domestic animals, rodents and possibly insects may be a source of infection for swine. It also may be found in contaminated fish meal, water and soil. Pigs can be infected by ingesting contaminated feed and water or through exposure of skin wounds.
What are the signs?
Infection may produce a combination of results. You may see no visible problems in pigs, have a sudden outbreak, or develop a chronic herd problem.
Again, healthy pigs can become infected with erysipelas, carry the organism and never show any outward signs of illness. By comparison, some infected pigs will appear mildly to extremely ill. You may see sudden death or pigs that become inactive, go off feed, have high fevers and appear lame or stiff. Sometimes abortions will occur in gestating sows.
Often red, raised, rhomboid skin lesions surface, giving erysipelas its nickname "diamond skin disease." Although red, diamond-shaped patches can be characteristic of this disease, don't jump to a diagnosis.
In some cases of erysipelas, red diamonds are not seen at all. Moreover, other bacteria (Actinobacillus suis, some kinds of Salmonella and others) that enter the pig's bloodstream have the potential to cause red diamonds on the skin.
Pigs that have recovered from a sudden infection can have chronic ailments including arthritis and heart problems (although that's a less frequent occurrence).
When should I call my veterinarian?
If you notice any of the signs listed, call your veterinarian to get a diagnosis. You might see a bluish or reddish tint to the snout, ears, tail, feet or belly. That's a sign of a bacterial blood infection.
When bacteria get into the bloodstream, the blood flow to the pig's extremities is impaired and the tissues begin to die due to lack of oxygen and nutrients.
Again, it's important to get a diagnosis because other bacteria besides E. rhusiopathiae can cause such signs. It's important to begin the correct treatment as soon as you can.
The good news is that erysipelas is easily treated with antibiotics. But remember to wait until your veterinarian collects samples from affected pigs before you begin. Treatment with antibiotics can interfere with the test by preventing bacterial growth on culture plates at the diagnostic lab. It's important to get good samples for an accurate diagnosis.
As soon as possible after your veterinarian has taken samples, start treating affected pigs for the suspected disease. When the diagnosis is confirmed, continue appropriate treatment and plan preventive strategies.
How can you minimize infection risk?
Start with preventive methods including biosecurity to prevent direct infection from other animals and sanitation to avoid feed and environment contamination. Modified-live-virus and killed-virus erysipelas vaccines are commercially available and usually work well if administered according to the label directions.
For example, if you are using a modified-live erysipelas vaccine in a water delivery system, it's important not to administer antibiotics in the water. Antibiotics will kill the erysipelas vaccine and render it ineffective.
In some cases, vaccination failures can occur when the serotype causing the outbreak was not contained in the vaccine. Vaccination can provide up to six months of protective immunity.
Most pre-breeding sow vaccines include erysipelas protection. I recommend that you talk with your veterinarian to decide whether you should consider vaccinating other pigs in your herd for the disease.
Sandy Amass is a veterinarian at Purdue University's Swine Production Medicine Group, West Lafayette, Ind.