(420) This is an important disease both in the young growing pig and the sow, caused by the bacterium Erysipelothrix insidiosa. This organism is a common inhabitant of normal healthy swine and it can be found in the tonsils in up to 50% of the population. It is passed out in faeces or via the mouth and in dirty conditions high levels of the organism can build up in the environment to present pigs with a heavy challenge. Wet feeding systems, particularly if whey or milk products are used may allow bacterial growth. The bacteria invade the blood stream through a variety of routes including a break in the skin or via the wall of the digestive tract and a septicaemia develops. Infection can also occur without clinical disease. The incubation period is 24 to 48 hours.

Clinical signs

Acute disease
This occurs as sudden death or animals acutely ill running a very high temperature. Skin lesions may also be evident as large raised diamond shaped areas over the body that turn from red to black. They may be easier to feel than to see in the early stages.

Sub acute disease
This is the more common picture with mild or few symptoms. Skin lesions are common and the pigs need not necessarily appear to be ill in spite of a temperature of up to 40ºC (104ºF). From the blood stream the organism may settle in the joints causing chronic arthritis and lameness. Joint problems can be responsible for condemnations at slaughter.

Diagnosis

An individual pig or a small number of pigs will show a high temperature and few other signs. Skin lesions are 10 to 50mm diamond shaped, raised and red to blue to black in colour. They are diagnostic.

The organism is easily cultured and tissue samples (e.g. spleen or liver) submitted to the laboratory provide confirmation.

The bacterium alone can cause the disease but concurrent virus infections, such as PRRS or influenza, may trigger off large outbreaks and this should be borne in mind in making a diagnosis.

Treatment

• The medicine of choice is penicillin and for ease of convenience a long-acting one should be used to reduce the necessity for daily injections. If the pig is acutely ill, twice daily injections of short-acting penicillin should be used initially for the first day. Continue antibiotic cover for four days.
• Where large numbers of pigs are involved it may be necessary to inject all the pigs in the groups at risk.
• Amoxycillin, phenoxymethyl penicillin or tetracyclines in the drinking water are also effective.
• Outbreaks involving pens or complete houses of pigs sometimes occur, particularly during summer months. If the disease is acute, treatment should commence immediately via the water and be continued with in-feed medication using phenoxymethyl penicillin (penicillin V) 200g/tonne or tetracyclines 500g/tonne. Pen. V can also be used for prevention in the face of an outbreak.
• In individual outbreaks finishing pens should be washed and disinfected between batches. If wet feeding is implicated the system must be cleaned out and disinfected.