Swine erysipelas is caused by a bacterium, Erysipelothrix rhusiopathiae that is found in most if not all pig farms. Up to 50% of animals may carry it in their tonsils. It is always present in either the pig or in the environment because it is excreted via saliva, faeces or urine. It is also found in many other species, including birds and sheep and can survive outside the pig for a few weeks and longer in light soils. Thus it is impossible to eliminate it from a herd. Infected faeces is probably the main source of infection, particularly in growing and finishing pens.
The bacterium alone can cause the disease but concurrent virus infections, such as PRRS or influenza, may trigger off outbreaks.
Disease is relatively uncommon in pigs under 8-12 weeks of age due to protection provided by maternal antibodies from the sow via the colostrum. The most susceptible animals are growing pigs, non vaccinated gilts and up to 4th parity sows.
The organism multiplies in the body, and invades the bloodstream to produce a septicaemia. The rapidity of multiplication and the level of immunity in the pig then determines the clinical symptoms.
Symptoms
Piglets
- Rarely in sucking pigs.
Sows
Per-acute or acute disease
- The onset is sudden.
- Often the only sign being death.
- Death – generalised infection.
- High temperatures 40?C (108?F) – Fever.
- Obviously ill, although others can appear normal.
- May cause abortion.
- Mummified piglets.
- Stillbirths.
- Restricted blood supply causes small raised areas called diamonds in the skin. These are clearly defined become red and finally black, due to dead tissue but no abscesses. Most heal in 7 – 10 days.
- Often these lumps can be palpated in the early stages before anything can be seen.
- Stiffness or reluctance to rise indicating joint infection – arthritis.
- Sudden death is not uncommon due to an acute septicaemia or heart failure.
Sub-acute disease
- Inappetence.
- Infertility.
- Characteristic skin lesions and ulceration.
- The temperature ranges from 39-40?C (102-104?F) – Fever.
- The disease can be so mild as to be undetected.
- Some piglets may die in the womb following sub-acute disease and become mummified.
- Abortion with ill sows and dead piglets.
Chronic disease
- This may or may not follow acute, or sub-acute disease.
- The organism either:
- Affects the joints producing lameness or
- The heart valves producing growths.
Boars
- Boars infected with erysipelas develop high temperatures and sperm can be affected for the complete development period of 5-6 weeks. Infertility is demonstrated by returns, sows not in pig and poor litter sizes.
Weaners & Growers
Acute infection:
- Sudden death.
- Acutely ill pigs running high temperatures.
- Characteristic skin lesions may also be evident as large 10 to 50mm raised diamond shaped areas over the body that may turn from red to black. They may be easier to feel than to see in the early stages and often resolve over 7 – 10 days.
Commonly the disease is less acute and mild.
- Skin lesions may appear but the pigs may not appear to be ill in spite of a high temperature 42?C (107?F).
- The organism may settle in the joints causing chronic arthritis and swellings which can be responsible for condemnations at slaughter.
- Lameness.
Causes / Contributing factors
- Wet dirty pens.
- Wet feeding systems, particularly if milk by-products are used, can become major sources for multiplication of the organism
- Continually populated houses with no all-in and all-out procedures and disinfection.
- Water systems that have become contaminated with the organism.
- Virus infections.
- Feed back of faeces.
- The movement of pigs involving mixing and stress.
- Sudden changes in temperature and warm summer weather.
- Sudden changes in diet.
- Common in straw based systems.
- Feeding milk waste products.
Diagnosis
This is determined by the clinical picture and isolation of the organism which is easy to grow in the laboratory. Serology will only indicate exposure to the organism and not necessarily disease. It can only be used to aid diagnosis if rising titres, 14 days apart, are demonstrated and if clinical signs are evident.