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Erysipelas

(217) 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.

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.

Clinical signs
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. These are of three types:

Per-acute or acute disease
The onset is sudden, often the only sign being death. This is seen rarely in sucking pigs. In boars and sows there are very high temperatures 40°C (108°F) and they are obviously ill, although others can appear normal. It is during this acute period that the disease may cause abortion. Alternatively, if abortion does not take place one or two piglets may die inside the womb and become mummified.

The organisms block tiny blood vessels to the skin over the back and sides of the body causing thrombosis. The restricted blood supply causes small raised areas called diamonds. These become red and finally black, due to dead tissue. Often these lumps can be palpated in the early stages before anything can be seen. Sudden death is not uncommon due to an acute septicaemia or heart failure.

Sub-acute disease
The sow appears inappetent and may show characteristic skin lesions. The temperature ranges from 39-40ºC (102-104ºF) but in some cases the disease can be so mild as to be undetected. Some piglets may die in the womb following sub-acute disease and become mummified.

Chronic disease
This may or may not follow acute, or sub-acute disease, and the organism either affects the joints producing lameness or the heart valves producing growths.

Sporadic disease is common in sows but if one sow in a group becomes infected the exposure is high from her urine and faeces and it is advisable to inject all contact animals with penicillin.

The important effects of erysipelas on reproductive failure:

  • Sick animals with high fevers.
  • Abortions during acute or sub-acute disease with ill sows and dead piglets.
  • The death of piglets inside the womb and mummification.
  • Abortions with decomposing piglets.
  • Absorption of embryos and delayed returns.
  • Normal returns if infection occurs immediately post-service.
  • Variable litter size.
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.

Diagnosis
This is determined by the clinical picture and isolation of the organism which is easy to grow in the laboratory. Serology will indicate exposure to the organism but it can only be used to confirm disease if rising titres, 14 days apart, are demonstrated.

The interpretation of titre levels (hemagglutination inhibition test)

  • 1:4 - 1:64 due to vaccination.
  • 1:32 - 1:320 suggests maternal antibody or exposure to the organism.
  • 1:640 suggests previous infection.
  • A rise in a titre level from 1:320 to 1:1280 would suggest active infection. Erysipelas may become a problem in herds where PRRS is endemic.
Treatment
  • The erysipelas organism is very sensitive to penicillin. Acutely ill animals should be treated with quick acting penicillin twice daily for three days. Alternatively a long-acting penicillin, given as a single dose to cover 48 hours of treatment, could be given and then repeated.
  • Treat by intramuscular injection 1ml per 10kg (300,000iu/ml).
  • Medicate the feed with 200g/tonne of phenoxymethyl penicillin for 10-14 days. This is a very effective method of prevention, and can be used in major outbreaks of disease.
Management control and prevention
  • If a boar is ill with a temperature and shows skin lesions, treat immediately and do not use for mating for a minimum period of four weeks. Alternatively, cross mate with boars that have no disease history or use AI.
  • Vaccinate all gilts and young boars twice, two to four weeks apart (according to manufacturer's instructions) from 14 weeks of age.
  • In herds where there is a high challenge it may be necessary to re-vaccinate gilts and boars so that a third dose of vaccine is given two months after the second often when the breeding animals arrive on the farm.
  • Re-vaccinate sows either two weeks prior to farrowing, or at weaning time, depending on the incidence and history of disease on the farm.
  • Make sure boars are re-vaccinated every six months.
  • If disease breakdowns occur in spite of vaccination it is likely that the levels of challenge from the environment are high. Assess hygiene in breeding pens and move to an all-in all-out method of housing.
  • Wet feeding systems, particularly if milk by-products are used, can become major sources for multiplication of the organism.
  • Killed vaccines are quite safe and have no adverse effects on the sow.


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