Background and history

Swine erysipelas is caused by a bacterium, Erysipelothrix rhusiopathiae (syn, insidiosa) that is found in most if not all pig farms. Up to 50 percent 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. Contaminated water also aids the spread of infection.

Disease is relatively uncommon in pigs under 8 to 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 fourth parity sows.

The bacterium alone can cause the disease but concurrent virus infections, such as porcine reproductive and respiratory syndrome (PRRS) or swine influenza (SI), may trigger outbreaks.

The organism enters the body through the tonsils, naturally occurring breaks in the integrity of the small intestine, or through wounds associated with fighting. 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.

Once a pig has been infected it will become immune and in many cases this is only associated with mild or sub-clinical disease.

It also causes local skin lesions in humans but this is rare. Strains of erysipelas vary in their capacity to produce disease, ranging from very mild to very severe.

The incubation period is 24 to 48 hours.

Clinical signs

The onset is sudden. Usually the disease is confined to two or three animals in any one outbreak although in the non-vaccinated herd 5 to 10 percent of animals could be affected any one time. Can be so mild that it goes unnoticed.

Sows

• Often the only sign is death due to an acute septicaemia or heart failure.
• 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.
• High temperatures 40°C (108°F; fever).
• Obviously ill (although some can appear normal).
• Often these lumps can be palpated in the early stages before anything can be seen.
• Stiffness or reluctance to rise indicating joint infection – arthritis.
• Inappetence.
• Infertility.
• Skin ulceration.
• The organism either affects:
  • The joints producing lameness.
  • The heart valves producing growths.

Boars

• Boars infected with erysipelas develop high temperatures and sperm can be affected for the complete development period of five to six weeks. Infertility is demonstrated by returns, sows not in pig and poor litter sizes.

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.

Weaners and growers

Commonly the disease is less acute and mild.

• 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 to 10 days.
• 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.

Diagnosis

This is determined by the clinical picture, with key features of:

• Inappetence.
• Very high temperature.
• Diamond shaped skin swellings – If the diamond markings are not obvious to the eye they can be felt if the hand is run over the skin of the back or behind the back legs and over the flanks.

Post-mortem and isolation of the organism will indicate disease, 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.

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

Causes

• Wet dirty pens, particularly if they are heavily contaminated with faeces that contain high numbers of organisms.
• 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.
• Feed-back of faeces.
• The movement of pigs involving mixing and stress, particularly when maternal antibody from the sow is disappearing.
• Sudden changes in temperature and warm summer weather.
• During warm summer weather when pigs foul their pens.
• Sudden changes in diet.
• Common in straw based systems.
• Diets that contain fungal toxins (mycotoxins) particularly aflatoxin.
• Heavy parasite burdens or low levels of coccidia that allow the bacteria to enter through the damaged wall of the intestine.
• The purchase of non-vaccinated boars or gilts.
• Virus infections particularly PRRS and SI.

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.
• In an outbreak remember that water, faeces, dung, nasal secretions, bedding and feed, harbour the organisms.
• Killed vaccines are quite safe and have no adverse effects on the sow.
• Efficient storage of the vaccine as per the manufacturers recommendation is essential.
• 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.
• Birds can also contaminate feed. Assess the levels of the exposure in your herd.
• If feed-back of faeces is practised in the herd, it should be stopped immediately or it will spread the disease faster.

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/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.
• In acute cases a quick acting penicillin injected twice in the first 24 hours should bring about a rapid response. Continue daily injections for three to four days.
• Where a large number of sows are involved water medication with amoxycillin or phenoxy-methyl penicillin should be carried out. The dose level will depend upon the purity of the antibiotic powder used.
• Amoxycillin, phenoxymethyl penicillin or tetracyclines in the drinking water are also effective.
• Where large numbers of pigs are involved it may be necessary to inject all the pigs in the groups at risk.
• 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 (pen. 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.