Erysipelothrix rhusiopathiae (previously known as Erysipelas insidiousinsidiosa) has been recognised as a cause of Erysipelas in pigs for more than a century. Capable of producing acute and chronic health problems, in both individuals and herds, the disease can have a serious effect on herd health, productivity and the economic viability of a pig business.

Mark White

However, it can be controlled effectively by hygienic farm practice, strategic vaccination and therapeutic treatment. This paper will explore the clinical picture, diagnosis, epidemiology, treatment, control and prevention of this common disease.

High-Risk Biology

Disease surveillance programmes in the UK frequently highlight the prevalence of Erysipelas in pigs even though there are a number of highly effective vaccination programmes available to producers that could prevent or control it.

E. rhusiopathiae is found throughout the animal kingdom. It affects a wide variety of wild mammals and birds, which tend to become asymptomatic carriers. It is present on most pig farms and up to 50 per cent of pigs can be identified as carriers. The pig is particularly susceptible to infection, although, other farm species such as turkeys and sheep are also vulnerable, as are marine animals including seals and other cetacea.

The organism can also survive outside the host - some claims suggest that it can exist for six months in soil and even longer in chilled animal tissue. There is also clear evidence that it can survive long enough in moist, deep bedding material to be able to carry over from one group of pigs to the next if housing is not adequately cleaned and disinfected between batches. The organism is also capable of surviving in wet feed systems.

It also harbours some health and safety implications for stockmen as the organism can be transferred to man. Erysipelothrix rhusiopathiae is viewed as an occupational pathogen causing 'Erysipeloid', a rare disease that is usually only seen in individuals exposed to high levels of infection such as workers on farms and in slaughterhouses, veterinarians, butchers and fishermen. However, this organism does not cause the human skin condition of 'Erysipelas', this which is the result of a Streptococcus bacterial infection.

In the author's opinion, no herd, irrespective of its health status, is likely to be free of Erysipelas infection and therefore all pig keeping enterprises must take active measures to minimise its impact.

More than 28 antigenic types of Erysipelothrix have been identified, although at least 25% are now categorised as the non-pathogenic E. tonsillarum. Of the remainder, most disease cases are due to serotypes 1 and 2 and there is no evidence available to suggest that any new strains are emerging or are becoming more significant. These factors have implications for long-term control.

Clinical Presentation

Erysipelas can be seen in all age groups of pigs, including the youngest piglets. It is evident in all production systems although solid floor, bedded types appear to be most vulnerable. Disease manifestations are most commonly seen in adults and growing pigs above 12 weeks of age.

Adults

• Peracute disease - In totally naive animals sudden death associated with severe septicaemia can occur, but this is rare. The most likely occurrence of the disease is in herds that are newly established following hysterectomy or medicated early weaning techniques.
• Acute disease - Pigs will be lose appetite and become depressed and have a high rectal temperature, frequently exceeding 42°C (108°F). The onset of classic diamond-shaped raised red legions on the skin, particularly over the back, usually occurs within 24-48 hours (Figure 1). However, these skin lesions do not always occur.

Figure 1. Prominent diamond lesions on the back of the growing pig

Abortion is likely in sows in the second-half of pregnancy, while those infected in the early stages may return to service. Disease very late in pregnancy can lead to mummification and stillbirths or possibly the birth of piglets that are acutely affected with the disease.

Boars can also be affected and, provided they survive, are likely to be sterile for up to eight weeks. The organism is not excreted in semen itself, but can contaminate the preputial diverticulum, so there is potential for venereal spread. While collected semen may be contaminated, the routine use of antibiotics in diluents should eliminate infection.

There are possibly two long term effects: heart disease and arthritis.

(i) Heart Disease - Bacteria within the blood system can 'settle out' on heart valves allowing them to proliferate and produce 'cauliflower-like' lesions on the valve itself. This can take 7 to 10 days to appear and can occur in an animal that has shown no other overt sign of Erysipelas. Sudden death, as a result of cardiac insufficiency (endocarditis), is usual (see Figure 2).

Figure 2. Cauliflower-like growths on heart valves (endocarditis) are a long-term consequence of erysipelas

(ii) Arthritis - The pigs attempt to fight off E. rhusiopathiae infection can lead to excessive antibody production causing complex immunological particles to form and block small blood vessels. It is these complexes that induce the 'diamond lesions' in the skin. They also cause deposits in the pigs joints with the result being a crippling and intractable arthritis - seen in animals that did not previously show any signs of having Erysipelas (Figures 3 and 4).

Figure 3. Chronic intractable arthritis in a young growing pig associated with erysipelas infection
^{(courtesy W.S. Smith)}

Figure 4. Severe cartilage erosion and osteoarthritis as a consequence of erysipelas

Further ailments

With the obvious exception of reproduction problems, each of the main disease manifestations can be seen in growing pigs usually over 12 weeks of age. In growing pigs, it is also possible for the disease to present itself only as diamond skin lesions without any systemic illness. It is worth noting that recovery from diamond lesions, arising from systemic illness or localised cutaneous disease, can cause areas of the skin to die and slough off (Figure 5). In some cases, extremities may become necrotic and ultimately drop off (a form of dry gangrene).

Figure 5. Cutaneous sloughing following necrosis as a long-term consequence of erysipelas infection

Outbreaks of endocarditis have been seen - without any other signs of erysipelas visible. Sudden death in groups of pigs is the only symptom and in severe outbreaks mortality can exceed 15 per cent.

Similarly, particularly in pigs kept in open barns in straw yards, chronic grumbling arthritis can occur, without any other evidence of erysipelas. This not only has health and welfare implications for the infected affected pigs, but also has implications for future breeding performance of gilts and/or potentially high rates of condemnations at slaughter. A key consideration is also simultaneous disease challenge within the herd. Any systemically active infection, such as PRRS, may also trigger Erysipelas outbreaks.

Pathology and Diagnosis

Any deaths associated with septicaemia or endocarditis in pigs may suggest Erysipelas and sampling of heart blood, liver, spleen or affected heart valves provide a good opportunity for bacterial culture in the laboratory. Similarly, aborted material from sows acutely affected will be a rich source of the organism. However, it is more difficult to isolate the pathogen from the physically visible symptoms (i.e. diamonds and chronic arthritis).

Diamond lesions, sampled by skin scraping, are a poor source of bacteria; a swab taken of blood from an acutely ill pig is more likely to yield E. rhusiopathiae.

In the live pig, high rectal temperature, in association with diamond lesions are strongly indication of Erysipelas, although not definitive. Similar skin lesions can occur with other conditions such as Actinobacillus suis, Haemophilus parasuis or PDNS infections.

The arthritic form of Erysipelas must be differentiated from other forms of infectious arthritis (e.g. Mycoplasma hyosynoviae) or physical joint problems such as osteochondrosis. However, in chronically lame animals, diagnosis can be difficult, as the organism may have disappeared from joints at this stage. While gross pathology and histopathology may be useful, serological diagnosis based on blood sampling may indicate rising immunity and suggest recent infection. Samples should be taken at the first signs of disease and again two to three weeks later.

Paired serology can be used to diagnose any of the forms of the disease, with single blood samples only useful as a guide. A broad interpretation of blood test results, using the Haemagglutination Inhibition Test, is shown in Table 1.

The more commonly used Serum Agglutination Test presents similar problems with interpretation of single blood samples - titres of less than 1:40 are non-specific; titres 1:40 and greater are positive. Higher titres of 1:640 or greater suggest exposure of vaccinates, repeated vaccination or recent field exposure. (Source: Veterinary Laboratories Agency - VLA).

In short, disease diagnosis should be based on paired serology - collecting sera from acute and convalescent pigs two to four weeks apart and demonstrating a 4-fold rise in titres in non-vaccinated pigs - or on culture of the organism from clinical cases.

Immunity

• An active response to exposure to the organism, with or without disease manifestation.
• An active response to vaccination - a mimic of natural infection without the risk of disease.
• Maternally derived antibodies (MDA) passed in the colostrum to the newborn piglet.

The latter provides short-term protection for the young piglet and will depend on the time of colostrum intake post parturition; the quality of colostrum ingested and the concentration of antibodies within this first milk. MDA protection is also influenced by the challenge to the young piglet that will 'soak' up its acquired antibodies.

Maternal immunity to E. rhusiopathiae will not last beyond 12 weeks of age, therefore any disease seen in the growing herd beyond this stage does not indicate the failure of breeding herd vaccination programmes.

Treating This Persistent Offender

E. rhusiopathiae is consistently sensitive to penicillin and acute cases will respond within 12 to 24 hours of treatment, although diamond lesions will not disappear that quickly.

Where outbreaks of disease occur, mass medication with penicillin or amoxycillin via water or via long-term in-feed treatment may be needed. This is particularly important in growers where outbreaks of endocarditis occurs or where disease arises in unvaccinated breeding herds.

Treatment of chronically lame pigs is more difficult. Use of cortisone or NSAIDs to reduce pain and relieve inflammation may be appropriate with breeding animals whereas early slaughter (if suitable) or euthanasia is usually a better option for growing pigs.

Prevention

Preventing Erysipelas relies on good biosecurity to minimise challenge from the organism and also establishing strong immunity in the most vulnerable and valuable animals.

Exposure to rodents and wild birds (infection vectors) should be minimised by using strict eradication and pest control programmes. Also, all buildings should be cleaned and disinfected between batches of pigs. These are basic hygiene principles, but are essential components of any health programme. They will break the cycle of infection with E. rhusiopathiae (and many other production diseases).

Cleaning protocols should include water systems and feed systems which can harbour infection. Wet feed systems should be periodically flushed with clean water and followed with an appropriate water disinfectant (e.g. FAM 30®: Dupont). Any cracked concrete floors should be covered with thick emulsion of hydrated lime and earth floors can be disinfected with a 50:50 mix of phenolic disinfectant (where available) and diesel oil. Also, the control of other concurrent diseases (e.g. PRRS) will also benefit Erysipelas control measures.

Vaccinate to Protect

Erysipelas vaccination programmes are not new and a number of safe and effective killed vaccines have been available for many years. In the UK one product has proved highly effective and economical for many years.

Although Porcilis Ery® (Intervet/SP Animal Health) is composed of antigens derived solely from serotype 2, (unlike one of its previous competitor products that included type 1 and 2 antigens), trials have demonstrated that there is reliable cross-protection between these 2 most common serotypes. As a result this vaccine provides protection against both serotypes.

However, to achieve full immunity, the vaccine programmes must be applied correctly.

In breeding stock the basic programme requires two x 2ml intramuscular doses, given four weeks apart and prior to breeding (boars included). A subsequent single booster dose must follow at approximately six-monthly intervals, i.e. each sow cycle. These boosters can be given at any stage of the breeding cycle &ndash during lactation, at weaning or gestation (with the exception of the last two weeks of pregnancy). Some practitioners advise booster vaccination given three to four weeks before farrowing to boost colostral immunity.

A sister product combining Erysipelas vaccine with Parvovirus vaccine (Porcilis Ery+Parvo®: Intervet/Schering Plough Animal Health) can be used in conjunction with Porcilis Ery both in the primary programme and for booster vaccination. The simplest programme to manage in practical terms involves the use of Porcilis Ery for 6 consecutive months followed by 6 consecutive months use of Porcilis Ery+Parvo. However, producers are advised to seek specific veterinary guidance for their own herds.

Where Erysipelas disease is a persistent problem in growing pigs, vaccination from 6 weeks of age is recommended. While two doses, given 4 weeks apart are usual, off-label advice by some vets is to use a single dose of vaccine at 9-12 weeks of age which appears to provide sufficient cover for the growing period. Under this regime, any future breeding stock will still require a two dose primary course prior to breeding.

It is also worth noting that vaccination in itself will not prevent the infection and will not actively control the arthritic form of Erysipelas. However, a long-term vaccine programme in growers will reduce field challenge and ultimately lead to a reduction in this form of the disease. It is vitally important that any vaccination regime ensures correct applications and avoids common pitfalls. Investigations over many years have shown that where vaccine has been called into question the following faults have been identified:

• Incorrect storage of vaccine
• Out of date vaccine
• Incorrect or dirty injection techniques
• Inappropriate timing of vaccination and failure to give a two dose primary course. This may often result from confusion over the vaccination status of incoming breeding stock
• Vaccination of animals whilst unwell
• Failure to vaccinate all of the pigs in a batch due to error
• Wrong diagnosis
• Excessive challenge/high stress levels
• Unreal expectations &ndash particularly expecting Erysipelas to be controlled in growing pigs over 12 weeks of age by vaccinating the breeding herd.

Value and the Bottom Line

The costs of Erysipelas disease is highly variable and difficult to quantify, but the following examples give an idea of potential losses:

A 400-sow breeder/feeder herd

Erysipelas outbreak in sows inducing abortion in 15 sows during 1 month (lost production = 158 weaned pigs) with 6 sows dying subsequently.
Farrowing rate declined by 7 per cent over subsequent 4 month period giving further shortfall of 22 farrowings in that period (230 pigs less weaned).
Total loss estimated at 388 pigs @ £35/head = £13,580 plus loss of cull value.
Cost, approximately £14,000 plus medication.
Estimated cost of annual vaccination is only £250 plus labour.

Batch finishing pigs affected late on with acute/sub-acute Erysipelas

Some 60 of the 200 pigs sent for slaughter with diamond skin lesions required skinning with loss of carcase weight 360kg plus downgrading.
Loss of income = ££1200.

A 600-sow breeder/feeder herd with straw-based finishers

Herd is experiencing chronic arthritis in grower/finishers due to Erysipelas caused by poor cleaning procedures and bird infestation.
Over a six-month period, 58 pigs were euthanased or unmarketable; 31 pigs were totally condemned at slaughter plus partial condemnation accounted accounting for 2.5 per cent of total remaining weight sold.
Total dead weight sold = 471793kg (6,553 pigs @ 72kg)
Total weight condemned = 13,971kg
Euthanased pigs: 58 @ £60 = £3,480
Cost in six months = £17451 (£2.66/pig sold)
Cost to vaccinate growing pigs x 2 = £0.50 per pig
Cost of cleaning and bird-proofing = £0.80 per pig


This article was first published in Veterinary Review.

Further Reading

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