NADIS is a network of 40 veterinary practices and six veterinary colleges monitoring diseases in cattle sheep and pigs in the UK.

NADIS data can highlight potential livestock disease and parasite incidence before they peak, providing a valuable early warning for the month ahead.


June 2004

By Mark White BVSc DPM MRCVS

 
 
  

NADIS Pig Disease Focus


Erysipelas Associated Lameness

The causative organism of Erysipelas in pigs is the ubiquitous bacterium Erysipelothrix rhusiopathiae, formally known as Erysipelas insidiosa. 

The bacterium can survive in soil or dung for 6 months or more but probably more significantly is carried by a wide range of wild birds as well as rodents, especially mice. 

Pigs are particularly susceptible to disease with this organism and the classical manifestations are the acute, septicaemic form producing sudden deaths or in milder cases “diamonds”. These forms of the disease can be controlled by a combination of hygiene, medication and vaccination.

However, arthritis due to Erysipelas is a far more complicated disease and can be very difficult to control. 

The difficulties arise because, in most cases, it is not the direct result of infection in joints with the organism. Erysipelas arthritis is what is termed as immune mediated or hypersensitivity reaction.

Whenever a mammal is challenged with a novel organism which it recognises as being potentially harmful, it will mount an immune reaction in which antibodies will be produced against the organism (antigen). 

In most “normal” infections, these antibody/antigen complexes will be “eaten” by scavaging immune cells and thus, the organism is rendered harmless. 

Unfortunately, in some instances, and Erysipelas is case in point, the initial reaction against the organism is excessive (i.e. hypersensitive) and the antibody/antigen complexes flood the system.

These circulate around the body and settle out primarily in the joints (although occasionally also in the skin) blocking blood supply through the tiny capillaries.

The end result is damage to the joint which is both progressive and irreversible.

The most significant factor clinically is that because the arthritis results from an immune medicated condition, it is not necessarily the case that the acute form of the disease will be seen prior to it. 

Moreover, it can occur in partially immune animals (i.e. pigs that are already sensitised to the organism) and, thus, can even be as a result of prior vaccination.

Clinical Presentation
The animal will rarely have a temperature and classical diamonds may not have been seen in the individual or pen mates. The arthritis produces a very severe lameness – particularly evident in the hind legs but rather than producing a pig that is “off its legs”, the legs stiffen and become very upright. 

The joints in the spine may also be affected, producing a hunched look where the back legs “bunny hop”.  Whilst appropriate treatment in the early stages – as prescribed by the veterinary surgeon – can arrest the damage – once they reach this crippled state, recovery is unlikely. 

The animals may not be fit to transport to slaughter and require on farm destruction but mild cases, which can be very common, may simply produce an awkward gait – maybe not even lame – that does not preclude slaughter, although condemnation can occur. 

However, when the disease occurs in future breeding stock, it can severely limit selection rates or even cause problems for the breeding gilt in future life in animals that slip through the selection process.

At post mortem examination, the joints of severe cases will reveal very obvious osteo (bony) arthritis explaining the irreversibility of advanced lesions.

Circumstances
Erysipelas arthritis is particularly evident in systems which allow or promote:

  • Contact with bird faeces
  • Mouse contamination
  • Access to solid muck

In practice, this means that the disease is most prevalent in straw based systems, particularly in open barns i.e. the supposed welfare friendly pig keeping system and tends to peak in the summer months.

Control
The key to preventing Erysipelas arthritis rests in limiting exposure to the organism.  These can come from several sources (i.e. birds, mice and other pigs).

Bird scarers, bird netting, proximity of birds of prey and coverage of feed hoppers etc will all reduce the chances that feed will become contaminated with bird faeces. 

Likewise, a vigorous rodent control programme is essential. (This also has benefits for Salmonella control and other biosecurity issues).

Hygiene is also important. Cleaning of yards between batches with washing and disinfection + lime washing will prevent a build up of organisms from batch to batch and, in particular, will avoid the pigs meeting a large challenge dose (which would be most likely to induce a hypersensitivity reaction) on arrival in yards.

Moreover, whilst vaccination is not in itself effective at preventing Erysipelas arthritis, a vaccine programme applied early in life (6-8 weeks old) will mean that pigs entering the finishing stage 1 month later will be immune and, thus, limit the multiplication of Erysipelas organisms that will then constitute a heavy challenge from penmates.

Diagnosis
Diagnosis is based on clinical signs supported by serological tests.  It is not usually possible to grow the organism from the joints.

On a herd basis, lameness and leg problems in finishing pigs particularly – but not exclusively – housed in straw yards should raise a suspicion of Erysipelas, particularly if this coincides with partial (leg) condemnation at slaughter. 

Confirmation of disease can then lead to a structured control programme to minimise the effects.


While every effort is made to ensure that the content of this forecast is accurate at the time of publication, NADIS cannot accept responsibility for errors or omissions. All information is general and will need to be adapted in the light of individual farm circumstances in consultation with your veterinary surgeon

Copyright © NADIS 2002


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