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Erysipelas


Diamond shaped lesions tyipical of Erysipelas
Diamond shaped lesions tyipical of Erysipelas
(262) This is an important disease in the dry sow caused by the bacterium Erysipelothrix rhusiopathiae (syn, insidiosa). It occurs in most parts of the world where pigs are produced. The same organism also causes disease in sheep, poultry and is carried by wild birds. It also causes local skin lesions in humans but this is rare. It survives outside the pig in faeces and soil for up to six months. The most important source of infection however is the pig itself. It is estimated up to 20% of normal healthy pigs carry the organisms in their tonsils, where they are passed out in the faeces or via mucous from the mouth, thus perpetuating low level infection in the environment. Contaminated water also aids the spread of infection. Strains of erysipelas vary in their capacity to produce disease, ranging from very mild to very severe. Adverse environmental changes, poor nutrition, fluctuating temperatures and movement and mixing can activate the disease. Once a pig has been infected it will become immune and in many cases this is only associated with mild or sub-clinical disease. The organism enters the body through the tonsils, naturally occurring breaks in the integrity of the small intestine, or through wounds associated with fighting.

Clinical signs

Acute disease
The organism gains entry into the blood stream and multiplies rapidly causing a septicaemia. The onset is usually sudden and sometimes the disease will progress so rapidly that the first thing seen is a dead pig. A consistent feature of the disease is a very high temperature from 41 to 42ºC (105 to 108ºF). Some sows may appear very sick while others appear relatively normal. Stiffness and discomfort when walking and a reluctance to rise are common, indicating joint infection. The organisms clump together and block the small blood vessels particularly those beneath the skin. In such cases pink to dark purple areas, often diamond shaped, develop on the skin. See chapter 10. These can be palpated in the early stages even before the colour changes start. Left untreated these areas die/necrose and eventually slough off.

In non-vaccinated or inadequately vaccinated herds infected sows with high temperatures may abort. In such outbreaks up to 20% of animals in a group may be affected. Some of these animals farrow with high stillbirth rates and increased numbers of mummified pigs. Erysipelas in the boar is a serious disease because the prolonged high temperature affects the development of sperm over its period of some five to six weeks. Thus fertility can be affected by small litter sizes and increased returns to mating at both normal and variable intervals.

Usually the disease is confined to two or three animals in any one outbreak although in the non-vaccinated herd 5 to 10% of animals could be affected any one time.

Sub-acute disease
Here the animals are not as ill and the temperature is much lower, sometimes no more than 40ºC (104ºF) or even normal. There may be skin lesions evident and most animals will recover after three to four days.

Chronic disease
This may arise after acute or sub acute disease, or without any other clinical signs. The organism settles in the joints causing a chronic arthritis. There is a considerable amount of pain and loss of body condition but more importantly condemnations may occur at slaughter. Infection of the heart valves may result in growths and subsequent heart failure, for example during farrowing.

Diagnosis

This is based on inappetence, a very high temperature and the diamond shaped skin swellings which if present are diagnostic. 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. This will assist in diagnosis. SE is easily grown in the laboratory and post-mortems and culture of the organism from the sudden deaths will confirm the diagnosis. Blood samples can be taken from the sow at the time of infection and again two weeks later and the antibody levels in the serum determined by the serum agglutination test. Titre levels of less than 1:60 would indicate sub-acute infection, low level exposure or a vaccine response. Titres of more than 1:320 would indicate recent exposure and a rising titre to tests, two weeks apart would help to confirm a diagnosis of disease. Serology however is not a reliable method of diagnosis, it only indicates exposure to the organism.



Treatment

  • Swine erysipelas is very susceptible to penicillin which is the medicine of choice.
  • Affected sows should be treated with long-acting preparations unless disease is acute. Usually a single injection is adequate but in severe cases it is necessary to repeat this two to three days later. The normal dose rate would be 1ml/10kg body weight.
  • In acute cases a quick acting penicillin injected twice in the first 24 hours should bring about a rapid response. Continue daily injections for 3-4 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. (See chapter 4 Water medication).
  • In prolonged outbreaks in-feed medication using 200-300g/tonne of phenoxymethyl penicillin for two weeks should control disease.
Management control and prevention
  • In the breeding herd all the females and males should be vaccinated. Reasonably effective killed vaccines are available and two doses would normally be given 2 to 4 weeks apart. Ideally breeding gilts should be vaccinated twice from 12 weeks of age onwards and given a third dose just prior to first mating.
  • Sows should be given a booster vaccination at each successive weaning.
  • The bacteria persist in the environment for long periods and in manure and soil.
  • Birds can also contaminate feed. Assess the levels of the exposure in your herd.
  • In an outbreak remember that water, faeces, dung, nasal secretions, bedding and feed, harbour the organisms.
  • Boars likewise should be vaccinated twice from 12 weeks of age and thereafter given a booster every six months.
  • Disease is sometimes seen in vaccinated animals either because the challenge has been too great, vaccination has been missed or wrongly administered, or the strain of erysipelas is not covered by the vaccine. Efficient storage of the vaccine as per the manufacturers recommendation is essential.
  • If feed back of faeces is practised in the herd, it should be stopped immediately or it will spread the disease faster.

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