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.