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This article was published in 1938
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.

The Symptomatology of Swine Dysentery

D. F. GRAY, B.V.Sc., P.P. Board's Veterinary Research Officer, Glenfield.

The first clinical evidence of the disease is a rapid loss in weight (up to 10 lbs.) in a period of approximately 24 hours, and a rise in temperature from 106.4 to 108 degrees Fahrenheit, associated with dullness aud loss of appetite. The affected animal will isolate itself from others in a secluded corner of the stye, and is obviously very ill. At this stage the eye usually presents a feverish appearance, the conjunctiva is intensely reddened, the eye has a glassy appearance, and there is almost constantly a slight gummy discharge.

Within 24 hours a soft diarrhoea supervenes, and in this traces of blood and mucus soon become evident. Abdominal discomfort is indicated by a tendency on the part of the affected animal to lie in troughs containing water or liquid food, or in the drain should water be flowing, and by resentment of palpation of the lower abdomen. Within a short period the faeces become even more fluid and consist of a blood and mucous impregnated thin discharge flowing from the anus, at first under pressure but, as the disease progresses, passively as a foetid stream, more particularly noticeable when the animal moves about after lying down. From this time onwards there is practically no evidence of normal ingesta in the excrement.

Thirst, with a preference for water rather than milk or soup, is a feature of the febrile stage, which seldom lasts more than 24 to 36 hours, but as the fever subsides neither fluid nor solid food appears to attract the animal.

Sick animals emit a characteristic rather offensive odour, which becomes more marked as the disease progresses. From the second day onwards the temperature remains, as a rule, fairly normal, and associated with complete suppression of appetite and constant dysentery, a rapid progressive cachexia ensues: small quantities of bright blood and thick mucus are frequently passed, and usually about the third day these are noted to contain an increasing proportion of shed mucous membrane.

A rather peculiar feature, considering the extent and severity of the lesions, is the almost complete absence of tenesmus (or straining) at any stage of the disease.

Death may occur from the third duy onwards, preceded by extreme weakness and uncertainty in co-ordination of the limbs, apparently mainly associated with loss of extensor control. Complete prostration soon supervenes, and at this stage the pig is unable to stand even if lifted, and when disturbed in any way emits a characteristic rather querulous and highly pitched squeal.

The normal course of a fatal case appears to be from 3 to 6 days, and in the more rapidly fatal forms a pneumonic respiration with frequent painful coughing is usually seen. The disease is not uniformly fatal. A number of cases have been noted in which animals receiving no curative treatment have shown dysentery and loss of appetite for only a few days, followed by a cessation of the dysentery and a return to normal in a very short period. This form is not, however, general, and the majority of animals which recover unaided follow a fairly typical course for 4 to 5 days and are then noted to be showing a little interest in feed. With the improvement in appetite, a gradual cessation of dysentery is noted, and the animal slowly recovers, usually only after a great deal of weight has been lost. Once the Appetite is normally re-established, such loss of condition is fairly rapidly regained.

Post-Mortem Examination.

1. Acute Type. This term is used to describe the form which is fatal within a short period. It is usually associated with a fairly extensive pneumonic condition which, although it may possibly be a secondary infection superimposed upon the initial dysentery, is more probably purely incidental and aggravated by the presence of the disease under consideration. This statement is made in view of the extremely common occurrence of uncomplicated cases of pneumonia in the pigs under observation.

2. Sub-acute Type. This form differs from the above only in the decreased incidence or the milder nature of the pneumonia, if present, and as the lesions of Swine Dysentery in each form show little variation, they will be covered under this heading.

Abdominal Cavity.

Gastric stony is almost invariably present. This is indicated by the presence in the stomach of undigested food in a very sour state, even in animals which are known to have eaten nothing for as long as seven days. Furthermore, the small intestine is invariably empty right down to the ileo-caecal valve. Occasionally there is some slight congestion throughout the entire length of the small intestine, but there is no evidence of any of the more severe inflammatory changes seen in the large intestine. The liver presents characteristic, slightly purplish discolouration, and an unusual soapy feeling, while the gall bladder is invariably empty. Even in advanced cases the kidneys and spleen show little variation from the normal.

Large intestine.

The main seat of the lesion of this disease is the colon, and as in very early cases killed for examination the lesions are usually confined to the lower loops of this organ and in progressively worse cases it is noted to spread proximally to involve the caecum. It is probable that the inflammatory changes commence in the former organ. The serous coat and the mesentery connecting the loops of the large intestine usually show congestion, and it is possible to determine the presence of lesions before the colon is opened owing to the appearance of general inflammation. When the colon is opened the subserous and submucous layers are considerably thickened and somewhat oedematous, the latter layer being intensely haemorrhagic. The mucous coat is practically entirely shed and lies free, admixed with blood and mucous, in the lumen of the bowel. Only in advanced cases is the caecum entirely involved. In which event the lesions resemble those in the colon. Distally, it is unusual to find lesions extending into the rectum.

SWINE DYSENTERY AND NECROTIC ENTERITIS—DIFFERENTIAL DIAGNOSIS.

1. CLINICAL

Swine Dysentery.

(1) Temperature high - up to 108.4

(2) Eye glassy: conjunctiva injected: usually a slight gummy discharge.

(3) Anorexia appears early and continues throughout course of disease. (4) Fluid faeces containing an increasing quantity of blood, mucus, and finally shed mucous membrane appear within 24 hours of onset.

(5) Abdominal discomfort evidenced by the desire of the animal to lie in a cool spot in ventral recumbency, and pain upon abdominal palpitation. (6)) Thirst, with a preference for water, marks febrile stage.

(7) Course relatively short, usually terminating in death or recovery within approximately 7 days.

Necrotic Enteritis.

(1) There is usually some rise in temperature, but seldom above 106.

(2) Conjunctiva normal ; no discharge

(3) Appetite is usually suppressed but not completely so

(4) Diarrhoea — usually yellowish at first and becoming darker within a few days. At no stage is there any sign of mucus or blood.

(5) No discomfort obvious.

(6) Thirst not evident.

(7) Course is far more chronic ranging from a minimum of two days in the septicaemic form up to one month, and may thereafter persist indefinitely with eventual recovery. This variation in duration appears to be associated with the virulence of the organ concerned in any particular outbreak and the resistance of the affected pigs. That is to say, there may be a relatively severe and rapid mortality, or few or no losses at all.

2. POST-MORTEM FINDINGS.

Swine Dysentery.

(1) Characteristic lesions are confined to the colon, the upper part of the rectum and the caecum.

(2) Lesions consist of an intense haemorrhagic inflammatory change involving the large bowel associated with thickening of the bowel wall, submucous haemorrhage and secretion of large quantities of mucous. The mucous membrane eventually becomes completely shed.

(3) A constant feature is a definite gastric atony resulting in the retention of undigested food in that organ for up to 7 days. This lends to the post mortem discovery of very fermented material, even when the animal is known to have ingested no food during that period. The small intestines are usually quite empty, with the exception of a small quantity of mucus, and frequently show slight congestion.

(4) Associated infection with pneumonia and/or pleurisy is fairly commonly noted and is considered at times to be the determining factor in fatal cases.

(5) The liver presents a characteristic purplish blotchy appearance, and has a soapy feel. The gall bladder is almost invariably empty.

(6) Other organs are almost invariably normal.

Necrotic Enteritis.

(1) Entirely confined to the colon and caecum.

(2) Necrotic button ulcers are found in varying numbers scattered over the mucous membrane of the colon and caecum. There is no obvious shedding of the mucous membrane nor blood or mucus extravasation.

(3) Peristalsis apparently continues at a rate concomitant with the degree of appetite manifested. The small intestines contain proportional mount of food material.

(4) Associated infection with pneumonia and/or pleurisy is fairly commonly noted and is considered at times to be the determining factor in fatal cases.

(5) Apparently little change occurs in this organ.

(6) Other organs normal except in rapidly fatal septicaemic form in which petechial haemorrhages are usually present in the heart wall, kidney and spleen.

 


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