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== Introduction ==

== Introduction ==

Swine dysentery is an infectious disease caused by the anaerobic spirochete, ''Brachyspira hyodysenteriae'', seen in pigs worldwide. It causes a severe mucohaemorrhagic colitis of pigs, causing dysentry with variable amounts of mucous and necrotic material passed in the faeces. It is quite prevalent in the United Kingdom and can be important economically.

Swine dysentery is an infectious disease caused by the anaerobic spirochete, ''Brachyspira hyodysenteriae'', seen in pigs worldwide. It causes a severe mucohaemorrhagic colitis of pigs, causing dysentry with variable amounts of mucous and necrotic material passed in the faeces. It is quite prevalent in the United Kingdom and can be important economically. Recently new isolates called ''Brachyspira hampsonii'' have been isolated in the United States that are genetically distinct, but have strong hemolysis and are associated with clinical cases of dysentery. 

The disease is not systemic and is localised to the large intestine only - in particular, the spiral colon. It predominantly affects pigs post weaning, at around 4 months of age, but all the herd will show signs of the disease. It can be particularly severe in sows mid - late lactation. If a herd becomes infected there is usually around 90% morbidity and 50% mortality.

The disease is not systemic and is localised to the large intestine only - in particular, the spiral colon. It predominantly affects pigs post weaning, at around 4 months of age, but all the herd will show signs of the disease. It can be particularly severe in sows mid - late lactation. If a herd becomes infected there is usually around 90% morbidity and 50% mortality.

Post mortem findings include; a shiny appearance of the serosa of the spiral colon, which will also be turgid and oedematous. Haemorrhage is sometimes seen. Characteristically in this disease, the small intestine is not affected. Fibrinous deposits are seen on the mucosa as the disease progresses and the mucosa underneath is eroded to expose blood vessels in lamina propria.

Post mortem findings include; a shiny appearance of the serosa of the spiral colon, which will also be turgid and oedematous. Haemorrhage is sometimes seen. Characteristically in this disease, the small intestine is not affected. Fibrinous deposits are seen on the mucosa as the disease progresses and the mucosa underneath is eroded to expose blood vessels in lamina propria.

Samples can be taken to perform silver stains to show organisms in the epithelium of the mucosa. The bacteria can also be cultured on blood agar with added antibiotics for at least 3 days - ''B. hyodysenteriae'' causes complete haemolysis whereas other spirochaetes cause partial haemolysis.

Samples can be taken to perform silver stains to show organisms in the epithelium of the mucosa. The bacteria can also be cultured on blood agar with added antibiotics for at least 3 days at 42 degrees under anaerobic conditions.  The best samples are from colon of clinically ill pigs, rectal swabs are not sensitive. - ''B. hyodysenteriae'' causes complete haemolysis whereas other spirochaetes cause partial haemolysis. This is called a "strong beta" reaction, where complete beta hemolysis is visible, especially after removing a plug of agar.  This is called a ring phenomenon and is indicative of a pathogenic Brachyspira infection. 

Immunofluorescence, DNA probes and biochemical tests can also be used though this is usually not cost effective. Serology using ELISA can be used on a herd basis as well as PCR, immunofluorescence or electron microscopy.

Immunofluorescence, DNA probes and biochemical tests can also be used though this is usually not cost effective. Serology using ELISA can be used on a herd basis as well as PCR, immunofluorescence or electron microscopy.  However, the gold standard and method of definitevely diagnosing Brachyspira is the presence of a strong beta hemolysis organisms isolated using selective media.

== Treatment and Control ==

== Treatment and Control ==

There is currently no vaccination for this disease.

There is currently no vaccination for this disease.

Complete eradication of the herd followed by scrupulous disinfection and cleaning can be undertaken in cases of farms wishing to improve or maintain their herd health status.

Complete eradication of the herd followed by scrupulous disinfection and cleaning can be undertaken in cases of farms wishing to improve or maintain their herd health status.  However, this is a difficult task as the organisms can remain viable for months in manure pits and lagoons.  It can also be spread and maintained in rodent populations.

== Prognosis ==

== Prognosis ==