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*** Lesions are caused by anaerobic organisms- convert mild diseases into more serious disease.
 
*** Lesions are caused by anaerobic organisms- convert mild diseases into more serious disease.
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==Salmonellosis==
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==[[Salmonellosis]]==
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* There are many different serotypes of [[Salmonella|''Salmonella'']].
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** All can produce disease BUT only a few commonly produce illness in UK.
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** ''Salmonella'' poses a serious risk to man.
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** Some serotypes tend to be more species specific, whereas others can affect a wide range of species. For example:
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*** [[Salmonella|'''''Salmonella enteritidis''''']]
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*** [[Salmonella|'''''Salmonella typhimurium''''']]
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**** Widespread in most species.
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*** [[Salmonella|''''' Salmonella dublin''''']]
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**** Cattle
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*** [[Salmonella|'''''Salmonella cholerae suis''''']]
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**** Pigs
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**** Usually speticaemic.
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**** Not very common now.
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*** [[Salmonella|'''''Salmonella montevideo''''']]
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**** Produces outbreaks from contaminated imported meat and bone meal.
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** Strains are often named after where they were first isolated.
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** Typing is important for epidemiology.
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** All strains can occur epizootically, enzootically and sporadically.
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** All strains can also produce very similar changes.
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* Salmonellosis is NOT very common in the dog and cat.
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* However, the horse is often a carrier.
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** Stress may precipitate the disease, meaning Salmonellosis is seen often in veterinary hospitals.
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===Pathogenesis===
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* Disease is often seen associated with stress.
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* organisms penetrate enterocytes before crossing the mucosa and entering macrophages.
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** After entering macrophages, organins may then either remain localised to the gut, or are carried round the body to cause disease.
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* There are 2 main types of disease- '''septicaemic''' and '''enteric'''.
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** Each outbreak causes only one type of disease.
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** Type of disease is linked to serotype- some serotyopres produce septicaemia, whereas others remain localised in the gut.
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====Septicaemic Salmonellosis====
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* Septicaemic salmonellosis is very dramatic and produces death quite suddenly.
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* [[Intestine Diarrhoea - Pathology|diarrhoea]] is often not seen before death.
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* This form of the disease is unusual in the very young.
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=====Pathogenesis===== 
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* The organism [[Colon - Anatomy & Physiology|colon]]ises bowel epithelium, where it affects the [[Peyer's Patches - Anatomy & Physiology|Peyers patches]].
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** It then invades macrophages, which enable it to invade across the epithelium to the submucosa. It may then either
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*** Remain localised to submucosa, or
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*** Spread to the lymph nodes and enter the circulation to become septicaemic.
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* Animals may die at this stage (30%), but this depends on such factors as the infecting dose and strain.
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* Is similar to septicaemic[[Escherichia coli|'' E. Coli'']].
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=====Clinical=====
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* Is usually post-weaning (is unusual in the very young animal).
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** 6 to 9 months in calves.
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** 6 to 10 weeks in piglets.
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* Animals suffer from pyrexia, and occasionally a little bit of [[Intestine Diarrhoea - Pathology|diarrhoea]].
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* Skin is reddened diffusely
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** Bruise-like dark purplish-red blotched may be seen.
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=====Pathology=====
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* Intestines
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** May show mild catarrhal enteritis, becoming fibrinous lower down.
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** The bowel is generally flaccid, reddened and filled with fluid.
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** Ecchymotic and petechial haemorrhages on serosa and mucosa.
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** Enlarged, haemorrhagic mesenteric lymph nodes.
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* Excessive blood-tinged peritoneal fluid.
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* Lungs are collapsed and frothy. 
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* Heart is often dilated with ecchymotic haemorrhages. 
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* Viscera have a "half-cooked appearance"
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** Pale in colour. 
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** The [[Liver - Anatomy & Physiology|liver]] and kidneys are also flabby and may have subcapsular haemorrhages.
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** The [[Liver - Anatomy & Physiology|liver]] may contain small white foci of necrosis known as '''paratyphoid granulomas'''.
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=====Diagnosis=====
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* By culture of blood and from mesenteric lymph nodes (which are oedematous and red).
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====Enteric Salmonellosis====
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* Enteric Salmonellosis shows differences in clinical presentation between species.
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** '''Horse''' - acute fatal colitis.
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** '''Cows''' - lingering febrile [[Intestine Diarrhoea - Pathology|diarrhoea]] with passage of pseudomembranes.
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** '''Calves''' - acute [[Intestine Diarrhoea - Pathology|diarrhoea]] like colibacillosis.
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** '''Dogs''' - acute bouts of [[Intestine Diarrhoea - Pathology|diarrhoea]].
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** '''Cats''' - febrile enterocolitis.
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** '''Pigs''' - septicemia or enterocolitis.
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=====Clinical=====
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* Affected animals produce acute [[Intestine Diarrhoea - Pathology|diarrhoea]], which causes many deaths.
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** Watery and yellow.
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** May be tinged with a little blood.
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* Animals may die from dehydration. 
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* In some outbreaks, particularly in pigs, chronic low-grade [[Intestine Diarrhoea - Pathology|diarrhoea]] only is seen.
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* Calves usually die in acute stage, but may also recover.
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=====Pathology=====
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* Enteritis is seen throughout the gut, but is worse further along the gut.
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** Inflammation is catarrhal in the [[Duodenum - Anatomy & Physiology|duodenum]].
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** By the ileocaecal junction enteritis is often fibrinous, sometimes with formation of diptheric membranes on the mucosal surface.
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* The necrotic and fibrinous changes particularly affect the Peyers patches and the caecal and [[Colon - Anatomy & Physiology|colon]]ic lymphoid nodules.
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** May lead to "button ulcers" in the terminal [[Ileum - Anatomy & Physiology|ileum]] and [[Colon - Anatomy & Physiology|colon]].
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*** These ulcers rupture very rarely.
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* Focal necrosis may also be seen.
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** Particularly in the [[Liver - Anatomy & Physiology|liver]], but also in the [[Spleen - Anatomy & Physiology|spleen]].
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** Histologically, foci show a central zone of necrosis, surrounded by macrophages and lymphocytes- [[Intestine Inflammatory - Pathology#Septicaemic Salmonellosis|paratyphoid granulomas]].
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*** Although this indicates the animal has had a systemic incfection, paratyphoid granulomas may be present without showing signs of septicaemia.
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*** Enteric cases of salmonella infection nearly always show some evidence of systemic spread.
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* Septicaemic form may relocalise in the gut, resulting in enteric disease.
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=====Sequelae=====
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* Animals can remain carriers for months/years following recovery from the acute [[Intestine Diarrhoea - Pathology|diarrhoea]] phase.
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** Bacteria is shed from the bile duct and mesenteric lymph nodes.
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*** A source of infection for other animals and people.
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*** Shed particularly in times of stress. 
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* '''Stricture of the [[Rectum - Anatomy & Physiology|rectum]]'''.
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** A possible sequel to acute salmonellosis, especially in the piglet.
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** Just a few centimetres in from the [[[[Anus - Anatomy & Physiology|anus]] - Anatomy & Physiology|[[Anus - Anatomy & Physiology|anus]]]].
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** Gives rise to:
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**# Difficulty in passing faeces.
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**# Mega[[Colon - Anatomy & Physiology|colon]]
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**# thin watery [[Intestine Diarrhoea - Pathology|diarrhoea]] in small 'pencils'.
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**# blown up abdomen
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** Animals eventually die from the stricture if they are not first destroyed.
      
==Swine Dysentery==
 
==Swine Dysentery==
Author, Donkey, Bureaucrats, Administrators
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