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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== | + | ==[[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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| − |
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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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| − |
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| − |
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| − | ====Septicaemic Salmonellosis====
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| − |
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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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| − |
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| − | =====Pathogenesis=====
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| − |
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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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| − |
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| − | =====Clinical=====
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| − |
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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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| − |
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| − | =====Pathology=====
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| − |
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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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| − |
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| − | =====Diagnosis=====
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| − |
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| − | * By culture of blood and from mesenteric lymph nodes (which are oedematous and red).
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| − |
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| − |
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| − | ====Enteric Salmonellosis====
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| − |
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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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| − |
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| − | =====Clinical=====
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| − |
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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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| − |
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| − | =====Pathology=====
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| − |
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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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| − |
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| − | =====Sequelae=====
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| − |
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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.
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| | ==Swine Dysentery== | | ==Swine Dysentery== |