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