Difference between revisions of "Salmonellosis"
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− | + | * There are many different serotypes of [[Salmonella|''Salmonella'']]. | |
− | There are many different serotypes of [[Salmonella|''Salmonella'']]. All can produce disease | + | ** 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. | |
+ | * [[Diarrhoea|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 | + | =====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 [[Diarrhoea|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 [[Diarrhoea|diarrhoea]] with passage of pseudomembranes. | ||
+ | ** '''Calves''' - acute [[Diarrhoea|diarrhoea]] like colibacillosis. | ||
+ | ** '''Dogs''' - acute bouts of [[Diarrhoea|diarrhoea]]. | ||
+ | ** '''Cats''' - febrile enterocolitis. | ||
+ | ** '''Pigs''' - septicemia or enterocolitis. | ||
− | === | + | =====Clinical===== |
− | |||
− | + | * Affected animals produce acute [[Diarrhoea|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 [[Diarrhoea|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- 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 [[Diarrhoea|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]]. | ||
+ | ** Gives rise to: | ||
+ | **# Difficulty in passing faeces. | ||
+ | **# Mega[[Colon - Anatomy & Physiology|colon]] | ||
+ | **# thin watery [[Diarrhoea|diarrhoea]] in small 'pencils'. | ||
+ | **# blown up abdomen | ||
+ | ** Animals eventually die from the stricture if they are not first destroyed. | ||
− | + | ==Ulcerative Enteritis== | |
− | |||
− | |||
− | + | **** Salmonella typically produces a broad spectrum of disease. | |
+ | **** Classically may produce 'button' ulcers, especially in the terminal small intestine and upper large intestine (Ileocaecocolic junction). | ||
+ | ***** Seen particularly in [[Salmonella|Salmonella cholerae suis]] in the pig. | ||
− | + | ==Hepatitis== | |
− | == | + | *''Salmonella dublin'' |
− | + | *calves | |
− | + | =====Clinical===== | |
− | + | *fever | |
− | + | *dehydration | |
− | + | *[[Diarrhoea|diarrhoea]] | |
− | + | =====Gross===== | |
− | + | *severe, often haemorrhagic, inflammation in the [[Ileum - Anatomy & Physiology|ileum]] | |
− | + | *'''paratyphoid nodules''' - pale foci of necrosis in the [[Liver - Anatomy & Physiology|liver]] | |
− | + | =====Microscopically===== | |
− | + | *foci of hepatocytic necrosis | |
− | + | *mixed mononuclear inflammatory cell infiltrate | |
− | + | NB: small foci of hepatocytic necrosis are often found as incidental lesions at post mortem examination | |
− | |||
[[Category:Enteritis, Fibrinous/Haemorrhagic]][[Category:Enteritis,_Bacterial]] | [[Category:Enteritis, Fibrinous/Haemorrhagic]][[Category:Enteritis,_Bacterial]] | ||
[[Category:Enteritis,_Ulcerative]] | [[Category:Enteritis,_Ulcerative]] | ||
− | [[Category:Hepatitis,_Bacterial]][[Category:Intestinal Diseases - Cattle]][[Category:To_Do_- | + | [[Category:Hepatitis,_Bacterial]][[Category:Intestinal Diseases - Cattle]][[Category:To_Do_-_Clinical]] |
Revision as of 16:57, 17 January 2011
- There are many different serotypes of 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 enteritidis
- Salmonella typhimurium
- Widespread in most species.
- Salmonella dublin
- Cattle
- Salmonella cholerae suis
- Pigs
- Usually speticaemic.
- Not very common now.
- 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.
- diarrhoea is often not seen before death.
- This form of the disease is unusual in the very young.
Pathogenesis
- The organism colonises bowel epithelium, where it affects the 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.
- It then invades macrophages, which enable it to invade across the epithelium to the submucosa. It may then either
- Animals may die at this stage (30%), but this depends on such factors as the infecting dose and strain.
- Is similar to septicaemic 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 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"
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.
Clinical
- Affected animals produce acute 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 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.
- 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 colonic lymphoid nodules.
- Focal necrosis may also be seen.
- Particularly in the liver, but also in the spleen.
- Histologically, foci show a central zone of necrosis, surrounded by macrophages and lymphocytes- 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 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.
- Bacteria is shed from the bile duct and mesenteric lymph nodes.
- Stricture of the rectum.
Ulcerative Enteritis
- Salmonella typically produces a broad spectrum of disease.
- Classically may produce 'button' ulcers, especially in the terminal small intestine and upper large intestine (Ileocaecocolic junction).
- Seen particularly in Salmonella cholerae suis in the pig.
Hepatitis
- Salmonella dublin
- calves
Clinical
- fever
- dehydration
- diarrhoea
Gross
- severe, often haemorrhagic, inflammation in the ileum
- paratyphoid nodules - pale foci of necrosis in the liver
Microscopically
- foci of hepatocytic necrosis
- mixed mononuclear inflammatory cell infiltrate
NB: small foci of hepatocytic necrosis are often found as incidental lesions at post mortem examination