Difference between revisions of "Salmonellosis"

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== Introduction ==
+
There are many different serotypes of [[Salmonella|''Salmonella'']].
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 and is hence a '''zoonosis''' and a public health issue. Disease in man is mostly contracted from poultry or cattle. Reptiles are also healthy carriers of Salmonella and these may also infect humans that are in frequent contact with these animals.
+
All can produce disease BUT only a few commonly produce illness in UK.  
<br>
+
''Salmonella'' poses a serious risk to man.
 +
[[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.
  
[[Salmonella|'''''Salmonella enteritidis''''']] and [[Salmonella|'''''Salmonella typhimurium''''']] are widespread in most species. [[Salmonella|''''' Salmonella dublin''''']] is a cause of disease in cattle and [[Salmonella|'''''Salmonella cholerae suis''''']] is prevalent in pigs and is usually septicaemic, although is now quite rare. [[Salmonella|'''''Salmonella montevideo''''']] causes disease in humans and animals from contaminated imported meat and bone meal.
 
<br>
 
  
 +
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.
  
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.
 
<br>
 
  
Salmonella strains are often named after where they were first isolated. All strains can occur epizootically, enzootically and sporadically. The strains can all produce similar clinical signs. Infection is via the faecal- oral route and 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. The type of disease is linked to serotype- some serotypes produce septicaemia, whereas others remain localised in the gut.
 
  
<br>
 
  
== Septicaemic disease ==
+
Septicaemic salmonellosis is very dramatic and produces death quite suddenly.
Septicaemic salmonellosis is very dramatic and produces death quite suddenly and [[Diarrhoea|diarrhoea]] is often not seen before death. This form of the disease is unusual in the very young and usually occurs post-weaning. This is around 6 to 9 months in calves and around 6 to 10 weeks in pigs.
+
[[Diarrhoea|diarrhoea]] is often not seen before death.
<br>
+
This form of the disease is unusual in the very young.
The organism colonises 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'']].
 
  
<br>
 
  
=== Clinical Signs ===
+
The organism [[Colon - Anatomy & Physiology|colon]]ises bowel epithelium, where it affects the [[Peyer's Patches - Anatomy & Physiology|Peyers patches]].
Animals suffer from pyrexia, and occasionally a little bit of [[Diarrhoea|diarrhoea]]. The skin is reddened diffusely and bruise-like dark purplish-red blotches may be seen. The intestines may show mild catarrhal enteritis, becoming fibrinous lower down. The bowel is generally flaccid, reddened and filled with fluid. Ecchymotic and petechial haemorrhages are often seen on the serosa and mucosa. There may also be enlarged, haemorrhagic mesenteric lymph nodes and excessive blood-tinged peritoneal fluid. The lungs are collapsed and frothy and the heart is often dilated with ecchymotic haemorrhages. The [[Liver - Anatomy & Physiology|liver]] and kidneys are also flabby and may have subcapsular haemorrhages and may contain small white foci of necrosis known as '''paratyphoid granulomas'''.
+
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'']].
  
<br>
+
=====Clinical=====
  
=== Diagnosis ===
+
* Is usually post-weaning (is unusual in the very young animal).
Diagnosis is by culture of blood and from mesenteric lymph nodes (which are oedematous and red).
+
** 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.
  
<br>
 
  
== Enteric Salmonellosis ==
+
Intestines
Enteric Salmonellosis shows differences in clinical presentation between species:
+
May show mild catarrhal enteritis, becoming fibrinous lower down.
'''Horse''' - acute fatal colitis.  
+
The bowel is generally flaccid, reddened and filled with fluid.
'''Cows''' - lingering febrile [[Diarrhoea|diarrhoea]] with passage of pseudomembranes.  
+
Ecchymotic and petechial haemorrhages on serosa and mucosa.
'''Calves''' - acute [[Diarrhoea|diarrhoea]] like colibacillosis.
+
Enlarged, haemorrhagic mesenteric lymph nodes.
'''Dogs''' - acute bouts of [[Diarrhoea|diarrhoea]].
+
Excessive blood-tinged peritoneal fluid.
'''Cats''' - febrile enterocolitis.
+
Lungs are collapsed and frothy.
'''Pigs''' - septicemia or enterocolitis.
+
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'''.
  
<br>
+
=====Diagnosis=====
  
=== Clinical Signs ===
+
By culture of blood and from mesenteric lymph nodes (which are oedematous and red).
Affected animals produce acute [[Diarrhoea|diarrhoea]], which causes many deaths by dehydration. The diarrhoea may appear watery and yellow and may be blood- tinged. In some outbreaks, particularly in pigs, chronic low-grade [[Diarrhoea|diarrhoea]] only is seen. Calves usually die in the acute stage of the disease, but may also recover.
 
<br>
 
Pathologically enteritis is seen throughout the gut, but is more severe proximally. 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. These may lead to "button ulcers" in the terminal [[Ileum - Anatomy & Physiology|ileum]] and [[Colon - Anatomy & Physiology|colon]], but 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. The septicaemic form may relocalise in the gut, resulting in enteric disease.
 
<br>
 
  
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, which is a source of infection for other animals and people. The pathogen is shed particularly in times of stress.
 
  
<br>
+
====Enteric Salmonellosis====
  
=== Diagnosis ===
+
Enteric Salmonellosis shows differences in clinical presentation between species.
Diagnosis is by culture of blood or faeces.  
+
** '''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.
  
<br>
+
=====Clinical=====
  
== Hepatitis ==
+
* Affected animals produce acute [[Diarrhoea|diarrhoea]], which causes many deaths.
''Salmonella dublin'' can cause hepatitis in calves.  
+
** Watery and yellow.
<br>
+
** May be tinged with a little blood.
Clinical signs will include pyrexia, dehydration and [[Diarrhoea|diarrhoea]].  
+
* 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=====
  
<br>
+
* 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.
  
== Treatment and Control ==
+
=====Sequelae=====
Treatment is mainly supportive with fluids and electrolytes being most important at preventing death by dehydration. Antimicrobial drugs can be given however, the use of antibiotics for salmonella enteritis without septicemia (bacteremia) is controversial as the population of normal intestinal bacterial microflora may be altered as well as the possible development of antibiotic resistance by salmonella organisms. NSAIDs should also be given in order to control pyrexia and for pain relief.
 
<br>
 
  
Prevention should involve decreasing the chances of exposure to the organism and increasing resistance in cattle.  
+
* Animals can remain carriers for months/years following recovery from the acute [[Diarrhoea|diarrhoea]] phase.
Ways of decreasing exposure are to have the herd serotested and cull carrier cows or to quarantine and serotest replacement stock. Isolation of sick cows is vital as is general hygiene and disinection of calf pens and maternity areas. Rodent and bird control is also important in the spread of the disease. Do not allow rendering trucks access to feed or animal areas. Do not use front-end loaders for manure or to haul dead animals and then haul feed with them.  
+
** Bacteria is shed from the bile duct and mesenteric lymph nodes.
<br>
+
*** 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.
  
Increasing resistance in the young calf can be accomplished in two ways. One method is to vaccinate pregnant cows in late gestation with a salmonella bacterin vaccine. The pregnant cow will respond by producing increased antibodies to salmonella that will be passed on to the calf through the colostrum. Salmonella bacterins are also helpful in building immunity when salmonellosis is a problem in adult beef and dairy cows. The second method to increase resistance is to supplement the antibodies by administering an antibody solution containing additional antibodies to salmonella.
+
==Ulcerative Enteritis==
  
<br>
+
**** 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.
  
== References ==
+
==Hepatitis==
Andrews, A.H, Blowey, R.W, Boyd, H and Eddy, R.G. (2004) Bovine Medicine (Second edition), Blackwell Publishing.
+
 
<br>
+
*''Salmonella dublin''
Blood, D.C. and Studdert, V. P. (1999) Saunders Comprehensive Veterinary Dictionary (2nd Edition), Elsevier Science.
+
*calves
<br>
+
=====Clinical=====
Divers, T.J. and Peek, S.F. (2008) Rebhun's diseases of dairy cattle Elsevier Health Scieneces.
+
*fever
<br>
+
*dehydration
Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial.
+
*[[Diarrhoea|diarrhoea]]
<br>
+
=====Gross=====
Nelson, R.W. and Couto, C.G. (2009) Small Animal Internal Medicine (Fourth Edition), Mosby Elsevier.
+
*severe, often haemorrhagic, inflammation in the [[Ileum - Anatomy & Physiology|ileum]]
<br>
+
*'''paratyphoid nodules''' - pale foci of necrosis in the [[Liver - Anatomy & Physiology|liver]]
Quinn, P.J., Markey, B.K., Carter, M.E., Donnelly, W.J., Leonard, F.C. (2007) Veterinary Microbiology and Microbial Disease, Blackwell Publishing.
+
=====Microscopically=====
<br>
+
*foci of hepatocytic necrosis
Radostits, O.M, Arundel, J.H, and Gay, C.C. (2000) Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses, Elsevier Health Sciences.
+
*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_-_Review]]
+
[[Category:Hepatitis,_Bacterial]][[Category:Intestinal Diseases - Cattle]][[Category:To_Do_-_Clinical]]

Revision as of 12:47, 30 March 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.

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.


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 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.


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. 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.


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 and kidneys are also flabby and may have subcapsular haemorrhages. The 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 with passage of pseudomembranes.
    • Calves - acute diarrhoea like colibacillosis.
    • Dogs - acute bouts of diarrhoea.
    • Cats - febrile enterocolitis.
    • Pigs - septicemia or enterocolitis.
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.
    • May lead to "button ulcers" in the terminal ileum and colon.
      • These ulcers rupture very rarely.
  • 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.
  • Stricture of the rectum.
    • A possible sequel to acute salmonellosis, especially in the piglet.
    • Just a few centimetres in from the anus.
    • Gives rise to:
      1. Difficulty in passing faeces.
      2. Megacolon
      3. thin watery diarrhoea in small 'pencils'.
      4. 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).

Hepatitis

  • Salmonella dublin
  • calves
Clinical
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