Salmonellosis

Salmonella reduction programmes

 

Causal agent

Bacteria belonging to the genus Salmonella. There are numerous types of Salmonella that can case a variety of 'disorders' in pigs. The classic salmonella of pigs is Salmonella choleraesuis var kunzendorf which is rare in EU but common in the USA and Salmonella typhimurium which is much more common worldwide.

Salmonella infections should be distinguished into two different problems

1. Salmonella infections as a disease of pigs which is covered in this note

2. Salmonella contamination of pork and retail products

Age group

All ages can be affected

Clinical signs

 

The clinical signs differ depending on the type of salmonella infecting the individual pig. Many salmonella show no clinical signs in the pig

Septicaemia

 

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Septicaemic salmonellosis is often associated with S. choleraesuis

This is generally seen in pigs 3 weeks to 5 months of age

It is rare in suckling pig, probably due to intestinal lactobacilli predominance

The disease presence as a piglet reluctant to move, anorexic, with a high temperature 40.5-41.6C

The piglet may have a shallow cough

The piglets are generally huddled

A few piglets may be found dead with purple (cyanotic) extremities

After a couple of days a yellow soft faeces/scour may be seen.

Diarrhoea faeces are often golden coloured

S. choleraesuis is a pathogen that can cause pneumonia and diarrhoea in the same pig

Mortality of infected pigs may be high

Enterocolitis

Enterocolitis is generally associated with S. typhimurium

The piglets present with a watery, yellow diarrhoea initially without blood or mucus

The diarrhoea may reoccur over the period of a couple weeks

Mortality is low, mainly associated with dehydration and potassium loss

A few pigs may remain unthrifty and some may develop rectal strictures

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Clinical signs of enterocolitis may only be mild wasting and diarrhoea. Initial treatment may be disappointing

Salmonella 3

 

Pigs may present with cyanosis of the ears, nose and extremities

Infectivity

 

Salmonella are hardy and ubiquitous (everywhere)

Salmonella can persist for weeks or even years in the right environment

However, they are readily destroyed by heat, desiccation and many common disinfectants

There is a carrier status for S. typhimurium which may last for 5 months

Salmonella is spread through contact with infected pigs

Salmonella is spread through contact with infected pigs faeces

Salmonella is spread through contact with contaminated water supplies

Salmonella cholerae suis is only rarely found in feed

A disease outbreak is more likely to occur in an animal which is stressed or has other diseases

Salmonella found in pork may be contracted during the short time spent in the slaughterhouse lairage and have nothing to do with the farm conditions. Salmonella may be found in intestinal lymph nodes within 30 minutes of oral ingestion of the salmonella.


 

Incubation period

 

24 to 48 hours to produce clinical signs in the pig. Note lairage contamination within minutes

Post-mortem Lesions

Septicaemia

With septicaemia there is cyanosis of the ears, feet, tail and abdomen

Together with an enlarged spleen. The lungs are congested possibly with interlobular oedema. Jaundice is not uncommon. There may be millary white foci of necrosis in the liver called paratyphoid nodules. If the pigs survive the initial stages it may also present with a necrotic enterocolitis

Enterocolitis

With enterocolitis there is focal or diffuse necrotic colitis and typhilitis (infected colon and caecum). This may also extend into the small intestine. Necrotic lesions may also be seen as adherent grey, yellow debris on the red roughened mucosal surface of an oedematous spiral colon and caecum. These may be well demarcated into button ulcers. The mesenteric lymph nodes are often greatly enlarged.

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Salmonellosis kim 5

Salmonella lung blotches

In enterocolitis intestinal changes may be mild with swollen lymph nodes (left) to a necrotic enteritis (middle). Lung changes may include blotchy consolidation (right)

Diagnosis

 

Isolation of the organism

Treatment In many countries all infected cases and isolates have to be reported to local authorities

Individuals

Salmonella live inside cells and are thus cannot be reached by many antimicrobial agents. Treatment can therefore be difficult and unrewarding. Provide water and electrolytes as the main component of your treatment regieme. Consider using probiotics to restore gut microflora.

Control

Minimum bacterial spread

Note that one diarrhoetic pig will massively infect the environment

Remove all sick pigs and materials and isolate the pig

Scrupulously adhere to cleaning regimes

Pay particular attention to water supplies. Reduce water pH to less than 4, especially post-weaning

Restrict staff and utensil movements

Reduce stress factors where possible

Apply strict all-in/all-out

It is possible to vaccinate, but many vaccines are overwhelmed in the face of a serious challenge. This may be used in a S. cholerasuis outbreak

Common differentials

Septicaemia

Aujeszky's disease (liver changes), Actinobacillus pleuropneumonia, Erysipelas, Classical Swine Fever

Enterocolitis

Swine Fever, Swine Dysentery, PE (Ileitis), Coccidiosis, Clostridial enteritis and other causes of diarrhoea

Zoonotic implications

 

Salmonella can infect human beings and may result in a fatal infection

 

Useful salmonella reduction programmes:

 

Cleaning and disinfection routines

Biosecurity in general

Pressure-washing

Lime-washing

Truck cleaning

 

Link to the UK BPEX ZAP Programme