SALMONELLOSIS

Salmonellosis

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		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 40.5-41.6•C
		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
			Clinical signs of enterocolitis may only be mild wasting and diarrhoea. Initial treatment may be disappointing	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.

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