SALMONELLOSIS (including S. Paratyphi infection)

Last updated: 08 April 2008

1. Reason for surveillance

• In an outbreak, to identify and control the source of the infection
• To detect the emergence of new strains of Salmonella
• To inform the development of better prevention strategies.

2. Case definition

A confirmed case requires laboratory definitive evidence only.

Laboratory definitive evidence

• Isolation or detection of Salmonella species (excluding S. Typhi which is notified separately under typhoid).

Clinical evidence
Not applicable.

Epidemiological evidence
Not applicable.

3. Notification criteria and procedure

Salmonella infection is to be notified by:

• Laboratories on isolation of Salmonella (ideal reporting by routine mail).

Only confirmed cases should be entered onto NDD.

4. The disease

Infectious agent
There are many different serotypes Salmonella that cause human disease.
Paratyphoid is caused by Salmonella Paratyphi serotypes A, B (most common in NSW) and C.

Mode of transmission
Salmonella infection is transmitted by:

• Eating contaminated food
• Drinking contaminated water
• Contact with infected animals
• Contact with an infected case who has diarrhoea

Timeline
The typical incubation period can vary from 6 hours to 3 days, (and occasionally longer), but is commonly 12 to 36 hours. For S. Paratyphi infections, the incubation period is 1 to 10 days.

Salmonellosis is infectious while the case's stools are positive, which can vary from several days to several weeks after onset. A temporary carrier state occasionally continues for months, particularly in infants. Long term permanent carriage occurs in <1% of the population.

Clinical manifestations
Salmonella infection usually presents as acute gastroenteritis, with sudden onset of headache, abdominal pain, diarrhoea, nausea and sometimes vomiting.

5. Managing notifications

Response time
Investigation
On same day of notification of

• a cluster of cases of any Salmonella serotype, or
• a single case of S. Paratyphi, or
• if asked by the Communicable Diseases Branch,

Investigation into single cases of other Salmonella infection is dependent on local epidemiology and at the discretion of the Public Health Unit Director. The identification of unusual or emerging pathogens may prompt an investigation.

Factors to be considered in cases identification
S.Paratyphi B and S.Paratyphi bioser java have the same antigenic forms but slightly different biochemical form. They can share phage types. It is not unusual to isolate S. Paratyphi B from one sample and S. Paratyphi bioser java from another in the same case. If enteric fever is present and the case is a food handler follow up as paratyphoid. Otherwise, cases of S. Paratyphi bioser java infection may be followed up as Salmonella infection.

Data entry
Within 3 working days of notification enter confirmed cases on NDD.

Within 1 working day of notification of the serogroup of the organism update NDD.

Response procedure
The response to a notification will normally be carried out in collaboration with the case's health carers. Where the PHU undertakes follow up, it should ensure that action has been taken to:

• Confirm the onset date and symptoms of the illness
• Confirm results of relevant pathology tests, or recommend the tests be done
• Find out if the case or relevant care-giver has been told what the diagnosis is before beginning the interview
• Seek the doctor's permission to contact the case or relevant care-giver
• Review case and contact management
• Identify whether the case is in a high risk occupation.

Investigation
Interview cases who are part of a cluster, or who have S.Paratyphi, or as requested by CDB using the Salmonella questionnaire
Education
The case or relevant care-giver should be informed about the nature of the infection and the mode of transmission. Emphasise the importance of correct food handling and hygienic practices, particularly hand washing before eating and preparing food and after going to the toilet.

Isolation and restriction

• Cases who are food handlers or who care for patients, children or the elderly and who have been unwell with a diarrhoeal illness should not attend work until 48 hours have elapsed after symptoms resolve. The case should be provided with information regarding hand washing and hygine before returning to work.
• other people with Salmonella infection should not attend work while diarrhoea is present
• For cases of S. Paratyphi infection (other than S. Paratyphi bioser java), before returning to work that involves food handling the case must demonstrate that 3 consecutive stool samples (taken at least 24 hours apart and at least 48 hours after any antibiotics have ceased) are free of S. Paratyphi
• Cases who reside in an institution should be isolated (separated from non-infected residents) if possible. Contact precautions should be used when caring for infected residents
• Children in childcare should be excluded until diarrhoea ceases. It is not necessary for them to be excluded if they have a positive stool sample but do not have symptoms.

Contact management

Identification of contacts
Persons at risk of infection are those exposed to an infective source. They include household members, carers of the case and others who may have eaten any implicated food.

Treatment
Close contacts should be encouraged to seek medical attention early if symptoms develop.

Education
Education should be provided to contacts of cases of paratyphoid if they have been exposed to the same source e.g., travel. The screening of stools of asymptomatic contacts is not required.

Isolation and restriction
None.