Typhoid and paratyphoid

Notification requirements for typhoid and paratyphoid

Typhoid and paratyphoid (Group A diseases) must be notified immediately by telephone, followed by written notification within 5 days.

This is a Victorian statutory requirement.

Primary School and children’s services centres exclusion for typhoid and paratyphoid

Exclude until approved to return by the department.

Work exclusions apply to food handlers and some healthcare workers (see ‘Control of environment’).

Infectious agent of typhoid and paratyphoid

Salmonella typhi, the typhoid bacillus, and S. paratyphi, with three recognised serovars (A, B and C), are the infectious agents.

Identification of typhoid and paratyphoid

Clinical features

Typhoid fever (enteric fever) is a septicaemic illness characterised initially by fever, bradycardia, splenomegaly, abdominal symptoms and ‘rose spots’, which are clusters of pink macules on the skin.

Complications such as intestinal haemorrhage or perforation can develop in untreated patients or when treatment is delayed.

Paratyphoid fever presents a similar clinical picture but is usually milder, shorter in duration and with fewer complications.

Diagnosis

Diagnosis is made by culture of typhoid or paratyphoid bacilli from the blood, urine or faeces. Repeated sampling may be necessary. Serology in the form of the Widal test is no longer routinely used and is not sufficient for confirmation of diagnosis.

Phage typing is used for characterising S. typhi and S. paratyphi isolates for epidemiological purposes and in outbreak settings. A number of phage types are recognised.

Incubation period for Salmonella typhi and Salmonella paratyphi

The incubation differs for typhoid and paratyphoid fever:

• The incubation period for typhoid fever is usually 8–14 days, but this depends on the infective dose and can vary from 3 days to 1 month.
• The incubation period for paratyphoid fever is usually 1–10 days.

Public health significance and occurrence of typhoid and paratyphoid

Typhoid and paratyphoid infections occur worldwide. Outbreaks occur in areas with poor sanitation and inadequate sewerage systems. Approximately 30 cases of typhoid and 20 cases of paratyphoid fever occur in Victoria each year. The majority of these are returned travellers, especially from southern Asia.

Reservoir for Salmonella typhi and Salmonella paratyphi

Reservoirs for typhoid and paratyphoid fever are:

• typhoid fever – human gallbladder carriers and, rarely, human urinary carriers
• paratyphoid fever – humans and, rarely, domestic animals.

Mode of transmission of Salmonella typhi and Salmonella paratyphi

Typhoid and paratyphoid are transmitted through contaminated water or food. They can also be transmitted by the faecal–oral route. Water, ice (if unboiled water is used), raw vegetables, salads and shellfish are important sources for travellers. The disease commonly occurs in association with poor standards of hygiene in food preparation and handling.

Period of communicability of typhoid and paratyphoid

The diseases are communicable as long as typhoid or paratyphoid bacilli are present in excreta. Some patients become permanent carriers.

Susceptibility and resistance to typhoid and paratyphoid

Everyone is susceptible to infection. Immunity following clinical disease or immunisation is insufficient to protect against a large infectious dose of organisms.

Control measures for typhoid and paratyphoid

Preventive measures

Vaccination is not routinely recommended, except for travellers who will be exposed to potentially contaminated food and water in countries such as in Asia, the Middle East, Africa, Latin America and the Pacific islands.

Vaccination should be considered for laboratory workers in potential contact with S. typhi.

Three typhoid vaccines are currently available in Australia. A combination hepatitis A and typhoid injectable vaccine is also available. All formulations are equally effective.

Vaccination does not offer full protection from infection, and travellers should be advised to exercise care in selecting food and drinks.

No vaccine is available against paratyphoid fever.

The community should be educated about personal hygiene, especially thorough handwashing after toilet use and before food preparation.

Control of case

Hospitalisation is usually required for acute infections.

Almost all typhoid and paratyphoid fevers (enteric fevers) are acquired outside Australia, with widely variable and changing rates of antimicrobial resistance globally. Reduced susceptibility to fluoroquinolones is common in infections acquired on the Indian subcontinent and in South-East Asia.

Unlike non-typhi salmonella, initial therapy is always recommended for typhoid and paratyphoid fevers. Additionally, re-treatment is generally recommended (and successful) if the organism persists on faecal screening following initial treatment.

Consult Therapeutic guidelines: antibiotic for guidance on appropriate treatment. The guidelines advise initial therapy while awaiting susceptibility results.

Education should be given to the patient regarding the importance of completing the course of antibiotics, the possibility of relapse, persisting excretion, the need for good personal hygiene and precautions in food preparation.

If the case is a child in a primary school or children’s service, they must be excluded until approval to return has been given by the department.

Follow-up of all cases is conducted by the department to identify possible sources of infection and other cases, and to manage any ongoing risks.

If the case is a food handler or works in a profession that poses a high risk of transferring infection to others, such as healthcare workers or childcare workers, they should be advised to cease work until advised by the department.

The department arranges the collection and testing of faecal specimens for S. typhi or S. paratyphi to be taken over 3 consecutive weeks, commencing no sooner than 48 hours after cessation of antibiotic treatment. Food handlers and workers in high-risk professions are generally excluded from high-risk work or patient care until they have had two consecutive negative faecal specimens.

Control of contacts

Contacts should be educated about the disease to reduce the risk of transmission and to allow early identification if they develop symptoms.

The decision to screen contacts of cases is dependent on the extent of contact and the likely source of the case’s infection. Faecal screening is generally arranged for co-travellers. Co-travellers in high-risk occupations (food handlers, healthcare workers, childcare workers or hospitality workers) are excluded by the department unless alternative work duties can be arranged.

Use of typhoid vaccine for contacts is not generally recommended. Typhoid vaccination is only recommended for people with intimate exposure to a documented typhoid fever carrier, such as occurs with continued household contact.

Control of environment

A public health investigation is carried out to determine the most likely source of infection. A history of travel to an endemic area is usually found.

If there is no history of any travel, local sources of infection are investigated to identify whether there are further cases, asymptomatic carriers, or contaminated food or water.

Food industry

If a case is involved in commercial food preparation, the department will determine the appropriate management of the workplace on an individual basis.

Outbreak measures for typhoid and paratyphoid

All cases are intensively investigated, whether sporadic or part of a cluster. Further actions to reduce the risk of infection during an outbreak may include:

• selective elimination of suspected contaminated food
• ensuring pasteurisation of milk
• ensuring appropriate chlorination or boiling of drinking water before consumption
• reviewing the integrity of waste and sewerage systems.

Widespread use of typhoid vaccine is not generally recommended.

Immunisation recommendations

Typhoid vaccination is recommended for all travellers 2 years of age or over going to endemic regions, where food hygiene may be suboptimal and drinking water may not be adequately treated. Travellers include the military. Vaccination should be completed at least 2 weeks before travel.

Individuals travelling to endemic regions to visit friends and relatives are probably at considerable risk of acquiring typhoid fever, and vaccination is strongly recommended for them.

Laboratory personnel routinely working with S. typhi should also be considered for vaccination.