Gladys Xavier, MSc, RGN, DipN, is deputy director of public health, Redbridge Primary Care Trust.
Typhoid and paratyphoid fevers - collectively known as enteric fevers - are bacterial infections. Typhoid is caused by the bacterium Salmonella typhi, while paratyphoid fever, which is usually a milder infection, is caused by Salmonella enteritidis paratyphi A, B and C. Unlike other salmonella species, both S. typhi and S. paratyphi colonise only humans and can be acquired from either patients or carriers (Engels et al, 1998).
The diseases mainly affect those living in poorer regions of the world where sanitation and clean water are lacking. The World Health Organization (2000) estimates that typhoid fever affects 17 million people a year, causing approximately 600,000 deaths. Typhoid fever has a typical case fatality rate of 10%, but this can be reduced to as little as 1% with appropriate antimicrobial therapy. Paratyphoid fever is a similar illness but tends to be milder, with a lower case fatality rate.
Primary healthcare professionals play a key role in preventing enteric fevers by offering typhoid vaccination and hygiene advice to travellers, and managing people who become infected.
Travel trends among UK residents
Travel history has been available for only around two-thirds of the people who contracted typhoid and paratyphoid since enhanced surveillance ceased in 1994. Of those whose recent travel history was stated, the Indian subcontinent was the most frequently reported region of travel, with North Africa and the Middle East also being cited in a significant number of reports on paratyphoid fever (HPA, 2005a).
Typhoid and paratyphoid in the UK
Incidences of typhoid and paratyphoid fevers in England and Wales are usually associated with foreign travel, although indigenous transmission may occur after contact with a carrier or a patient, especially in family settings (Engels et al, 1998). Information on their incidence in the UK comes from laboratory reports and statutory notifications of infectious diseases.
Both notifications and laboratory reports declined between 1994 and 2002, but increased in 2003. There were 203 laboratory reports of S. typhi in England and Wales in 2003, which was the highest number reported since 1996, and three reported in Northern Ireland (HPA, 2005a; 2005b).
The HPA advises that notifications of typhoid fever should be interpreted with caution, as they are usually based on clinical suspicion only. Laboratory reports are the most accurate indication of trends.
Between 1990 and 1995 an average of around 175 cases of typhoid fever were reported from people who travel abroad each year; this represented about 75% of all cases reported in England.
Since 1995, there have been fewer reports in which foreign travel was known. There has, however, been an increase in the number of reports in which information about travel history is not stated. The reports of a decrease in travel-associated typhoid may therefore be inaccurate (HPA, 2003).
The main reservoir for S. typhi is the human intestinal tract, although people with typhoid fever also carry the bacteria in their bloodstream. In addition, a small number of carriers recover from typhoid fever but continue to carry the bacteria. Both ill people and carriers shed S. typhi in their faeces (Chinn, 2000). Transmission therefore occurs following the ingestion of food or water that has been heavily contaminated by S. typhi (typhoid) or S. paratyphi (paratyphoid).
S. typhi can be passed in the faeces of patients who are acutely ill with typhoid fever or are chronic carriers. The bacteria may then enter the food chain and water supply if personal and food hygiene and/or sanitation measures are poor. Direct faecal-oral transmission may occur if vegetables fertilised with human waste are eaten raw, while shellfish that have been harvested from sewage-contaminated beds, and milk products contaminated by workers’ hands all may result in typhoid infection (Connor and Schwarz, 2005).
In countries where the enteric fevers are endemic, risk factors for contracting them include eating or drinking contaminated food or water, inadequate sanitation and living conditions, poor personal hygiene and close contact with those infected with S. typhi or S. paratyphi (Ericsson, 2003).
The risk of contracting typhoid fever is highest for travellers to the Indian sub-continent (India, Pakistan and Bangladesh), South East Asia and parts of Latin America and Africa. In these region, the attack rate for travellers has been estimated at 10 per 100,000. The risk of typhoid and paratyphoid fevers in resource-rich countries such as Europe, North America and Australia is less than one case per million visits (Lee and Leese, 2001).
Signs and symptoms
Typhoid fever is a systemic disease that varies in severity, but nearly all patients experience fever and headache. Some young children will experience a mild illness that is treatable with antibiotics, but they may also suffer from severe disease.
The incubation period for typhoid fever is usually 7-14 days, but this can be shorter or longer depending on how many bacteria are ingested. Symptoms include:
- Low-grade fever (which typically becomes higher as the illness progresses)
Patients may also experience abdominal discomfort and constipation, and diarrhoea may occur early in the course of the illness. Moderate enlargement of the liver and/or spleen occurs in about of 50% of patients, while in some, rose spots appear on their trunk, although these may be difficult to see in dark-skinned patients (Chinn, 2000).
Paratyphoid fever is clinically similar, but the disease is usually milder and of shorter duration. It often manifests as acute gastroenteritis (Steffan et al, 2003).
Complications occur in 10-15% of all patients and are more likely in those who are untreated and present late in the course of the illness. They include:
- Intestinal haemorrhage and perforation;
- Toxic myocarditis;
- Typhoid encephalopathy and meningitis (usually in young children).
The fatality rate is usually less than 1% with prompt antibiotic therapy, but may be as high as 20% in untreated patients.
All patients with typhoid and paratyphoid fevers excrete the organisms at some stage during their illness. About 10% of patients with typhoid fever excrete S. typhi for at least three months following the acute illness, and 2-5% become long-term carriers (more than one year).
The likelihood of becoming a chronic carrier increases with age, especially in females and those with biliary tract abnormality. Chronic carriers require prolonged courses of antibiotics to clear the organism (HPA, 2005a; 2005b).
Prevention and treatment
There are two methods of avoiding typhoid infection:
- Avoiding the consumption of foods and drinks that are at risk of contamination;
There is currently no vaccine available against paratyphoid fever, so prevention involves taking hygiene measures and avoiding risky foods (Steinberg et al, 2004).
Typhoid fever can be successfully treated with antibiotic therapy and general medical support. Strains of S. typhi have become increasingly resistant to antibiotics, particularly in South East Asia (Threlfall and Ward, 2001). This has implications for the treatment of typhoid fever, as traditional antibiotic therapy (chloramphenicol, co-trimoxazole and amoxycillin) may not be effective. Treatment is usually with quinolones; third-generation cephalosporins or azithromycin may need to be given in resistant cases.
Relapse will occur in less than 10% of patients treated with antibiotics and is usually milder and of shorter duration than the original illness. Those treated with quinolones are less likely to suffer relapse or to go on to become chronic carriers (Threlfall and Ward, 2001). Following natural infection with typhoid, an immune response develops that may partially protect patients against reinfection and severity of disease (WHO, 2000).
The role of primary care professionals
Effective prevention and control of imported typhoid or paratyphoid infections require an evidence-based risk assessment approach by nurses in primary care (Xavier, 2003). Primary care professionals should make every effort to:
- Improve public understanding of the risk factors and trends of typhoid and paratyphoid infections;
- Understand the potential threat to wider public health from typhoid and paratyphoid infections;
- Monitor the effectiveness of prevention, including immunisation against typhoid fever, by checking the health status of returning travellers;
- Ensure that people who return after acquiring the infections from countries where they are endemic receive a high standard of primary and secondary care and have access to specialist advice when appropriate (Xavier, 2003).
Box 1 lists the prevention messages people should be given before travelling to countries where typhoid fever is endemic.
The vaccines available in the UK for typhoid fever are composed of purified Vi capsular polysaccharide from S. typhi. A four-fold rise in antibody against Vi antigen has been detected seven days following primary immunisation.
Maximum antibody response is achieved one month after vaccination, and persists for about three years (Klugman et al, 1996).
Protective antibody titres to Vi antigen fall over time, and re-vaccination is necessary if continuing protection is required. Additional doses of Vi vaccine do not boost serum antibody levels; re-vaccination returns antibody levels to those achieved after the primary immunisation (Keitel et al, 1994).
Primary care professionals need to be aware that vaccination may offer less protection if a large number of infective organisms are ingested.
Because of this limited protection, the importance of scrupulous attention to personal, food and water hygiene must still be emphasised to those travelling to areas where typhoid fever is endemic (Klugman et al, 1996).
People may feel well on returning to the UK after travelling to areas where the enteric fevers are endemic, but may fall ill some time later. This has implications for primary care professionals, who need to be alert to the possibility of imported infections in these people (DH, 2001).
Public health risks can arise from travellers returning with illness, as they may infect family members and work or school colleagues.
Managing patients, carriers, contacts and outbreaks
The local health protection unit (HPU) should be informed immediately if a patient is suspected of having typhoid fever - reporting should not wait for laboratory confirmation. Primary care professionals have an important role in identifying the source of infection and containing the disease.
Patients, carriers and their close contacts in the following groups may pose an increased risk of spreading infection and may be considered for exclusion from work or school (Working Party of the PHLS Salmonella Committee, 1995):
- Food handlers;
- Staff of healthcare facilities;
- Children under five years of age who attend nurseries or other similar groups;
- Older children or adults unable to maintain good standards of personal hygiene.
Both patients and carriers of S. typhi should be advised to be scrupulous in hand hygiene practices.
Carriers should be referred for special clinical management. Advice on exclusion from work or school must be sought from the local HPU.
Typhoid vaccine is not recommended for close contacts of either patients or carriers, or if there were an outbreak of typhoid fever in the UK (DH, 2005).
A full understanding of the enteric fevers caused by S. typhi and S. paratyphi, their impact, trends and risk factors requires partnership working between primary care professionals, microbiologists, health protection staff, those working in environmental health and in the travel industry.
The public health issues arising from an outbreak should be part of the training of professionals working in primary care.