Typhoid fever

The disease and its effect
Typhoid fever is a waterborne disease. Infection caused by Salmonella enterica serotype Typhi is still an important medical and public health problem in many developing countries. It is estimated that 21 million cases attract the disease each year and it causes more than 0.2 million deaths. In recent years morbidity and mortality has increased, partly due to the emergence and spread of strains that are resistant to the commonly used antibiotics. Multi-drug resistance (MDR) typhoid is very common.

Transmission
Typhoid fever is a waterborne disease that is transmitted through
• the faecal-oral route by
• the consumption of contaminated water and food stuff.

Vaccines for typhoid are available but their use is not widely promoted in endemic countries. Chronic carriers carrying the pathogen in the gallbladder and secreting the pathogen with their faeces are an important factor in the spread and the continued maintenance of the disease in a population.

Prevention
Infection may be prevented by
• the provision of clean water supplies
• proper cooking of drinking water and food stuff

Diagnosis
To make an accurate diagnosis the clinical diagnosis should be confirmed by laboratory testing. Blood culture provides direct evidence of the infection but is not widely available and its sensitivity varies with the duration of illness and is influenced by the use of antibiotics. The diagnostic value of the classical serological test, the Widal test, is limited.

Point-of-care test
To improve the diagnosis of typhoid fever we have developed a user and patient friendly point-of-care test which may be used at the bedside. This simple and rapid lateral flow assay may be performed on a drop of blood collected by finger prick.

Treatment after proper diagnosis
Patients should be treated with antibiotics after a proper diagnosis has been made.

Pathotypes
Typhoid fever is endemic in most of Indonesia, but MDR typhoid is still rare which contrasts with the situation in the surrounding countries. The genome of S. Typhi is highly conserved and few mutations have been detected. Systematic investigation of the genome of isolates from different countries has indicated that S. Typhi strains circulating in Indonesia belong to a separate branch on the genomic tree. Some of these strains are unique and harbour a flagellin gene with a large deletion in the central portion of the gene or carry an extra chromosomal heterologous flagellin gene.

The lifecycle of S. Typhi is complex and the flagellum could have an important function not only in motility but also in passing the gastro-epithelial lining when invading the human body or in cell-entry when hiding inside cells and evading the immune system. Could S. Typhi strains from Indonesia belong to a distinct pathotype with unique pathogenic properties?