Typhoid fever and paratyphoid fever

Written by Dr Charlie Easmon, specialist adviser in travel medicine

What is typhoid fever?

Typhoid fever is an infectious feverish disease with severe symptoms in the digestive system in the second phase of the illness.

Classic typhoid fever is a serious disease. It can be life-threatening, but antibiotics are an effective treatment. The disease lasts several weeks and convalescence takes some time.

The disease is transmitted from human to human via food or drinking water, and it is therefore mainly hygiene and sanitary conditions that determine its spread. It is primarily for this reason that it is no longer so commonly seen in Europe.

In the UK, of the 1735 cases reported between 1980 and 1989, it is estimated that 87 per cent were infected abroad.

What causes typhoid fever and paratyphoid fever?

Typhoid fever is caused by an infection with the bacterium Salmonella typhi, which is only found in humans and may lead to serious illness.

When the bacterium passes down to the bowel, it penetrates through the intestinal mucosa (lining) to the underlying tissue.

If the immune system is unable to stop the infection here, the bacterium will multiply and then spread to the bloodstream, after which the first signs of disease are observed in the form of fever.

The bacterium penetrates further to the bone marrow, liver and bile ducts, from which bacteria are excreted into the bowel contents.

In the second phase of the disease the bacterium penetrates the immune tissue of the small intestine, and the often violent small-bowel symptoms begin.

Paratyphoid fever is caused by Salmonella paratyphi, a similar and generally milder disease. Salmonella enteriditis and Salmonella typhimurium are other salmonella bacteria that are unfortunately quite familiar within the UK and cause food poisoning and diarrhoea. The term 'murine typhus' is used for salmonella in animals.

How is typhoid fever spread?

Salmonella typhi can only attack humans, so the infection always comes from another human, either an ill person or a healthy carrier of the bacterium. The bacterium is passed on with water and foods and can withstand both drying and refrigeration.

As it is necessary for someone to be exposed to a certain quantity of bacteria before symptoms occur, the storage of foods is also of great significance. They must be kept refrigerated and prepared correctly, as required by general hygiene, so that any bacteria present are not able to multiply significantly.

Where does typhoid fever occur?

Typhoid fever is not a tropical disease and is related to hygiene and sanitary conditions rather than the climate itself.

Typhoid fever is found in large parts of Asia, Africa, Central and South America, where it occasionally causes epidemics. The WHO estimates that there are approximately 16 million cases a year, which result in 600,000 deaths. Many of those infected get the disease in Asian countries.

What are the symptoms of the disease?

The incubation period is 10 to 20 days and depends on, among other things, how large a dose of bacteria has been taken in.

In the mild disease, the bacterium is eliminated very early in the course of the disease and there are perhaps only mild symptoms. It is possible to become a healthy carrier of infection.

There are two phases of classic typhoid fever:

1st phase: the patient's temperature rises gradually to 40ºC and the general condition becomes very poor with bouts of sweating, no appetite, coughing and headache. Constipation and skin symptoms may be the clearest symptoms. Children often vomit and have diarrhoea. The first phase lasts a week and towards the end the patient shows increasing listlessness and clouding of consciousness.

2nd phase: in the second to third weeks of the disease, symptoms of intestinal infection are manifested and the fever remains very high and the pulse becomes weak and rapid. In the third week the constipation is replaced by severe pea-soup-like diarrhoea. The faeces may also contain blood. It is not until the fourth or fifth week that the fever drops and the general condition slowly improves.

Complications

Intestinal perforation or profuse bleeding from the intestinal mucosa may occur if typhoid fever is left untreated.

Outlook

There are good prospects of cure with antibiotics and the patient can be discharged from hospital when the general condition is stable. However, good general hygiene (as always) should be maintained in the home, as bacteria may continue to be excreted for several more weeks. If the patient is a food handler then they will need to stay off work until at least two stool samples show absence of the infection.

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