Typhoid

Introduction

Typhoid fever is an acute, systemic infection presenting as fever with abdominal symptoms, caused by Salmonella typhi and paratyphi. Before the 19th century, typhus and typhoid fever were considered to be the same. Enteric fever is an alternative name for typhoid. Salmonella typhi and paratyphi colonise only humans. The organisms are acquired via ingestion of food or water contaminated with human excreta from infected persons. Direct person-to-person transmission is rare. Typhoid is a global health problem. It is seen in children older than the age of one. Outbreaks of typhoid in developing countries result in high mortality. Recently, the development of antibiotic resistant organisms is causing much concern.





Cause and Pathogenesis

Salmonella are non-encapsulated, rod-shaped organisms that are motile by means of flagellae. They express several antigens, including 'H' and 'O'. These bacteria, after ingestion through contaminated food, move into the small bowel where they interact with the intestinal wall. After they enter the intestinal wall, they survive in macrophages, which are white blood cells that swallow the typhoid bacilli. They are then disseminated to several organs through the bloodstream. There is a secondary phase where the typhoid bacilli enter the blood stream to cause the clinical symptoms of typhoid. They are also excreted in the urine and faeces.





Symptoms and Signs

The incubation period for the disease varies from five to twenty-one days depending on the number of bacteria ingested. Fever is a classical sign. Only 20 to 40 percent of patients will have abdominal pain at presentation. A few patients develop diarrhoea also. Non-specific symptoms such as chills, sweating, headache, loss of appetite, weakness, sore throat and muscle pains are often present. Psychosis and confusion occur in 5 to 10 percent of patients. Coma is a rare complication. Physical examination of the patient reveals an acutely ill patient. A slow pulse rate disproportional to the degree of fever (Relative Bradycardia) may be noted. Thirty percent of patients may have rose spots on the trunk. On examination, abdominal tenderness with an enlarged liver and spleen may be observed.

Many of the complications of untreated typhoid fever occur in the late stages of the disease, in the third or fourth week of infection. These include intestinal bleeding or perforation, inflammation of testes, abscess in the liver or spleen.

Investigations and Diagnosis


Laboratory findings of typhoid include anaemia and frequent leucopenia. Elevated liver function tests and muscle enzymes are common. The definitive diagnosis of typhoid requires isolation of Salmonella typhi or paratyphi by culturing blood, urine, stool or bone marrow. Widal test is not sensitive, specific or reliable for clinical use.





Treatment and Prognosis

A number of antibiotics are useful in the treatment of typhoid fever including quinolones, chloramphenicol, co-trimoxazole and beta-lactams. Chloramphenicol given orally was the drug of choice. With the development of resistance to chloramphenicol and subsequently to other drugs, quinolones are currently the treatment of choice. Unfortunately, quinolones cannot be routinely used in children or pregnant women. Third generation cephalosporins such as ceftriaxone are often used. Without antibiotic therapy, fever and most symptoms resolve by the fourth week of infection in 90 percent of patients. However, weakness, weight loss and debility may persist for months. After appropriate treatment, fever usually resolves in three to five days. One to four percent of individuals become chronic carriers and excrete Salmonella in stool and urine for up to a year. Prolonged administration of antibiotics is required to eradicate the carrier state.

Prevention


Typhoid can be prevented by vaccination. Protective efficacy is 70 to 90 percent. The vaccine is available either as injections or as an oral capsule. The course involves three capsules every other day or two injections one month apart. The protection lasts for at least three years. The vaccines are safe and have minimal complications.


Source

Dr. V.Ramasubramaniam MBBS, MD, MRCP.



Dr.V.Ramasubramaniam is an Assistant Professor of Medicine and heads the Division of Infectious Diseases at the Sri Ramachandra Medical College and Research Institute

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