Typhoid fever is an infection of the small intestine that is caused by salmonella typhi following ingestion of contaminated food (particularly eggs and poultry products).
Following ingestion the organisms colonize the small intestine and perforate Peyer's patches (which are lymphoid aggregates present in the wall of the small intestine. The organisms are then carried through the lymphatics, enter the blood stream (phase I of the disease) and are thereby transported to the reticuloendothelial system (the lymph system of the body which includes the spleen and lymph nodes) in phase II of the disease (see below).
Incubation period: 10-14 days.
Symptoms classically pass through 4 stages during a period of 4 weeks (1 week per stage).
1. 1st week: This phase is characterized by fever which is remittent and gradually rises in a step ladder fashion. Headache, constipation (as diarrhea occurs only late in the course of the disease) and the patient looks and feels toxic with relative bradycardia. During this phase the diagnosis can only be made by blood culture - as the organisms pass to the blood stream.
2. 2nd week: This phase is characterized by the appearance of a swelling of the spleen and liver as well as the lymph nodes (as the organism reaches the reticuloendothelial system) as well as rose spots on the trunk & abdomen. There may be right iliac fossa tenderness. The diagnosis is made by urine & stool culture during this period.
3. The week of complications: This is when the organisms invade the various tissues of the body leading to some rather severe complications which include:
- Lobar pneumonia
- Hemolytic anemia
- Peripheral neuropathy
- Aseptic arthritis and Reiter's syndrome
- Acute cholecystitis
- Urinary tract infection
- Intestinal perforation and hemorrhage
4. the week of convalescence.
The blood counts reveal neutropenia.
Blood cultures are helpful in the first phase (fever) and urine and stool cultures in the second phase (lymphadeopathy).
Widal test measures serum agglutinins against the "O" and "H" antigens. A four-fold increase in titre in subsequent blood samples is suggestive of salmonella infection
Antibiotics known to be effective against typhoid fever are chloromphenicol and ciprofloxacine.