Typhoid fever is caused by Salmonella typhi bacteria. Typhoid fever is rare in industrialized countries. However, it remains a serious health threat in the developing world, especially for children.
Typhoid fever spreads through contaminated food and water or through close contact with someone who’s infected. Signs and symptoms usually include high fever, headache, abdominal pain, and either constipation or diarrhea.
Most people with typhoid fever feel better within a few days of starting antibiotic treatment, although a small number of them may die of complications. Vaccines against typhoid fever are available, but they’re only partially effective. Vaccines usually are reserved for those who may be exposed to the disease or are traveling to areas where typhoid fever is common.
Typhoid fever is contracted by drinking or eating the bacteria in contaminated food or water. People with acute illness can contaminate the surrounding water supply through stool, which contains a high concentration of the bacteria. Contamination of the water supply can, in turn, taint the food supply. The bacteria can survive for weeks in water or dried sewage.
About 3%-5% of people become carriers of the bacteria after the acute illness. Others suffer a very mild illness that goes unrecognized. These people may become long-term carriers of the bacteria — even though they have no symptoms — and be the source of new outbreaks of typhoid fever for many years.
All pathogenic SALMONELLA species, when present in the gut are engulfed by phagocytic cells, which then pass them through the mucosa and present them to the macrophages in the lamina propria. Nontyphoidal salmonellae are phagocytized throughout the distal ileum and colon. With toll-like receptor (TLR)–5 and TLR-4/MD2/CD-14 complex, macrophages recognize pathogen-associated molecular patterns (PAMPs) such as flagella and lipopolysaccharides. Macrophages and intestinal epithelial cells then attract T cells and neutrophils with interleukin 8 (IL-8), causing inflammation and suppressing the infection.
In contrast to the nontyphoidal salmonellae, S TYPHI and paratyphi enter the host’s system primarily through the distal ileum. THEY have specialized fimbriae that adhere to the epithelium over clusters of lymphoid tissue in the ileum (Peyer patches), the main relay point for macrophages traveling from the gut into the lymphatic system. The bacteria then induce their host macrophages to attract more macrophages.
S TYPHI has a Vi capsular antigen that masks PAMPs, avoiding neutrophil-based inflammation, while the most common PARATYPHI serovar, PARATYPHI A, does not. This may explain the greater infectivity of typhi compared with most of its cousins.
Typhoidal salmonella co-opt the macrophages’ cellular machinery for their own reproduction as they are carried through the mesenteric lymph nodes to the thoracic duct and the lymphatics and then through to the reticuloendothelial tissues of the liver, spleen, bone marrow, and lymph nodes. Once there, they pause and continue to multiply until some critical density is reached. Afterward, the bacteria induce macrophage apoptosis, breaking out into the bloodstream to invade the rest of the body.
The bacteria then infect the gallbladder via either bacteremia or direct extension of infected bile. The result is that the organism re-enters the gastrointestinal tract in the bile and reinfectsPeyer patches. Bacteria that do not reinfect the host are typically shed in the stool and are then available to infect other hosts.
Signs and symptoms are likely to develop gradually — often appearing one to three weeks after exposure to the disease.
Once signs and symptoms do appear, you’re likely to experience:
- Fever that starts low and increases daily, possibly reaching as high as 104.9 F (40.5 C)
- Weakness and fatigue
- Muscle aches
- Dry cough
- Loss of appetite and weight loss
- Abdominal pain
- Diarrhea or constipation
- Extremely swollen abdomen
If you don’t receive treatment, you may:
- Become delirious
- Lie motionless and exhausted with your eyes half-closed in what’s known as the typhoid state
In addition, life-threatening complications often develop at this time.
In some people, signs and symptoms may return up to two weeks after the fever has subsided.
You should see your GP if you think you have typhoid fever, particularly if you’ve recently returned from travelling abroad.
Your GP will want to know whether you’ve travelled to parts of the world where the infection is present, or whether you’ve been in close contact with someone who’s travelled to these areas.
Parts of the world where the infection is most common include the Indian subcontinent, Africa, South East Asia and South America.
Antibiotic therapy is the only effective treatment for typhoid fever.
COMMONLY PRESCRIBED ANTIBIOTICS
- Ciprofloxacin (Cipro). In the United States, doctors often prescribe this for nonpregnant adults.
- Ceftriaxone (Rocephin). This injectable antibiotic is an alternative for people who may not be candidates for ciprofloxacin, such as children.
These drugs can cause side effects, and long-term use can lead to the development of antibiotic-resistant strains of bacteria.
PROBLEMS WITH ANTIBIOTIC RESISTANCE
In the past, the drug of choice was chloramphenicol. Doctors no longer commonly use it, however, because of side effects, a high rate of health deterioration after a period of improvement (relapse) and widespread bacterial resistance.
In fact, the existence of antibiotic-resistant bacteria is a growing problem in the treatment of typhoid fever, especially in the developing world. In recent years, S. typhi also has proved resistant to trimethoprim-sulfamethoxazole and ampicillin.
Other treatments include:
- Drinking fluids. This helps prevent the dehydration that results from a prolonged fever and diarrhea. If you’re severely dehydrated, you may need to receive fluids through a vein (intravenously).
- Surgery. If your intestines become perforated, you’ll need surgery to repair the hole.