TYPHOID FEVER

TYPHOID FEVER 

Typhoid fever is also called enteric fever. It is an acute infectious illness associated with fever that is most often caused by the Salmonella typhi bacteria. It can also be caused by Salmonella paratyphi, a related bacterium that usually leads to a less severe illness. The bacteria are deposited through fecal contamination in water or food by a human carrier and are then spread to other people in the area. Typhoid fever is rare in industrial countries but continues to be a significant public health issue in developing countries. 

Pathophysiology 

All the 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 proprietor. 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. 

S typhi has a VI capsular antigen that masks PAMPs, avoiding neutrophil-based inflammation, while the most common paratyphi serova, 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. 

Epidemiology 

Typhoid fever occursprimarily in developing nations whose sanitary conditions are poor. Typhoid fever is endemic in Asia, Africa, Latin America, the Caribbean, and Oceania, but 80% of cases come from Bangladesh, China, India, Indonesia, Laos, Nepal, Pakistan, or Vietnam. Within those countries, typhoid fever is most common in underdeveloped areas. Typhoid fever infects roughly 21.6 million people (incidence of 3.6 per 1,000 population) and kills an estimated 200,000 people every year. In the United States, most cases of typhoid fever arise in international travelers. The average yearly incidence of typhoid fever per million travelers from 1999-2006 by country or region of departure was as follows: 

• Canada - 0

• Western hemisphere outside Canada / United States - 1.3

• Africa - 7.6

• Asia - 10.5

• India - 89 (122 in 2006)

• Total (for all countries except Canada/United States) - 2.2

Symptoms and Complications

• Constipation,

• Cough,

• Headache,

• Loss of appetite,

• Stomach pains,

• Sore throat.

Rarer symptoms include: 

• Bleeding from the rectum,

• Delirium,

• Diarrhoea.

Treatment 

Typhoid fever is treated with antibiotics that kill the Salmonella bacteria. Prior to the use of antibiotics, the fatality rate was 20%. Death occurred from overwhelming infection, pneumonia, intestinal bleeding, or intestinal perforation. With antibiotics and supportive care, mortality has been reduced 

to 1%-2%. With appropriate antibiotic therapy, there is usually improvement within one to two days and recovery within seven to 10 days. Several antibiotics are effective for the treatment of typhoid fever. 

1. Chloramphenicol was the original drug of choice for many years. Because of rare serious side effects, chloramphenicol has been replaced by other effective antibiotics. 

2. Fluoroquinolones like Ciprofloxacin, Gatifloxacin, and Ofloxacin are the most frequently used drugs for nonpregnant patients.

3. Ceftriaxone an intramuscular injection medication is an for pregnant patients. 

Prevention 

• Wash hands thoroughly with soap and water after going to the toilet and before eating.

• Boil or disinfect all water before drinking it – use disinfectant tablets or liquid available in pharmacies or drink commercially bottled (preferably carbonated) beverages. Peel all fruit and vegetable skins before eating. 

• Watch out for ice cubes, ice cream, and unpasteurized milk, which can easily be contaminated.

• Cook all food thoroughly and eat it while it is hot.

• Be aware of the "danger foods” shellfish, salads, and raw fruit and vegetables.

• Do not eat food or drink beverages from street vendors.