(Enteric fever, Typhus abdominalis)

Identification• A systemic bacterial disease with insidious onset of sustained

fever, marked headache, malaise, anorexia, relative bradycardia, splenomegaly, nonproductive cough in the early stage of the illness, rose spots on the trunk in 25% of white-skinned patients and constipation more often than diarrhea in adults.

• The clinical picture varies from mild illness with low-grade fever to severe clinical disease with abdominal discomfort and multiple complications.

• Factors such as strain virulence, quantity of inoculum ingested, duration of illness before adequate treatment, age and previous exposure to vaccination influence severity.

• Inapparent or mild illnesses occur, especially in endemic areas; 60%–90% of patients with typhoid fever do not receive medical attention or are treated as outpatients.

• Mild cases show no systemic involvement but severe forms associated with high case-fatality rates.

• The case-fatality rate of 10%–20% observed in the pre antibiotic era can fall below 1% with prompt antibiotherapy,

depending on the antimicrobials used.

• 15%–20% of patients may experience relapses (generally milder than the initial clinical illness).

• The causal organisms can be isolated from blood early in the disease and from urine and feces after the first week.

• Blood culture is the diagnostic mainstay for typhoid fever, but bone marrow culture provides the best bacteriological confirmation even in patients who have already received antimicrobials.

• Because of limited sensitivity and specificity, serological tests based on agglutinating antibodies (Widal) are generally of little diagnostic value.

• New rapid diagnostic tests based upon the detection of specific antibodies appear very promising; they must be evaluated further with regard to sensitivity and specificity.

IDL Tubex detects IgM09 antibodies with in few minutes

Typhidot test that detects presence of IgM and IgG in one hour (sensitivity>95%, Specificity 75%)

Typhidot-M, that detects IgM only (sensitivity 90% and specificity 93%)

Typhidot rapid (sensitivity 85% and Specificity 99%) is a rapid 15 minute immunochromatographic test to detect IgM.

Infectious agents

• In the recently proposed nomenclature for Salmonella the agent formerly known as S. typhi is called S. enterica subsp. enterica serovar Typhi (commonly S. Typhi).

• For paratyphoid fever, mainly S. Paratyphi A and Paratyphi B.

Occurrence• Worldwide; the annual estimated incidence of typhoid fever

is about 17 million cases with approximately 600 000 deaths.

• Strains resistant to chloramphenicol and other recommended antimicrobials have become prevalent in several areas of the world.

• Most isolates carry an R factor plasmid encoding resistance to those multiple antimicrobial agents that were previously the mainstay of oral treatment including chloramphenicol, amoxicillin and trimethoprim/sulfamethoxazole.

Reservoir• Humans for both typhoid and paratyphoid.

• Family contacts may be transient or permanent carriers. A carrier state may follow acute illness or mild or even subclinical infections.

• In most parts of the world, short-term fecal carriers are more common than urinary carriers.

• The chronic carrier state is most common (2%–5%) among persons infected during middle age, especially women.

• carriers frequently have biliary tract abnormalities including gallstones, with S. Typhi located in the gallbladder.

Mode of transmission• Ingestion of food and water contaminated by feces and urine

of patients and carriers.

• Important vehicles in some countries include raw fruit, vegetables fertilized by night soil and eaten raw, contaminated milk/milk products (usually through hands of carriers) and missed cases.

• Epidemiological data suggest that, while waterborne transmission of S. Typhi usually involves small inocula, foodborne transmission is associated with large inocula and high attack rates over short periods.

Incubation period

• Depends on inoculum size and on host factors; from 3 days to over 60 days—usual range 8–14 days.

• The incubation period for paratyphoid is 1–10 days

Period of communicability

• As long as bacilli appear in excreta, usually from the first week throughout convalescence.

• About 10% of untreated typhoid fever patients discharge bacilli for 3 months after onset of symptoms; 2%–5% become permanent carriers.

• Fewer persons infected with paratyphoid organisms may become permanent gallbladder carriers.

Susceptibility

• Susceptibility is general and is increased in individuals with gastric achlorhydria and possibly in those who are HIV-positive.

• Relative specific immunity follows recovery from clinical disease, inapparent infection and active immunization.

• In endemic areas, typhoid fever is most common in preschool children and children 5–19.

Methods of control

• Preventive measures:

1) Educate the public regarding the importance of handwashing. particularly for food handlers and attendants involved in the care of patients and children.

2) Dispose of human feces safely and maintain fly-proof latrines. Under field conditions,dispose of feces by burial at a site distant and downstream from the source of drinking-water.

3) Protect, purify and chlorinate public water supplies, and avoid possible backflow connections between water and sewer systems.

4) Control flies by screening and use of insecticidal baits and frequent garbage collection.

5) Use scrupulous cleanliness in food preparation and handling; refrigerate as appropriate. Pay particular attention to the storage of salads and other foods served cold.

6) Pasteurize or boil all milk and dairy products. 7) Enforce suitable quality-control procedures in industries that

prepare food and drink for human consumption.

8) boil all milk and water used for infant feeding.

9) Administration of 750 mg of ciprofloxacine or 400 mg of norfloxacine twice daily for 28 days provides successful treatment of carriers in 80% of cases. Follow-up cultures are

necessary to confirm cure.

10) Immunization for typhoid fever is not routinely recommended in non-endemic areas. WHO recommends vaccination for people travelling to endemic high risk areas and school-age children living in endemic areas where typhoid fever control is a priority.

Epidemic measures1) Search intensively for the case/carrier who is the source of infection and for the vehicle (water or food) through which infection was transmitted.

2) Selectively eliminate suspected contaminated food on epidemiological evidence, until safety is ensured.

3) Chlorinate suspected water supplies adequately under competent supervision or avoid use.

4) Use of vaccine should be considered before or during an Outbreak.

International measures

1) For typhoid fever: Immunization is advised for international travelers to endemic areas, Immunization is not a legal requirement for entry into any country.

2) WHO Collaborating Centers.