Enteric fevers
Typhoid feverParatyphoid fever A, B & C
1. Identification:
A systemic bacterial disease with insidious onset of sustained fever, marked headache, anorexia, relative bradycardia, splenomegaly and rose spots on trunks in 25% of white-skinned patients in 2nd week (2-3 mm in diameter that fades on pressure, disappear in 3-4 days).
Inapparent or mild illnesses occur, especially in endemic areas in 60-90% of typhoid patients. Severe cases with complications can occur (bleeding or perforation) in 1% of cases.
In severe cases, the CFR → 10% - 20% in pre-antibiotic era, which drop below 1% with prompt antibiotic.
15%-20% of patients may experience relapses (generally milder than the initial clinical illness).
Paratyphoid fever A and B presents a similar clinical picture, but tends to be milder, and the CFR is much lower. Relapses occur in approximately3 – 4 %.
Diagnosis
Clinical picture → unexplained prolonged fever
Isolation of M.O by culture:
Blood first 7-10 days+ve
2nd – 3rd W 50% +ve
Bone marrow +ve even with A.B
Stool 1st W 50% +ve
2nd 3rd W 100% +ve
Urine 20-30 % +ve after 1st W
Serology:
a) Widal test:
Infection S. typhi → O&H → the human body
Vaccination S. paratyphi A-B Ag. will form
In vitro we add Ag → O&H Agglutination Ab
Problems of Widal test:
Antigenic sharing between Salmonella genes, false positive (FP) result.
Antigenic sharing with other M.O (FP in: malaria, typhus fevers, E. coli infections as UTI, other infections and cirrhosis).
TAB vaccination (FP).
It can be negative test in up to 30% of culture proved typhoid patients (FN).
O -Ab → Appear in 6-8 days and remain for 6-12 months.
H -Ab →Appear in 10-12 days and remain for years.
A single Widal test is generally of little diagnostic value.
A four fold raised in paired sera (1st in the acute stage and the 2nd in the convalescent stage) is diagnostic, but this is difficult to apply practically.
b) Vi Ab present in high titer in chronic carriers and can be used as a screening test for chronic carriers.
c) New serological test:
IDL Tubex test: Swedish company, rapid result (2 minutes). It detects IgM 09. Sensitivity and specificity better than Widal test.
Typhidot test: developed in Malaysia, 3 hours, EIA test, sensitivity 75%, specificity 95%, detect specific IgM & IgG.
Newer Typhidot-M test: detect specific IgM.
IgM dipstick test: developed in Netherland.
2. Infectious agents:Typhoid fever → S. Typhi Paratyphoid fever → S. Paratyphi A and B.
3. Occurrence:
Worldwide; occur in all areas where water supplies and sanitation are substandard. The annual I. of typhoid fever is about 21 million cases with approximately 200 000 deaths. Almost 80% of cases and deaths are in Asia and most of others occur in Africa and Latin America. In Nineveh 2005-2014: 30 000 cases and 70% of them affecting young age groups (15-45).
4. Reservoir:
Humans all ages - both sexes
cases & carriers
Cases: mild, missed or severe
Carriers: temporary (convalescent) or chronic carrier.
Convalescent carriers → excrete the bacilli for 6 -8 weeks, after 3 months only 4%.
After 1 year only 3% → chronic carrier (either fecal or urinary carrier). In most chronic carriers, the microorganisms persist in the gallbladder and in the biliary tract. “Typhoid Mary”: an Irish cook in New York City in early 1900s.
5. Mode of transmission:
Feco-oral route by ingestion of water and foods contaminated by feces and urine of patients and carriers.
-Raw fruits and vegetables especially when human excreta used as fertilizer.
-Sea food (shell fish, oysters).
-Contaminated milks and milk products,
-Flies may infect foods in which the organism then multiplies to infective doses.
6. Incubation period:
8 - 14 days but it may be as short as 3 days up to 60 days.
7. Period of communicability:
As long as the bacilli appear in the excreta. Usually from 1st week throughout the convalescence. (10% of untreated cases excrete bacilli for 3 months after onset of symptoms).
8. Susceptibility: Is general, and increase in person with gastric achlorhydria, and possibly in those with HIV (+ve).
Serum antibodies (O &H) are not the primary defenses against infection; S. typhi being an intracellular organism, cell-mediated immunity play a major role in combating the infection. The immunity is temporal, 2nd attacks infection may occur.
9. Method of control:
A- Preventive measures:
Educate the public
Personal hygiene particularly food handlers.
Sanitary sewage disposal.
Provide, protect, purify and chlorinate public and private water supplies.
Control flies.
Use of sanitary practices for food preparation, handling and storage especially of salads.
Pasteurization or boiling of milk and diary products.
Exclusion of typhoid carriers from handling foods until 3 consecutive negative stool cultures (and urine in areas endemic for schistosomiasis) at least 1 month apart and at least 48 hours after antimicrobial therapy has stopped.
Rx of chronic carriers → ciprofloxacin or norfloxacin twice daily for 28 days → 80% successful.
Surgery → cholecystectomy + Ampicillin therapy.
The management of carriers continues to be an unsolved problem. This is the crux of the problem, in the elimination of typhoid fever.
Immunization
Vaccination of high-risk populations is considered the most promising strategy for the control of typhoid fever. Immunization is not routinely recommended in non-endemic areas.
1- TAB vaccine:
Killed, injectable, 2 doses at one month interval. Side effect → redness, fever, nausea and headache. Booster every 3 years. Age: adults and children ≥ 2 years.
WHO recommended → TAB vaccine should be discontinued.
2- Injectable Vi vaccine:
Licensed in 1994, the vaccine is progressively introduced into school attending children vaccination programs in Asian countries. 75% protection. Age: adults and children ≥ 2 years.
3- Oral vaccine Ty 21a (Vivotif or Typhoral) → oral, live attenuated, completely devoid of pathogenicity. It colonizes the gut. Enteric-coated capsule: one capsule/dose (+ antacid), 3 doses: day 1, 3 and 5.
Protection commences 2 weeks after taking the last capsule and last for at least 3 years. Therefore, a booster every 3 years,
- Age: adults and children > 6 years
- Three years protection around 90%.
- Now > 60 countries adopted.
Indications of vaccine:
Food handlers
Workers in water, sewage plantsobligatory in Iraq
Swimming pools attendances
Visitors to endemic areas
School-age children living WHO
in endemic areas.
B- Control of patients, contacts and immediate environment:
Reporting: Class II.Isolation: Enteric precaution while ill (hospital care in acute illness). Release from supervision until 3 consecutive negative cultures of stool (and urine in patients with schistosomiasis) on 3 separate days and at least 48 hours after antimicrobial therapy has stopped and not earlier than 1 month after onset. If any of these is positive, repeat cultures at monthly interval during 12 months.
Disinfection: of feces and urine.
Quarantine: not applicable.
Immunization of contacts: is of limited value.
Investigation of contacts and source of infection: (by Vi Ag).
Specific treatment: ciprofloxacin for 2 weeks or ceftriaxone or azithromycine.
Chloramphenicol, amoxicillin, ampicillin and trimetheprine-sulfamethoxazole are equally effective.
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