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TYPHOID FEVER. Typhoid fever is the result of systemic infection by Salmonella typhi , found only in man. Term enteric fever includes both typhoid & paratyphoid fevers.
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Typhoid fever is the result of systemic infection by Salmonella typhi, found only in man. Term enteric fever includes both typhoid & paratyphoid fevers. Improved sanitation, living condition, introduction of antibiotics have drastically reduced the occurrence of typhoid.
Agent factors: Agent: * S. typhi is the major cause. * S. para A & S. para B infrequent cause. * S. typhi has 3 major antigens – O, H & Vi and number of phage types. * Phage typing is an epidemiological tool in tracing the source of epidemic.
Reservoir of infection: * Both cases and carriers. * Case or carrier are infectious as long as bacilli appear in stools or urine. * Persons who excrete bacilli for more than 1 year after a clinical attack are termed as chronic carriers. Organism persist in gall bladder / biliary tract. Organism are discharged either continuously / intermittently for several years. TYPHOID MARY * Faecal carrier more frequent than urinary carrier.
Source of infection: * Faeces & urine of case or carrier (primary) * Contaminated water, food, fingers & flies (secondary) Host Factors: Age: Any age, mostly 5 – 19 years. Sex: More cases are males, carrier rate > in females.
Immunity: * All age susceptible * Antibody to somatic antigen (O) is higher in diseasedpatients. * Antibody toflagellerantigen (H) is higher in immunizedpersons. * 2nd attack may occur after natural typhoid Environmental and social factors: * Through the year. The peak in July – September : coincides with the rainy season and ↑ in fly population.
* Outside human body, bacilli found in water, ice, food, milk and soil. * Bacilli may multiply in food (bad conductor of heat) & milk. * Social factors as pollution of drinking water, open air defecation & urination, low standards of food & personal hygiene & health ignorance. Thus typhoid fever is regarded as an index of general sanitation in any country.
Incubation Period and Period of Communicability : * Incubation period is usually 10 - 14 days. For paratyphoid it is 4 to 5 days. * When the disease is water -borne, the incubation period tends to be longer.
Mode of Transmission : * Faecal-oral or urine-oral route. * Direct transmission: From an actual case / carrier through contamination of hands, while handling patients or their excreta. * Indirect transmission: Medium of contaminated water, food, milk and vegetables or through flies. * In explosive outbreaks: water, milk or milk products adulterated by contaminated water or handling by carriers.
Clinical features * High grade remittent fever (step ladder) with headache and malaise. Non - productive cough and constipation may be present. Diarrhoea (pea soup) uncommon and vomiting mild. * By 2nd week, in absence of treatment, patient toxic and apathetic, high fever with abdominal distension. Relative bradycardia, leucopenia, abdominal tenderness and hepato–splenomegaly. Ill defined rose - spots, hardly visible in dark skinned person (may be). * Complications: Confusion, delirium, intestinal perforation, myocarditis and death. * Up to 20% of cases relapse after treatment and initial recovery. CFR 1 to 4%.
Diagnosis * Blood culture in 1st week of illness: most common diagnostic test. Organism can also be isolated from urine and stool in 2nd & 3rd week. Bone marrow cultures frequently positive (90% of cases) and more likely to yield s. typhi than any other culture. * Felix-Widal test measures antibody response to ‘O’ and ‘H’ antigens, is not definitive & only suggests the diagnosis. A rising titer is more suggestive than a single raised titer of Widal test. * Dipstick test: Detection of specific IgM antibody.
Multidrug resistant strains of S. typhi:Chloramphenicol + Cotrimoxazole+ Ampicillin • Cases should be isolated till 3 bacteriologicallynegative stools & urine reports are obtained on 3 separate days.
Prevention & Control (a) Provision of protected and chlorinated water supply (b) Pasteurization or boiling of milk (c) Proper sanitary disposal of night soil (d) Strict anti - fly measures (e) Protection and cleanliness of fruits and vegetables (f) High standard of food handlers’ hygiene (g) Personal hygiene and avoidance of unhygienic food habits
Immunization – Recommended in: (i) Those living in endemic areas (ii) Household contacts (iii) Group at risk like school children, hospital staff (iv) Travellers going to endemic areas (v) Those attending melas
Vaccines – Not 100% effective Heat killed, phenol preserved whole cell S. typhi : Parenteral vaccines; not recommended by WHO. Vi capsular polysaccharide vaccine : * Individuals older than 2 years * 0.5 ml single subcutaneous or intramuscular dose * Effective for 3 years; booster every 3 years * Vaccine can be given simultaneously with other vaccines relevant for international travellers such as yellow fever and hepatitis A * Efficacy 70%
(c) Live Oral Vaccine (Ty21a vaccine): * Available in enteric – coated or liquid formulation (children), is approved for ≥ 5 years. * Three doses – 1, 3 and 5th day. * Antimicrobials should be avoided for 7 days before or after vaccination. * Booster dose every 3 years. * In endemic areas and travellers should be revaccinated annually. * Not recommended for immunodeficient, since live.
