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Enteric Fevers
IDENTIFICATION
This group includes typhoid and paratyphoid A, B and c .
Is a life-threatening illness caused by the bacterium Salmonella Typhi.
Typhoid fever is still common in the developing world, where it affects
about 21.5 million persons each year.
Typhoid is a continuous fever lasting 3 to 4 weeks, usually with headache,
bronchitis and gastrointestinal symptoms .
Onset is slow. In a classical case, the fever rises daily in a step ladder
pattern during the first week, remains continuously high during the second
and third weeks and comes down gradually by the fourth week.
The patient becomes much more ill, appearing exhausted and often
prostrated. In early part of the disease, there may be marked constipation
or diarrhea, along with marked abdominal distention.
During the early part, physical signs are few. Later, splenomegaly,
abdominal distention, tenderness, relative bradycardia and occasionally
meningismus appear.
The rash (rose spots), is a pink papule 2-3 mm in diameter that fades on
pressure is found principally on the trunk which commonly appears during
the 2nd week of disease and disappears by 3 - 4 days.
Death may occur in the third week due to perforation or hemorrhage from
ulcers in the intestine.
High fever, bronchopneumonia or heart failure may also lead to death.
This classical presentation is seen only in a minority of patients.
Convalescence is prolonged. Relapse may occur after a week or 10 days of
afebrile period, lasting for 10 to 15 days.
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History and Prevalence
o Enteric fevers occur all over the world but are more common in tropical
and subtropical countries .
o Typhoid is found in endemic form in all big towns and even
o Large villages.
o Incidence rises in summer. Epidemics may occur when water and milk
supplies are contaminated.
Causative
Agent
1. Typhoid is caused by Salmonella typhi. It is readily killed
2. On heating to 60°C for 15 minutes or on boiling.
3. It can survive in ice for considerable time and for some days
4. In fresh or salt water, withstand drying, dust and dry excreta or
soiled clothes also play a part in the spread.
5. It survives very long in oysters and shellfish and can multiply freely in milk
and butter without changing their taste or appearance. It can survive in
cheese and lives in sewage or sewage contaminated water for sufficient
time
o Infection with typhoid or paratyphoid fever results in a low-grade
septicemia.
o Although blood culture is the mainstay of diagnosis in typhoid fever, a
single culture is positive in only approximately 50% of cases. Multiple
cultures increase the sensitivity and may be required to make the
diagnosis.
o Bone marrow culture increases the diagnostic yield to approximately 80%
of cases.
o Stool culture is not usually positive during the earliest phase of the
disease.
o The Widal test is unreliable but is widely used in developing countries
because of its low cost. It is a serologic assay for IgM and IgG to the O and
H antigens of Salmonella Typhi,
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o False positives can be encountered because S. typhi and S. paratyphi A
share the antigenic structure not only with other salmonellae but also with
some non-salmonella enteric organisms.
o Antibiotics and other febrile diseases may alter the pattern of Widal
antibodies. Because of these limitations, Widal’s test cannot be used
reliably for diagnosis of enteric fever.
o Because there is no definitive serologic test for typhoid or paratyphoid
fever, the initial diagnosis often has to be made clinically. The combination
of a history of risk for infection and a gradual onset of fever that increases
in severity over several days should raise suspicion of typhoid or
paratyphoid fever.
A person should be declared non infective only
when three weekly stool cultures are negative.
Source of Infection:-
Man harboring the infection, either as a clinical or subclinical case or as
carrier. Stools and urine of infected persons contain a large number of
typhoid bacilli.
Period of Infectivity: -
The patient becomes infective after a
week or 10 days and remains so for a week or two after the fever comes
down .
Carriers are infective for varying period and are of three types:
1. Convalescent Carriers: Usually the bacilli are passed during
convalescence for 1 to 2 weeks after the temperature comes down.
This period may be longer in some cases
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2. .Temporary carriers: They are fecal or urinary carriers who pass
bacilli for 6 to 12 weeks. About 10 % of untreated cases belong to
this category.
3. Permanent carriers: When gallbladder or kidney are involved, bacilli
are passed for a long time with periods of remission in between, 2%
cases develop into such permanent carriers. Such persons should not
handle milk, food or water.
Female carriers are three times more common than male
carriers .
Modes of Spread:-
Salmonella Typhi lives only in humans. Persons with typhoid fever
carry the bacteria in their bloodstream and intestinal tract. Once
Salmonella Typhi bacteria are eaten or drunk, they multiply and
spread into the bloodstream. The body reacts with fever and other
signs and symptoms.
Carriers infect food, water, milk, ice cream and other articles of food
while handling.
Water or milk-borne epidemics breakout when sewage finds its way
into a drinking water channel or dairy water supply.
Flies, fomites, dust and fingers also play some role in spread.
Vegetables from sewage farms, especially if eaten raw.
Shellfish and oysters infected by sewage entering the sea or near a
beach.
Utensils washed in a polluted well, tank, or river.
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Susceptibility and Resistance:-
There is a general susceptibility to typhoid and no age or sex is immune.
Persons with achlorhydria are more susceptible .
Clinical disease, subclinical infection and active immunization provide
some resistance to subsequent infection but this is only relative and does
not provide protection when a large number of organisms are ingested.
The attack rate usually declines with increasing age. Males suffer more
than females but fatality is higher in the latter.
Overall mortality without treatment is 10-25%. The carrier stage is more
common in women. Some families are more prone than others.
INCUBATION PERIOD:-
10 to 14 days; varies from 4 to 21 days
PREVENTION AND CONTROL:-
Food & Water Precautions(Safe food and water precautions and frequent
hand washing are important in preventing typhoid and paratyphoid fever)
IMMUNIZATION
Vaccines available for typhoid fever include the following.
Inactivated whole cell vaccine: It is not recommended for use by the WHO
or the CDC.
Live oral Ty21a vaccine: The vaccine has efficacy being 50% at 3 years. This
is an orally administered, live attenuated Ty21 strain of Salmonella typhi, is
available in two formulations
a liquid suspension or as enteric coated capsules. Three doses of Ty21a
capsules/ liquid formulation are administered on alternate days .
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It is also recommended that this series should be repeated once in every 3
years as a booster dose.
Injectable VI polysaccharide vaccine: The vaccine has efficacy being 55 %
at 3 years. It is a subunit vaccine composed of purified Vi capsular
polysaccharide
The Vi vaccine is given as a single subcutaneous or intramuscular dose of
0.5 ml, and a booster is recommended once in every 3 years
Paratyphoid Fevers: These are usually milder than typhoid and are
indistinguishable from it. The onset is abrupt with continuous fever lasting
1 to 2 weeks .
The causative agents are Salmonella paratyphi A, B or C. Of these,
paratyphoid B is the most common .
A is less common and C is rare. Paratyphoid usually occurs in those places
where typhoid is controlled. Foods such as milk, custard and icecream are
the common vehicles .
Source of infection is man
Prevention and control measure similar. Chloramphenicol and antityphoid
drugs provide effective treatment.
Done by: #MOHDZ Dr.Zahraa
community medicine