Transcript 3-Epidemiology of typhoid

Epidemiology
of
Typhoid fever
• Typhos in Greek means ,smoke and typhus
fever got its name from smoke that was
believed to cause it. Typhoid means typhuslike and thus the name given to this disease.
• The term Typhoid was given by Louis 1829
to distinguish it from typhus fever.
• It is a disease of poor environmental
sanitation and hence occurs in parts of the
world where water supply is unsafe and
sanitation is substandard.
• In 1880s, the typhoid bacillus was first
discovered by Eberth in spleen sections and
mesenteric lymph nodes from a patient who
died from typhoid.
• Robert Koch confirmed a related finding and
succeeded in cultivating the bacterium in
1881.
• Serodiagnosis of typhoid was thus made
possible by 1896.
• Wright and his team prepared heat killed
vaccine from S.Typhi in 1896
• Disease caused by Salmonellae typhi.
Non-spore-forming. gram – ve rods, aerobic, motile
with flagella,
• Salmonella currently comprise 2000 serotypes
Two groups a) Enteric fever group
b) Food poisoning group
• The proportion of typhoid to paratyphoid A is 10:1.
• The bacilli are killed at 55ºc in one hour or
at 60ºc in 15 minutes.
• They are killed within 5 minutes by
mercuric chloride or 5% phenol.
• Boiling or chlorination of water and
pasteurization of milk destroy the bacilli
Salmonella enterica.
• In past, many deaths were due to typhoid
fever worldwide.
Now mostly
• localized to developing countries.
• People are not only become ill and die but
can become colonized by S. typhi resulting
in being carriers and spread typhoid
fever.
• An acute infection with prolonged fever due
to Salmonella typhi sometimes lead to
severe complications.
• Globally 16 million cases with 600000
deaths annually.
• Salmonella paratyphi A & B lead to milder
disease.
• Peak age 4-19 years.
Typhoid Fever
Ingest S. typhi
Bacteria invades intestinal cells and translocates to systemic organs
Multiplies to high number in liver and spleen
Spreads to bloodstream
Bacteria move to gallbladder
Shed in Bile
Bacteria persists
in gallbladder
DEATH
Bacteria shed in
feces
TYPHOID
Poorer Countries are Vulnerable
• Typhoid Fever seems to
matriculate in places
with poor sanitary
conditions.
• Places where water is
not sanitized provides
the perfect environment
for Typhoid Fever.
• Age group : Typhoid fever may occur at
any age but it is considered to be a
disease mainly of children and young
adults. In endemic areas, the highest
attack rate occurs in children aged 8-13
years. In a recent study from slums of
Delhi, it was found that contrary to popular
belief, the disease affects even children
aged 1-5 years
Gender and race : Typhoid fever cases are
more commonly seen in males than in
females. On the contrary, females have a
special predilection to become chronic
carriers.
Occupation : Certain categories of persons
handling the infective material and live
cultures of S. typhi are at increased risk of
acquiring infection.
Socio-economic factors : It is a disease of
poverty as it is often associated with
inadequate sanitation facilities and unsafe
water supplies.
• Environmental factors : Though the cases
are observed through out the year, the
peak incidence of typhoid fever is reported
during summer. This period coincides with
July - September rainy season and a
substantial increase in fly population.
• Social factors : pollution of drinking water
supplies, open air defecation, and urination,
low standards of food and personal
hygiene, and health ignorance.
Nutritional status :Malnutrition may enhance the
susceptibility to typhoid fever by altering the
intestinal flora or. other host defences.
Incubation period : Usually 10-14 days but it may
be as short as 3 days or as long as 21 days
depending upon the dose of the inoculums.
Reservoir of infection : Man is the only
known reservoir of infection - cases or
carriers
Period of communicability: A case is
infectious as long as the bacilli appear in
stool or urine.
Risky groups
• Children and young adults in endemic
areas.
• Contacts of chronic carriers.
• Microbiology technicians.
• Food handlers.
• Travelers and military personnel
Typhoid carriers
• About 1–5% of people who are infected with
S. typhi become asymptomatic chronic
carriers.
• The carrier state may follow acute or mild
illness or subclinical infection.
• The incidence of chronic carriage is higher
among women and persons with biliary tract
abnormalities.
•
• Antibiotic use and antibiotic resistance
may also affect the propensity to become
a chronic carrier.
• A chronic urinary carrier state occurs in
individuals with schistosome infection.
• Carriers who handle food without
observing proper hygiene can transmit
infection to others.
Transmission
• Typhoid is spread by the faecal-oral route.
Occasionally transmission may be direct,
but usually it occurs following the ingestion
of contaminated water or food.
• In developing countries with contaminated
water supplies and primitive sewage
disposal systems, water is the most likely
vehicle of transmission.
Epidemics originating from water
contamination are particularly explosive.
Because:
• a water source may serve a large
population.
• Water dilutes gastric acid which would
otherwise inactivate pathogenic agents.
• Water and other beverages remain in the
stomach only very briefly.
• In more developed countries, with good
sanitation, typhoid transmission is more
likely to be associated with food
contamination..
To summarize:
Modes of transmission:
• Water contaminated with fecal materials.
• Contaminated food.
• Food handlers.
Reservoir:
Only human (cases & carriers)
Communicability
• Typhoid is communicable as long as S. typhi
organisms are excreted, usually from the
first week and throughout convalescence.
• About 10% of untreated typhoid fever
patients will excrete bacteria for 3 month
after onset of symptoms.
Carriers
may be temporary or chronic.
• Temporary (convalescent or incubatory)
carriers usually excrete bacilli up to 6-8
weeks.
• Chronic carriers : By the end of one year,
3-4 per cent of cases continue to excrete
typhoid bacilli.
Prevention and control
• Basic sanitary and hygienic measures
Purifying water supplies.
Improving water delivery and sewage control.
Construction and use of latrines.
Boiling water
Supervision of foodhanders.
Vaccines
•
Three vaccines to typhoid fever:
1. Killed whole bacteria with side effects.
2. Capsular material (Vi antigen) that is safer and more
effective.
3. Live oral vaccine, attenuated S. typhi strain (Ty21a).
Oral vaccines are still being developed to distribute in
developing countries. Ty21a is also being used to
carry foreign antigens from Shigella and V.
cholerae.
Number
Time
of doses
between
necessar
doses
y
Total
time
Minimu
needed
m age
to set
for
aside for vaccinati
vaccinati
on
on
Booster
needed
every...
Vaccine
Name
How
given
Ty21a
(Vivotif
Berna,
Swiss
Serum
and
Vaccine
Institute)
------------
1
capsule
by
mouth
4
2 days
2 weeks
6 years
5 years
ViCPS
(Typhim
Vi,
Pasteur
Merieux)
Injection
1
N/A
2 weeks
2 years
2 years
• Indication of vaccination:
Travellers to endemic areas.
People in refugee camps.
Microbiologists.
• Treatment:
Antibiotics : Ciprofloxacin, pefloxacin &
cephalosporins
If you know you are traveling to an at risk location:
• Avoid Ice
• Drink Only Bottled Water
• Make sure all food is
thoughoughly cooked.
INTERNET REFERENCES
www.worldwidevaccines.com
www.health.gov
www.rush.edu/worldbook/medical
www.cdc.gov
www.nlm.nih.gov
www.who.int