TOPIC 16: Typhoid

Question 1

typhoid is caused by…

Answer 1

Salmonella enterica serotype Typhi
* Gram negative bacterium

Question 2

typhoid is also called…

Answer 2

enteric fever

Question 3

______: Number one cause of blood borne bacterial infection in south Asia

Answer 3

typhoid

Question 4

T/F: 14 million infections per year globally with 136,000 deaths due to typhoid
* 7 million in South Asia- 75,000 deaths

Answer 4

true!!

Question 5

Paratyphoid fever is caused by Salmonella enterica serotype ______
* Responsible for ~20% of all cases of enteric fever

Answer 5

Paratyphi A

Question 6

how is typhoid spread?

Answer 6

Spread via the fecal/oral route
* Allows indirect person to person transmission when using washrooms
* Can also be acquired from carriers that show no signs or symptoms of infection

Question 7

where is salmonella enterica found?

Answer 7

Found in areas with poor water and sewage treatment systems

Question 8

In south Asia prevalence of ______ is highest due to rapid urbanization, poor
water sanitation, and common practice of open defecation
* In India more than 130 million people don’t have access to clean water
* ~75% of the water supply is contaminated with infectious material or
chemicals
* Greater access to washroom facilities in urban areas than in rural areas
* Discrimination based on sex, wealth, education and caste contribute to
unequal access to sanitation

Answer 8

typhoid

Question 9

~10% of recovered patients will continue to shed S. Typhi in stool and
urine for as long as _____ post-infection

Answer 9

3 months

Question 10

T/F: A smaller percentage of infected patients will become carriers shedding the
bacterium in stool for prolonged periods of time

Answer 10

true!!

Question 11

• Chronic carriers of typhoid shed bacteria for more than _____
• Shed from the gall bladder- increased risk for gall bladder cancer

Answer 11

one year

Question 12

what are the common sources for infection with typhoid?

Answer 12

Common sources include:
* Non-bottled, non-boiled water either for drinking or ice cubes
* Raw/poorly cooked shellfish and street vendors are a common source of S.
Typhi
* Raw fruits and vegetables that can’t be peeled
* Ex: Fruits that have been fertilized with night soil (sewage)
* Unpasteurized dairy
* Shellfish that’s been contaminated with sewage water

Question 13

when do the signs and symptoms of typhoid begin presenting?

Answer 13

Signs and symptoms begin 7-21 days post-exposure
* Can be as long as 60 days in some patients

Question 14

what are the symptoms of typhoid?

Answer 14

Patients present with:
* Diarrhea- can also more commonly be constipation
* Muscle aches
* Sweating
* Weakness
* Headache
* Rash on trunk
* Swollen stomach, stomach pain
* Cough
* Very high fever
* Fever can gradually increases and can reach 39-40.5oC
* Vomiting occurs in severe cases
* Blood in stools
* Signs of hypovolemic shock and organ failure

Question 15

when attempting to diagnose typhoid, it can be difficult because it presents similarly to other prevalent diseases… what presents similarly to it?

Answer 15

Presents similar to Rickettsial typhus and Leptospirosis
* Different fever pattern than malaria

Question 16

______ can be used to diagnose S. Typhi
* Poor sensitivity due to:
* Low sample volume
* Antibiotic use
* Low level bacteremia

Answer 16

Blood culture

Question 17

Necessity for empirical treatment for typhoid while waiting 2-3 days for culture results, why?

Answer 17

need IMMEDIATE treatment for diarrheal diseases or else death is quick… we can refine the antibiotic later when we get the test results back

Question 18

why do we take blood samples from both arms?

Answer 18

to screen for contamination!! if the pathogen us found in both samples, its obviously in the patient

if only in one, might be contaminated!!

Question 19

how do we diagnose typhoid?

Answer 19

Diagnosed with the Widal test in many countries
* Looks for a 4 fold increase in antibody titer between the acute stage of
infection and the convalescent stage of infection
* Detects antibodies against the H and the O antigen from S. Typhi
* Suspensions of bacteria of serotypes typhi and paratyphi that have been treated in
order for them to maintain only the H and the O antigen

Question 20

the ________ test is meant to be used to increase evidence of infection, what must be done next?

Answer 20

widal test

Followed up with culture from blood, urine or stool for conclusive diagnosis

Question 21

In many countries ______ is used as a primary diagnostic tool
* Lots of cross reactivity with other infectious organisms
* Used in Nepal after the earthquake- cross reacted with Rickettsia
* Treatment for typhoid was given- ineffective against Rickettsia
* Over diagnosis of typhoid fever
* Unnecessary/incorrect use of antibiotics has driven up resistance

Answer 21

widal test

Question 22

T/F: Treatment of typhoid with antibiotics results in less than 1% mortality

Answer 22

true!!

Question 23

T/F: Untreated typhoid leads to >10% mortality

Answer 23

• Can become blood borne, lead to gI bleeds and perforation of the intestines
  causing peritonitis
• Can also cause encephalitis

Question 24

there is LOTS of AMR for typhoid, so what must we do to combat this?

Answer 24

Surveillance and communication of results is critical to inform prescription of
antibiotics

Use of combination therapy could be an option to prevent development of
resistance
* Can also be effective when diagnostics are not available or when co-infection with
other organisms are suspected

Question 25

is there a vaccine for typhoid?

Answer 25

yes! Two older vaccines with questionable efficacy 1. An oral vaccine Ty21a * Taken in coated capsules one time per day over a period of 3 days 2. Intramuscular injection of single dose Vi polysaccharide vaccine

Question 26

why are the typhoid vaccines not cost effective?

Answer 26

Protection is short-lived requiring booster doses every 3 years * Not very cost-effective

Question 27

typhoid vaccine cannot be given in children <2 years old, why is this unfortunate?

Answer 27

they're at highest risk for severe disease!!

Question 28

Novel vaccine for typhoid developed in India in 2018 * Can be given to children >6 months of age * Better immunogenicity * Conjugated vaccine Typbar-TCV * Only licensed in India and Nepal- needs approval and funding for other nations * Does not protect against ______

Answer 28

paratyphi

Question 29

why does the novel typhoid vaccine need to be given to children OVER the age of six months?

Answer 29

have to wait for mother's antibodies to degrade, otherwise it would be useless (mom's Ab would just attack and breakdown)