Typhoid and paratyphoid Flashcards
What is the infectious agent?
Salmonella enterica subspecies enterica serovar Typhi (S. Typhi)
Salmonella enterica subspecies enterica serovars Parathyphi A, B and C.
S. Paratyphi A is the most common globally.
What are the reservoirs for S. Typhi and S. Paratyphi.
S. Typhi - only humans
S. Paratyphi A - only humans
S. Paratyphi B and C - principally humans but also domestic animals
Typhi and Paratyphi can survive in the environment.
How are Typhoid and Paratyphoid transmitted?
Faecal-oral route. Ingest contaminated food, water.
Direct human-human transmission rare.
What are the incubation periods for Typhi and Paratyphi?
Typhi - typically 8-14 days (range 3-60 days)
Paratyphi - shorter; 1-10 days
The inoculum size and vehicle greatly influence incubation period and attack rate. Paratyphi has a higher infective dose than Typhi.
What are the infectious periods for Typhi and Paratyphi?
Typhi - as long as bacteria excreted in faeces. Untreated - 10% infectious up to 3 months and 3-5% chronic carriers (years). Females, elderly, gallstones more likely chronic.
Paratyphi - similar to most other salmonellae; most excrete for 5-6 weeks, some months or years; biliary excretion also.
What are the clinical presentations and outcomes?
Typhoid - ASx to mild with fever to severe systemic. Fever, headache malaise initially. Also anorexia, abdo pain, splenomegaly, constipation, diarrhoea, rose spots on trunk.
Paratyphoid - similar to typhoid but more benign course.
Note: chronic carriers of typhoid difficult to ID as ASx. 90% have gallstones.
Who is at increased risk of disease?
General susceptibility. Endemic areas - pre-school children and those 9-15 years.
Unvaccinated returned travellers to endemic areas.
What are the routine prevention activities?
Educate - public about food handling, hygiene practices (hand washing after toilet and before preparing/handling food)
Ensure suitable hand-washing facilities for food handlers, people caring for patients or children.
Vaccination - no full protection for typhoid. No vaccine for paratyphoid. Vaccine only for >= 2 and adults travelling to endemic areas, military, laboratory personnel.
Travellers - avoid raw/undercooked meat, untreated water/ ice, food from street vendors
What are the case definitions?
Lab definitive evidence only.
What is the public health response to cases?
Begin F/U within 1 working day.
ID the country of acquisition and sources of exposure.
Liaise with lab - determine relatedness and ABx sensitivity
Prevent spread of infection - cases aware of hygiene precautions, public health action for high-risk cases and contacts
