Diarrhoea Flashcards
What is the epidemiology and global burden of diarrhoeal illness?
1.3 million deaths per year
Leading cause of infectious death globally
Sub saharan africa > SEA > South America
What is the GEMS trial?
Global Enteric Multicentre Study, which provided ground breaking information about the most common causes of childhood diarrhoeal illness
It also found out that shigella does not always cause dysentery, and absence of dysentery does not rule out shigella
What 4 causes of diarrhoea cause the most deaths globally?
Rotavirus
Shigella
Salmonella
Cryptosporidium
What are the 6 main causes of diarrhoeal illness in children as per the GEMS trial?
Rotavirus
Shigella
ST-ETEC (enterotoxic e coli)
Cryptosporidium
adenovirus
Campylobacter
What is the global burden of cholera?
1.3 billion people at risk
95 000 deaths per year
Occurs in epidemics
**Be concerned re: cholera if you have adults dying of diarrhoeal illness
What is the global burden of shigella?
Accounts for 50% of all dysentery
One of the top 5 causes of diarrhoeal illness in children
What is microbiology of shigella?
Gram negative straight bacillus
Aerobic
What are the 4 common types of shiga bacteria?
Sonnei
flexneri
Boydi
dysenteriae
Which shigella spp. is most common in HICs?
Shigella Sonnei
Which shigella spp. is most common in LMICs?
Shigella flexneri
Which shigella spp. is assocaited with outbreaks during conflict/displacment?
Shigella dysenteriae
Who is at high risk of shigella infection?
Children
MSM
Travellers
Poverty
Overcrowding
Areas of poor water sanitation
Is shigella resistant to gastric acid?
YES
This is important because it means that you don’t need to come into contact with very much of the bacteria to get sick…
Also helps to account for the fact that shigella can cause epidemics
What is the incubation of shigella?
1-8 days
What is the presentation of shigella?
High fever
Watery ± bloody diarrhoea
Malaise
Abdo Pain
Vomiting
What are the complications of shigella infection?
- Death
- Rectal prolapse
- Toxic megacolon ± intestinal perforation
- Dehydration
- Hyponatraemia and hypoglycaemia
- Leukaemiod reaction
- HUS
What is the diagnosis of shigella?
PCR
Culture
Rectal Swabs
**Note that serology is NOT helpful
What is the treatment of shigella?
ORS / IV fluids if not tolerating oral intake
Zinc supplements
Ciprofloxacin for 3/7 at least
- ADULTS: 500mg BD for 3/7
- CHILDREN: 15mg/kg BD for 3/7
What second line antibiotics can be used in shigellosis?
Ceftriaxone
Azithromycin
What is antibiotic resistance common in shigellosis?
Significant S. Sonnei resistance in Europe
What are the side effects of ciprofloxacin
Arthropathy
Tendonitis and tendon rupture
How can shigella be prevented?
Improved sanitation –> highly sensitive to chlorine!!!
What is the WHO definitiion of cholera?
(a) in area where cholera not known to be present, patient ≥ 5 years develops severe dehydration or dies from acute watery diarrhoea;
(b) Area in which there is a cholera outbreak, any patient ≥ 5 years who develops acute watery diarrhoea with or without vomiting
How many global cholera pandemics have there been?
7; all seem to have stemmed from bangladesh area
What is the bacteriology of cholera?
Vibrio cholera
Gram negative curved bacilli
Multiple serogroups
What are the serotypes of vibrio cholerae?
Serogroup O1
- Classical
- El Tor
Serogroup O139
What is the infectious dose of vibrio cholerae?
10000-100000 organisms
What is the pathophysiology of cholera?
Cholera passes through the stomach (sensitive to gastric acid, which is why you need to be infected by so many organisms to get an infection)
The bacteria that make it through the intestine colonise the small bowel, where they attach to the bowel mucosa. They contain 2 binding sites, which produce toxic response
Toxin: 2 subunits
B= binding
A= active
A enters cell -> stimulates cAMP -> NaCl absorption inhibited, Cl excretion stimulated -> net loss of water, NaCl, K, bicarbonate
What are the symptoms of cholera?
- ASYMPTOMATIC (75%)
- Mild - Moderate Illness
Rice water stools
+/- bloating
+/- vomiting
Ileus
Muscle weakness/cramps - Severe requiring hospitalisation (2%)
Severe dehydration
What are the complications of cholera infection?
Hypoglycaemia (especially in children)
Arrythmias
ARF
Shock
Coma
Death
Mortality 5-10%
What is the mortality of cholera?
5-10%
Where is the majority burden of cholera globally
Sub- saharan Africa (primarily east africa)
South East Asia
What are the reservoirs/hosts of cholera?
Humans
Shellfish
Which cholera strain is most associated with pandemics?
O1 El Tor
Which diarrhoeal illnesses are sensitive to chlorine?
Shigella
Cholera
Which diarrhoeal illnesses are not sensitive to chlorine?
E. Histolytica
Giardia
Cryptosporidia
How is cholera diagnosed?
- Clinical diagnosis based on WHO definition
- Stool culture
- VC RDT
- Dark Field Microscopy
How do you manage Cholera?
IV Fluids
±IV Abx
±ORS
+Zinc in children
What IV fluids should you give to children with severe shock secondary to cholera + fluid losses?
<1 year: 30ml/kg over 60min + 70ml/kg over 5 hours
> 1 year: 30ml/kg over 30 min + 70ml/kg over 2.5 hours
How does ORS improve dehydration?
Changes lumenal osmolality levels, which adjusts fluid shifts
Shortens duration of diarrhoea
Reduces stool volume
Reduces need for unscheduled iv fluids
How can you quickly make your own ORS solution if none is available?
One level teaspoon of salt + eight level teaspoons of sugar + one litre of clean water
What antibiotic can be used in cholera?
Azithromycin in epidemics
otherwise:
Doxycycline (adults only, ideally): 4mg/kg stat
OR
Erythromycin
OR
Ciprofloxacin
During an epidemic, what is the expected ‘attack rate’ of cholera?
Of these, what percentage are likely to require parenteral intervention?
5%
75% are likely to need IVF in epidemic cholera
How can cholera be prevented?
Early case detection
Water chlorination
Improve hygiene practices
Vaccination (in outbreaks only)
Safe corpse disposal
Is there a cholera vaccine?
Yes, multiple
Dukoral –> oral cholera vaccine
Used in epidemics/outbreaks only
Licensed to be used in people >1 years old. Two doses 14 days apart required
Bacteriologically, shigella are…?
Gram negative straight rods
Which strain of shigella has been absent since the 1990s?
Shigella boydii
What effect does cholera toxin have on Chloride?
Prevents the re-absorption of chloride at via CFTR channels
Inhibits sodium chloride
absorption resulting in an efflux of chloride ions and
secretion of hydrogencarbonate ions, sodium and potassium ions, and water.
Loss of chloride prompts
substantial fluid secretion into the small intestine,
overwhelming the resorptive capacity of the large intestine, resulting in severe watery diarrhoea.
What is Typhoid Fever?
‘Enteric Fever’
A bacterial diarrhoeal illness with rapidly growing worldwide AMR
What is the epidemiology of TF?
GLOBAL BURDEN:
14 million cases a year
Highest incidence in ASIA: Bangladesh, India, Pakistan but occurs in Africa, South + Central america too
Commonest cause of bacterial fever in the returning traveller
Children > Adults
What are the causative organisms of TF?
Salmonella Typhi
Salmonella paratyphi A + B
What is the bacteriology of Typhoid Fever?
Salmonella Typhi
Salmonella paratyphi A + B ARE:
Gram negative obligate intracellular organism (i.e. it hangs out in the macrophages)
How is TF spread?
Faecal-oral spread
What are the risk factors for severe typhoidal infection?
PPI Use
Infection with AMR strain
What is the pathophysiology of Typhoid Fever?
Patient ingests Typhoid (need to consume at least 100 000 bacteria for infection to occur)
passes through the stomach
Goes into the small intestine at the PEYER’S PATCHES where it is taken up by macrophages where it goes to the mesenteric lymph nodes
Spleen and Liver via blood
Gall bladder
enters into the small bowel
colonises the S.I where the PEYER’S PATCHES
Symptoms occur when S. Typhi is in the blood stream
In chronic carriers of S. Typhi / S paratyphi, where is the organism likely to sequester?
Gall bladder and biliary tree
What are the symptoms of TF?
Acute Fever, slowly rising over a few days
Faget’s sign
Headache, malaise
Hepatosplenomegaly , abdo distension, mild ascites
Rose Spots
What three infectious diseases are known to cause Faget’s sign?
Typhoid Fever
Yellow Fever
Brucellosis
What is the DDx for Typhoid Fever?
You must rule out Malaria and Dengue
Leptospirosis
Brucellosis
Schistosomiasis
Viral GE
How do you diagnose Typhoid Fever?
Blood Culture is the gold standard (negative result does not rule out TF)
- Two sets of paired samples are recommended as it is notoriously hard to get a good lab result
Bone Marrow biopsy (bit brutal)
Widal test (serology) is no longer recommended – not sensitive or specific
VI Serology can be used in non-endemic settings (e.g. UK) to cool for chronic carriage of Salmonella Typhi
Bloods: Mild transamintis
RDTs: lots exist, but arent great; none test for S. Paratyphoid
How do you manage Typhoid Fever?
** Lots of AMR globally, especially in South Asia
Ciprofloxacin 20mg/kg for 7/7 ± Doxycycline
If AMR: Azithromycin 20mg/kg for 77
+/- Steroids if concerns about severe disease
What are the complications of Typhoid Fever
Complications start to occur >10 after illness starts
Typhoid Encephalopathy (up to 12%)
Nephritis
Hepatitis
UGIB
GI Perf
Dead (CFR 2.5%)§
How do you prevent Typhoid Fever?
WASH techniques
Typhoid Vacccine (TCV Vax, safe to use in children >6 months old)
Which country is assocaited with highest number of cases of Multidrug resistant Typhoid Fever?
Pakistan
What is the prognosis of Typhoid Fever?
Prolonged febrile illness with bacteraemia
90% uncomplicated
10% severe complicated disease
10% + mortality with no treatment
< 1% mortality if adequate treatment
Which parasitic co-infection is associated with chronic carriage of Typhoid?
Shistosomiasis (unknown why)
How is Typhoid Fever usually transmitted?
Typhoid is usually acquired through ingestion of food or water contaminated by faeces of a patient or carrier
What is the incubation of typhoid?
10-20 days
How do you manage fluid loss in Diarrhoeal Illness?
What are the differences between Typhoid and Invasive Non-typhoidal Salmonella?
Typhoid
- Salmonella Typhi and S. Paratyphi
- invasive (always)
- mortality up to 20%
- humans are the only host
iNTS
- S. Typhimurium and S. Enteritidis
- HIV (200x more likely if HIV+ve)
-Case fatality rate up to 20%
- multiple hosts, not just humans (usually spread from animal contact)
What two bacteria are responsible for iNTS?
Salmonella Enteritidis
Salmonella Typhimurium
How does iNTS present?
** have a suspicion in any HIV patient with fever, hepatosplenomegaly, diarrhoea and cough
Very non-specific and could be the very bottom of your list if differentials so keep an eye out for it
What are the complications of iNTS?
- Recurrence (higher risk of mortality with each subsequent recurrence)
- Death
- Concurrent infections
