WEEK 1: Diarrheal Diseases Flashcards
Define the following terms:
- Diarrhea
- Dysentery
- Gastroenteritis
- Enterocolitis
- Diarrhea:
Abnormal fecal discharge characterized by frequent, fluid stool resulting from disease of the small intestine leading to increased fluid and electrolyte loss.
> 3 loose/watery stools per day or approximately 10mL/kg/day - >200 mL/kg/day fluid lost through stool.
- Dysentery:
An inflammatory disorder of the GIT often associated with blood and pus in the feces and accompanied by symptoms of pain, fever, abdominal cramps, usually resulting from disease of the large intestine.
- Gastroenteritis:
A syndrome characterized by gastrointestinal symptoms including nausea, vomiting, diarrhea and abdominal discomfort. - Enterocolitis:
Inflammation involving the mucosa of both small and large intestine.
Discuss Classifications of Diarrhea – Duration Definitions.
- Acute Diarrhoea
Sudden onset and lasts less than two weeks.
*90% are infectious in etiology
*10% are caused by medications, toxin ingestions, and ischemia - Chronic Diarrhoea
-Diarrhoea which lasts for more than 4 weeks
Most of the causes are non-infectious. - Persistent Diarrhoea
-Diarrhoea lasting between 2 to 4 weeks
Discuss the Epidemiology of Diarrhoea
Second leading cause of death in children under five years old.
*1300 children die daily of diarrhea (unicef 2019)
*525 000 children die from diarrhea annually
*1.7 billion cases of diarrheal disease every year.
Leading cause of malnutrition in children under five years old.
Main cause of death from acute diarrhea is dehydration.
Preventable and treatable: through safe drinking-water and adequate sanitation and hygiene.
Discuss Route of Infection.
Infections of the gastrointestinal tract can be grouped into those that remain localized in the gut and those that invade beyond the gut to cause infection in other sites in the body.
In order to spread to a new host, pathogens are excreted in large numbers in the feces and must survive in the environment for long enough to infect another person directly or indirectly through contaminated food or fluids.
Discuss Causes of infectious gastroenteritis.
Toxin in food: < 6 hours incubation:
Bacillus cereus
Staph. aureus
Clostridium spp. enterotoxin
Bacterial: 12-72 hours incubation
Vibrio cholerae
Enterotoxigenic E. coli (ETEC)
Shiga toxin-producing E. coli (EHEC)*
Enteroinvasive E. coli (EIEC)*
Vibrio parahemolyticus
Salmonella*
Shigella*
Campylobacter*
Clostridium difficile*
Yersinia enterocolitis
Viral: incubation ( 12-72 hrs)
Rotavirus
Calicivirus -Norovirus
Astrovirus
Adenovirus
HIV
Hepatitis
Protozoal: long incubation
Giardiasis
Cryptosporidium
Microsporidiosis
Amoebic dysentery *
Cystoisosporiasis
Discuss Non-infectious causes of diarrhoea.
Gastrointestinal
Malabsorption
Inflammatory bowel disease
Irritable bowel syndrome
Bowel malignancy
Metabolic
Diabetic ketoacidosis
Thyrotoxicosis
Uraemia
Neuroendocrine tumours releasing (e.g.) VIP or 5-HT
Drugs and toxins
Medications- Laxatives
Antibiotics- Clindamycin , Erythromycin
NSAIDs
Cytotoxic agents
Proton pump inhibitors
Plant toxins – legumes and beans in G6PD deficient individuals
Fungi and Mushrooms
Heavy metals –Thallium, Cadmium
Fish poisoning -shellfish
State the causes of Watery Diarrhoea
1.Viral infections
Rota virus
Noro virus
Adenovirus (serotypes 40,41)
Astro virus
HIV
- Bacterial infections
Salmonella
Campylobacter
Escherichia coli
Vibrio cholera
Clostridium difficile
Bacillus cereus
Staphylococcus aureus - Parasitic diseases
Giardia lamblia
Cryptosporidium
Cystoisospora belli
Microsporidium
Outline the causes of dysentery.
- Bacterial infection
Shigella
E. coli (EHEC, EIEC)
Campylobacter
Yersinia enterocolitis
Clostridium difficile - Parasitic Infection
Entamoeba histolytica
Balantidium coli
Discuss results from Study of under 5 in Gaborone.
Results: 153 hospitalized children with diarrhea, 97% were 2 years old; 88% of these were not breastfeeding.
HIV was diagnosed in 18% of children and 64% of mothers.
Cryptosporidium and Enteropathogenic Escherichia coli were common;
Severe acute malnutrition (kwashiorkor or marasmus) developed in 38 (25%) patients, and 33 (22%) died.
Only one breastfeeding child died.
Many children who died had been undersupplied with formula.
Conclusions: Most of the severe morbidity and mortality in this outbreak occurred in children who were HIV negative and not breastfed.
Discuss the major causes of diarrhea worldwide.
- Rotavirus: 20%
- Unknown causes: 20%
- EPTEC: 15%
- Campylobacter: 12.5%
- Cryptosporidium: 10%
- Shigella: 10%
- Vibrio cholera: 7,5%
- Salmonella: 2,5%
Discuss the mechanism of rotavirus diarrhea.
- The ingested virus spreads on the epithelial cells of the small intestine and spreads to large numbers of these cells.
- Release of virus particles into the lumen.
- Infected cells damaged leaving immature cells with low absorption capacity of carbs, water and sugar.
- Fluid accumulation in the lumen.
DAY 2-4
- Diarrhoea and dehydration
- Virus replication ceases.
- Crypts cells repopulate villi
6-7 days
8. Normal appearances regained.
Single-stranded RNA viruses, non enveloped
Cause ‘winter vomiting disease’.
Include the Norovirus or Norwalk-like viruses (NLV).
Highly infectious, spread rapidly and nosocomial infection is common.
Major cause of gastroenteritis outbreaks in healthcare settings and crowded environments such as cruise ships and camps.
Food- or water-borne routes -eating sewage-contaminated shellfish such as cockles or mussels.
Infection is common in older children and adults.
Presents with chills, headache, myalgia or fever as well as nausea, abdominal pain, vomiting and diarrhea, but recovery occurs within 24-48 h.
Name the microorganisms.
Caliciviruses
Single-stranded RNA viruses of which five serotypes are known.
Characteristic five- or six-pointed star patterns.
Most infections occur in childhood and are mild.
Name the microorganism.
Astroviruses
Non enveloped, double-stranded DNA viruses , icosahedral shape
Types 40 and 41 are associated with gastroenteritis.
They are second to rotaviruses as a cause of acute diarrhoea in young children in temperate climates.
Name the microorganisms.
Adenovirus
Discuss the Diagnosis of Viral diarrhea.
*Direct and immune Electron microscopy
*Antigen detection- EIA with hyper immune sera , EIA with monoclonal antibody
*Antibody detection-ELISA
*Culture
*Hybridization probes- for adeno viruses
*PCR
