Class 3- Diarrheal diseases Flashcards
(40 cards)
Disease Tests
- Microscopy
- Cell culture
- Genetic testing: PCR, Sequencing
- Serology: ELISA, Western Blots
- Rapid Diagnostic tests
Microscopy
Most straight forward test
- Examine sample under microscope!
Electron Microscope
- Decreases resolution from .2 micron with light microscope to .0005 microns
- Has lead to a greater understanding of intercellular pathways and structure
Cell culture
Applying specimen to culture plate, with source of nutrient ex. agar
- Pathogen will survive and populate plate
Can be used for:
- Drug sensitivity tests
- Pathogen identification:
- Virus or bacteria or parasite
Different levels of bio safety level (BSL)
How many BSL are there?
Four. 1 is the lowest
Genetic testing
Polymerase Chain Reaction (PCR)
- Primers used determine area of interest
Single nucleotide polymorphisms (SNPs)
- Mutations in DNA, - Can be used track origin - Determine risk
Sequencing
- Whole or partial genome experiments
- Examines entire DNA fragments without necessarily looking for a specific region
- Great tool for stacking multiple studies
- Expensive
- Bps are dyed and captured by dye terminator reader
Serology
Enzyme Linked Imunosorben Assay (ELISA) - Indirect and Sandwich
ELISA Great tool for exposure studies
Diarrheal Infections: Fecal Oral Route
- Cholera – bacterial
- Shigellosis – bacterial
- Cryptosporidiosis – parasitic
- Giardiasis – parasitic
- Amebiasis – parasitic
- Norovirus (Norwalk)– viral
- Rotavirus – viral
*Constant fecal exposure causes constant general inflammation in the body*
Cholera summary
Causative agent: Vibrio cholerae
Reservoir- main reservoir is Humans, recent studies have discovered environmental reservoirs
Route- ingestion of water or food that has been directly contaminated with feces Incubation period - a few hours to 5 days!
Primary symptoms- rice water diarrhea, profuse vomiting, nausea. (only cholera causes rice water diarrhea)
Communicability period – as long as stools are positive (two days after recovery)
Cholera is one of the oldest and best understood epidemic diseases. Its strongly linked with consumption of unsafe water and food, poor hygiene, poor sanitation, and crowding
WHO Case definition of cholera
Disease unknown in area
- severe dehydration or death from acute watery diarrhea in a patient over the age of 5
Endemic country
- acute watery diarrhea with or without vomiting in a patient over the age of 5
Epidemic country
- acute watery diarrhea with or without vomiting in any patient
Shigellosis
Shigella species are broken up into 4 supgroups
Reservoir – Humans
Route – person to person and contaminated food
Incubation – 1 to 3 days
Symptoms- loose stool (usually contains blood), fever, nausea, vomiting and painful stomach cramps.
Communicability- up to 4 weeks after recovery (if untreated) Illness is usually self limiting lasting 4-7 days. Secondary attack rates can be as high as 40% in households
S. dysentary1 Group A
Most dangerous sub-species of Shigella High case fatality rate Antibiotic resistant Incubation as high as 1 week.
Cryptosporidiosis
Causative Agent: C. parvum – parasitic agent
Reservoir- Human and more than 45 animals
Route- fecal oral Incubation
Incubation- 1 to 12 days, 7 days average
Symptoms- watery diarrhea, abdominal cramping, and vomiting. Symptoms wax and wane over a duration of 30 days in healthy people!
Crypto is NASTY… Outbreaks have also been associated with public sources of drinking water, recreational water sources, and contaminated beverages
Cryptosporidiosis Life cycle
Oocyst can survive outside the body for 2-6 months
- Infected continue to shed oocyst for weeks after recovery.
Hence the importance of WASH: Water, Sanitation, and
Hygiene 1993 Milwaukee outbreak
Giardiasis
Causative Agent: Giardia lamblia - Protozoan parasite
Reservoir- Humans and wild/domestic animals
Route – Person- to person (hand to mouth transfer of cysts), ingestion of contaminated sources
Incubation – 3 to 25 days (median 7-10)
Symptoms- frequent loose pale greasy stool, steatorrhea (excess fat in stool). Often asymptomatic
Communicability – entire period of infection
Chlorine does not kill Giardia. Associated with cold streams and water with chances of human/animal fecal matter
Amebiasis
Causative Agent: Entomoeba histolytica- protozoan parasites
- Protozoas is Latin for “first animal”.
Reservoir – humans. Usually chronically ill or asymptomatic cysts carriers
Route – fecal oral
Incubation – 2 to 4 weeks
Symptoms- usually asymptomatic
Communicability- as long as cysts are carried, which can be upwards of years
Norovirus
Extremely infectious and contagious
Reservoir: Humans
Route of exposure- probably fecal oral, suspected airborne transmission (through farts). Spreads like wild fire through hospitals, cruises
Incubation- 10-50 hours
Symptoms- Diarrhea, throwing up, nausea, stomach pain. Usually self-limited
Communicability – acute stage and 48 hours after symptoms stop
Rotavirus
Reservoirs- Probably human
Route- Oral/fecal
Incubation – 24 to 72 hours
Symptoms- vomiting, fever, and water diarrhea
Communicability – up to 8 days after infection (4-6 days after symptoms)
Susceptibility- Children 6 to 24 months old at highest risk. Why not under 6 months or over 24 months?
Foodborne infections
- Brucellosis- bacterial
- Camplyobacter jejuni- bacterial
- Escherichia coli – bacterial
- Helicobacter pylori – bacterial
- Listeriosis - bacterial
- Salmonellosis – bacterial
- Typhoid fever – bacterial
Brucellosis
Reservoir- cattle, swine, goats, and sheep
Route- dermal contact with animal fluids, ingestion of unpasteurized milk products
Incubation- 5 to 60 days
Symptoms- intermittent fever, chills, sweating, malaise
Communicability – rare person to person
Campylobacter
C. jejuni
Reservoir – Poultry and cattle
Route- ingestion of undercooked meat, or contaminated water, person to person transmission is uncommon
Incubation – 2 to 5 days
Symptoms – bloody stool, abdominal pain, fever nausea, vomiting
Communicability – throughout the course of infection usually several days, if untreated 2-7 weeks
One of the most common causes of diarrheal disease in the US
- FoodNet surveillance indicates 14 cases per 100,000
- Only takes a few organisms to make some one sick (less than 500)
- Remember discussion on infectiousness vs. contagiousness
Types of E. coli
- Enterohemorrhagic E. coli (EHEC)
- Enteropathogenic (EPEC)
- Enterotoxigenic (ETEC)
Lots of different types
- Different clinical characteristics
- All transmitted through contaminated food, water, or hands, or direct contact with animals
EHEC
Enterohemorrhagic E. coli (aka E. coli O157:H7)
This is the nasty/deadly version of e coli.
- Produce Shiga toxins
- Can kill adults and children
Primary reservoir: cattle, humans can maintain for person to person
Incubation- 2 to 10 days
Symptom- Hemorrhagic colitis
Communicability- 1 week
ETEC
Enterotoxigenic E. coli
Causes as many as 380,000 deaths in children under 5
- Malnourished children are at an increased risk
Reservoir – Humans
Incubation – 12 -72 hrs
Communicability – duration of diarrhea
Symptoms usually last less than 5 days
Leading cause of Traveler’s Diarrhea - Don’t eat salads abroad! - Peel or boil…
EPEC
Enteropathogenic E. coli
Confined to infants
Route – contaminated formula and weaning foods
Incubation – 9-12 hours
Major agent of infant diarrhea in developing world
