Lecture 10 Review Questions and Answers (H20 born infections and arsenic) Flashcards
What are the four major classes of infectious agents?
Bacteria (Vibrio Cholerae), Protozoa (Cryptospodium), Viruses (Rotavirus which causes diarrhea), Fungi (spores), and Helminths[worms] (hookworm).
What is the definition of diarrhea?
The passage of 3 or more loose or liquid stool per day. Water and electrolytes (salt) are lost, dehydration occurs when these losses are not replaced. Death can follow severe dehydration.
What are the four steps of treating diarrhea? And what is ORS?
1) Rehydration with intravenous fluids and/or ORS (oral rehydration solution) which is a mixture of clean water, salt and sugar. It replaces what was lost in the feces.
2) Zinc supplements: reduces duration of diarrhea episode
3) Nutrient-rich food: breaks vicious cycle of malnutrition and diarrhea.
4) Prevention: access to safe drinking water, improved sanitation, good breastfeeding in first 6 months of life and good personal and food hygiene, Rotavirus vaccination and a nutritious diet.
Host-microbe relationships. What are definitions of commensal, pathogenic, pathogen, principal pathogen, etc.
Commensal: non harmful coexistence
Symbiotic: mutually beneficial
Parasitic: microbe benefits at the expense of the host
Pathogenic: damages/harms host and causes disease
Pathogen: microorganism that can cause disease
Virulence: measure of pathogenicity or likelihood of disease
Principle pathogen: regularly cause disease
Opportunistic pathogen: cause disease when one is immunocompromised
What is the life cycle of cholera? thinking about Rita Orwell, how does environment influence its growth?
The bacteria, vibrio cholera proliferates in aquatic reservoirs by attaching to copepods. It uses these host organisms for nutrition and shelter and its most favorable condition is where there is low salt in the water and where temperature is a bit warmer in the water. Humans will ingest the bacteria when they drink contaminated water or eat seafood containing these bastards. Once inside the human host, they are able to multiply by attaching to the walls of the small intestine. These fuckers will then secrete cholera toxins which the human will excrete in their stool. In this hyper infectious state, it can then be transmitted through vectors like flies and amplified through the fecal-oral pathway, fomites, infected water, and contaminated food pathways in the community.
Ways the vibrio cholera can be transmitted in humans
fecal-oral pathway fomites (surface) infected water contaminated food pathways flies
Health effects associated with cholera
Diarrhea, vomitting, and mortality if left untreated
How do we treat the effects of cholera
ORS (oral rehydration solution), IV fluids and antibiotics which shorten the duration of symptoms.
What causes cryptosporidosis and what are the symptoms?
Caused by the protozoa cryptosporidium and its symptoms are: gastrointestinal, watery diarrhea, vomiting, fever, malnutrition and weight loss, impaired cognitive function.
How is crypto transmitted?
Host range of humans and mammals Oocysts fully infective upon excretion Ubiquitous distribution in environment life cycle in single host not all infected people are symptomatic highly infectious Large number of oocysts may be shed Highly resistant to disinfection like chlorine No effective treatment
What population is at greatest risk to this disease? Why is it such a problem in our water?
Population at risk is immunocompromised patients (AIDS cancer, children and elderly).
It is a problem in water because it is resistance to chlorine and a breach could lead to huge outbreak
What are likely sources of crypto exposure? evidence?
Cattle, sheep, deer, humans, and cats are hosts. Increased outdoor activities and contact with animal shit and there was outbreak of crypto in US from 1984 to 2007 and it was found to be in drinking, treated and untreated recreational water.
How did the arsenic problem happen in bangladesh? Why did they switch to ground water?
They changed to ground water from drinking surface water because the water was filled with naturally occurring arsenic and it was causing diarrhea.
What are some of the health effects associated with high level exposure to arsenic?
Early effects: Skin lesions (melanosis, darkening skin and keratosis, thickening skin)
Late effects: skin cancer, bladder cancer, lung and liver cancer, CVD, hypertension and heart attacks, neurodevelopment effects and immune system effects.
What evidence was presented that arsenic in well water most likely causes skin lesions?
There was a longitudinal study done to see the incidence of disease outcomes. They measured the level of arsenic in water and creatinine from urine in about 9000 subjects and it was found that there is a dose response relationship between household water, arsenic and the risk for skin lesions.
