Host Parasite Flashcards
HOW DO EPIDEMICS LIKE AIDS AND ZIKA GET STARTED?
-Africa’s AIDS Crisis and Resulting Orphans
Is the Zika Virus now an epidemic in North and South America?
wait for answer
MOST HUMAN DISEASES CAUSED BY MICRO-ORGANISMS INVOLVE A HOST-PARASITE RELATIONSHIP
•Parasite – an organism dependent on another organism for its existence;
–Term not limited to helminths and protozoans
–Terms not limited to organisms that have a detrimental effect on humans; includes beneficial microorganisms that colonize humans
•Host – the organism the parasite is dependent upon
•Infection – establishment of a host-parasite relationship by multiplication of the parasite in or on the host
•Disease – injury or abnormal finding in an organism which results in recognizable effects
–Morbidity - illness
–Mortality – death
–MMWR is a publication of the Center for Disease Control and Prevention (CDC)
INFECTIOUS VERSUS NON-INFECTIOUS DISEASES
- infectious disease(morbidity [illness]) = one that results from an infection with an organism resulting from a parasite growing on a host.
- a non-infectious disease = one that does not result from infection with an organism; e.g. broken leg, high blood pressure, toxic algae poisoning;
HOW DO WE BECOME INFECTED WITH MICRO-ORGANISMS?
•Reservoir- place where parasite normally lives and multiplies
–Soil
•usually saprophytic micro-organisms – free living; utilize dead organic material as nutrients;
•infection of humans and animals is accidental as opposed to parasites
–Nonhuman animals
•Called zoophilic micro-organisms; disease is a zoonosis
•particular animals are the usual hosts
–Other humans •Humans are the usual hosts for the micro-organism
PORTALSOF ENTRY
- eye
- ears
- nose
- mouth
- anus
- broken skin
- placenta
- vagina
- urethra
- mammary glands
Portals of Exit
- eyes (tears)
- nose (secretions)
- mouth (saliva, sputum)
- ear (ear wax)
- broken (blood)
- skin (flakes)
- anus (feces)
- urethra (urine)
- seminal vesicle (semen & lubricating secretions)
IN FEMALES
- mammary glands (milk, secretions)
- vagina (secretions, blood)
MAIN ROUTES OF TRANSMISSION OF MICRO-ORGANISM FROM RESERVOIR TO HOST
•Respiratory route
–Reservoir is humans or animals
–Portal of exit is respiratory tract of infected human or animal
–Portal of entry is respiratory tract of uninfected human
–Fomites (inanimate vehicles) may be involved
•Fecal-oral route
–Reservoir is humans or animals
–Portal of exit is gastrointestinal tract of infected human or animal
–Portal of entry is mouth of uninfected human
–Fomites (vehicles) are usually involved: contaminated food, water, human hands
MAIN ROUTES OF TRANSMISSION OF MICRO-ORGANISM FROM RESERVOIR TO HOST
•Blood-borne route
–Reservoir is humans or animals
–Portal of exit is wound of infected human/animal
–Portal of entry is wound of uninfected human
–Insect vectors, and fomites are usually involved
•Contact route
–Reservoirs are humans, animals, and soil
–Portal of exit may be lesion (sore), body fluid of an infected person/animal
–Portal of entry usually a wound of uninfected person
–Fomites are frequently involved
VECTORS ARE ARTHROPODS THAT TRANSMIT MICROORGANISMS FROM RESERVOIR TO HOST
•Mechanical vector – transfers infectious agent passively with no multiplication within vector (this is why it is mechanical), e.g. housefly
•Biological vector – part of life cycle (multiplication) occurs within vector
–Insects (6 legs)
–Arachnids (8 legs)
COMMON FOMITES INVOLVED IN TRANSMISSION FROM RESERVOIR TO HOST
•Water, food •Air •Door knobs, banisters, bus/train poles •Fabrics –Towels –Soiled tissues •Needles –Injections –Tattoo/body piercing •Eating utensils and toys
ARE ALL DISEASES CAUSED BY MICRO-ORGANISMS INFECTIOUS?
- Infectious and communicable diseases – can be transmitted from one host (human or animal) to another
- Infectious but not communicable – occurs with most micro-organisms whose reservoir is soil;
^^^ important to remember about the soil
•Neither infectious nor communicable – microorganisms multiply in an environmental reservoir and produce a toxin ingested by the human or animal; the microorganism does not establish a host-parasite relationship;
–Paralytic shellfish poisoning – eukaryotic algae (dinoflagellates) multiplying in water produce toxins taken up by shellfish
–Some types of food poisonings caused by bacteria
INFECTION MANIFESTATIONS
•Duration of disease in an individual
–Acute – disease comes on suddenly and patient generally recovers within a month or less
–Chronic – diseases comes on more slowly and may last for years or even a lifetime
–Subclinical (asymptomatic) infection – no disease develops
•Incubation period – time between infection and appearance of disease
“ICEBERG” CONCEPT OF INFECTION AND INFECTIOUS DISEASE
Above water:
- at the top death of host
Under water
- classical and sever disease
- moderate severity mild illness
- infection w/o clinical illness (asymptomatic infection)
-important to know why it is called ice berg concept and know why it is called that (cuz the deeper you go the more complex it becomes)
TYPES OF DISEASE PATTERNS
•Extent of disease in a population
–Incidence – frequency of new cases in a population
–Prevalence – frequency of all existing cases including chronic cases
•Disease patterns
–Endemic - Prevalence in the population at a fairly high frequency; may be an acute or chronic disease
–Sporadic -Incidence/prevalence in the population at very low level and often absent for long periods; may be an acute or chronic disease
–Epidemic - Incidence in the population increases significantly and suddenly; usually acute but may be chronic
–Pandemic - An epidemic that becomes worldwide or at least continent wide; usually acute but may be chronic
ENDEMIC AND EPIDEMIC
- shows that in 1977 and 1982-1991 there was an epidemic of measles
- shows that an endemic diease can become epidemic (lack of vaccination can cause it)
