THE DYNAMISCS OF DISEASE TRANSMISSION AND CAUSATION

health

is the state of complete physical and mental, and social well- being

health

is the successful defense of the host against forces tending to disturb the body's equilibrium

disease

is the failure of the body's defense mechanism to cope with the forces tending to disturb the body's equilibrium

disease

is the result of the imbalance between the forces of the agent and the host

disease is the result of imbalance

imbalance depends on nature of agent and host

nature of agent and host and interaction between the environment

3 premises of the ecological concept of disease

the lever, the epidemiologic triangle, the wheel, the web of causation

4 ecological models

presence of infectious organism, if it is taken in massive doses, if the agent increases in virulence, if the host resistance is overcome

when does disease occur? (4)

agent

any element, substance, or force whether living or non-living

agent

the presence or absence of which can initiate or perpetuate a disease process

chemical agents, physical and mechanical agents, nutrient agents

3 types of non-living agents

exogenous, endogenous

2 kinds of chemical agents

exogenous

agent; chemicals which arise from outside the host (poisons, prions, proteinaceous infectious particles)

endogenous

agent; chemicals which arise from inside the host (renal shutdown, acidosis of diabetes)

physical and mechanical agents

agent; eg. extreme temperature, lightning, electricity, physical trauma

nutrient agents

agent; deficiency agents

nutrient agents

agent; excess in nutrients

nutrient agents

agent; hypersecretion of hormones

bacteria, fungi, protozoa, cestodes, nematodes, trematodes, viruses

7 living agents

inherent characteristics, physical, biological requirements, chemical requirements, viability and resistance

5 characteristics of living agents

infectivity, pathogenicity, virulence, antigenicity

4 characteristics of living agents directly related to man

infectivity

the ability to gain access and adapt to the human host to the extent of finding lodgment and multiplication

pathogenicity

the ability of an agent to set up a specific reaction, local or general, clinical or sub-clinical

virulence

a measure of the severity rather than constancy of the reaction produced and is usually measured in terms of fatality

antigenicity

the ability to stimulate the host to produce defense mechanism

reservoir of sources, modes of transmission

2 characteristics of agents in relation to the environment

reservoir of sources

the source of infections (man, animals, soil, inanimate organic matter)

modes of transmissions

the mechanisms by which an infectious agent is transported from the reservoir to a susceptible host

contact, vehicle, vector, airborne

4 modes of transmissions

contact

MOT; direct, indirect, droplet conact

vehicle

MOT; water, food, milk, blood

vector

MOT; arthropod bites, mechanical vectors

airborne

MOT; droplets, environment-lab, droplet nuclei, inhalation from dusts

host

is the individual exposed to the agent; the patient, the carrier

age, sex, race, habits/lifestyle, customs, religion

6 characteristics of hosts

environmental factors

the sum total of an organism's external surrounding, conditions, and influences that affect its life and development

physical environment, biological environment, socio-economic environment

3 environmental factors

physical environment

eg. climate, geography

biological environment

eg plants, animals, human beings

syndenstricker

he who classified the socio-economic environment into five

arising out of social environment, essential concomitants, inherent in the nature, arising from out of maladjustments, psychological

5 classifications of socio-economic environment

kinds of community life, existence of social stratification, social standards of the community

3 factors arising out of social environment aside from the economic status and aside from social stratification due to difference in economic status

element of wealth and distribution, periods of prosperity depression and unemployment, available medical services, general technologies of the place

4 factors that are essential concomitants and results of the economic system of the era

immune suppression, changes in the normal microbiota, introduction of a member of the normal flora into an unusual site in the body

3 conditions that create opportunities for pathogens

mutualism, commensalism, parasitism

3 types of symbiotic relationships

mutualism

symbiotic; organism 1 and 2 both benefit

commensalism

symbiotic; organism 1 benefits while organism 2 neither benefits nor harmed

parasitism

symbiotic; organism 1 benefits while organism 2 is harmed

mutualism

symbiotic; ex: bacteria in human colon

commensalism

symbiotic; ex: tapeworm in human intestine

parasitism

symbiotic; ex: tuberculosis bacteria in human lung

Staphylococcus, Streptococcus, Moraxella, Haemophilus, Lactobacillus, Veillonella, Fusobacterium, Candida (fungus)

resident microbiota; upper respiratory tract

SOME SILLY MICROBES HANG LOVELY VERY FIRMLY AND COZY

Lactobacillus, Haemophilus, Actinomyces, Bacteroides, Treponema, Neisseria, Corynebacterium, Entamoeba (protozoan), Trichomonas (protozoan)

resident microbiota; upper digestive tract

Lazy Happy Animals Bring Tiny Nice Chewy Edible Tasty

Bacteroides, Fusobacterium, Escherichia, Lactobacillus, Clostridium, Bifidobacterium, Enterococcus, Proteus, Shigella, Candida (fungus), Entamoeba (protozoan), Trichomonas (protozoan)

resident microbiota; lower digestive tract

Big Friendly Elephant Like Crunchy Banana Every Picnic Sometime Cute

Lactobacillus, Streptococcus, Staphylococcus, Bacteroides, Clostridium, Candida (fungus), Trichomonas (protozoan)

resident microbiota;Female Urinary and Reproductive Systems

Lovely Sisters Sing Beautifully Creating Cool Tunes

Staphylococcus, Streptococcus, Mycobacterium, Bacteroides, Fusobacterium, Peptostreptococcus

resident microbiota; Male Urinary and Reproductive Systems

Some Strong Men Bring Food Peppers

Skin: Propionibacterium, Staphylococcus, Corynebacterium, Micrococcus, Malassezia

Conjunctiva: Staphylococcus

resident microbiota; eyes and skin

Pretty Skin Cares More Maybe

nose

cooler than the rest of the respiratory system and has some unique microbiota

trachea, bronchi

have sparse microbiota compared to the nose and mouth

alveoli

part of the upper respiratory tract with no natural microbiota

teeth, gingiva, lining of cheeks, pharynx

microbes colonize these surfaces of the upper digestive tract

anaerobes

bacteria in the lower digestive tract are mostly strict ____________

acidity

microbiota in the female urinary and reproductive system change as ___________ in the vagina changes during menstrual cycle

urine

the flow of __________ prevents extensive colonization of the urethra

outer, dead layers

microbiota live on the ___________ of the skin and in hair follicles and pores of glands

tears

wash most microbiota from the eyes

toxoplasma gondii, treponema pallidum, listeria monocytogenes, cytomegalovirus, parvovirus b19, lentivirus, rubivirus rubella

some pathogens that cross the placenta

toxoplasma gondii (protozoa)

toxoplasmosis

toxoplasma gondii (protozoa)

effect: abortion, epilepsy, encephalitis, microcephalus, mental retardation, blindness, anemia, jaundice, rash, pneumonia, diarrhea, hypothermia, deafness

treponema pallidum (bacteria)

syphilis

treponema pallidum (bacteria)

effect: abortion, multiorgan birth defects, syphilis

listeria monocytogenes (bacteria)

listeriosis

listeria monocytogenes (bacteria)

effect: granulomatosis infantiseptica, death

cytomegalovirus (dna virus)

usually asymptomatic (virus)

cytomegalovirus (dna virus)

effect: deafness, microcephaly, mental retardation

parvovirus b19 (dna virus)

erythema infection

parvovirus b19 (dna virus)

effect: abortion

lentivirus (HIV) (RNA virus)

AIDS

lentivirus (HIV) (RNA virus)

effect: immunosuppression (AIDS)

rubivirus rubella (RNA Virus)

german measles

rubivirus rubella (RNA Virus)

effect: severe birth defects or death

direct contact, indirect contact

2 kinds of contact transmission

airborne, waterborne, foodborne

3 kinds of vehicle transmission

mechanical, biological

2 kinds of vector transmission

direct contact

MOT; cutaneous anthrax

direct contact

MOT; genital warts

direct contact

MOT; gonorrhea

direct contact

MOT; herpes

direct contact

MOT; rabies

direct contact

MOT; staphylococcus infections

direct contact

MOT; syphilis

indirect contact

eg drinking glasses, toothbrushes, toys, punctures, droplets from sneezing and coughing

indirect contact

MOT; common cold

indirect contact

MOT; enterovirus infections

indirect contact

MOT; influenza

indirect contact

MOT; measles

indirect contact

MOT; Q fever

indirect contact

MOT; pneumonia

indirect contact

MOT; tetanus

indirect contact

MOT; whooping cough

airborne

e.g. dust particles