chapter 11 - principles of disease and epidemiology pathologystudy of disease etiologystudy of the...
TRANSCRIPT
Chapter 11 - Principles of Disease and Epidemiology
• Pathology Study of disease
• Etiology Study of the cause of a disease
• Pathogenesis Development of disease
• Infection Colonization of the body by pathogens
• Disease An abnormal state in which the body is not functioning normally
• Transient microbiota may be present for days, weeks, or months
• Normal microbiota permanently colonize the host
• Symbiosis is the relationship between normal microbiota and the host
Normal Microbiota and the Host
• In one organism is benefited and the other is unaffected.
• In both organisms benefit.
• i.e. E. coli produces vitamin K (and some B)
• In parasitism, one organism is benefited at the expense of the other.
Normal Microbiota and the Host:
Figure 14.2
• Locations of normal microbiota on and in the human body
Normal Microbiota and the Host:
• Microbial antagonism is competition between microbes.
• Normal microbiota protect the host by:
• occupying niches that pathogens might occupy
• producing acids
• producing bacteriocins
Normal Microbiota and the Host:
Normal Microbiota and the Host:
• Some normal microbiota are opportunistic pathogens.
• (vaginal yeast infection)
• Normal location: vagina, mouth
• (urinary tract infections)
• Normal location: large intestine
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Normal Microbiota and the Host:
• (hospital acquired diarrhea; may cause pseudomembranous colitis)
• Normal location: large intestine
• (a major cause of meningitis)
• Normal location: nasopharynx
• are live microbes applied to or ingested into the body, intended to exert a beneficial effect.
• are chemicals used to promote growth of beneficial microbiota
Classifying Infectious Diseases
• Symptom A change in body function that is felt by a patient as a result of disease
• Sign A change in body function that can be measured or observed as a result of disease.
• Syndrome A specific group of signs and symptoms that accompany a disease.
Classifying Infectious Diseases
• Communicable disease A disease that can be spread from one host to another.
• Contagious disease A disease that is easily spread from one host to another.
• Noncommunicable disease A disease that is not transmitted from one
host to another.
• i.e. Chicken pox, measles, common cold are contagious
• i.e. Tetanus, Anthrax are noncommunicable
• Incidence Number of new cases of a disease during a specific time period.
• Prevalence Total number of old and new cases of a disease during a specific time period.
• Sporadic disease Disease that occurs occasionally in a population.
• i.e. Eastern Equine Encephalitis
Occurrence of Disease
Occurrence of Disease• Disease constantly present in a
population. i.e. common cold
• Epidemic disease Disease acquired by many hosts in a given area in a short
time. i.e. influenza,
• Pandemic disease Worldwide epidemic. i.e. influenza; AIDS
• Immunity in most of a population.
• Acute disease Symptoms develop rapidly, but last a short time. i.e. influenza, cold
• Chronic disease Disease develops slowly, lasts a long time. i.e.
Hepatitis B
• Subacute disease Symptoms between acute and chronic. i.e. gingivitis
• Latent disease Disease with a period of no symptoms when the “microbe”
is inactive. i.e. genital herpes,
Severity or Duration of a Disease
• Local infection Pathogens limited to a specific area of the body. i.e.
pulmonary Tuberculosis; Strep throat
• Systemic infection An infection throughout the body.
• Focal infection Systemic infection that began as a local infection.
i.e. Tuberculosis; Tetanus
• Bacteremia Bacteria in the blood
• Septicemia Growth of bacteria in the blood
Extent of Host Involvement
• Toxemia Toxins in the blood
• Viremia Viruses in the blood
• Primary infection Infection that causes the initial illness; often acute
•
• Secondary infection Opportunistic infection after a primary (predisposing) infection
Extent of Host Involvement
The Stages of a Disease
Figure 14.5
• Reservoirs of infection are the primary receptacles of the infectious agent. They may or may not be the direct source of the infection.
• Animal
• dogs, bats, racoons, foxes, other mammals
• Rocky Mountain Spotted Fever: ticks
• soil, infected cows, sheep, other animals
• may be transmitted to humans
Reservoirs of Infection
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Reservoirs of Infection
• Human — HIV, gonorrhea
• Carriers may have inapparent infections or latent diseases
• Nonliving —
• Soil: Botulism (Clostridium botulinum), Tetanus (Clostridium tetani)
• Water: Cholera (Vibrio cholerae)
• Food: Tapeworm
• Contact
• Direct Requires physical contact between infected and susceptible host
• Indirect Spread by
• Droplet Transmission via airborne droplets; usually travel less than one
meter
Transmission of Disease
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
Microbiology
B.E Pruitt & Jane J. Stein
AN INTRODUCTIONEIGHTH EDITION
TORTORA • FUNKE • CASE
• Vehicle Transmission by an inanimate reservoir (food, water, air)
• Vectors Insects, especially fleas, ticks, and mosquitoes
• Insect carries pathogen on feet.
• Pathogen reproduces in vector. i.e. Malaria, Rocky
Mountain Spotted Fever disease
Transmission of Disease
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
Microbiology
B.E Pruitt & Jane J. Stein
AN INTRODUCTIONEIGHTH EDITION
TORTORA • FUNKE • CASE
Figure 14.7, 9
• Are acquired as a result of a hospital stay
• 5-15% of all hospital patients acquire nosocomial infections
• A leading cause of death in U.S.
Nosocomial (Hospital-Acquired) Infections
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Relative frequency of nosocomial infections
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
Common Causes of Nosocomial Infections
• Diseases that are new, increasing in incidence, or showing a potential to increase in the near future.
• Contributing factors:
• Evolution of new strains
•
• Inappropriate use of antibiotics and pesticides
• Antibiotic/pesticide resistant strains
• Changes in weather patterns (and global warming?)
• (and malaria)
Emerging Infectious Diseases
• Contributing factors:
• Modern transportation
•
• Ecological disaster, war, expanding human settlement
• Ebola
• Animal control measures
•
• Public Health failure
• Diphtheria
Emerging Infectious Diseases
• The study of where and when diseases occur
• How they’re transmitted
• How many infected
Epidemiology
Figure 14.11
EpidemiologyJohn Snow 1848-1849 Mapped the occurrence of
cholera in London
Ignaz Semmelweis 1846-1848 Showed that hand washing decreased the incidence of puerperal fever
Florence Nightingale 1858 Showed that improved sanitation decreased the incidence of epidemic typhus; backed by statistics
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
• Descriptive Collection and analysis of data regarding occurrence of disease
Snow
• Analytical Comparison of two different diseased groups OR diseased and healthy groups
Nightingale
• Experimental Study of a disease using controlled experiments
Semmelweis
• Case reporting Health care workers report specified disease to local, state, and national offices
• Nationally Notifiable Diseases
Physicians are required to report occurrence
Copyright © 2004 Pearson Education, Inc., publishing as Benjamin Cummings
PowerPoint® Lecture Slide Presentation prepared by Christine L. Case
Microbiology
B.E Pruitt & Jane J. Stein
AN INTRODUCTIONEIGHTH EDITION
TORTORA • FUNKE • CASE
Table 14.7
• Collects and analyzes epidemiological information in the U.S.
• Publishes Morbidity and Mortality Weekly Report (MMWR) www.cdc.gov
• Morbidity: incidence of a disease
• Mortality: death from disease
Centers for Disease Control and Prevention (CDC)