bio 156 chapter 15 powerpoint pp07

8/14/2019 BIO 156 Chapter 15 Powerpoint PP07

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BIO 156

Chapter 15


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Human Infectious Disease


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The Infection Agents of Human Disease

Pathogens are microbes that cause disease. Infectious microbes invade and grow in body

tissues.

Contagious microbes can be easily transmittedfrom one organism to another.

Microorganisms may cause disease in evennormally healthy individuals, but those withweakened immune systems are more at risk.


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Many infectious diseases remain dangerous today. The germ theory of disease, generated from

Pasteur and Kochs work, increased our understanding of how microorganisms relate todisease.


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Viruses and bacteria are among the most

common infectious agents.

Viruses are composed of

a nucleic acid core, consisting of either DNA or RNA

a coat of protein molecules called the capsid.

Some capsids are covered by a viral envelope.


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Viral life cycle

The virus

attaches to target cellsenters the cell through phagocytosisreplicates its genetic informationassembles genetic information in capsids andformsnew viral particles

are released from the host cell


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AnimalVirus

Lifecycle


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Bacteria are single-celled organisms shaped likerods , spheres , or spirals . They reproduce by

replicating their DNA and splitting into twoidentical cells.


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Binary

Fission


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Fungi, protozoa, and helminths also

cause disease. Fungi include yeasts, molds, and

mushrooms.

Protozoa are single-celled eukayoticorganisms. Many harmless protozoa live inhuman intestines, while others invade thebody and cause disease.

Helminths are parasitic worms, such asflatworms and roundworms.


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MalariaLifecycle


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The Course of a Human Disease

Infection refers to the state of being infectedby a microorganism or to the process of beinginfected.

Disease is a change from the healthy state of the body.

Pathogens differ in their ability to causedisease. Pathogenicity is a microorganism or viruss

ability to enter the hosts tissues and cause

a change resulting in poor health.


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A pathogen produces a set of

disease characteristics. Every disease that infects the bodychanges the body structures andfunctions in specific ways.

Signs are detectable and measurablechanges in body function (fever, swollenlymph).

Symptoms are un-measurable changesin the body (headache, tiredness).

A syndrome is a specific group of signsand symptoms.


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A disease typically follows a series of five stages.

1. Incubation period 4. Period of decline2. Prodromal phase 5. Period of convalescence3. Acme period


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How Pathogens Cause Disease

Infection depends on a pathogensability to adhere to cells in specifictissues.

Pathogenicity and virulence depend onkey metabolic characteristics.

Ezymes and toxins released by thepathogen affect the microorganisms abilityto penetrate and damage cells.


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Toxins, microbial poisons, have twocategories: exotoxins and endotoxins. Exotoxins are protein molecules made by

bacteria present in body tissues. Evenminute amounts of an exotoxin can befatal.

Endotoxins are a lipid portion of the cell

wall of many bacteria. When the cell dies,endotoxins may be released.


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How Infectious Diseases are Transmitted

Pathogens must be transmitted to other hosts to spread disease. Endemic diseases occur in a small region

to a small number of individuals.

Epidemic diseases spread a larger thannormal number of individuals in a largepopulation.

An outbreak is a disease that occurs to alarger number of individuals within a smallpopulation.

A pandemic disease occurs worldwide.


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Direct transmission may occur throughdirect physical contact.

Direct transmission method include: Person-to-person contact mother-to-child contact

animal-to-person contact airborne particles and respiratory droplets


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Diseases can be transmitted by indirect

contact. Indirect transmission includes:

Touching inanimate objects covered with

pathogens Breathing pathogens carried on aerosols,

tiny airborne particles Being bitten by arthropods (mosquitoes,

flies, ticks) Consuming contaminated food and water


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Methods of Transmitting Disease


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Emerging Infectious Diseases and Bioterrorism

The emergence and resurgence of infectiousdiseases have several causes.

Emerging diseases are those that have

recently appeared in a population. Expanding world population is one major cause for emerging diseases.

Worldwide animal transport is another cause.

Increased international travel may spread diseaseto new areas.

Changes in food handling or processing mayspread disease as well.


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Reemerging infectious diseases haveexisted in the past but now showing anincrease in frequency or geographicrange.Causes for reemerging diseases

Antibiotic resistance Lowered immunity to infectious disease Poor public health programs

Climate change may be a cause for emerging and reemerging diseases.


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Emerging and Reemerging Diseases in the 1990s


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Bioterrorism is an attempt to use

infectious disease agents to inflict pain,suffering, and even death on largepopulations. Pathogens that cause the most concern

are those that can be spread throughaerosols and substances that can spreadto food and water supplies.

Developing and maintaining medicaltreatments is one of the best defensesagainst bioterrorism.


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End of Chapter 15

bio 156 chapter 15 powerpoint pp07

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