PowerLecture: Chapter 18 Life at Risk: Infectious Disease.

PowerLecture:PowerLecture:Chapter 18Chapter 18

Life at Risk: Life at Risk: Infectious DiseaseInfectious Disease

Learning ObjectivesLearning Objectives

Differentiate between the microorganisms Differentiate between the microorganisms that normally live on and in you and those that normally live on and in you and those which cause infection and disease.which cause infection and disease.

List the general characteristics of viruses, List the general characteristics of viruses, bacteria, and other parasites. bacteria, and other parasites.

Describe the different patterns of infectious Describe the different patterns of infectious disease and how you can protect yourself. disease and how you can protect yourself.

Impacts/IssuesImpacts/Issues

Virus, Virus EverywhereVirus, Virus Everywhere

Virus, Virus Everywhere Virus, Virus Everywhere

West Nile virus is a virus with historical West Nile virus is a virus with historical and present-day importance.and present-day importance.

In 324 B.C. it quite possibly killed In 324 B.C. it quite possibly killed

Alexander the Great.Alexander the Great. In 1999 West Nile virus In 1999 West Nile virus

was discovered in the U.S., was discovered in the U.S.,

the first time it had ever the first time it had ever

been seen in the Western been seen in the Western

Hemisphere.Hemisphere.

Figure 18.15Figure 18.15

Virus, Virus Everywhere Virus, Virus Everywhere

Avian (bird) flu, caused by the H5N1 virus, Avian (bird) flu, caused by the H5N1 virus, is rapidly spreading around the globe, is rapidly spreading around the globe, evidence that no place is safe when it evidence that no place is safe when it comes to infectious disease.comes to infectious disease.

Video: West Nile VirusVideo: West Nile Virus

This video clip is available in CNN Today This video clip is available in CNN Today Videos for Anatomy and Physiology, 2003, Videos for Anatomy and Physiology, 2003, Volume VII. Instructors, contact your local Volume VII. Instructors, contact your local sales representative to order this volume, sales representative to order this volume, while supplies last.while supplies last.

Useful References for Impacts/IssuesUseful References for Impacts/Issues

The latest references for topics covered in this section can be found at The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articleswww.thomsonedu.com to access InfoTrac articles. .

CDC: West Nile VirusCDC: West Nile Virus CDC: Avian InfluenzaCDC: Avian Influenza InfoTrac: Avian Flu, West Nile Virus, and InfoTrac: Avian Flu, West Nile Virus, and

Lyme Disease. Robert Charles Moellering Jr. Lyme Disease. Robert Charles Moellering Jr. et al. et al. Patient Care for the Nurse PractitionerPatient Care for the Nurse Practitioner, , April 2006.April 2006.

How Would You Vote?How Would You Vote?To conduct an instant in-class survey using a classroom response To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main system, access “JoinIn Clicker Content” from the PowerLecture main menu. menu.

Killing mosquitoes is the best defense Killing mosquitoes is the best defense against West Nile virus. Some people object against West Nile virus. Some people object to spraying, fearing harmful effects on health to spraying, fearing harmful effects on health or wildlife. Would you support a spraying or wildlife. Would you support a spraying program in your area?program in your area? a. Yes, spraying pesticides to kill mosquitoes is a. Yes, spraying pesticides to kill mosquitoes is

an effective way to limit the spread of this an effective way to limit the spread of this disease.disease.

b. No, the pesticides used to control the virus do b. No, the pesticides used to control the virus do more harm than good. more harm than good.

Useful References for Useful References for How Would You Vote?How Would You Vote?

The latest references for topics covered in this section can be found at the book The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articleswww.thomsonedu.com to access InfoTrac articles. .

InfoTrac: Suit over West Nile Spraying Goes InfoTrac: Suit over West Nile Spraying Goes Forward against City. Forward against City. New York Law JournalNew York Law Journal, June , June 13, 2005.13, 2005.

InfoTrac: Study Claims Risks of West Nile Spraying InfoTrac: Study Claims Risks of West Nile Spraying Exaggerated. Exaggerated. Pesticide & Toxic Chemical NewsPesticide & Toxic Chemical News, , May 3, 2004.May 3, 2004.

InfoTrac: A Global Market Isn’t as Easy as It Looks. InfoTrac: A Global Market Isn’t as Easy as It Looks. Business Week, Business Week, Sept. 3, 2001.Sept. 3, 2001.

Maine Environmental Policy Institute: OverkillMaine Environmental Policy Institute: Overkill

Section 1Section 1

Some General Principles Some General Principles of Infectious Diseaseof Infectious Disease

Some General Principles of Some General Principles of Infectious Disease Infectious Disease

The body is home to a great many “friendly” The body is home to a great many “friendly” microorganisms.microorganisms.

Many species of microorganisms colonize the Many species of microorganisms colonize the epithelial tissues of the skin, mouth, nasal epithelial tissues of the skin, mouth, nasal cavity, conjunctiva, GI tract, urethra, and cavity, conjunctiva, GI tract, urethra, and vagina.vagina.

All possess some sort of adhesion proteins on All possess some sort of adhesion proteins on their surfaces that allow them to “stick” to our their surfaces that allow them to “stick” to our tissues; pathogens, on the other hand, often do tissues; pathogens, on the other hand, often do not have this ability to “stick.”not have this ability to “stick.”

Fig. 18.1, p.340

conjunctivae of eyes

nasal cavity and nasopharynx

mouth

skin

intestinal tract

urethra vagina (females)


Different types of pathogens cause disease Different types of pathogens cause disease in different ways.in different ways.

An An infectioninfection occurs when a pathogen enters occurs when a pathogen enters cells or tissues and multiplies; if this growth cells or tissues and multiplies; if this growth interferes with normal body function, then it is interferes with normal body function, then it is termed a termed a diseasedisease..

Infectious diseases are those diseases that can Infectious diseases are those diseases that can be passed from one person to another.be passed from one person to another.


PathogensPathogens produce disease in different ways. produce disease in different ways.• Some bacteria produce Some bacteria produce toxinstoxins, chemicals that are , chemicals that are

poisonous to human tissues; the disease poisonous to human tissues; the disease botulismbotulism is is caused by a bacterial toxin produced by caused by a bacterial toxin produced by Clostridium Clostridium botulinumbotulinum..

• Septic shockSeptic shock is another condition resulting from is another condition resulting from bacterial toxins.bacterial toxins.

• Viruses cause disease by invading and destroying Viruses cause disease by invading and destroying body cells; others become body cells; others become latentlatent in the cell, only in the cell, only manifesting some time after infection.manifesting some time after infection.

• Some pathogenic fungi release enzymes to digest Some pathogenic fungi release enzymes to digest human tissues; parasitic worms and protozoa may human tissues; parasitic worms and protozoa may damage tissues directly or trigger harmful immune damage tissues directly or trigger harmful immune responses.responses.


To cause an infection, pathogens must To cause an infection, pathogens must meet several requirements.meet several requirements.

Pathogens must have a Pathogens must have a hosthost, an organism that , an organism that a pathogen can infect; a a pathogen can infect; a reservoirreservoir is a place is a place where the organism where the organism

can survive and can survive and

remain infectious, remain infectious,

including other including other

organisms (organisms (carrierscarriers), ),

soil, and water.soil, and water.


• The pathogen must have a way to leave the reservoir The pathogen must have a way to leave the reservoir and enter a host, attach to the host’s body, and enter and enter a host, attach to the host’s body, and enter the tissues.the tissues.

• Pathogens must have some way to avoid the host’s Pathogens must have some way to avoid the host’s defenses so that it can reproduce inside the host.defenses so that it can reproduce inside the host.

• The pathogen finally must be able to return to a The pathogen finally must be able to return to a reservoir or move to a new host.reservoir or move to a new host.

Infectious diseases are sometimes grouped Infectious diseases are sometimes grouped according to reservoirs; a according to reservoirs; a zoonosiszoonosis is an is an infectious disease carried by animals that can infectious disease carried by animals that can also infect humans.also infect humans.


Emerging diseases present new challenges.Emerging diseases present new challenges. Emerging diseasesEmerging diseases are those that only are those that only

recently have begun to infect humans or which recently have begun to infect humans or which were present only in limited areas previously.were present only in limited areas previously.

Factors influencing the emergence of new Factors influencing the emergence of new diseases include increased human population diseases include increased human population density, ease of travel, and such medical density, ease of travel, and such medical concerns as antibiotic resistance.concerns as antibiotic resistance.

Some General Principles of Some General Principles of Infectious DiseaseInfectious Disease

Many of these diseases are viral; examples Many of these diseases are viral; examples include West Nile virus, SARS virus, Ebola virus, include West Nile virus, SARS virus, Ebola virus, and Lyme disease.and Lyme disease.


Useful References for Section 1Useful References for Section 1


Centers for Disease Control and PreventionCenters for Disease Control and Prevention CDC: Emerging Infectious DiseasesCDC: Emerging Infectious Diseases InfoTrac: Antibiotics Alter the Normal InfoTrac: Antibiotics Alter the Normal

Bacterial Flora in Humans. Bacterial Flora in Humans. Biotech WeekBiotech Week, , April 7, 2004.April 7, 2004.

InfoTrac: Botulism. Jeremy Sobel. InfoTrac: Botulism. Jeremy Sobel. Clinical Clinical Infectious DiseasesInfectious Diseases, Oct. 15, 2005., Oct. 15, 2005.

Section 2Section 2

Viruses and Viruses and Infectious ProteinsInfectious Proteins

Viruses and Infectious ProteinsViruses and Infectious Proteins

A A virusvirus is a tiny, noncellular pathogen that is a tiny, noncellular pathogen that can infect the cells of almost every other can infect the cells of almost every other organism.organism.

A virus consists of a DNA, or RNA, core A virus consists of a DNA, or RNA, core surrounded by a protein coat (surrounded by a protein coat (capsidcapsid); some ); some viruses additionally have an outer lipid en viruses additionally have an outer lipid en velope.velope.

Viruses can replicate only after infecting a cell Viruses can replicate only after infecting a cell and taking over that cell’s metabolic machinery.and taking over that cell’s metabolic machinery.

viral RNA

rodlike virus

protein subunits of coat

Fig. 18.3a, p.342a

polyhedral virus

spike proteins

Fig. 18.3b, p.342

b

DNA protein coat

sheath

tail fiber

complex virusFig. 18.3c, p.342

c

viral RNA envelope

viral coat (proteins)

viral enzyme

enveloped polyhedral virus

spike proteins

Fig. 18.3d, p.342

d


Viruses multiply inside a host cell.Viruses multiply inside a host cell. Replication of a virus involves five basic steps:Replication of a virus involves five basic steps:

• A virus recognizes, and attaches to, a host cell.A virus recognizes, and attaches to, a host cell.• The virus, or its genetic core, enters the cell.The virus, or its genetic core, enters the cell.• Viral DNA, or RNA, directs the host cell in producing Viral DNA, or RNA, directs the host cell in producing

copies of viral nucleic acids and in making viral copies of viral nucleic acids and in making viral enzymes and other proteins.enzymes and other proteins.

• Viral nucleic acids and proteins are assembled into Viral nucleic acids and proteins are assembled into new viral particles.new viral particles.

• Newly formed viruses are released from the infected Newly formed viruses are released from the infected cell.cell.

viral DNA

some proteins for viral coat

coat surrounded by envelopea An enveloped DNA virus particle contacts the plasma membrane of host cell and fuses with it.

plasma membrane of host cell

nuclear envelope

other proteins for viral envelope

viral DNA

Fig. 18.4, p.342

DNA virus particleb Once inside thecytoplasm, viral DNAand viral coat separate.

c Host metabolicmachinery transcribesthe viral genes.

d Host machinery replicatesviral DNA.

e Genetic information translated into viral proteins

f Many new virusparticles assembled.

g Viral envelopeproteins becomeinserted into host’splasma membrane.

i Virus particles bud from plasmamembrane. Their viral coat becomeswrapped in protein-spiked membrane,which becomes the viral envelope.

j The finished particleis equipped to infect anew potential host cell.

h Particles leave nucleus,move to plasma membrane.


A cell will serve as a host for the synthesis of A cell will serve as a host for the synthesis of new viral particles only if the original virus can new viral particles only if the original virus can recognize and lock onto the cell’s surface. recognize and lock onto the cell’s surface.

Some viruses do not kill their host cells outright Some viruses do not kill their host cells outright but enter a period of latency.but enter a period of latency.

• One example is the herpes virus, introduced One example is the herpes virus, introduced previously as an example of a sexually transmitted previously as an example of a sexually transmitted disease.disease.

• Epstein-Barr virus (EBV) is also a herpes virus; it Epstein-Barr virus (EBV) is also a herpes virus; it causes causes infectious mononucleosisinfectious mononucleosis..


• RetrovirusesRetroviruses are RNA viruses that use an enzyme are RNA viruses that use an enzyme called reverse transcriptase to synthesize a DNA called reverse transcriptase to synthesize a DNA molecule for insertion into the host DNA; the molecule for insertion into the host DNA; the integrated form is called a integrated form is called a provirusprovirus. HIV is a . HIV is a retrovirus.retrovirus.

Figure 18.14aFigure 18.14a


Prions are infectious proteins.Prions are infectious proteins. PrionsPrions are small, infectious proteins linked to are small, infectious proteins linked to

several rare, fatal degenerative diseases of the several rare, fatal degenerative diseases of the nervous system.nervous system.

• Prions are misfolded versions of normal proteins Prions are misfolded versions of normal proteins found on brain neurons and other cell types.found on brain neurons and other cell types.

• Prions can bind to normal proteins and refold them, Prions can bind to normal proteins and refold them, creating clumps of protein in the brain, destroying creating clumps of protein in the brain, destroying brain tissue.brain tissue.


BSE (BSE (bovine spongiform encephalitisbovine spongiform encephalitis) or “mad ) or “mad cow disease” affects cows and can cause cow disease” affects cows and can cause variant Creutzfeldt-Jakob diseasevariant Creutzfeldt-Jakob disease (vCJD) in (vCJD) in humans; prions are also associated with a long humans; prions are also associated with a long known human-only version of CJD.known human-only version of CJD.

Figure 18.5bFigure 18.5b



InfoTrac: Cannibals to Cows: The Path InfoTrac: Cannibals to Cows: The Path of a Deadly Disease. of a Deadly Disease. NewsweekNewsweek, Mar. , Mar. 12, 2001.12, 2001.

InfoTrac: Cold Sore Virus Can Evade InfoTrac: Cold Sore Virus Can Evade Immune System. Immune System. UPI NewsTrackUPI NewsTrack, July , July 17, 2006.17, 2006.

Video: Mad Cow VictimVideo: Mad Cow Victim

This video clip is available in CNN Today This video clip is available in CNN Today Videos for Anatomy and Physiology, 2003, Videos for Anatomy and Physiology, 2003, Volume VII. Instructors, contact your local Volume VII. Instructors, contact your local sales representative to order this volume, sales representative to order this volume, while supplies last.while supplies last.

Section 3Section 3

Bacteria—Bacteria—

The Unseen MultitudesThe Unseen Multitudes

Bacteria—The Unseen Multitudes Bacteria—The Unseen Multitudes

Bacteria are prokaryotic cells.Bacteria are prokaryotic cells. Structural features appear rather simple Structural features appear rather simple

compared to more complex cells.compared to more complex cells.• There is no nucleus or other membrane-bound There is no nucleus or other membrane-bound

organelles.organelles.• Most bacteria have a cell wall that makes them Most bacteria have a cell wall that makes them

strong, semirigid, and gives them shape; coccus, strong, semirigid, and gives them shape; coccus, bacillus, and spirillum (bacillus, and spirillum (spirochetespirochete) are common cell ) are common cell shapes.shapes.

bacterial flagellumpilus

capsule

cell wall

plasma membrane

cytoplasm

DNA

ribosomes in cytoplasm

Fig. 18.6, p.344


• Bacterial flagellaBacterial flagella allow for motility; allow for motility; pilipili help bacteria help bacteria

attach to objects or each other.attach to objects or each other.

Figures 18.7 and 18.14bFigures 18.7 and 18.14b


Bacteria reproduce by prokaryotic Bacteria reproduce by prokaryotic fissionfission, a , a process that can be repeated every 20 minutes.process that can be repeated every 20 minutes.

• The chromosome is a single, circular DNA.The chromosome is a single, circular DNA.• Some bacteria possess Some bacteria possess plasmidsplasmids, small circles of , small circles of

extra DNA; plasmids may allow for fertility and for the extra DNA; plasmids may allow for fertility and for the transfer of drug resistance.transfer of drug resistance.

StreptococcusStreptococcus is a species of bacteria that is a species of bacteria that causes respiratory tract infections and causes respiratory tract infections and strep strep throatthroat; these bacteria possess the ability to ; these bacteria possess the ability to transfer genes. transfer genes.


Bacteria play both positive and negative Bacteria play both positive and negative roles in human society.roles in human society.

Some bacteria are useful, such as those used Some bacteria are useful, such as those used to make cheese and therapeutic drugs, but to make cheese and therapeutic drugs, but most are notorious for the diseases they cause.most are notorious for the diseases they cause.

AntibioticsAntibiotics are the products of some bacteria are the products of some bacteria and fungi that can be used to kill other bacteria.and fungi that can be used to kill other bacteria.

Antibiotics do not work against viruses; rather, Antibiotics do not work against viruses; rather, body defenses such as body defenses such as interferonsinterferons may block may block replication of viruses inside cells.replication of viruses inside cells.


A biological backlash to antibiotics is under A biological backlash to antibiotics is under way.way.

Because antibiotics have been both overused Because antibiotics have been both overused and in some cases inappropriately prescribed, and in some cases inappropriately prescribed, large numbers of bacterial species that were large numbers of bacterial species that were once susceptible to antibiotics are now resistant once susceptible to antibiotics are now resistant to their effects.to their effects.

Staphylococcus aureusStaphylococcus aureus

may soon be resistant to may soon be resistant to

all available antibiotics.all available antibiotics.



Bacteria cause some important emerging Bacteria cause some important emerging and reemerging diseases.and reemerging diseases.

Lyme diseaseLyme disease, caused , caused

by the spirochete by the spirochete

Borrelia burgdorferiBorrelia burgdorferi, is , is

an important emerging an important emerging

disease in the disease in the

United States.United States.

Figure 18.8aFigure 18.8a


TuberculosisTuberculosis (TB), caused by (TB), caused by Mycobacterium Mycobacterium tuberculosistuberculosis, is a reemerging disease., is a reemerging disease.

• Antibiotics had made TB rare by the 1970s in Antibiotics had made TB rare by the 1970s in developed nations, but many factors have since developed nations, but many factors have since allowed the number of TB cases to rise.allowed the number of TB cases to rise.

• In some areas of the world, all new cases of TB are In some areas of the world, all new cases of TB are antibiotic resistant.antibiotic resistant.

Figure 18.8bFigure 18.8b

Video: Salon InfectionsVideo: Salon Infections

This video clip is available in CNN Today This video clip is available in CNN Today Videos for Biology, 2003, Volume VII. Videos for Biology, 2003, Volume VII. Instructors, contact your local sales Instructors, contact your local sales representative to order this volume, while representative to order this volume, while supplies last.supplies last.


The latest references for topics covered in this section can be found at the book The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articleswww.thomsonedu.com to access InfoTrac articles. .

InfoTrac: Overdoing Antibiotics. InfoTrac: Overdoing Antibiotics. Harvard Harvard Health LetterHealth Letter, Nov. 2002., Nov. 2002.

InfoTrac: Chronic Middle Ear Infections InfoTrac: Chronic Middle Ear Infections Linked to Resistant Biofilm Bacteria. Linked to Resistant Biofilm Bacteria. PR PR NewswireNewswire, July 11, 2006., July 11, 2006.

Section 4Section 4

Infectious Fungi, Infectious Fungi, Protozoa, and WormsProtozoa, and Worms

Infectious Fungi, Protozoa, and Worms Infectious Fungi, Protozoa, and Worms

Parasitic fungi and protozoa are small but Parasitic fungi and protozoa are small but potentially dangerous.potentially dangerous.

Common fungal infections include yeast Common fungal infections include yeast infections, ringworm, and athlete’s foot.infections, ringworm, and athlete’s foot.

• Fungi in athlete’s foot and ringworm Fungi in athlete’s foot and ringworm

release enzymes that degrade keratin release enzymes that degrade keratin

in skin; inflammation can also occur.in skin; inflammation can also occur.• Yeast infections occur in the vagina Yeast infections occur in the vagina

and other mucous membranes and other mucous membranes

following changes to the chemistry following changes to the chemistry

of the organ system.of the organ system. Figure 18.9aFigure 18.9a


Several protozoa are important pathogens.Several protozoa are important pathogens.• Entamoeba histolyticaEntamoeba histolytica causes causes

amoebic dysenteryamoebic dysentery; it enters ; it enters

the body in food and water the body in food and water

contaminated with feces.contaminated with feces.• Giardia intestinalisGiardia intestinalis causes causes

giardiasis; it typically enters giardiasis; it typically enters

the body through water.the body through water.

Figure 18.9b-cFigure 18.9b-c


• Trypanosoma bruceiTrypanosoma brucei is transmitted by the tsetse fly is transmitted by the tsetse fly to humans, where it invades the central nervous to humans, where it invades the central nervous system and causes system and causes African sleeping sicknessAfrican sleeping sickness; ; untreated, it is fatal.untreated, it is fatal.

• Cryptosporidium parvumCryptosporidium parvum, which causes , which causes cryptosporidiosis, is an emerging disease in the U.S.; cryptosporidiosis, is an emerging disease in the U.S.; this organism is highly resistant to common this organism is highly resistant to common disinfectants.disinfectants.

Figure 18.9dFigure 18.9d


Worms also can be a serious threat.Worms also can be a serious threat. PinwormsPinworms are small, white roundworms that are small, white roundworms that

are easily transferred as eggs from the anal are easily transferred as eggs from the anal area of one person (usually a child) to the area of one person (usually a child) to the mouth of a new host via contaminated fingers.mouth of a new host via contaminated fingers.

Other notorious worms such as tapeworms, Other notorious worms such as tapeworms, hookworms, whipworms, and the large hookworms, whipworms, and the large AscarisAscaris intestinal worms can cause damage to body intestinal worms can cause damage to body tissues and organs.tissues and organs.



Structural Genomics of Pathogenic Protozoa: Structural Genomics of Pathogenic Protozoa: African TrypanosomiasisAfrican Trypanosomiasis

InfoTrac: Dark Fungi Emerging as Cause of InfoTrac: Dark Fungi Emerging as Cause of Lethal Infections. Nancy WalshLethal Infections. Nancy Walsh. Family . Family Practice NewsPractice News, May 15, 2006., May 15, 2006.

Section 5Section 5

Malaria: Efforts to Malaria: Efforts to Conquer a KillerConquer a Killer



CDC: MalariaCDC: Malaria WHO: MalariaWHO: Malaria InfoTrac: Fatal Inaction: There Is a Silver Bullet for InfoTrac: Fatal Inaction: There Is a Silver Bullet for

Africa’s Malaria Epidemic. Joshua Kurlantzick. Africa’s Malaria Epidemic. Joshua Kurlantzick. Washington MonthlyWashington Monthly, July–Aug. 2006., July–Aug. 2006.

InfoTrac: Push for New Tactics as War on Malaria InfoTrac: Push for New Tactics as War on Malaria Falters. Celia W. Dugger. Falters. Celia W. Dugger. The New York TimesThe New York Times, , June 28, 2006.June 28, 2006.

Malaria: Efforts to Conquer a Killer Malaria: Efforts to Conquer a Killer

MalariaMalaria kills nearly 3 million people kills nearly 3 million people annually, mostly children in Africa; 110 annually, mostly children in Africa; 110 million new cases arise each year.million new cases arise each year.

The cause of the disease is a protozoan The cause of the disease is a protozoan called called PlasmodiumPlasmodium, which is transmitted by , which is transmitted by the female the female AnophelesAnopheles mosquito. mosquito.

Fig. 18.10, p.347

g Female mosquito bites, sucks blood from infected human.Gametocytes in bloodenter her gut and matureinto gametes, whichfuse to form zygotes.

a Plasmodium zygotesdevelop in the gut offemale mosquitoes. Theybecome sporozoites,which migrate to theinsect’s salivary glands.

b Mosquito bites human,bloodstream carries thesporozoites to liver.

e Some of themerozoites enterliver, cause moremalaria episodes.

f Others developinto male, femalegametocytes thatare released intobloodstream.

sporozoite

male gametocyte in red blood cell

d Offspring (merozoites) enter

blood, invade red blood cells and reproduce.

They can do so over a prolonged period. Disease

symptoms (fever, chills, shaking) become more and

more severe.

merozoite

c Sporozoites reproduce in liver cells.

sporozoites

Fig. 18.10, p.347

g Female mosquito bites, sucks blood from infected human.Gametocytes in bloodenter her gut and matureinto gametes, whichfuse to form zygotes.

a Plasmodium zygotesdevelop in the gut offemale mosquitoes. Theybecome sporozoites,which migrate to theinsect’s salivary glands.

b Mosquito bites human,bloodstream carries thesporozoites to liver.

e Some of themerozoites enterliver, cause moremalaria episodes.

f Others developinto male, femalegametocytes thatare released intobloodstream.

male gametocyte in red blood cell

sporozoite

d Offspring (merozoites) enter

blood, invade red blood cells and reproduce.

They can do so over a prolonged period. Disease

symptoms (fever, chills, shaking) become more and

more severe.

merozoite

c Sporozoites reproduce in liver cells.

sporozoites

Stepped Art

Malaria: Efforts to Conquer a Killer Malaria: Efforts to Conquer a Killer

The symptoms of the disease are periodic The symptoms of the disease are periodic bouts of severe chills, high fever, sweats, bouts of severe chills, high fever, sweats, and shaking leading to debilitation and and shaking leading to debilitation and possibly anemia over time.possibly anemia over time.

Individuals who inherit one copy of the gene for Individuals who inherit one copy of the gene for sickle-cell anemia are partially protected from sickle-cell anemia are partially protected from the effects of malaria.the effects of malaria.

Many strains of Many strains of PlasmodiumPlasmodium are resistant to are resistant to drug therapy; drugs are also expensive.drug therapy; drugs are also expensive.

Current efforts seek to devise a malaria Current efforts seek to devise a malaria vaccine.vaccine.

Section 6Section 6

Patterns of Patterns of Infectious DiseasesInfectious Diseases

Patterns of Infectious Diseases Patterns of Infectious Diseases

Infectious pathogens spread in four ways.Infectious pathogens spread in four ways. There are four general ways by which infectious There are four general ways by which infectious

diseases can move between hosts:diseases can move between hosts:• Direct contactDirect contact with a pathogen by touching the with a pathogen by touching the

infected person.infected person.• Indirect contactIndirect contact, as by touching doorknobs or , as by touching doorknobs or

tissues previously in contact with the infected person; tissues previously in contact with the infected person; this could include food and water.this could include food and water.


• Inhaling pathogensInhaling pathogens that have been released by that have been released by coughs and sneezes from the infected person; this is coughs and sneezes from the infected person; this is the most common mode of transmission. the most common mode of transmission.

• Contact with a vectorContact with a vector, such as mosquitoes, flies, , such as mosquitoes, flies, fleas, and ticks, which can transfer the pathogen; fleas, and ticks, which can transfer the pathogen; these vectors are often called these vectors are often called disease vectorsdisease vectors. .



Nosocomial infectionsNosocomial infections are hospital acquired are hospital acquired infections affecting 5-10% of all hospitalized infections affecting 5-10% of all hospitalized patients each year; most are acquired by direct patients each year; most are acquired by direct contact. contact.


Diseases occur in four patterns. Diseases occur in four patterns. During an During an epidemicepidemic, disease rates increase , disease rates increase

above predicted levels; cholera is an example.above predicted levels; cholera is an example. When epidemics occur in several countries When epidemics occur in several countries

around the world in a given time frame, a around the world in a given time frame, a pandemicpandemic is declared; AIDS is an important is declared; AIDS is an important example.example.

A A sporadicsporadic disease breaks out irregularly and disease breaks out irregularly and affects few people; whooping cough manifests affects few people; whooping cough manifests this way.this way.


An An endemicendemic disease occurs more or less disease occurs more or less continuously; the common cold may be the best continuously; the common cold may be the best known example.known example.

Virulence is a measure of the damage a Virulence is a measure of the damage a pathogen does.pathogen does.

VirulenceVirulence is the relative ability of a pathogen to is the relative ability of a pathogen to cause serious disease; how fast the pathogen cause serious disease; how fast the pathogen invades tissues, how severe the damage is, invades tissues, how severe the damage is, and where the damage is all help define and where the damage is all help define virulence.virulence.

Antibiotic resistance in certain bacteria has Antibiotic resistance in certain bacteria has made those microbes highly virulent.made those microbes highly virulent.


There are many public and personal There are many public and personal strategies for preventing disease.strategies for preventing disease.

PreventionPrevention is the best way to combat infectious is the best way to combat infectious disease; hand washing is probably the single disease; hand washing is probably the single most important preventative tool.most important preventative tool.

Public health measures include vaccination Public health measures include vaccination programs, ensuring standards for safe water, programs, ensuring standards for safe water, food, and medical supplies, and dissemination food, and medical supplies, and dissemination of correct and current information.of correct and current information.

Fig. 18.13, p.349

SkinPreventative measures:• Hand washing• Limit contact with items used by an infected

BloodPreventative measures:• Avoid/prevent needle sharing/ IV drug abuse• Maintain pure public blood supplies• Vaccination programs against blood-borne pathogens (e.g., hepatitis B) GI tract

Preventative measures:• Hand washing• Proper food storage, handling, and cooking• Good public sanitation (sewage, drinking water)

Respiratory tractPreventative measures:• Hand washing• Cover mouth when coughing or sneezing• Proper disposal of used tissues• Vaccination programs

Infectious Infectious Diseases: Diseases:

Global Global Health Health ThreatsThreats

Video: Whooping Cough ImmunizationVideo: Whooping Cough Immunization

This video clip is available in CNN Today This video clip is available in CNN Today Videos for Anatomy and Physiology, 2004, Videos for Anatomy and Physiology, 2004, Volume VIII. Instructors, contact your local Volume VIII. Instructors, contact your local sales representative to order this volume, sales representative to order this volume, while supplies last.while supplies last.

Video: Global AIDSVideo: Global AIDS

This video clip is available in CNN Today This video clip is available in CNN Today Videos for Biology, 2003, Volume VII. Videos for Biology, 2003, Volume VII. Instructors, contact your local sales Instructors, contact your local sales representative to order this volume, while representative to order this volume, while supplies last.supplies last.

Useful References for Section 6 Useful References for Section 6


InfoTrac: The Science of Clean Water. InfoTrac: The Science of Clean Water. Elettra Ronchi. Elettra Ronchi. OECD ObserverOECD Observer, Mar. , Mar. 2003.2003.

InfoTrac: Pandemic Dilemma: Who Gets InfoTrac: Pandemic Dilemma: Who Gets the Shot? the Shot? Chicago Tribune, Chicago Tribune, June 27, June 27, 2006.2006.

PowerLecture: Chapter 18 Life at Risk: Infectious Disease.

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Transcript of PowerLecture: Chapter 18 Life at Risk: Infectious Disease.