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Chapter 13
Immunity and Infection
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The Chain of Infection
Transmitted through a chain of infection
Pathogen: Disease-causing microorganism
Reservoir: Natural environment of the pathogen
Can be a person, an animal, or an environmental component
Portal of exit
Means of transmission
Direct transmission
Indirect transmission
Vectors: Carrier of the pathogen from one host to another
Portal of entry
Penetration of the skin
Inhalation through mouth or nose
Ingestion
New host
Local infection or systemic infection
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3. The Body’s Defense System
Physical and chemical barriers
Skin
Mucous membranes
Cilia
The immune system
Immunological defenders
Neutrophils
Macrophages – “big eaters”
Natural killer cells
Dendritic cells – eat pathogens and activate lymphocytes
Lymphocytes
T-cells
Helper, Killer, and Suppressor
B-cells
Antibodies
Memory T and B cells
Antigens
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The Immune System
The inflammatory response
Histamine causes dilation of blood vessels, heat, redness, and swelling
Draws white blood cells to the area to attack invaders
The immune response
Natural (innate) response
Acquired (adaptive) response
Response has four specific phases
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5. Figure 13.1 The immune response
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The Immune System
Immunity
An infected person will never get the same illness again
Acquired immunity
Symptoms and contagion
Incubation: Viruses and bacteria are actively multiplying
Will not feel symptoms until the second or third phase of the immune response cycle
Prodromal period: Symptoms first appear
Symptoms often due to the immune response not the illness
Cytokines – chemical messengers released by cells to amplify and coordinate immune response, cause fever
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7. Contagion & Immunization
Epidemics and Pandemics
Epidemic: rapidly spreading disease or health-related concern
Pandemic: a widespread epidemic
Antigenic drift, antigenic shift
Immunization: process of ‘priming’ the body to remember an encounter with a specific antigen
Types of vaccines
Vaccine: Introduction of a killed or weakened pathogen to stimulate the body to produce antibodies
Active immunity: Person produces his or her own antibodies to the microorganism
Passive immunity: Injection of antibodies produced by other human beings or animals
Gamma globulin
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8. Allergy: The Body’s Defense System Gone Haywire
Allergies result from a hypersensitive and overactive immune system
Allergens: Substances that provoke response
The allergic response
Production of immunoglobulin E antibody (IgE)
Histamine: released by mast cells, causes inflammatory response
Anaphylaxis: Most serious, but rare, kind of allergic reaction
Dealing with allergies
Avoidance
Medication
Immunotherapy
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Pathogens and Disease
Bacteria: Microscopic single-celled organisms
Pneumonia
Meningitis
Strep throat and other streptococcal infections
Toxic shock syndrome and other staphylococcal infections
Tuberculosis
Tickborne infections
Ulcers
Heliobacter pylori
Antibiotic treatments
Both naturally occurring and synthetic substances that can kill bacteria
When misused, pathogens can become resistant to their effects
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10. Figure 13.2 Pathogens and associated infectious diseases
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Pathogens and Disease
Viruses
Parasites taking what they need for growth and reproduction, can’t reproduce by themselves, need host
Most common form of contagious disease
The common cold
Influenza
Chicken pox, cold sores, and other herpesvirus infections
Viral hepatitis
Jaundice
Human papillomavirus (HPV)
Treating viral illnesses
Antiviral drugs
Most viral diseases must simply run their course
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Pathogens and Disease
Fungi
Yeast infections, athlete’s foot, jock itch, and ringworm
Protozoa
Microscopic single-celled organism
Malaria, giardiasis, trichomoniasis, trypanosomiasis, and amoebic dysentary
Parasitic worms
Largest organisms that can enter the body to cause infection
Tapeworm and pinworm
Prions
Proteinaceous infectious particles
Linked to fatal degeneration disorders of the CNS
Lack DNA and RNA and consist only of protein
Do not trigger an immune response
Form deposits in the brain
Associated with transmissible spongiform encephalopathies (TSEs) that cause sponge-like holes in the brain
Creutzfeldt-Jakob disease (CJD)
Mad cow disease (Bovine spongiform encephalopathy, or BSE)
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13. Emerging Infectious Diseases
Selected infections of concern
West Nile virus
Severe acute respiratory syndrome (SARS)
Rotavirus
Escherichia coli 0157:H7 (strain of E. coli)
Hantavirus
Ebola
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14. Factors Contributing to Emerging Infections
Drug resistance
Poverty
Breakdown of public health measures
Environmental events
Travel and commerce
Mass food production and distribution
Human behaviors
Bioterrorism
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15. Other Immune Disorders: Cancer and Autoimmune Diseases
Immune system can break down
Autoimmune diseases
Rheumatoid arthritis
Systemic lupus erythematosus
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16. Supporting Your Immune System
Eat a balanced diet and maintain a healthy weight
Get enough sleep (6-8 hours a night)
Exercise, but not when you’re sick
Don’t smoke
Moderation of alcohol
Wash your hands frequently
Avoid contact with contagious people
Practice safe sex and don’t inject drugs
Receive all recommended vaccinations
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The Major STDs
Also known as sexually transmitted infections (STIs)
Spread of an infection from person to person mainly through sexual activity
STDs that pose a major health threat:
HIV/AIDS
Hepatitis
Syphilis
Chlamydia
Gonorrhea
Herpes
Human papillomavirus (HPV)
CDC (2008) estimated 65 million Americans were infected with an STD, and about 19 million Americans become newly infected with an STD each year
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HIV Infection and AIDS
Human immunodeficiency virus (HIV) is the virus which causes AIDS (acquired immunodeficiency syndrome)
Without treatment, AIDS kills nearly all of its victims
Approximately 65 million people around the world have been infected with HIV since the epidemic began
Nearly 1% of the world’s population
About 3.5 million new infections per year
21% of HIV-infected Americans are unaware of their condition
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What Is HIV Infection?
Chronic disease that progressively damages the body’s immune system
HIV attacks and invades CD4 T-cells and other essential elements of the immune system
HIV enters a human cell and converts its own genetic material, RNA, into DNA
Inserts this DNA into chromosomes of host cell
The viral DNA takes over the CD4 cell and replicates, destroys the immune functions of CD4 cell
People with AIDS are vulnerable to a number of serious opportunistic (secondary) infections
Once initial symptoms resolve, the asymptomatic period, also called the latency phase, may last from 2 to 20 years
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20. Transmitting the Virus
HIV lives only within cells and body fluids
Three primary means of transmission:
Specific kinds of sexual contact
Direct exposure to infected blood
HIV-infected women to her fetus or to infant during breastfeeding
Not through casual contact
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21. Populations of Special Concern for HIV Infection
Most common means of exposure:
Sexual activity between men
Injection drug use
Heterosexual contact
African American men and women are vastly overrepresented among people newly diagnosed with AIDS
Increasingly a disease that effects minorities, women, and the poor
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22. Figure 13.3 Routes of HIV transmission among Americans
Figure 18-2 Routes of HIV transmission among adults
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23. Symptoms of HIV Infection
Within a few days or weeks (on average, 2 to 4 weeks after exposure to the virus), some people will develop symptoms of primary (acute) HIV infection
Specialized test HIV RNA assay
Symptoms take months or years to develop, but as immune system weakens, variety of symptoms develop
Swollen lymph nodes
Lumps, rashes, sores
Pneumocystis pneumonia (fungal infection)
Kaposi’s sarcoma
Difficult-to-treat yeast infections in women
Tuberculosis
Weight loss, fevers, sweats
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24. Diagnosing HIV Infection
Most common tests check for the presence of antibodies to the virus
HIV antibody tests
ELISA (first test)
Western blot or immunoflourescence assay is done to confirm results
If HIV-positive, the next step is to determine the disease’s severity to plan appropriate treatment
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Treatment
Antiviral drugs
Reverse transcriptase inhibitors
Protease inhibitors
Entry inhibitors
HAART and Postexposure Prophylaxis (PEP)
Treatments for opportunistic infections
HIV and pregnancy
Treatment challenges
How can you protect yourself?
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Figure 13.4 What’s risky and what’s not: The approximate relative risk of HIV transmission of various sexual activities
Figure 18-4 What’s risky and what’s not: The approximate relative risk of HIV transmission of various sexual activities.
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Chlamydia
Most prevalent bacterial STD in the U.S.
Can cause sterility in men and women
In women, it can lead to pelvic inflammatory disease, infertility and ectopic (tubal) pregnancy
In men, chlamydia is the most common cause of epididymitis (inflammation of sperm-carrying ducts), and causes half of all cases of urethritis (inflammation of the urethra)
Symptoms
Usually asymptomatic in women, some have vaginal discharge, burning with urination, pain or bleeding with intercourse, and lower abdominal pain
In men, painful urination, watery discharge from penis, pain around testicles and in lower abdominals
Symptoms appear in 7-21 days
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Chlamydia
Diagnosis and treatment
Laboratory tests on a urine sample or a small amount of fluid from the urethra or cervix
Once diagnosed, infected person and partner are given antibiotics
Expedited partner therapy
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Gonorrhea
330,000 new cases reported to the CDC in 2008
Can cause arthritis, rashes, eye infections, PID, epididymitis, urethritis, and gonococcal conjunctivitis or gonorrheal infection of blood or joints in infants of infected mothers
Can infect throat or rectum through oral or anal sex
Symptoms
Usually asymptomatic in women, may have painful urination, increased vaginal discharge, and severe menstrual cramps
Thick yellow-white discharge, and painful urination in men, lips of urethral opening might become inflamed and swollen, lymph glands in groin may become enlarged and swollen, half of men have minor or no symptoms
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Gonorrhea
Diagnosis and treatment
Microscopic exam of discharge can diagnose infection
Oral antibiotics can cure the disease
Growing number of drug-resistant strains of gonorrhea is a major concern, only 1 class of antibiotics remains consistently effective
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31. Pelvic Inflammatory Disease (PID)
Occurs when initial infection by chlamydia or gonorrhea travels upwards into reproductive organs
Often serious enough to require hospitalization and surgery
25% of affected women have long-term problems
Leading cause of infertility in young women
Smoking, large number of sexual partners, and IUD usage are all risk factors for infection
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32. Pelvic Inflammatory Disease (PID)
Symptoms
Women can be asymptomatic
Long and painful periods, discharge, spotting, abdominal pain, fever, chills, nausea, and vomiting
Diagnosis and treatment
Diagnosis made on basis of symptoms, physical examination, ultrasound, and laboratory tests, may require laparoscopy
Antibiotics and sometimes hospitalization are required for treatment
Very important that partners be treated, many men asymptomatic
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33. Human Papillomavirus (HPV)
Most common STD in the U.S.
Causes a variety of human diseases:
Common warts
Genital warts
Genital cancers
Highly contagious, can spread through oral sex
Very common among young people
Two vaccines for HPV: Gardasil and Cervarix
Gardasil
Protects against four types of HPV virus that account for 90% of genital warts and 70% of cervical cancers
Most effective before the onset of sexual activity
Approved for boys and men
Cervarix
Doesn’t protect against genital warts, but may be more effective in protections against cervical cancer
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34. Human Papillomavirus (HPV)
Symptoms
Small bump on the skin or a large, warty growth
Cauliflower-like mass
May cause irritation and bleeding , painful urination
Diagnosis and treatment
Diagnosed based on the appearance of lesions
Often detected during routine PAP tests
Special tests can detect HPV and distinguish among the more common strains, including those that cause most cases of cervical cancer
Treatment focuses on reducing the number and size of warts
Cryosurgery (freezing)
Electrocautery (burning)
Laser surgery
Acid treatments
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Genital Herpes
1 in 5 adults in the U.S. has genital herpes
Two forms cause genital herpes and oral-labial herpes (cold sores)
HSV 1 (Type 1)
Usually exposed to virus during childhood
Oral-labial herpes (cold sores)
50-80% of U.S. adults have antibodies to HSV-1
HSV 2 (Type 2)
Almost always sexually transmitted
Usually occurs during adolescence and early adulthood
Asymptomatic in 80-90% of people
If you ever have an outbreak, consider yourself always contagious and inform partners
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Genital Herpes
Symptoms
90% of infected people have no symptoms
First episode causes flulike symptoms and genital lesions
Recurrent outbreaks
Diagnosis and treatment
Diagnosed through symptoms, physical examination, lab tests
No cure, carry virus for life
Antiviral drugs taken at the beginning of an outbreak can shorten the severity and duration of symptoms
Vaccines are in development
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Hepatitis B (HBV)
Inflammation of the liver which can cause serious and permanent damage to the liver
Highly contagious but preventable with vaccine
Transmitted through the exchange of bodily fluids and sharing needles or contaminated items
Can spread through nonsexual close contact
Symptoms
Can be asymptomatic
Flulike symptoms, nausea, vomiting, dark-colored urine, abdominal pain, and jaundice
Diagnosis and treatment
Diagnosed through blood tests
Most people recover, but can be chronic
carriers
Can be fatal, no cure
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Syphilis
Caused by bacterium: Treponema pallidum
Can be effectively treated with antibiotics
Symptoms
Primary phase: days after exposure
Characterized by painless ulcers, called chancres, highly contagious
Secondary phase: 3-6 weeks after chancre
Characterized by flulike symptoms and highly contagious skin rash
Late, or tertiary, phase
Damage to organs, dementia, cardiovascular damage, blindness, and death
Diagnosis and treatment
Diagnosed by examination of infected tissues and with blood tests
Treated by antibiotics but damage from late stages of infection can be permanent
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Other STDs
Trichomoniasis
Most common curable STD among young women
Single-celled organism
Bacterial vaginosis (BV)
Most common cause of abnormal vaginal discharge
Caused by unhealthy species of normal vaginal bacteria
Pubic lice and scabies
Contagious parasitic infections
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What You Can Do
Education
Diagnosis and treatment
Get vaccinated
Be alert for symptoms
Get tested
Inform your partners
Get treated
Prevention
Think and talk about responsible sexual behavior
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Chapter 13
Immunity and Infection
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