Download Sexually Transmitted Diseases

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Sexually Transmitted
Diseases
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STDs and Venereal Disease
•Until recently, sexually
transmitted diseases (STDs)
were called venereal diseases,
after Venus, the Roman
goddess of love.
•The archetypal venereal
disease was syphilis,
supposedly transported from
America to Europe by
Columbus in 1492, and then
returned to America by the
colonists. People with the
disease were thought to bring it
upon themselves by engaging
in sinful behavior, and their
suffering was evidence of their
wrongdoing.
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STDs and Venereal Disease
•Currently, 65 million Americans are living with an incurable STD, and
15 million more Americans acquire STDs every year.
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Pubic Lice, Scabies Mites, and Trichomoniasis
• Pubic lice (“crabs”) are very small dark or tan-colored
flat insects with clawlike legs that grasp pubic hair
and gorge on human blood.
• They lay eggs, or “nits,” and glue them onto hairs.
Nits hatch in about a week and repeat the cycle. Lice
infestations come about by either direct or indirect
contact with bedding, towels, and so on.
• Itching is treated with over-the-counter insecticidal
lotions or shampoos containing permethrin or
pyrethrins (such as Rid) or the prescription
insecticide Lindane.
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Pubic Lice, Scabies Mites, and Trichomoniasis
•Pubic lice (“crabs”) are very small dark or tan-colored
flat insects with clawlike legs that grasp pubic hair and
gorge on human blood.
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Pubic Lice, Scabies Mites, and Trichomoniasis
(cont’d)
•Scabies are caused by mites
and are transmitted either
sexually or nonsexually.
•Female mites dig tunnels
within hairless layers of skin
and live for about 2 months,
laying eggs every few days.
•Eggs hatch, return to the skin
surface, mate, burrow into the
skin, and renew the cycle.
Infestation causes severe
itching that can be treated with
topical application of permethrin
lotion.
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Pubic Lice, Scabies Mites, and Trichomoniasis
(cont’d)
•Trichomoniasis is an infection of
the vagina or male urethra and
prostate gland caused by a
protozoan, Trichomonas vaginalis.
•Symptoms in women include
– a malodorous greenish or
frothy vaginal discharge
– vaginal itching and redness,
and
– an urge for frequent urination.
•A single oral dose of metronidazole
(Flagyl) can cure the disease. Males
may be asymptomatic carriers and
must be treated to prevent passing
the infection to others.
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Sexually Transmitted Bacterial Infections
•Syphilis is caused by infection with the corkscrew-shaped
bacterium, or spirochete, Treponema pallidum, and is spread by
direct contact, nearly always sexually.
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Sexually Transmitted Bacterial Infections
•The infection usually comes
from contact with a syphilitic
chancre, a painless sore that
exudes a fluid loaded with
spirochetes. These penetrate
the skin and multiply,
producing a chancre in the
newly infected person.
•Left unchecked, the infection
leads to a rash and flu-like
symptoms (the secondary
stage), the invasion of the
organism into the
cardiovascular, nervous, and
skeletal systems (the tertiary
stage), and eventually death.
Syphilis can be cured with
penicillin.
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Sexually Transmitted Bacterial Infections (cont’d)
•The main symptom of
secondary syphilis is a
painless rash, typically on
the palms or soles of the
feet.
•During tertiary syphilis,
the final stage of the
disease, the heart, central
nervous system and
skeleton are affected.
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17Box 17.1 Society, Values, and the Law: The Tuskegee Syphilis
Study
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Sexually Transmitted Bacterial Infections (cont’d)
• Gonorrhea (“clap” or “drip”) is caused by infection
with the bacterium Neisseria gonorrhoeae.
• Symptoms appear within 2 to 10 days and consist of
a yellow or bloody discharge from the vagina or
discharge of a thick pus from the urethra (in males).
• Infection spreads into the reproductive organs of
females and the epididymis of males, and is treatable
with penicillin or tetracycline unless it is a strainresistant form of the bacterium, in which case
ciprofloxacin or ceftriaxone is effective.
• Left untreated, gonorrhea can cause reduced fertility.
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by painful urination
1717.7 Gonorrheal urethritis in men is marked
and a discharge of pus
17.8 Geographic and racial/ethnic distribution of gonorrhea (Part
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1)
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17.8 Geographic and racial/ethnic distribution of gonorrhea (Part
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2)
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Sexually Transmitted Bacterial Infections (cont’d)
• Chlamydia, the most common of all reported
infectious diseases, is caused by the virus-like
bacterium Chlamydia trachomatis and is spread by
genital contact.
• Symptoms include a watery discharge and burning
pain during urination. Infection in the reproductive
tract can cause infertility and sterility.
• Chlamydia can be cured with azithromycin or
doxycycline.
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Sexually Transmitted Bacterial Infections (cont’d)
• Bacterial vaginosis refers to alterations in the normal
composition of vaginal microorgansisms. Vaginal
douching and sexual activity increase the likelihood
of developing bacterial vaginosis.
• Urethritis, or bacterial infections of the lower urinary
tract, are common and not always due to sexual
transmission.
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Viral STDs Live in Host Cells or in Virion Form
• The four classes of STD viruses are:
– Herpes simplex viruses (HSV), the cause of oral
and genital herpes
– Human papilloma viruses (HPV), the cause of
genital warts
– Hepatitis viruses, which attack the liver
– Human immunodeficiency virus (HIV), the cause
of AIDS
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Viral STDs Live in Host Cells or in Virion Form (cont’d)
• Herpes simplex 1 causes oral herpes in the form of
fever blisters or cold sores on the lips or inside the
mouth.
• Herpes simplex 2 causes genital herpes. Symptoms
include an outbreak of painful blisters or sores at the
site of infection, usually the penis, labia, or vaginal
walls. Blisters break, leaving ulcers that weep a clear
exudate containing immense numbers of highly
infectious virions. After a few days, the sores dry up
and disappear. Recurrent outbreaks may occur
because there is no cure for herpes. Acyclovir in
topical ointment or oral tablets can shorten the
outbreak period.
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17.9 Particles of herpes simplex virus 2 (HSV-2)
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on the shaft of the
17 17.10 Herpes outbreaks commonly occurpenis
or on the vulva
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Viral STDs Live in Host Cells or in Virion Form (cont’d)
•Human papillomaviruses
(HPV) cause genital warts
(Condylomata acuminata)
which infect the urogenital tract
or the skin near the genitalia
and are the principal cause of
cervical cancer. Warts can be
removed by surgery, freezing
with liquid nitrogen, or the
application of podophyllin, but
they may recur.
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17.12 Normal cervix (left) and cervical cancer (right), as seen on
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visual examination
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HPV Vaccine
• HPV Vaccine
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Viral STDs Live in Host Cells or in Virion Form (cont’d)
•Hepatitis virus B is
sexually transmitted;
symptoms include
jaundice, fever, and
swelling of the liver.
Chronic hepatitis B can be
treated (but not cured)
with lamivudine. A vaccine
is available.
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Viral STDs Live in Host Cells or in Virion Form (cont’d)
• AIDS is caused by HIV, the human immunodeficiency
virus, which exists in the body fluids of an infected
person. The four modes of transmission are:
– Vaginal and anal sexual intercourse
– Contaminated blood transfusions
– Sharing injection needles
– Passage of the virus from an infected mother to
her fetus or infant
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route of
1717.15 New cases of AIDS or HIV infection in 2003 byinfection
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Viral STDs Live in Host Cells or in Virion Form (cont’d)
• HIV attacks the blood cells and lymph nodes,
especially the CD4 lymphocytes (white cells of the
immune system), which it gradually destroys.
• When CD4 levels drop below 200 cells, or when
certain opportunistic infections occur, an HIV positive
person is considered to have AIDS.
• There is neither a cure nor a vaccine for AIDS.
Treatment involves combination therapy (HAART)
involving multiple drugs.
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Viral STDs Live in Host Cells or in Virion Form (cont’d)
•Treatment of AIDS is
directed at the
complications of the
disease and at the viral
replication cycle.
Antiretroviral therapies
include reverse
transcriptase inhibitors,
protease inhibitors, and
fusion inhibitors.
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Prevention or Reduction of Sexually Transmitted Diseases
• Ways to prevent or reduce the likelihood of STD
transmission include abstinence from sex, careful
choice of sexual partners, fewer partners, avoidance
of risky sexual behaviors, and the use of condoms.
• Public health campaigns can alter sexual behavior
and reduce the incidence of STDs. Programs that
teach practical skills, such as how to use a condom
and how to refuse a sexual invitation, are effective,
as are programs that deliver safer-sex messages
through peer networks.
• Abstinence-only programs offer limited success.
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