1

17Sexually Transmitted

Diseases

17 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.

2

17 STDs and Venereal Disease

•Currently, 65 million Americans are living with an incurable STD, and

15 million more Americans acquire STDs every year.

17 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.

3

17 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.

17Pubic 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.

4

17Pubic 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.

17 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.

5

17 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.

17 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.

6

17Box 17.1 Society, Values, and the Law: The Tuskegee Syphilis

Study

17 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 strain-

resistant form of the bacterium, in which case

ciprofloxacin or ceftriaxone is effective.

• Left untreated, gonorrhea can cause reduced fertility.

7

1717.7 Gonorrheal urethritis in men is marked by painful urination

and a discharge of pus

1717.8 Geographic and racial/ethnic distribution of gonorrhea (Part

1)

8

1717.8 Geographic and racial/ethnic distribution of gonorrhea (Part

2)

17 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.

9

17 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.

17 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

10

17 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.

17 17.9 Particles of herpes simplex virus 2 (HSV-2)

11

1717.10 Herpes outbreaks commonly occur on the shaft of the

penis or on the vulva

17 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.

12

1717.12 Normal cervix (left) and cervical cancer (right), as seen on

visual examination

17 HPV Vaccine

• HPV Vaccine

13

17 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.

17 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

14

1717.15 New cases of AIDS or HIV infection in 2003 by route of

infection

17 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.

15

17 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.

17 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.