HUMAN BIOLOGY

reprodUCtIVe systeMs 321

of the uterus (hysterectomy). A woman’s partner should
also be treated, even if there are no symptoms.

Gonorrhea may have no symptoms at first

Like chlamydia, gonorrhea can be cured if it is diagnosed
soon after the infection starts. Gonorrhea is caused by
Neisseria gonorrhoeae (Figure 16.16B). This bacterium, also
called gonococcus, can infect epithelial cells of the genital
tract, the rectum, eye membranes, and the throat. Each
year in the United States there are about 650,000 new cases
reported; there may be up to 10 million unreported cases.
Part of the problem is that the initial stages of the disease
can be so uneventful that, as with chlamydia, a carrier may
be unaware of being infected.
Early symptoms in males usually are easy to see. Pus
begins to ooze from the penis and urinating becomes
painful and more frequent. A man can become sterile if
untreated gonorrhea leads to inflammation of his testicles
or scarring of the vas deferens.
In females, the early stages of gonorrhea can be much
more difficult to notice. For example, a woman may not
experience burning while urinating, and she may not have
an abnormal vaginal discharge. As a result, a woman’s
gonorrhea infection may well go untreated while the
gonococcus is spreading into her oviducts. Eventually, she
may experience violent cramps, fever, and vomiting. She
may even become sterile if PID develops and her oviducts
become blocked with scar tissue.
Antibiotics may be able to kill the gonococcus and thus
prevent complications of gonorrhea. Penicillin was once
the most commonly used drug treatment. Unfortunately,
antibiotic-resistant strains of gonococcus have developed.
At least one strain is resistant to all available antibiotics.
As a result, many doctors now order testing to determine
the strain responsible for a particular patient’s illness and
then treat the infection with an appropriate antibiotic—if
one is available.
Many people believe that once cured of gonorrhea, they
can’t be reinfected. That is not true, partly because there are
many different strains of N. gonorrhoeae.

Syphilis eventually affects many organs

Syphilis is caused by the bacterium Treponema pallidum
(Fig u re 16.16C). The bacterium is transmitted by sexual
contact. Once it reproduces, an ulcer called a chancre
(“shanker,” Figure 16.17A) develops. Usually the chancre
is flat rather than bumpy, is not painful, and teems with
trepo nemes. It becomes visible 1 to 8 weeks after infection
and is a symptom of the primary stage of syphilis. Syphilis
can be diagnosed in a cell sample taken from a chancre.
By then, however, bacteria have already moved into the
person’s bloodstream.
The secondary stage of syphilis begins a couple of months
after the chancre appears. Lesions can develop in mucous
membranes, the eyes, bones, and the central nervous
system. A blotchy rash breaks out over much of the body

Figure 16.17 Skin ulcers are signs of syphilis. A An ulcer

called a chancre (“shanker”), a sign of the first stage of

syphilis. B Chancres typical of secondary syphilis.

B CNRI/Science Source

A Biophoto Associates/Science Source

chancre

(Figure 16.17B). After the rash heals, the infection enters

a latent stage that can last for years. During that time, the

disease does not produce major outward symptoms and

can be detected only by laboratory tests.

The tertiary stage of syphilis usually begins from

5 to 20 years after infection. Lesions may develop in the

skin and internal organs, including the liver, bones, and

aorta. Scars form; the walls of the aorta can weaken. Trepo-

nemes also damage the brain and spinal cord in ways that

lead to various forms of insanity and paralysis. Infected

women who become pregnant typically have miscarriages,

stillbirths, or sickly infected infants.

Penicillin may cure syphilis during the early stages,

although antibiotic-resistant strains have now developed.

Table 16.4 Frequency and Causes of STDs

STD U.S. Cases Pathogen

Trichomoniasis 7,400,000 Protozoan

HPV infection 6,000,000 Virus

Chlamydia 1,200,000 Bacteria

Genital herpes 1,000,000 Virus

Gonorrhea 650,000 Bacteria

Syphilis 70,000 Bacteria

AIDS 40,000 Virus

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