1. Most of the bacteria that cause STDs survive poorly in the environment and require intimate contact for transmission.
Gonorrhea (Table 25.8)
1. Gonorrhea is caused by Neisseria gonorrhoeae, has been generally declining in incidence, but it is still one of the most commonly reported bacterial diseases. (Figures 25.8,25.9)
2. Men usually develop painful urination and thick pus draining from the urethra; women may have similar symptoms, but they tend to be milder and are often overlooked.
3. Expression of different surface antigens allows attachment of N. gonorrhoeae to different types of cells, and frustrates development of a vaccine.
4. Inflammatory reaction to the infection causes scarring, which can partially obstruct the urethra or cause sterility in men and women.
Chlamydial Genital System Infections (Table 25.9, Figure 25.10)
1. Chlamydial genital infections, caused by Chlamydia trachomatis, are reported more often than any other bacterial disease.
2. Symptoms and complications of chlamydial infections are very similar to those of gonorrhea, but milder; asymptomatic infections are common, and readily transmitted.
3. Sexually active individuals should be tested at least once a year so that transmission can be halted and complications prevented.
Syphilis (Tables 25.10, 25.11)
1. Syphilis, caused by Treponema pallidum, is called "the great imitator" because its many manifestations can resemble other diseases. (Figure 25.12)
2. Primary syphilis is noted by a painless firm ulceration called a hard chancre; the organisms multiply and spread throughout the body. (Figure 25.11)
3. In secondary syphilis, skin and mucous membranes show lesions, which teem with the organisms; a latent period of months or years separates secondary from tertiary syphilis. (Figure 25.13)
4. Tertiary syphilis is not contagious. It is manifest mainly by damage to the eyes and the cardiovascular and central nervous systems. An inflammatory, necrotizing mass called a gumma can involve any part of the body. (Figure 25.14)
5. Syphilis in pregnant women can spread across the placenta to involve the fetus, resulting in congenital syphilis. (Figure 25.15)
Chancroid (Table 25.12)
1. Chancroid is another widespread bacterial STD, but it is not commonly reported because of difficulties making a bacterial diagnosis. Epidemics in the United States have been associated with prostitution.
2. Caused by Haemophilus ducreyi, chancroid is characterized by single or multiple soft, tender genital ulcers, and enlarged, painful groin lymph nodes. (Figure 25.16)
3. Some strains of H. ducreyi possess R factors, making treatment more difficult.
25.7 Viral STDs
1. Viral STDs are at least as common as bacterial STDs, but they are not yet curable.
Genital Herpes Simplex (Table 25.13, Figure 25.17)
1. It is a very common disease, important because of the discomfort and emotional trauma it causes, its potential for causing death in newborn infants, its association with cancer of the cervix, and the increased risk it poses of transmitting HIV infection and AIDS.
2. Symptoms may include a group of vesicles with itching, burning, or painful sensations; these break, leaving a tender superficial ulcer. Local lymph nodes enlarge. Many infections have few or no symptoms; some have painful recurrences.
3. The virus establishes a latent infection in sensory nerves and cannot be cured; it can be transmitted in the absence of symptoms, but the risk is greatest when lesions are present.
Papillomavirus STDs: Genital Warts and Cervical Cancer (Table 25.14)
1. Papillomavirus STDs are probably more prevalent than any other kind of STD; HPVs are the main cause of abnormal Pap smears in young women.(Figure 25.19)
2. They are manifest in two ways, as warts on or near the genitalia (Figure 25.18), and as precancerous lesions. The latter are asymptomatic and can only be detected by medical examination.
3. The causative agents, human papillomaviruses, are small DNA viruses that have not been cultivated in the laboratory.
AIDS (Table 25.15)
1. AIDS is the end stage of disease caused by human immunodeficiency virus (HIV). Worldwide, more than 5 million new HIV infections and 2.5 million deaths from AIDS occur each year (Figure 25.20). Advances in treatment, available to HIV disease victims in some countries, are not available to most of the world's HIV victims.
2. HIV disease is usually first manifest as a "flu"-like illness that develops about 6 days to 6 weeks after contracting the virus.
An asymptomatic interval follows that typically lasts almost 10 years, during which the immune system is slowly and progressively destroyed. Unusual cancers and infectious diseases then herald the onset of AIDS.
3. No vaccine or medical cure is yet available, but spread of infection could be significantly slowed by consistent use of condoms, and employment of sterile needles by injected-drug abusers. A marked reduction in mother to newborn transmission can be achieved with medication.
1. Intestinal protozoan diseases such as giardiasis and cryptosporidiosis are transmitted by the fecal-oral route in those individuals who engage in oral-genital and -anal contact as part of sexual activity.
"Trich" (Trichomoniasis) (Table 25.16)
1. Symptoms include itching, burning, swelling, and redness of the vagina, with frothy, sometimes smelly, yellow-green discharge, and burning on urination; men may have discharge from the penis, burning on urination, sometimes accompanied by painful testes and a tender prostate gland. Many women and most men are asymptomatic.
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