Chlamydia Infection
Chlamydia Infection
Disease History, Characteristics, and Transmission
Introduction
Chlamydia trachomatis is the most common cause of sexually transmitted disease (STD) around the world. Any sexually active individual is at risk of chlamydia, as this infection is often known. Because the majority of cases produce no symptoms, people often do not realize they are infected and go on to infect others. Chlamydia can have serious consequences for a woman's reproductive health and often leads to infertility. Certain strains of C. trachomatis cause an eye disease called trachoma, which is responsible for about six million cases of infectious blindness in the developing world. In addition, C. psittaci is a Chlamydia species carried by birds that occasionally infects humans, resulting in an unusual form of pneumonia. The other important Chlamydia species is C. pneumoniae, which infects approximately one half of the world's population and sometimes causes upper and lower respiratory tract infections. All of these infections can be treated successfully with antibiotics, but many people go undiagnosed or do not have access to treatment.
Disease History, Characteristics, and Transmission
The three main Chlamydia species are among the world's most prevalent microbial pathogens (diseasecausing organisms) and are a significant cause of ill health. When C. trachomatis infects the genital tract it often produces no symptoms at all, but women may report a burning sensation on urination and a vaginal discharge. Men may experience a discharge from the penis, as well as itching and a burning sensation. Chlamydia infection, if left untreated, can cause extensive damage to the female reproductive system, leading to pelvic inflammatory disease and infertility. It can also lead to ectopic pregnancy, a potentially fatal condition where a fertilized egg begins to develop within one of the fallopian tubes instead of in the womb. Women with chlamydia are also up to five times more likely to become infected with HIV if exposed to it.
Trachoma is a chronic inflammation of the conjunctiva, which are the membranes covering the inside surfaces of the eyelids, the white of the eye, and the cornea. The infection leads to blindness through scarring of these tissues. C. psittaci causes a pneumonia of gradual onset over one to two weeks, with severe headache and a cough that may result in spitting up blood. C. pneumoniae can cause a range of infections including sinusitis, pharyngitis (throat infection), bronchitis, and pneumonia. It is responsible for up to 12% of cases of community-acquired pneumonia.
WORDS TO KNOW
FOMITE: A fomite is an object or a surface to which an infectious microorganism such as bacteria or viruses can adhere and be transmitted. Transmission is often by touch.
SEXUALLY TRANSMITTED DISEASE (STD): Sexually transmitted diseases (STDs) vary in their susceptibility to treatment, their signs and symptoms, and the consequences if they are left untreated. Some are caused by bacteria. These usually can be treated and cured. Others are caused by viruses and can typically be treated but not cured. More than 15 million new cases of STD are diagnosed annually in the United States.
C. trachomatis is transmitted from person to person through genital, oral, and anal sexual intercourse, and can affect anyone who is sexually active. Young women are especially at risk, because the infection is more likely to take hold where the cervix is not fully matured. C. trachomatis can also be transmitted from mother-to-child during childbirth. Newborns exposed to C. trachomatis from their mother's cervix may develop conjunctivitis or pneumonia. The strains of C. trachomatis that cause trachoma are transmitted from hand-to-hand and also by handling fomites, objects that have been used by an infected person. Common fomites include sheets, crockery, clothing, books, and papers. Trachoma is more common in conditions of poor hygiene and overcrowding; it is often found in arid countries where access to water is limited. Reinfection between family members is common. Finally, C. pneumoniae is spread from hand-to-hand and by coughs and sneezes.
Scope and Distribution
Chlamydia is the most frequently reported bacterial sexually transmitted disease in the United States, according to the Centers for Disease Control and Prevention (CDC), with nearly one million cases reported in 2004. The true number is probably much greater than this—maybe three to five million cases per year—because so many people are unaware that they are infected. World Health Organization (WHO) data gathered from screening programs show that chlamydia is a significant public health problem the world over. In Australia, for instance, it is the most common sexually transmitted disease, while in Europe, rates among pregnant women range from 2.7% in Italy, to 6.2% in the United Kingdom, 6.7% in Denmark, and 8% in Iceland. In African countries, rates of chlamydia infection among pregnant women range 6–13%. Globally, the WHO estimates there are around 92 million new cases of chlamydia infection each year, about 50 million of which are among women.
IN CONTEXT: CONDOM USE BY YOUNG PEOPLE
Condom use can decrease transmission of sexually transmitted disease. The list below reflects selected data from the World Health Organization regarding condom use by young people (15–24), a group considered at higher risk due for sexually transmitted diseases.
The list below contains data from 20 countries selected to show the full spectrum (maximum and minimum) in results reported by WHO as of February 2007. Data was not available for all countries, including a lack of inclusion of data from countries such as Australia, Belgium, Brazil, China, France, Germany, Italy, Russian Federation, Thailand, Ukraine, United Kingdom, United States of America, and Zimbabwe.
Condom use by young people 15 to 24 years old (with the year data was gathered or reported):
- Madagascar Males: 12%; Females: 5% (2003)
- Chad Males: 25%; Females: 17% (2004)
- Ethiopia Males: 30%; Females: 17% (2000)
- Haiti Males: 30%; Females: 19% (2000)
- Mali Males: 30%; Females: 14% (2001)
- Mozambique Males: 33%; Females: 29% (2003)
- Bolivia Males: 37%; Females: 20% (2003)
- Rwanda Males: 41%; Females: 28% (2004)
- Zambia Males: 42%; Females: 33% (2001)
- Nigeria Males: 46%; Females: 24% (2003)
- United Republic of Tanzania Males: 46%; Females: 34% (2004)
- Kenya Males: 47%; Females: 25% (2003)
- Gabon Males: 48%; Females: 33% (2000)
- Uzbekistan Males: 50%; Females: % (2002)
- Ghana Males: 52%; Females: 33% (2003)
- Uganda Males: 55%; Females: 53% (2004)
- Cameroon Males: 57%; Females: 46% (2004)
- India Males: 59%; Females: 51% (2001)
- Viet Nam Males: 68%; Females: % (2005)
- Namibia Males: 69%; Females: 48% (2000)
- Botswana Males: 88%; Females: 75% (2000)
SOURCE: Multiple Indicator Cluster Survey and Demographic and Health Surveys. WHOSIS (WHO Statistical Information System), World Health Organization.
In some parts of the developing world, 90% of the population is infected with one of the strains of C. trachomatis that can cause trachoma. Despite ongoing efforts at control, there are still more than 500 million people at high risk of infection, over 140 million infected, and six million trachoma-blinded individuals in Africa, the Middle East, Central and Southeast Asia, and certain countries in Latin America, according to WHO data.
Treatment and Prevention
Treatment of chlamydia infections is straightforward, using antibiotics, such as tetracylines, macrolides, or fluoroquinolones. Resistance of the bacterium to these drugs is uncommon. However, diagnosis of the sexually acquired infection requires laboratory equipment that is not often available in less developed countries. Diagnosis involves a urine test and sometimes a swab of fluids from the cervix or penis. The sexual partners of those infected should also be tested and treated, if necessary, to prevent reinfection. Moreover, persons with chlamydia should abstain from sexual intercourse until treatment is completed. Condoms provide some protection against transmission of the bacterium.
Screening, that is, testing people who do not have symptoms, is an important part of monitoring the prevalence of chlamydia. Many countries have adopted screening programs. The CDC recommends annual screening for all sexually active women aged 25 or younger. Older women with risk factors, such as a new sex partner or multiple sex partners, are often advised to have an annual screening as well, as should all pregnant women.
According to the WHO, a vaccine against C. trachomatis, administered prior to adolescence and which would be effective through the childbearing years, would be the best way to halt the toll of the infection globally. There are two such vaccines currently in development.
Impacts and Issues
The greatest impact of sexually transmitted C. trachomatis is the silent nature of the infection. Three-quarters of those infected are unaware of the fact because they have no symptoms. This means they can infect others and continue to do so until the disease is diagnosed. For women, the damage that untreated chlamydia inflicts on the reproductive system is also silent. Over one-third of women with untreated chlamydia develop pelvic inflammatory disease and can lose fertility, often without even being aware of the reason why. Screening is important so that infection can be dealt with before permanent damage to the uterus, fallopian tubes, and the surrounding tissues develops.
The control of chlamydia and other sexually transmitted diseases, like HIV, involves education aimed at reducing risky sexual behaviors. Both sexual abstinence and having sexual intercourse only with a partner who is not infected are effective ways of avoiding infection with C. trachomatis. Having sex with multiple partners increases the risk. International health officials attempt to offer advice and present facts about sexual behaviors and their link to sexually transmitted diseases such as chlamydia in a non-judgmental manner, taking into account cultural differences in differing populations.
The impact of trachoma in less developed countries has important social and economic implications. Loss of vision from trachoma often starts in middle life, although the infection may be present much earlier. It is also two to three times more common among women, probably due to the fact that women generally spend a greater time in close contact with small children, who are the main reservoir of infection. Middle-aged women often make an important contribution to the family income and, therefore, disability in this group has a severe economic impact. That is one of the reasons why the WHO launched a global health alliance in 1997 with the goal of eliminating trachoma as a blinding disease by 2020.
See AlsoChlamydia pneumoniae; Psittacosis; Sexually Transmitted Diseases; Trachoma.
BIBLIOGRAPHY
Books
Wilson, Walter, and Merle A. Sande. Current Diagnosis & Treatment in Infectious Diseases. New York: McGraw Hill, 2001.
Web Sites
Centers for Disease Control and Prevention (CDC). “Chlamydia—CDC Fact Sheet.” April 2006. <http://www.cdc.gov/std/chlamydia/STDFactChlamydia.htm> (accessed January 28, 2007). World Health Organization Department of HIV/AIDS.
“Global Prevalence of Selected Curable Sexually Transmitted Infections: Chlamydia.” <http://www.who.int/docstore/hiv/GRSTI/003.htm> (accessed January 29, 2007).
World Health Organization Initiative for Vaccine Research (IVR). “Sexually Transmitted Diseases.” <http://www.who.int/vaccine_research/diseases/soa_std/en/index.html> (accessed January 28, 2007).
World Health Organization Prevention of Blindness and Visual Impairment. “Trachoma.” <http://www.who.int/blindness/causes/priority/en/index2.html> (accessed February 14, 2007).
Susan Aldridge