Clueing in on Chlamydia

Abstract

It can be as sneaky as an ingrown toenail and as innocuous-seeming as the common cold. It infects more people in the United States than any other sexually transmitted disease, yet it ranks as one of the least familiar of those rarely divulged afflictions. It leads to infertility in more than 20,000 women in the United States each year, but many of them won't discover they have had the disease until they try to get pregnant. The bacterium responsible for this trickery, Chlamydia trachomatis, has managed to escape much of the public recognition it deserves for its role in female infertility. Yet scientific studies conducted over the last decade have consistently shown that about 75 percent of women who cannot get pregnant because of a fallopian tube blockage also test positive for chlamydia antibodies, indicating past or present infection, notes H. Hunter Handsfield, an epidemiologist at the University of Washington in Seattle. Scientists have also begun to blame chlamydia for a dramatic rise in ectopic, or tubal, pregnancies over the past two decades. This dangerous complication of early pregnancy occurs when the fertilized egg becomes wedged within a fallopian tube instead of making its way to the uterus, where it belongs. When the misplacement becomes apparent, physicians must remove the fetus and repair any damaged tissue. Otherwise, the growing fetus may burst through the fragile tubean emergency that can cause massive blood loss and send the mother into physiological shock. Last December, the Centers for Disease Control reported that more than 88,000 women in the United States developed ectopic pregnancies in 1987 a nearly fourfold increase over the 1970 rate. Ectopic pregnancy now ranks as the leading cause of pregnancy-related death among women in the first trimester. Although other sexually transmitted diseases can also cause ectopic pregnancy, the rising numbers appear inextricably linked with chlamydia, asserts A. Eugene Washington, an epidemologist and gynecologist at the University of California, San Francisco. Chlamydia may be responsible for as much as 50 to 80 percent of the increase in ectopic pregnancies, he says. But scientists might avert the infection's tragic reproductive effects if new avenues of research live up to their early promise. Investigators have begun to unravel the basic biology of how chlamydia causes such lasting problems, and in doing so they have uncovered links to a class of proteins with mysterious connections to other diseases such as leprosy and tuberculosis. Eventually, such work may suggest ways to refine the clinical diagnosis of chlamydia, and may even yield the first effective vaccine against the disease. Another facet of this research could produce a test that would offer women with a history of chlamydia a way to gauge their risk of infertility or ectopic pregnancy, and would assist physicians in determining which of these patients need more extensive testing to detect hidden damage resulting from the infection. Findings emerging from this work already offer clues to help explain why so many chlamydia-infected women experience no symptoms.