Listeria monocytogenes

over several days. Combs and brushes should be plunged into very hot water to kill any attached eggs. The National Pediculosis Association discourages the use of lindane products (such as Kwell), because they appear to be potentially more toxic and no more effective than other treatments. Still, no product kills 100 percent of nits. Lice medications are not intended to be used on a routine or preventive basis.

All lice-killing medications are pesticides, and therefore should be used with caution. A pharmacist or physician should be consulted before using or applying pesticides when the person is pregnant, nursing, or has lice or nits in the eyebrows or eyelashes or has other health problems (such as allergies). Head lice pesticides can be absorbed into the bloodstream; therefore, they should not be used on open wounds on the scalp or on the hands of the person applying the medication. These pesticides should not be used on infants and should be used with caution on children under age two. Instead, lice and nits can be removed manually or mechanically.

The product should be used over a sink (not a tub or shower) to minimize pesticide absorption and exposure to the entire body. Eyes of the affected individual must be kept covered while administering the pesticide.

All nits must be removed from the hair shaft. Bedding and recently worn clothing should be washed in hot water and dried in a hot dryer. Combs and brushes should be cleaned and then soaked in hot (not boiling) water for 10 minutes. Lice sprays should not be used, according to the National Pediculosis Association. Vacuuming is the best way to remove lice and attached nits from furniture, mattresses, rugs, stuffed toys, and car seats.

Neighborhood parents and the child's school, camp, or child care provider should be notified of the infestation. Children should be checked once a week for head lice.

Body lice can be killed by placing infested clothing in a hot dryer for five minutes, by washing clothes in very hot water, or by burning.

Pubic lice can be treated with an over-the-counter treatment, including A-200 Pyrinate, Rid, and Nix or with Kwell, a prescription medication (not recommended for use by pregnant women).

For more information about lice, contact. The National Pediculosis Association, P.O. Box 149, Newton, MA 02161 or call (800) 446-4NPA. For more information about head lice treatment, write for a free brochure to: The Office of Public Affairs, Nonprescription Drug Manufacturers Association, 1150 Connecticut Avenue NW, Washington, DC 20036.

Listeria monocytogenes A species of bacteria that infect many domestic and wild animals and in humans cause MENINGOENCEPHALITIS and sometimes infections of the womb. See also PREGNANCY AND INFECTIOUS DISEASE; LISTERIOSIS.

listeriosis A food-borne illness that may cause no symptoms in healthy people but that is particularly dangerous to a fetus or newborn, the elderly, and people with damaged immune systems. The illness is common among cattle, pigs, and poultry.

Listeriosis occurs in about 7.5 cases for every 1 million people. Once thought to be exclusively a veterinary problem, it was identified as a human disease in 1981 when a Canadian outbreak was linked to tainted cole slaw made from cabbage grown in soil fertilized with Lzsiena-infected sheep manure. Four years later, another outbreak was traced to Mexican-style soft cheese in California, which sickened 150 people including many pregnant women, resulting in newborn deaths.

From 1987 to 1992, the government recalled cooked products from 27 firms, including hot dogs, bologna and other luncheon meat, chicken salad, ham salad, sausages, chicken, sliced turkey breast, and sliced roast beef. Cheese, dairy, sandwich, prepared salad, and smoked fish recalls from 1987 to 1992 included 516 products from 105 firms.

Cause Listeriosis is caused by one species in a group of bacteria called Listeria monocytogenes, found in cow's milk, animal and human feces, soil, and leafy vegetables. In the past 10 years, there have been several outbreaks that seem to have been linked to the ingestion of soft cheeses (such as feta, some types of Mexican cheeses, Camembert, blue-veined cheeses) and deli-type lunch-meats. One recent study found that 20 percent of hot dogs tested contained the bacterium L. monocytogenes. Those with impaired immune systems may catch the disease from undercooked chicken.

The bacteria is remarkably tough, resisting heat, salt, nitrite, and acidity much better than many other organisms. It can survive on cold surfaces and can multiply slowly at temperatures as low as 34 degrees F. (Refrigeration at 40 degrees F or below stops the multiplication of many other food-borne bacteria.) Freezing the food will stop the bacteria from multiplying, and commercial pasteurization will eliminate the organism in dairy products. Listeria does not change the taste or smell of food.

When Listeria is found in processed products, the contamination probably occurred after processing (rather than due to poor heating or pasteurizing).

Listeriosis also can be spread through sexual contact, although it is not known how common this is.

Babies can be born with listeriosis if their mothers eat contaminated food during pregnancy. Pregnant women are 20 times more likely than other healthy adults to get listeriosis; about one third of all cases happen during pregnancy. However, it is newborns rather than their mothers who suffer the most serious effects of infection during the pregnancy.

Patients with AIDS are 300 times more likely to get listeriosis than healthy people. Others at increased risk include persons with cancer, diabetes, kidney disease, those who take glucocorticosteroid drugs, or the elderly. While healthy adults and children sometimes become infected, they rarely become seriously ill.

Symptoms Healthy adults may not have any symptoms at all or may experience a flulike illness with fever, muscle aches, and nausea or diarrhea. If infection spreads to the nervous system, it can cause a type of meningitis, leading to symptoms including headache, stiff neck, confusion, loss of balance, or convulsions.

If a pregnant woman develops the infection, she may experience fever, tiredness, headache, sore throat, dry cough, or back pain. After a few days she will feel better but notice that the fetus is not moving; she may miscarry up to the sixth month or go into labor prematurely; some infants may be stillborn.

If the fetus is affected early in the pregnancy, the baby will probably be born prematurely, with low birth weight and very ill, with breathing problems, blue skin, and low body temperature. If the baby survives, there may be a bloodstream infection or MENINGITIS. Half of these babies die, even if treated. Fetuses affected later in the pregnancy may be carried to term with normal birth weight; if infected during delivery, they may develop meningitis; 40 percent may die. Some surviving babies may have permanent brain damage or mental retardation.

Complications Adults with impaired immune systems may develop MENINGITIS with fever, intense headache, nausea, and vomiting. This is followed by delirium, coma, collapse, and shock; sometimes, abscesses and skin rash appears.

Diagnosis There is no routine screening test for susceptibility during pregnancy as there is for rubella and some other infections. A blood or spinal fluid culture will reveal the infection. During pregnancy, a blood test is the most reliable way to diagnose the infection.

Treatment Antibiotics are most helpful in pregnant women to prevent disease in the fetus. Babies with listeriosis receive the same antibiotics as adults, although a combination of antibiotics may be used until diagnosis is certain. Even with prompt treatment, some infections result in death, especially those with other serious medical problems.

Prevention While most people don't have to worry about the disease, scientists at the Atlanta-based Centers for Disease Control warn that pregnant women, the very old, and those with damaged immune systems might want to avoid deli-counter foods and soft cheeses (there is no risk for hard cheese, processed slices, cottage cheese, or yogurt). Those at risk are advised to cook hot dogs to a steaming 160 degrees for several minutes to avoid contamination; hot dogs at restaurants, ball parks, etc., should be avoided, since cooking temperatures can't be verified. One study found that garlic inhibits the growth of this harmful bacteria in the intestine, probably because of a sulfur compound found in fresh garlic.

liver fluke See FLUKE; SCHISTOSOMIASIS, lockjaw See TETANUS.

loiasis (loaisis or loaiasis) A form of the tropical parasitic disease FILARIASIS caused by an infestation of the Loa loa worm, which may travel for 10 or 15 years underneath the skin and causes an inflammation known as a calabar swelling.

Sometimes the migrating worms can be seen underneath the conjunctiva in the eye. Commonly called the eye worm, the name loa loa actually means "worm worm." The disease is limited to the region of the rain forests in the Congo River area in central and western Africa and equatorial Sudan; it is especially common in Cameroon and on the Ogowe River. An estimated 20 million people are infected with the worm; in the Congo

River basin, up to 90 percent of villagers in some areas are infected.

Cause The disease is acquired through the bite of an infected African deer fly Once inside the body, the infective larvae develop slowly into a mature adult (the process takes about a year). During this period, it lives and moves around underneath the skin. In periods of growth and development, Loa loa makes frequent excursions through the connective tissues, where it is often noticed by the victim. Adult worms (which live for up to 15 years) move in the subcutaneous tissues where the female deposits the microfilariae. Microfilariae may become apparent in the victim's blood within five to six months of infection and may remain in the blood for as long as 17 years. They move into peripheral blood during the day and into the lungs at night.

Symptoms Symptoms of loiasis generally don't appear until several years after the bite of the infected fly, although they have been known to appear within four months. Most of the symptoms observed in victims infected with Loa loa occur during periods when the migrating adults appear near the surface of the skin. The worms often appear near the eye, where they can be easily seen and extracted before they damage the conjunctiva.

Allergic reactions to the migrating worms can cause calabar swellings in the arms and legs, triggered by metabolic products from the worm that sensitize the victim. The painful swellings develop quickly and last three to five days, appearing when the worms are still and disappearing when the worms move on. Recurrent swelling can create painful cystlike enlargements of the connective tissues around the tendons.

Occasionally, the adult worm migrates into the conjunctiva and cornea, causing pain and swelling.

Dying worms can cause chronic abscesses.

Diagnosis Lab diagnosis is based on finding microfilariae during the day, or adults in the subcutaneous tissues.

Treatment Diethylcarbamazirie has been the preferred drug for the past 40 years, and usually cures the disease, and may also be useful as a preventive measure. The drug kills both worms and microfilariae. However, it should be used with caution in patients with heavy infestations of worms, since this can provoke eye problems. Antihistamines and prednisone may be needed to ease allergic reactions due to the disintegration of microfilariae.

Complications Caucasians may experience a strong allergic response, causing giant hives and swelling of the mucous membranes accompanied with fever. Evidence of heart or kidney problems may be found in up to 20 percent of these cases.

Prevention Repellents containing DEET or dimethyl phthalate, wearing long pants, and sleeping in well-screened areas are important ways to protect against insects.

lower respiratory tract infections See RESPIRATORY TRACT INFECTIONS.

lung fluke See FLUKE; SCHISTOSOMIASIS.

Lyme disease A recently identified tick-borne illness whose hallmark symptom is a bull's-eye red rash surrounding the tick bite. Untreated, Lyme disease can cause a host of problems, including arthritis and disorders of the heart and central nervous system. It is most commonly found in the northeast coastal states from Maine to Maryland, in the upper Midwest, and on the Pacific coast. It is most often contracted 'in the late spring or early summer when ticks are abundant, although it may occur whenever the temperature is above 40° F for several consecutive days.

While the disease has been portrayed in sometimes frightening fashion in the media, most of the time it is easily treated and does not progress to the chronic stage. It probably causes severe long-term effects in less than 10 percent of untreated patients; moreover, recent studies indicate that many people who think they have Lyme disease actually have other conditions.

In the United States, the disease was first recognized in Lyme, Connecticut, after two mothers were told in 1975 that their children had juvenile rheumatoid arthritis. This type of arthritis is a disabling condition of children in which joints are swollen and painful. When the women discovered many others in the area had the disease—which does not normally occur in clusters—they took their concerns to Yale University.

By the late 1970s, Yale researchers Allen Steere and Stephen Malawista found that many patients they studied were afflicted with a mysterious disease that produced a variety of symptoms, in addition to the joint swelling. They determined the cause was apparently a microorganism transmitted by at least one species of tick found widely in the woods around Lyme. In 1982, it was identified by Willy Burgdorfer of Rocky Mountain Labs in Hamilton, Montana, who discovered the spiral-shaped bacterial species that today bears his name: Borrelia burgdorferi.

Now that scientists knew the cause, they could confirm that a group of skin conditions and neurological syndromes identified in Europe were also manifestations of Lyme disease. Since then, researchers have identified the disease throughout the world, including Australia, Africa, and Asia. It also occurs in almost every state in the United States, although it remains concentrated in the northeast, Minnesota, and northern California.

While it was only recently identified in this country, Lyme disease is not a new affliction. German scientists have found evidence of the disease in 19th-century ticks, making these insects the bacterium's earliest known hosts. The ticks came from the Vienna Natural History Museum in Austria, which supplied 21 ticks pickled in alcohol to the scientists. The genetic material in two matched that of Borrelia garinii, one of three forms of the bacteria that can induce Lyme disease. The 21 ticks had come from a Hungarian cat in 1884, and from a fox caught in Austria in 1888. Scientists suspect that the disease may have occurred even earlier, but finding even older ticks to study has been difficult.

European victims of Lyme disease suffer slightly different forms of the disease, probably because there are differences in the strains of B. burgdorferi active in different parts of the world. Europeans patients experience long-term neurological complications, such as cognitive deficits and dementia; up to 10 percent of untreated Europeans also suffer for many years with a skin condition in which affected areas of the skin become red, thin, and wrinkled. In the United States, these symptoms are rare.

Cause The disease is caused by BOKRELLA BURGDORFERI, a spirochete form of bacteria. It is transmitted primarily by the deer tick, the tiniest of which is about the size of the period at the end of this sentence, which are found on deer, birds, filed mice, and other rodents. The tick must be attached to its victim for between 36 to 48 hours before an infectious dose of B. burgdorferi can be transmitted. For this reason, simply by checking themselves often for ticks, most people can avoid becoming infected.

Most people are diagnosed in the spring, summer, or early fall because this reflects the life cycle of the infected tick. In the northeastern United States, about half of all adult I. scapularis ticks are infected. In some places (Block Island and Nantucket Island) the numbers are even higher. Even so, in most sections of the northeast, only between 1 and 3 percent of people have contracted Lyme disease.

The tick that transmits Lyme diseases in California relies on intermediate hosts (such as lizards) that are resistant to infection; for this reason, ticks—and consequently humans—in the west are infected much less often than in the northeast. The same is true for species that transmit Lyme in some areas of Europe and Asia.

Symptoms Most people who do become infected will usually display one or more symptoms. Between three days and a month after becoming infected, about 60 percent of victims will notice a small red spot that expands over a period of days or weeks, forming a circular, triangular, or oval-shaped rash called ERYTHEMA CHRONICUM MIGRANS. The reddened area, which usually appears at the bite site, neither itches nor hurts. Sometimes the rash resembles a red raised bull's-eye rash with a clear center at the site of the bite.

The rash can range in size from a dime to the entire width of a person's body. As the infection spreads, several rashes can appear at different sites on the body. Without treatment, the rash begins to disappear within days or weeks.

As the spirochetes move through the body via the bloodstream, other symptoms affecting other parts of the body may appear. These may include flulike symptoms (such as headache, stiff neck, appetite loss, body aches, and fatigue). Although these symptoms may resemble those of common viral infections, Lyme disease symptoms tend to persist or may occur intermittently.

Early neurological problems may also appear in about 20 percent of patients. Some patients may experience Bell's palsy in one or both sides of the face, which may become paralyzed for weeks or months before returning to normal. Other symptoms may include MENINGITIS, ENCEPHALITIS, or numbness and tingling of other parts of the body.

Complications After several months of being infected, slightly more than half of those people not treated with antibiotics develop recurrent attacks of painful and swollen joints that last a few days to a few months. The arthritis can shift from one joint to another; most often, the knee is infected. About 10 to 20 percent of untreated patients who experience temporary arthritic symptoms will go on to develop chronic Lyme arthritis. In contrast to many other forms of arthritis, Lyme arthritis typically is not symmetrical.

One out of 10 Lyme patients develop heart problems (such as irregular heartbeat) for a few days or weeks, generally appearing several weeks after infection. Most people won't be aware of this problem unless a physician detects it, although some patients might realize they can't exercise as they once did. This condition usually lasts only for a week to 10 days and almost never requires a pacemaker. Other nervous system complications include subtle changes such as memory loss, difficulty with concentration, and change in mood or sleeping habits. Nervous system abnormalities usually develop several weeks, months, or even years after an untreated infection. These symptoms often last for weeks or months, and may recur. Less often, Lyme disease causes eye inflammation, hepatitis, or severe fatigue. Pregnant women who contract the disease rim the risk of miscarriage, stillbirth, or birth defects.

Diagnosis Lyme disease is not easy to diagnose because its symptoms and signs mimic those of many other diseases, such as viral infections or MONONUCLEOSIS. Joint pain can be misdiagnosed as inflammatory arthritis, and neurologic signs may be misidentified as a primary neurologic disease such as MULTIPLE SCLEROSIS.

Diagnosis of Lyme disease includes consideration of exposure to ticks (especially in Lyme disease areas), symptoms, and the result of blood tests to determine whether the patient has antibodies to Lyme bacteria. The tests are most useful in later stages. Lab tests for Lyme disease have not yet been standardized across the country.

Treatment Antibiotics (tetracycline or amoxicillin) usually provide a complete recovery if given early enough. Most patients who are treated in later stages of the disease also respond well. Pregnant women may require hospitalization.

Unfortunately, cases that are not diagnosed soon enough may resist antibiotic therapy. In a few patients, symptoms of persistent infection may continue or the disease may recur, so that physicians prescribe repeated long courses of antibiotic therapy. The value of this approach, which can have serious side effects (such as inducing formation of gallstones) remains controversial.

Patients with late chronic Lyme disease may exhibit varying degrees of permanent damage to joints or the nervous system. In general, this occurs among patients who were not diagnosed in the early stages of the disease, or for whom early treatment was not successful. Deaths from Lyme disease have been reported only very rarely.

Prevention A vaccine has been developed and is being tested in a large number of patients. A vaccine is already available for field dogs at risk for developing the disease because of the area in which they live.

Experts at the Centers for Disease Control don't recommend preventive treatment with antibiotics after a tick bite. It's better to avoid tick bites in the first place; avoiding their habitat is the best way to prevent tick bites, but ticks may also be found in lawns, gardens, and on bushes adjacent to homes.

When walking in the woods, stay on trails and avoid brushing up against low bushes or tall grass. Ticks do not hop, jump, fly, or descend from trees—a person must come in direct contact with them (they may blow in a strong breeze). To prevent bites, wear protective clothing (light-colored, long-sleeve shirts and light-colored pants tucked into boots or socks); this allows ticks to be more easily spotted.

An insect repellent preferably containing no more than 30 percent DEET (N-diethyl-metatoluamide) may be used on bare skin and clothing. Duranon can be applied to clothing only, but not to the skin. All insect repellent should be used with caution (especially on children) and should not be applied to the hands or face.

Ticks and hosts (mice, chipmunks, voles, and other small mammals) need moisture, a place hidden from direct sun, and a place to hide. Therefore, the clearer the area around a house, the less chance there will be of getting a tick bite. All leaf litter and brush should be removed as far as possible away from the house. Low-lying bushes should be pruned to let in more sun. Rake up leaves every fall, since ticks prefer to overwinter in fallen leaves. Woodpiles are favorite hiding places for mammals carrying ticks; woodpiles should be neat, off the ground, in a sunny place, and under cover.

Gardens should be cleaned up every fall; foliage left on the ground over the winter provide shelter for mammals that may harbor ticks. Stone walls on the property increase the potential for ticks.

Shady lawns may support ticks in epidemic areas; lawns should be mowed and edged. Entire fields should be mowed in fall, preferably with a rotary mower.

Birdfeeders attract birds that carry infected ticks; don't place feeder too close to the house. Clean up the ground under the feeder regularly. Suspend bird feeding during late spring and summer, when infected ticks are most active. Building eight-foot fences to keep out deer may significantly reduce the abundance of ticks on large land parcels. Examine pets allowed outside on a daily basis; tick collars and/or dips may be needed.

Three pesticides may help: chlorpyrifos (Dursban), carbaryl (Sevin), and cyfluthrin (Tempo). One or two applications a year in late May and September can significantly reduce the tick population.

For more information, contact: The American Lyme Disease Foundation, Inc., Mill Pond Offices, 293 Rte. 100, Ste. 204, Somers, NY 10589; telephone (914) 277-6970 or (800) 876-LYME; fax (914) 277-6974.

lymphangitis Inflammation of the lymphatic vessels that cause tender red streaks to appear on the skin above the lymphatic vessels. The infection may spread to the bloodstream. This condition is a clear indication of serious infection and requires immediate treatment with antibiotics.

Cause The infection is caused by a spread of bacteria (usually streptococci) from an infected wound into the lymphatic channels.

Symptoms The red streaks extend from the site of infection toward the nearest lymph nodes; there is usually a fever, chills, headache, and general feeling of illness.

Treatment Antibiotics together with warm, moist compresses, usually clear up the infection without complication.

lymphogranuloma venereum (LGV) A sexually transmitted disease involving the lymph glands in the genital area caused by a specific strain of CHLAMYDIA. The incidence of the disease is highest among sexually active people in the tropical or subtropical climates; it has also been found in some areas of the southern United States.

Cause The infection is spread by sexual contact.

Symptoms The first symptom is a small, painless pimple on the penis, female external genitalia, or vagina that appears from 3 to 30 days after exposure; it is so small it often goes unnoticed. The infection then spreads to the lymph nodes in the groin, and from there it moves to surrounding tissue. An individual remains infectious as long as there are active lesions.

Treatment The disease responds to certain antibiotics such as tetracycline or sulfamethoxazole.

Prevention There are several ways to prevent the spread of LGV, including using condoms, washing genitals after sex, avoiding sexual contact if infected, notifying all partners in case of infection, and reducing the number of sex partners.

Complications Inflamed and swollen lymph glands, which may drain and bleed.

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