babesiosis (babesiasis) A rare, occasionally fatal, disease caused by a tick-borne microorganism similar to both LYME DISEASE and human granulocytic ehrlichiosis (HGE). Also known as Nantucket Fever, it is most often seen in the elderly and those with impaired immune systems. Severe cases have been diagnosed in those who have had their spleen removed prior to exposure.
Most cases of babesiosis have been reported in summer and fall in the northeastern United States, especially Nantucket, Shelter Island in New York, and other offshore islands in New England. However, cases have recently been identified in the upper Midwest, the Pacific Coast states, and Europe. A related species has caused a babesiosis-like illness in Washington and California.
Cause Babesiosis is caused by protozoa similar to those that cause MALARIA (the species Babesia microti); it is passed via the bite of ticks; the most common is the species Ixodes dammini. The tick is carried by meadow voles, mice, and deer. The disease can also be transmitted via contaminated blood transfusions. The protozoa causing babesiosis was first identified by Roman bacteriologist Victor Babes, for whom the organism and the disease was named.
Symptoms Babesiosis typically causes mild illness in otherwise healthy people, but it can be overwhelming to those with impaired immune systems. Symptoms appear within 1 to 12 months after infection and include fever, fatigue, and hemolytic anemia lasting from several days to several months. A person may also have the disease with no symptoms at all. It is not known if a past infection renders a patient immune.
Diagnosis Molecular tests are being developed, but currently the disease is diag nosed by microscopic examination of blood smears.
Treatment Standardized treatments have not been developed; however, a combination of antimalarial drugs as quinine and an antibiotic (clindamycin) are usually the drugs of choice.
Prevention The spread of babesiosis can be curtailed with the control of rodents around houses and the use of tick repellents.
bacillary angiomatosis An infectious disease that causes blood vessels to grow out of control in bone, liver, and skin, forming tumorlike masses that look like those of KAPOSI'S SARCOMA.
bacillary dysentery See SHIGELLOSIS.
Bacillus (pi. bacilli) A large genus of gram-positive, spore-bearing bacteria (in the family Bacillaceae) that includes 33 species, three of which cause disease. They are found in soil and air and are responsible for many diseases, including ANTHRAX and FOOD POISONING. Most feed on dead matter and are responsible for food spoilage. The genus includes bacillus anthracis, bacillus polymyxa and bacillus subtilis.
Bacillus anthracis A species of gram-positive bacteria that causes ANTHRAX, a disease mostly affecting cattle and sheep. If inhaled, the spores of this organism can cause a pulmonary form of anthrax. Spores live for many years in hides and wool.
Bacillus pestis See pasteurella pestis.
Bacillus polymyxa A species of Bacillus that is commonly found in soil and is the source of the polymyxin group of antibiotics.
Bacillus subtilis A species of Bacillus that may cause CONJUNCTIVITIS in humans; it is also used to produce the antibiotic bacitracin.
bacteremia An invasion of bacteria into the bloodstream. This is an uncommon complication of STREP THROAT, TONSILLITIS, or streptococcal skin infection; it may also occur a few hours after minor surgery. Infection can spread via the bloodstream to other parts of the body, producing abscesses, peritonitis (inflammation of the abdomen), inflammation of the heart, or MENINGITIS. Bacteremia may also lead to shock, causing a generalized illness with high fever, circulatory collapse, and eventually, organ failure.
Those at greatest risk include patients with an impaired immune system, children with CHICKEN POX, burn victims, elderly patients with CELLULITIS, diabetes, blood vessel disease, cancer, or anyone taking steroids or chemotherapy. TV-drug users are also at risk.
Bacteremia may occur as well in healthy young adults with no known risk factors.
bacteria Bacteria are microbes whose genetic material is not organized into a cell nucleus, like plants or animals. Some bacteria feed on other organisms, some make their own food (like plants do) and some bacteria do both. Some need air to survive, and others exist without air (anaerobic). Some move by themselves, and others can't move at all. Bacteria also come in a variety of shapes, colors, and sizes.
It's important to remember that not all bacteria are harmful; most are helpful, such as those that break down dead plant and animal matter in the soil. Some (like the actinomycetes) produce antibiotics such as streptomycin. Plants can't grow without nitrogen, and bacteria help nitrogen to form in the soil. Bacteria are also used to make cheese out of milk and leather out of animal hide. Grazing animals use bacteria to digest the grass they eat.
Bacteria can be found in the air, the water, food, and everything we touch. Since few of these are harmful, humans are seldom bothered by them. When harmful bacteria do enter the body, the immune system usually can kill the invading microbes.
They are of incredible importance because of their extreme flexibility, capacity for rapid growth and reproduction, and their ancient age—the oldest known fossils are those of bacteria-like organisms that lived nearly 3.5 billion years ago.
Bacteria in humans are essential to digestion. More than 400 different kinds help digest food and fill niches in the intestine that might otherwise be colonized by harmful bacteria.
At least one type of bacteria (Bacteroides thetaiotaomicron) interacts with cells lining the intestine, benefitting both the human host and the bacteria. Without this type of bacteria, cells in the intestines may fail to produce a sugar found in human milk that is used as food by the bacteria and other beneficial intestinal organisms. When these naturally occurring bacteria are killed (because of ANTIBIOTIC use or other illnesses) harmful bacteria can take over. Diarrhea is one result.
As scientists understand more about the interaction between helpful bacteria and intestines, they may be able to use these bacteria to protect a patient with an impaired immune system or who is taking antibiotics. See also DIARRHEA AND INFECTIOUS DISEASE; ANTIDIARRHEAL DRUGS; TRAVELER'S DIARRHEA.
Unfortunately, some disease-causing bacteria are beginning to become resistant to many of the antibiotics doctors use to treat the infections. A 1996 World Health Organization report found that drug-resistant strains of microbes causing MALARIA, TUBERCULOSIS, PNEUMONIA, CHOLERA, and traveler's diarrhea are on the rise. Certain drug-resistant microbes in the United States cause up to 60 percent of hospital-acquired infections, the report adds.
bacterial infections One of the most important types of infectious disease. These include gonorrhea, bacterial meningitis, whooping cough, bacterial pneumonia, tuberculosis, typhoid fever, and many others.
bacterial pneumonia See pneumonia, bacterial.
bactericide Any substance that kills bacteria.
Bang's disease The common name for brucellosis.
Bartonella A genus of small, gram-negative coccobacilli that infect red blood cells and cells of the lymph nodes, liver, and spleen. Named for the 18th-century Peruvian bacteriologist who discovered them (Alberto Barton), they are transmitted at night by the bite of a sandfly of the genus Phlebotomus. The only known species of Bartonella is B. bacilli-formis, the organism that causes bartonel-losis.
bartonellosis An acute or chronic bacterial infection transmitted to humans by the bite of the sandfly. The risk of this disease exists in the mountain valleys of southwest Colombia, Ecuador, and Peru, at altitudes between 2,500 and 8,000 feet.
Cause The Phlebotomus sandfly carries the disease-producing bacterium Bartonella bacilli-formis. Transmission occurs between dusk and dawn (which is sandfly feeding time).
Symptoms Bartonellosis has two distinct types: Oroya fever and Veruga peruana. Symptoms of Oroya fever begin between two to three weeks after being bitten, with fever, weakness, headache, and bone or joint pain followed by severe anemia and swollen lymph nodes. The disease lasts between two and six weeks and then subsides, but it is occasionally fatal. Death is usually associated with secondary and overwhelming Salmonella infection.
Veruga peruana is characterized by the appearance of nodules on the face and limbs that bleed easily and last for up to a year. They finally heal without scarring.
Treatment Chloramphenicol or ampicillin is the preferred treatment, although tetracycline, penicillin, or streptomycin also are effective. More recently, doctors may combine two or more antibiotics because of the frequent presence of Salmonella.
Prevention This disease can be prevented by avoiding high-risk areas between sundown and sunup, together with the use of insect repellents.
B DV See borna disease virus.
bird flu See avian flu.
black death See plague.
blastomycosis A mild, often self-limiting yeast infection that usually begins in the lungs and spreads to other sites in the body, especially skin and bone. The disease is found most often in children and in men between the ages of 40 and 60.
The disease is also known as Chicago disease, Gilchrist's disease, and North American blastomycosis.
Cause The disease is caused by the yeast Blastomyces dermatiidis; it can be confused with Coccidioides immitis or Cryptococcus neoformans.
Symptoms The amount and type of inflammation may vary from one site on the body to another and from one patient to another. There is usually widespread inflammation in the lungs, with small areas of abscesses.
Treatment Amphotericin B is the drug of choice; hydroxystilbamidine has been successful in treating the form of the disease that affects the skin, but it is less helpful with other forms. Both ketaconazole and itraconazole have been used successfully.
blepharitis A chronic or long-term inflammation of the eyelids and eyelashes affecting people of all ages. It is characterized by red, irritated scaly skin at the edges of the lids.
Cause Among the most common causes are poor eyelid hygiene, excess oil produced by the glands in the eyelids, a bacterial infection, or an allergic reaction. Seborrheic blepharitis is the most common form. It is often associated with dandruff of the scalp or skin conditions such as acne.
Symptoms Blepharitis usually appears as greasy flakes or scales around the base of the eyelashes and as a mild redness of the eyelid. Sometimes, seborrheic blepharitis may result in a roughness of the tissue that lines the inside of the eyelids or in nodules on the eyelids. Styes can also result from an acute infection of the eyelids.
A less common form of blepharitis is ulcerative blepharitis. It is characterized my matted, hard crusts around the eyelashes which, when removed, leave small sores that may bleed or ooze.
Treatment Blepharitis is usually not serious. In many cases, good eyelid hygiene and a regular cleaning routine can control it. Scales can be removed with cotton moistened with warm water. The inflammation often recurs, which requires more treatment. Ulcerated eyelids must be treated by a physician, since severe cases can lead to problems with the cornea.
blood-borne infectious disease See infectious diseases.
blood fluke See fluke.
blood poisoning See septicemia.
boil An inflamed, pus-filled section of skin (usually an infected hair follicle) found often on the back of the neck or moist areas such as the armpits and groin. Very large boils are called a carbuncle.
Cause Boils are usually caused by infection with the bacterium Staphylococcus aureus, which invades the body through a break in the skin, where it infects a blocked oil gland or hair follicle. When the body's immune system sends in white blood cells to kill the germs, the resulting inflammation produces pus.
Symptoms A boil begins with a red, painful lump that swells as it fills with pus, until it becomes rounded with a yellowish tip. It may either continue to grow until it erupts, drains, and fades away or is reabsorbed by the body. Recurrent boils may occur in people with known or unrecognized diabetes melli-tus or other diseases involving lowered body resistance.
Treatment Putting pressure on a boil might spread the infection into surrounding tissue. Instead, apply a hot compress for 20 minutes every two hours to relieve discomfort and hasten drainage and healing. After treating a boil, wash hands thoroughly before cooking to guard against staph infection getting into food or breaks in the skin.
It may take up to a week for the boil to break on its own. To further reduce chance of infection, take showers, not baths. If the boil is large and painful, a physician may prescribe an antibiotic or open the boil with a sterile needle to drain the pus. Occasionally, large boils must be lanced with a surgical knife; this is usually done using a local anesthetic.
Complications More seriously, bacteria from a boil may find its way into the blood, causing blood poisoning; for this reason, doctors advise against squeezing boils that appear around the lips or nose, since the infection can be carried to the brain. (Other danger areas include the groin, the armpit, and the breast of a nursing woman.) Signs of a spreading infection include generalized symptoms of fever and chills, swelling lymph nodes, or red lines radiating from the boil.
Prevention Some experts note that boils are usually infected cysts and recommend leaving cysts untouched or having them lanced by a physician. For patients prone to boils, some experts recommend washing the skin with an antiseptic soap.
Keep skin around a boil clean while drainage is occurring, and take showers to lessen the chance of spreading the infection.
Bordetella A genus of gram-negative bacteria discovered by Belgium bacteriologist Jules J. B. V. Bordet. Some species cause respiratory disease in humans involving the bacteria Bordetella bronchiseptica, B. parapertussis, and B. pertussis. See whooping cough.
Bordetella pertussis A species of tiny gram-negative anaerobic bacterium (in the genus Bordetella) that causes whooping cough, one of the most common infections on earth. All the other species of the Bordetella genus cause diseases that resemble whooping cough.
It is extremely virulent, infecting more than 90 percent of susceptible victims after close contact. It usually strikes during childhood; before the advent of modern medicine it was a major cause of infant death around the world. It is still a significant health problem in underdeveloped areas, causing about 40 million cases worldwide and about 400,000 deaths. A vaccine against the bacteria was developed in the mid-1940s, although local outbreaks still occur among unvaccinated individuals.
The disease was named pertussis (from the Latin word for "intense cough") and was known popularly as "whooping cough" in the 17th century; earlier, it was called "chin cough." French physicians called it quinta because of the five-hour respites between coughing spasms, or "coqueluche." Since 1940, the vaccine against Bordetella pertussis (a combination of diphtheria, tetanus, and pertussis), or "DPT," has cut the incidence of whooping cough by 99 percent, but the shot was linked to rare but serious side effects, including high fever, convulsions, and rarely, brain damage and death. In 1988, the United States established an $80 million fund to compensate children who were injured by the vaccine, which initiated 4,700 claims. Since then, the National Institutes of Health spent $16 million to develop a safer vaccine—the acellu-lar vaccine, so named because it was derived from only part of a B. pertussis cell.
Borna disease virus (BDV) A type of virus known to cause behavior disruptions and neurological disease in several animal species, and recently found in humans as well. Infection with this virus may trigger depressive episodes in humans who are already vulnerable to major depression or manic-depression.
Borna disease virus is a single-stranded RNA virus that establishes a persistent infection without directly damaging host cells. BDV infection may contribute to depressive illness by altering neuronal cells in the limbic system. The leading hypothesis is that BDV, as it inserts itself into neurons, may disrupt the function of those cells by binding to neurotransmitter receptors.
It causes neurological symptoms in domestic animals, which is where it gets its nickname, "crazy virus." The neurological symptoms resemble those seen in humans with manic-depression. This virus is entirely separate from mad cow disease, although the neurological symptoms are what led researchers to study BDV more closely.
The virus infects cells of the limbic system implicated in many psychiatric disorders, including bipolar depression and schizophrenia. BDV infects cells in the nervous system just as its distant viral relative, rabies, does, causing brain damage in animals and humans. Previous studies have shown that a large proportion of psychiatric patients with certain affective disorders, such as depression and manic-depressive disorder, have antibodies specific to proteins of BDV. Since Borna viral material tends to appear during episodes of depression, scientists suspect that the virus brings on depressive episodes in people predisposed to mood disorders by their genes or other factors (perhaps by disrupting communication between brain cells). In most people, however, the infection appears to cause no problems.
It's too soon to say how big a factor Borna virus might be in depression or manic-depression, and it's not clear whether Borna virus can jump from animals to people, nor how it might spread between people. However, scientists do know that humans can't get Borna virus from eating meat or other products of infected animals.
BDV was first reported more than a century ago as a cause of neurological disease in horses in Borna, Germany. Since then, outbreaks of the virus have been documented in cattle, sheep, and cats. Rats injected with BDV exhibit damage to brain cells in the limbic system, the part of the brain that governs mood and emotions. Interestingly, the virus affects various animal species differently. While rats' brains are destroyed, the virus causes only subtle abnormal social patterns in tree shrews. Further animal studies as well as larger studies of psychiatric patients may help scientists better understand how the virus causes disease and how to develop a way to diagnose and treat it.
The cause of most of the common psychiatric disorders, including depression, manic-depression, anxiety, and schizophrenia, remains a mystery. In some cases, symptoms appear suddenly and the disease follows a catastrophic course, while in other cases the disease may be intermittent. Despite a large amount of research, and a lot of familial association evidence, the search for causative genes has produced mixed results. This has helped fuel the search for other factors, such as viral infection.
One group of investigators at the National Institute of Mental Health is pursuing the hypothesis that schizophrenia might be caused by viruses transmitted from household pets to pregnant women or young children. Another group of researchers at the University of Southern California is looking for a link between chronic fatigue syndrome and "stealth viruses" (viruses that have been incorporated into the host DNA and are no longer recognized by the immune system). These viruses cannot be detected by standard immunological methods or standard culture techniques. However, they can be detected with PCR based techniques, matching DNA sequences with known viral DNA.
borrelia See RELAPSING FEVER.
Borrelia burgdorferi A species of large parasitic spirochete bacteria (in the genus Borrelia) that cause LYME DISEASE. The species B. dut-tonii, B. persica, and B. recurrentis cause RELAPSING FEVER.
botulism The most common type of the infectious disease known as botulism is a food-borne illness involving the toxin produced by the bacteria Clostridium botulinum, which is both rare and very deadly (two thirds of those afflicted die). Another type is known as "infant botulism," an uncommon illness that strikes infants tinder the age of one. Because botulism is technically a poisoning, not an infection, the patient cannot infect others even though the bacteria will be excreted in feces for months after the illness.
Botulism is more common in the United States than anywhere else in the world, owing to the popularity of home canning; there are about 20 cases of food-borne botulism poisoning each year. Botulism got its name during the 1800s from botulus, the Latin word for "sausage," because of a wave of poisoning from contaminated sausages.
Cause Botulism toxins are a type of neurotoxin that attaches to the nerves, blocking the messages that are sent to the muscles. The
C. botulinum spores (latent form of the bacteria) are found in air, water, and food; they are harmless until deprived of oxygen (such as inside a sealed can or jar). If conditions are favorable, the spores will start to generate and multiply, producing one of the most deadly toxins known—7 million times more deadly than cobra venom.
Cases of botulism from commercially canned food are rare because of strict health standards enforced by the U.S. Food and Drug Administration, although some people have gotten botulism from eating improperly handled commercial pot pies. In Canada, cases have been reported from seal meat, smoked salmon, and fermented salmon eggs. Most cases occur during home canning.
Canned foods that are highly susceptible to contamination include green beans, beets, peppers, corn, and meat. Although the spores can survive boiling, the ideal temperature for their growth is between 78 degrees F and 96 degrees F. They can also survive freezing.
Botulism can also occur if the C. botulinum bacteria in the soil enters the body through an open wound, although this is extremely rare.
Symptoms Onset of symptoms may be as soon as three hours or as late as 14 days after ingestion, although most symptoms usually appear between 12 and 26 hours. The first sign is usually muscle weakness beginning with the head, often leading to double vision. This is followed by problems in swallowing or speaking, followed by the paralysis of the muscles needed to breathe. Other symptoms can include nausea, vomiting, diarrhea, and stomach cramps. The earlier the onset of symptoms, the more severe the reaction. Symptoms generally last between three to six days; death occurs in about 70 percent of untreated cases, usually from suffocation as a result of respiratory muscle paralysis. In infants, symptoms may go unrecognized by parents for some time until the poisoning has reached a critical stage.
Diagnosis Large commercial labs or state health labs can test for the toxin in food, blood, or stool; it's also possible to grow the bacteria from food or stool in a special culture. The diagnosis is most often made by an astute health care practitioner who recognizes the signs and symptoms. In an outbreak, the first victim to become sick usually dies.
Treatment Prompt administration of the antitoxin (type ABE botulinus) lowers the risk of death to 10 percent. Most untreated victims will die. The Centers for Disease Control is the only agency with the antitoxin, and it makes the decision to treat. Local health departments should be called first for this information. While induced vomiting may help following ingestion of food known to contain botulism toxin, it may not be complete. Because the disease can occur with only a small amount of toxin, botulism may still develop.
Patients are usually put on a respirator to ease breathing. In infant botulism, if symptoms are present it is often too late to administer antitoxin, since the damage has probably already been done.
Prevention It is easy to prevent, since botulism is killed when canned food is boiled at 100 degree C for one minute, or if the food is first sterilized by pressure cooking at 250 degrees F for 30 minutes. If you're going to eat it—heat it.
While the tightly fitted lids of home-canned food will provide the anaerobic environment necessary for the growth of botulism toxins, the spores will not grow if the food is very acidic, sweet, or salty (such as canned fruit juice, jams and jellies, sauerkraut, tomatoes, and heavily salted hams).
Even though botulism spores are invisible, it's possible to tell if food is spoiled by noticing if jars have lost their vacuum seal; when the spores grow, they give off gas that makes cans and jars lose the seal. Jars will burst or cans will swell. Any food that is spoiled or whose color or odor doesn't seem right inside a home-
canned jar or can should be thrown away without tasting or even sniffing, since botulism can be fatal in extremely small amounts.
botulism, infant Unlike botulism in adults, which occurs after eating contaminated food, infant botulism occurs in babies under six months of age and is less serious. While all botulism are caused by toxins given off by Clostridium botulinum bacteria, in infant botulism the baby does not ingest the toxin. Instead, the spores from botulism bacteria reproduce the toxin in the baby's digestive tract, which then travels to the baby's nerve cells.
Fortunately, most babies will recover with prompt hospital treatment.
Cause This rare disease may be difficult to trace, since the spores may survive for a long time in the environment. It is clear that about 10 percent of commercial honey contains botulism spores and occasionally, light and dark corn syrup also harbors the bacteria. For this reason, parents are advised not to feed either food to infants under a year of age. The illness is found in all races in North and South America, Asia, and Europe. In 1993, there were only 65 reported cases in the United States.
Although an infected baby will excrete toxin for weeks in feces, the baby cannot pass on the infection to others.
Symptoms Infant botulism symptoms include constipation, facial muscle flaccidity, sucking problems, irritability, lethargy, and floppy arms and legs.
Complications Some experts believe that infant botulism may be responsible for up to 5 percent of all cases of Sudden Infant Death Syndrome.
Treatment The antitoxin used to treat adults with botulism is not safe for infants. Antibiotics may be used to treat secondary infections. In severe cases, the baby may need breathing assistance; while recovery may be slow, most usually completely recover.
Prevention Babies under age one should not be fed honey or corn syrup. They should be kept away from dust (both from vacuum cleaners and from the outdoors), especially around construction sites.
bouba See YAWS.
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