Bovine spongiform encephalopathy

medical name for MAD COW DISEASE, an infectious illness of cows that may have emerged in the human population. BSE was first identified in Britain in 1986, and is one of a group of similar neurologically degenerative diseases that occur in several animal species. The dis-eas is thought to have been transmitted to a dozen people via contaminated meat and bone meal.

Eleven human deaths from this disease in Great Britain were traced to exposure to beef that contained a piece of protein called a prion, thought to be the cause of bovine spongiform encephalopathy. The United Kingdom appears to be the only country with a recent incidence of the disease, and the cases there seem to have been associated with the recycling of affected cow material back to cattle in their food prior to 1988. The incidence of the disease declined significantly in the United Kingdom, although the epidemic has not yet been clearly defined as such. The worldwide distribution of BSE is not precisely known, but it has been reported at a much lower incidence than in the U.K. In the United States, officials restricted imports of live cattle and meat from countries with bovine spongiform encephalopathy in 1989.

brain abscess A pocket of infection, most commonly found in the frontal and temporal lobes, usually caused by the spread of infection from another part of the body, such as the sinuses. A brain abscess also may result from spread of an infection in the bones, the nervous system outside the brain, or the heart. These abscesses cause symptoms due to increased pressure and local brain injury.

About 10 percent of cases are fatal; the remaining patients often have some brain function impairment. A seizure disorder is a common complication.

Cause Brain abscesses are almost always caused by infection spreading from somewhere else in the body. About 40 percent of abscesses are from middle ear or sinus infections. Blood-borne infections may also cause multiple brain abscesses.

Symptoms The most common symptoms are headache, sleepiness, and vomiting. There may be visual problems, with fever and seizures. There may be evidence of local brain damage as well, including partial paralysis or speech problems.

Diagnosis Brain scans (CT scans or magnetic resonance imaging) of the brain can diagnose a brain abscess.

Treatment High doses of antibiotics and usually surgery; the abscess may be accessible via a small hole in the skull.

Brazilian purpuric fever A serious systemic illness that may be caused by bacterial infection, it was first recognized in 1984 in Brazil. Since then, scientists have identified other cases, including an outbreak of 17 illnesses in a town in a neighboring Brazilian state. Cases have appeared in other states of Brazil, as well.

It is not known whether the disease occurs in areas other than southern Brazil. Cases being treated for presumed meningococcemia may in actuality be cases of BPF. In many areas a blood culture may not have been drawn to determine the diagnosis. Researchers caution that the occurrence of clusters in areas separated by 250 miles suggests the potential for spreading of the disease.

Cause Brazilian purpuric fever appears to be related to Haemophilus aegyptius (H. influenzae, biotype III). If untreated, the infection spreads and can lead to fatal purpura (bleed ing into the skin), release of toxins, and overwhelming shock.

Symptoms The illness typically begins with eye infection caused by H. influenzae III; in a small number of patients, the bacteria spread throughout the body, causing fever and bleeding into the skin. If untreated, this bleeding continues; the bacteria release a toxin that overwhelms the body's defenses and ends in death. Symptoms resemble meningococcemia.

Treatment Systemic antibiotics to treat BPF (usually ampicillin with or without chloramphenicol) before the skin bleeding begins may prevent progression of the disease.

breast cancer and virus New evidence has contributed to a controversial claim that suggests breast cancer may be linked in some form to a virus. Cancerous breast cells often contain genetic sequences similar to an infectious virus that triggers mammary tumors in mice, according to research by virologists at Mount Sinai medical school in New York City. These findings raise decades-old questions of whether some infectious virus plays a role in at least some types of breast cancer.

Over the last few decades, investigators have linked a number of viruses (specifically retroviruses) to cancer in animals and people. A retrovirus can transform a normal cell into a cancer cell by inserting its genetic material into the cell, disrupting the function of crucial genes. For example, mouse mammary tumor virus (MMTV) produces cancer in about 95 percent of the mice it infects.

The idea that viruses may cause some types of breast cancer dates to the 1930s, when scientists identified viruslike particles in mothers' milk. While mice can transmit MMTV to their babies through milk, no evidence was found that children who were breast-fed by mothers with breast cancer had a higher chance of developing the disease themselves.

Still, over the decades since then, research groups have reported some genetic evidence that an MMTV-like virus is associated with breast cancer. The problem with those reports was that in those days, scientists couldn't tell the difference between MMTV-like viruses and human endogenous retrovirus (HER), an ancient virus whose genetic code is integrated into everyone's genome.

In recent years, however, scientific procedure has become more sophisticated. Scientists have sequenced many of MMTV's genes and found regions of various genes that differ quite a bit from those of HER. The new research looked at samples of human breast tissue for MMTV-specific gene fragments. In 1995, the group reported that in almost 40 percent of breast cancer tissue tested, they found sequences similar to those in one of the MMTV's genes. Less than 2 percent of normal breast samples yielded this so-called env gene. This env gene encodes a protein that helps form the outer surface of the virus.

In 1996, the group reported that they found a different sequence of the env gene in 13 of 19 breast cancer samples, and in none of the normal breast tissue samples. Interestingly, hormones such as estrogen stimulate the activity of an MMTV-like env gene in a cell line derived from breast cancer cells.

The findings are far from conclusive proof that a virus may cause some forms of breast cancer. Other scientists are trying to replicate the Mount Sinai research.

bronchiolitis An acute viral infection of the small airways in the lungs that primarily affects infants and young children. Winter epidemics tend to occur every two or three years, affecting thousands of children in the United States. A virus that may induce only a mild head or chest infection in an adult can cause a severe bronchiolitis in an infant. With prompt treatment, even the sickest infants usually recover completely within a few days.

Cause The smaller airways that branch off the bronchial tubes become inflamed, usually because of the RESPIRATORY SYNCYTIAL VIRUS (RSV INFECTION), although other viruses may be responsible. Adult attacks may follow BRONCHITIS brought on by INFLUENZA. The viruses may be transmitted from person to person through airborne drops and are highly contagious. Hospitalized patients will be placed in respiratory isolation.

Symptoms Cough, shortness of breath, and (in severe cases) blue-purple skin color. A physician can hear bubbling noises in the lungs. A baby or young child with a cold and cough that suddenly gets worse should see a physician.

Treatment Sometimes no treatment is needed, but in severe cases the child may need to be hospitalized for oxygen and respiratory therapy to clear the mucus. Antibiotics and CORTICOSTEROID DRUGS won't work against this viral infection, although antibiotics may be prescribed anyway to prevent a secondary bacterial infection. Sometimes a child may need to be placed on artificial ventilation until normal breathing returns.

bronchitis Inflammation of the airways that connect the windpipe (trachea) to the lungs, resulting in persistent cough with quantities of phlegm or sputum. Attacks usually occur in the winter among smokers, babies, the elderly, and those with lung disease, although anyone can get bronchitis.

Bronchitis presents in one of two forms: acute (of sudden onset and short duration) and chronic (persistent over a long period, and recurring several years).

Cause Acute bronchitis is usually a complication of a viral infection (such as a cold or the flu), although it can also be caused by air pollution. A bacterial infection also may lead to acute bronchitis. Attacks occur most often in winter.

Cigarette smoking is the primary cause of chronic bronchitis, because it stimulates the production of mucus in the lining of the bronchi and thickens the bronchi's muscular walls and those of smaller airways in the lungs, narrowing those passages. The passages then become more susceptible to infection, which cause further damage. Air pollution can have the same effect. The disease is most prevalent in industrial cities and in smokers, and more common in manual and unskilled workers.

Symptoms The symptoms of both chronic and acute bronchitis are the same. As the bronchial tubes swell and become congested, symptoms appear: wheezing, breathlessness, and a persistent cough that produces yellow or green phlegm. There also may be pain behind the breastbone. Acute bronchitis is also characterized by fever.

In chronic bronchitis, symptoms don't quickly clear up, and there is usually no fever. The persistence of symptoms also differentiates this disease from chronic asthma, in which wheezing and breathlessness vary in severity from day to day. As the disease progresses, emphysema may develop. The lungs become more resistant to the flow of blood, leading to pulmonary hypertension. Those with chronic bronchitis usually have two or more episodes of acute viral or bacterial infection of the lungs every winter. Occasionally, blood may be coughed up.

Treatment Humidifying the lungs either with a humidifier or by inhaling steam will ease symptoms. Drinking plenty of fluids also helps bring up phlegm. Most acute bronchitis clears up on its own without further treatment. If there is a suspicion of an underlying bacterial infection, antibiotics will be prescribed.

In chronic bronchitis, an inhaler containing a bronchodilator may relieve breathlessness. In specific cases, the patient may improve by inhaling oxygen from a cylinder. Antibiotics may treat or prevent any bacterial lung infection.

Complications Pleurisy or PNEUMONIA may rarely occur in cases of acute bronchitis.

A physician should be consulted if any of the following symptoms appear:

• severe breathlessness

• audible wheezing

• no improvement after three days

• fever over 101 degrees F

• if patient has underlying lung disease

Chronic bronchitis often leads inexorably to increased shortness of breath; eventually, the patient may become housebound.

Brucella A genus of gram-negative spherical or rodlike parasitic bacteria that cause BRUCELLOSIS (undulant fever) in humans, and contagious abortion in animals. The principal species include B. abortus and B. melitensis. The genus was named after David Bruce, a surgeon who first identified the bacteria in 1887.

brucellosis A chronic bacterial disease, carried by farm animals, that may be transmitted to humans, affecting various organs of the body. It is also known as undulant fever, Malta fever, Gibraltar fever, Bang's disease, or Mediterranean fever.

Anyone is susceptible to the bacteria, and may get the disease if exposed, but it is more likely to be found among those who work with livestock. Up to 200 cases of brucellosis are diagnosed in the United States each year. In areas where milk pasteurization is not widely practiced (such as in Latin America and in the Mediterranean) the disease is contracted from eating unpasteurized dairy products. Untreated, the disease may persist for years.

Cause The disease is caused by several different species of bacteria of the genus BRUCELLA. B. abortus is found in cattle. B. suis is most often isolated in hogs and is more deadly when contracted by humans than the version found in cattle. B. melitensis is found in goats and sheep and causes the most severe illness in humans. B. rangiferi occurs in reindeer and caribou, and B. canis in dogs.

The bacteria are transmitted to humans by contact with an infected animal (through a cut or breathing in bacteria) or by consuming nonpasteurized contaminated milk or fresh goat cheese. It is also found in the afterbirth from infected cattle or goats that have aborted a fetus. It is not likely that the disease spreads from person to person or that a person will be reinfected after recovery. In the United States the disease is primarily confined to workers at slaughterhouses. President Richard Nixon suffered from brucellosis as a child.

Symptoms The disease is not usually fatal, but the intermittent fevers (a source of the name, "undulant fever"), can be debilitating. Symptoms usually appear within 5 to 30 days after exposure. The acute form of the disease includes a single bout of high fever, shivering, aching, and drenching sweats that last for a few days. Other symptoms include headache, poor appetite, backache, weakness, and depression. Mental depression can be so severe that the patient may be suicidal. In rare, untreated cases, an acute attack is so serious it can cause fatal complications such as PNEUMONIA or bacterial MENINGITIS. B. melitensis can cause abortions in women, especially during the first three months of pregnancy.

Chronic brucellosis is characterized by symptoms that recur over a period of months or years.

Diagnosis Blood tests can diagnose the disease.

Treatment Prolonged treatment with antibiotics (including tetracyclines plus streptomycin) and sulfonamides is effective. Bed rest is imperative. After an apparent recovery, the disease sometimes recurs a few months later, requiring another course of treatment.

Prevention Immunization of livestock that have first been checked to make sure they are not already infected will prevent human disease. Infected animals are usually destroyed.

bubonic plague See PLAGUE.

bunyavirus One of a group of mosquito-borne viruses that can infect humans, causing California ENCEPHALITIS, RIFT VALLEY FEVER, and others. Symptoms include headache, weakness, low-grade fever, facial pain, and rash. Outbreaks have occurred in North America, South America, Africa, and Europe.

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