Ecology of Infectious Disease

Human diseases
Many disease organisms that threaten humans worldwide have complex life histories that are affected by both human and non-human attributes of the ecosystems in which they occur. For example,

• Lyme disease is carried by ticks that move about on mammal hosts such as deer and mice - environmental parameters that affect these non-human hosts have implications for human exposure to Lyme disease
• Rabies is a disease that is contracted by wildlife and can be passed on to humans. NCEAS researchers have assembled and analyzed an extensive database documenting rabid raccoons, refining predictions of rabies dynamics
• The bacterium causing the gastrointestinal disease cholera is waterborne and associated with microscopic crustaceans - climatic and environmental factors that affect hydrodynamics and the ecology of aquatic food webs can influence the dynamics of cholera
• The brain parasite that causes toxoplasmosis is passed among rats, cats, and humans; in humans, infection is associated with lifelong personality changes that may influence human culture
• NCEAS ecologists have formulated and applied cutting edge approaches in analysis and synthesis of human disease scenarios in recent years, improving our understanding of human disease risk

Disease and ecosystems
Ecologists have a growing awareness of the importance of pathogens and parasites in the evolution and ecology of natural systems.  Researchers at NCEAS have examined the evolutionary relationships between disease organisms and their hosts, as well as more modern alterations of pathogen and parasite dynamics by humans . For example:

• Introduced species have escaped many of the parasites of their native ranges ;
• The removal of predators that normally select sick individuals from prey groups may increase pathogen transmission among their populations, when diseased individuals continue living within groups ;
• Primate researchers have examined the role of social and feeding behavior in moderating infection by sexually transmitted diseases and parasites in non-human primates ;
• Disease is considered to be among the most significant causes of the modern coral reef decline, and warmer temperatures encourage some of the most common diseases on coral reefs ;
• Environmental warming and human activities, such as fishing, may have complex disease effects as warm temperatures seem to favor some pathogens and parasites, while decreasing the prevalence or severity of others , and human activities alter host abundance, behavior and environment

Respiratory Failure

Respiratory failure is nearly any condition that affects breathing function or the lungs themselves and can result in failure of the lungs to function properly. The main tasks of the lungs and chest are to get oxygen from the air that is inhaled into the bloodstream, and, at the same to time, to eliminate carbon dioxide (C02) from the blood through air that is breathed out. In respiratory failure, the level of oxygen in the blood becomes dangerously low, and/or the level of C02 becomes dangerously high. There are two ways in which this can happen. Either the process by which oxygen and C02 are exchanged between the blood and the air spaces of the lungs (a process called "gas exchange") breaks down, or the movement of air in and out of the lungs (ventilation) does not take place properly.
Respiratory failure often is divided into two main types. One of them, called hypoxemic respiratory failure, occurs when something interferes with normal gas exchange. Too little oxygen gets into the blood (hypoxemia), and all organs and tissues in the body suffer as a result. One common type of hypoxemic failure, occurring in both adults and prematurely born infants, is respiratory distress syndrome, a condition in which fluid or tissue changes prevent oxygen from passing out of the air sacs of the lungs into the circulating blood. Hypoxemia also may result from spending time at high altitudes (where there is less oxygen in the air); various forms of lung disease that separate oxygen from blood in the lungs; severe anemia ("low blood"); and blood vessel disorders that shunt blood away from the lungs, thus precluding the lungs from picking up oxygen.

The other main type of respiratory failure is ventilatory failure, occurring when, for any reason, breathing is not strong enough to rid the body of C02. Then CO2 builds up in the blood (hypercapnia). Ventilatory failure can result when the respiratory center in the brainstem fails to drive breathing; when muscle disease keeps the chest wall from expanding when breathing in; or when a patient has chronic obstructive lung disease that makes it very difficult to exhale air with its C02. Many of the specific diseases and conditions that cause respiratory failure cause both too little oxygen in the blood (hypoxemia) and abnormal ventilation.
Several different abnormalities of breathing function can cause respiratory failure. The major categories, with specific examples of each, are:

Obstruction of the airways. Examples are chronic bronchitis with heavy secretions; emphysema; cystic fibrosis; asthma (a condition in which it is very hard to get air in and out through narrowed breathing tubes).

Weak breathing. This can be caused by drugs or alcohol, which depress the respiratory center; extreme obesity; or sleep apnea, where patients stop breathing for long periods while sleeping.

Muscle weakness. This can be caused by a muscle disease called myasthenia; muscular dystrophy; polio; a stroke that paralyzes the respiratory muscles; injury of the spinal cord; or Lou Gehrig's disease.

Lung diseases, including severe pneumonia. Pulmonary edema, or fluid in the lungs, can be the source of respiratory failure. Also, it can often be a result of heart disease; respiratory distress syndrome; pulmonary fibrosis and other scarring diseases of the lung; radiation exposure; burn injury when smoke is inhaled; and widespread lung cancer.

An abnormal chest wall (a condition that can be caused by scoliosis or severe injury of the chest wall).

A majority of patients with respiratory failure are short of breath. Both low oxygen and high carbon dioxide can impair mental functions. Patients may become confused and disoriented and find it impossible to carry out their normal activities or do their work. Marked C02 excess can cause headaches and, in time, a semi-conscious state, or even coma. Low blood oxygen causes the skin to take on a bluish tinge. It also can cause an abnormal heart rhythm (arrhythmia). Physical examination may show a patient who is breathing rapidly, is restless, and has a rapid pulse. Lung disease may cause abnormal sounds heard when listening to the chest with a stethoscope: wheezing in asthma, "crackles" in obstructive lung disease. A patient with ventilatory failure is prone to gasp for breath, and may use the neck muscles to help expand the chest.
The symptoms and signs of respiratory failure are not specific. Rather, they depend on what is causing the failure and on the patient's condition before it developed. Good general health and some degree of "reserve" lung function will help see a patient through an episode of respiratory failure. The key diagnostic determination is to measure the amount of oxygen, carbon dioxide, and acid in the blood at regular intervals. A sudden low oxygen level in the lung tissue may cause the arteries of the lungs to narrow. This, in turn, causes the resistance in these vessels to increase, which can be measured using a special catheter. A high blood level of C02 may cause increased pressure in the fluid surrounding the brain and spinal cord; this, too, can be measured.
Nearly all patients are given oxygen as the first treatment. Then the underlying cause of respiratory failure must be treated. For example, antibiotics are used to fight a lung infection, or, for an asthmatic patient, a drug to open up the airways is commonly prescribed.

A patient whose breathing remains very poor will require a ventilator to aid breathing. A plastic tube is placed through the nose or mouth into the windpipe and is attached to a machine that forces air into the lungs. This can be a lifesaving treatment and should be continued until the patient's own lungs can take over the work of breathing. It is very important to use no more pressure than is necessary to provide sufficient oxygen; otherwise ventilation may cause further lung damage. Drugs are given to keep the patient calm, and the amount of fluid in the body is carefully adjusted so that the heart and lungs can function as normally as possible. Steroids, which combat inflammation, may sometimes be helpful but they can cause complications, including weakening the breathing muscles.

The respiratory therapist has a number of methods available to help patients overcome respiratory failure. They include:

Suctioning the lungs through a small plastic tube passed through the nose, in order to remove secretions from the airways that the patient cannot cough up.

Postural drainage, in which the patient is propped up at an angle or tilted to help secretions drain out of the lungs. The therapist may clap the patient on the chest or back to loosen the secretions, or a vibrator may be used for the same purpose.

Breathing exercises often are prescribed after the patient recovers. They make the patient feel better and help to strengthen the muscles that aid breathing. One useful method is for the patient to suck on a tube attached to a clear plastic hosing containing a ball so as to keep the ball lifted. Regular deep breathing exercises are simpler and often just as helpful. Another technique is to have the patient breathe out against pursed lips to increase pressure in the airways and keep them from collapsing.
The outlook for patients with respiratory failure depends chiefly on its cause. If the underlying disease can be effectively treated, with the patient's breathing supported in the meantime, the outlook is usually good.

Care is needed not to expose the patient to polluting substances in the atmosphere while recovering from respiratory failure; this could tip the balance against recovery. When respiratory failure develops slowly, pressure may build up in the lung's blood vessels, a condition called pulmonary hypertension. This condition may damage the vessels, worsen hypoxemia, and cause the heart to fail. If it is not possible to provide enough oxygen to the body, complications involving either the brain or the heart may prove fatal.

If the kidneys fail or the diseased lungs become infected, the prognosis is worse. In some cases, the primary disease causing the lungs to fail is irreversible. The patient, family, and physician together then must decide whether to prolong life by ventilator support. Occasionally, lung transplantation is a possibility, but it is a highly complex procedure and is not widely available

Because respiratory failure is not a disease itself, but the end result of many lung disorders, the best prevention is to treat any lung disease promptly and effectively. It is also important to make sure that any patient who has had lung disease is promptly treated for any respiratory infection (even of the upper respiratory tract). Patients with lung problems should also avoid exposure to pollutants, as much as is possible. Once respiratory failure is present, it is best for a patient to receive treatment in an intensive care unit, where specialized personnel and all the needed equipment are available. Close supervision of treatment, especially mechanical ventilation, will help minimize complications that would compound the problem.
A common form of lung disease in which breathing, and therefore gas exchange, is labored and increasingly difficult.

Gas exchange
The process by which oxygen is extracted from inhaled air into the bloodstream, and, at the same time, carbon dioxide is eliminated from the blood and exhaled.

Hypoxemia
An abnormally low amount of oxygen in the blood, the major consequence of respiratory failure, when the lungs no longer are able to perform their chief function of gas exchange.

Pulmonary fibrosis
An end result of many forms of lung disease (especially chronic inflammatory conditions). Normal lung tissue is converted to scarred, "fibrotic" tissue that cannot carry out gas exchange.

Laryngitis

Laryngitis is caused by inflammation of the larynx, resulting in hoarseness of the voice.

When air is breathed in (inspired), it passes through the nose and the nasopharynx or through the mouth and the oropharynx. These are both connected to the larynx, a tube made of cartilage. The vocal cords, responsible for setting up the vibrations necessary for speech, are located within the larynx. The air continues down the larynx to the trachea. The trachea then splits into two branches, the left and right bronchi (bronchial tubes). These bronchi branch into smaller air tubes which run within the lungs, leading to the small air sacs of the lungs (alveoli).

Either food, liquid, or air may be taken in through the mouth. While air goes into the larynx and the respiratory system, food and liquid are directed into the tube leading to the stomach, the esophagus. Because food or liquid in the bronchial tubes or lungs could cause a blockage or lead to an infection, the airway must be protected. The epiglottis is a leaf-like piece of cartilage extending upwards from the larynx. The epiglottis can close down over the larynx when someone is eating or drinking, preventing these substances from entering the airway.

In laryngitis, the tissues below the level of the epiglottis are swollen and inflamed. This causes swelling around the area of the vocal cords, so that they cannot vibrate normally. A hoarse sound to the voice is very characteristic of laryngitis. Laryngitis is a very common problem, and often occurs during the course of an upper respiratory tract infection (cold).

Laryngitis - Causes and Symptoms

Laryngitis is caused almost 100% of the time by a virus. The same viruses which cause the majority of simple upper respiratory infections (colds, etc.) are responsible for laryngitis. These include parainfluenzae virus, influenza virus, respiratory syncytial virus, rhinovirus, coronavirus, and echovirus. Extremely rarely, bacteria such as Group A streptococcus, M. catarrhalis, or that which causes tuberculosis may cause laryngitis. In people with faulty immune systems (particular due to acquired immunodeficiency syndrome, or AIDS), infections with fungi may be responsible for laryngitis.

Symptoms usually begin along with, or following, symptoms of a cold. A sore, scratchy throat, fever, runny nose, achiness, and fatigue may all occur. Difficulty swallowing sometimes occurs with streptococcal infections. The patient may cough and wheeze. Most characteristically, the patient's voice will sound strained, hoarse, and raspy.

In extremely rare cases, the swelling of the larynx may cause symptoms of airway obstruction. This is more common in infants, because the diameter of their airways is so small. In that case, the baby may have a greatly increased respiratory rate, and exhibit loud high-pitched sounds with breathing (called stridor).

Laryngitis - Diagnosis

Diagnosis is usually made by learning the history of a cold followed by hoarseness. The throat usually appears red and somewhat swollen. Listening to the chest and back with a stethoscope may reveal some harsh wheezing sounds with inspiration (breathing in).

In long-standing (chronic laryngitis), tuberculosis may be suspected. Using a scope called a laryngoscope, examination of the airway will show redness, swelling, small bumps of tissue called nodules, and irritated pits in the tissue called ulcerations. Special skin testing (TB testing) will reveal that the individual has been exposed to the bacteria causing TB.

Laryngitis - Treatment

Treatment of a simple, viral laryngitis simply addresses the symptoms. Gargling with warm salt water, pain relievers such as acetaminophen, the use of vaporizers to create moist air, and rest will help the illness resolve within a week.

In an infant who is clearly struggling for air, it may be necessary to put in an artificial airway for a short period of time. This is very rarely needed.

An individual with tubercular laryngitis is treated with a combination of medications used to treat classic TB. In people with fungal laryngitis, a variety of anti-fungal medications are available.

Laryngitis - Alternative treatment

Alternative treatments include aromatherapy inhalations made with benzoin, lavender, frankincense, thyme, and sandalwood. Decoctions (extracts made by boiling an herb in water) or infusions (extracts made by steeping an herb in boiling water) can be made with red sage (Salvia officinalis var. rubra) and yarrow (Achillea millefolium) or with licorice (Glycyrrhiza glabra). These are used for gargling, and are said to reduce pain. Echinacea ( Echinacea spp.) tincture taken in water every hour for 48 hours is recommended to boost the immune system. Antiviral herbs, including usnea (Usnea spp.), lomatium (Lomatium dissectum), and ligusticum (Ligusticum porteri), may help hasten recovery from laryngitis. Homeopathic remedies are recommended based on the patient's symptoms. Some people may get relief from placing cold compresses on the throat.

Laryngitis - Prognosis

Prognosis for laryngitis is excellent. Recovery is complete, and usually occurs within a week's time.

Laryngitis - Prevention

Prevention of laryngitis is the same as for any upper respiratory infections. The only way to even attempt to prevent such illnesses is by good handwashing, and by avoiding situations where one might come in contact with people who might be sick. However, even with relatively good hygiene practices, most people will get about five to six colds per year. It is unpredictable which of these may lead to laryngitis.

Key Terms

Epiglottis
A leaf-like piece of cartilage extending upwards from the larynx, which can close like a lid over the trachea to prevent the airway from receiving any food or liquid being swallowed.

Larynx
The part of the airway lying between the pharynx and the trachea.

Nasopharynx
The part of the airway into which the nose leads.

Oropharynx
The part of the airway into which the mouth leads.

Trachea
The part of the airway which leads into the bronchial tubes.

Hantaviruses

Hantaviruses, any of several members of the virus family Bunyaviridae that infect vertebrates (animals with backbones, including humans). Unlike most members of this family, which are carried by mosquitoes, ticks, or flies, hantaviruses are carried by specific rodent hosts and are transmitted directly from host to host by virus-laden saliva, urine, and feces. Humans are infected through exposure to the dried excretions from infected rodents. Hantaviruses cause two different human diseases: hemorrhagic fever with renal syndrome, in which damage to the kidneys is common, and acute respiratory distress syndrome, in which damage to the lungs is common.

Hantaviruses are spherical and are 90 to 100 nanometers (1 nanometer equals 1 billionth of a meter, or 4 x 10-8 inches) in diameter. They are composed of an envelope covered with spikes surrounding three protein-wrapped, circular pieces of ribonucleic acid (RNA). Although many hantaviruses have been identified recently, their true number and potential for causing disease is probably far greater than is presently thought.

Acute respiratory distress syndrome is one of two human diseases caused by hantavirus. Dust containing virus-infected rodent feces becomes airborne and is inhaled. The virus embeds in the lungs where the infection begins. Flulike symptoms appear in about a week, followed by the collection of fluid and white blood cells in the lungs, causing respiratory failure, then death.

HANTAAN VIRUS

The first human disease known to be due to a hantavirus infection was hemorrhagic fever with renal syndrome, identified in the early 1950s during the Korean War. Thousands of United Nations troops developed a mysterious disease marked by fever, headache, hemorrhage, and acute kidney failure. Despite much research, the cause remained unknown for 26 years until a new virus, named Hantaan virus, was isolated in Korea from field mice in 1976.

Hemorrhagic fever with renal syndrome is widespread in the Far East, particularly in China and Korea. There are two seasonal disease peaks, associated with the harvesting of wheat in summer and of rice in late fall. During these times the host rodent populations peak and the fields are full of dust containing dried, virus-laden excrement. The disease is fatal in about 5 to 10 percent of cases. A milder form of the disease, caused by Seoul virus and transmitted by rats, occurs in Japan, Korea, China, and the United States, especially in seaports, where rats are common. Symptoms are less severe and include nephritis (inflammation of the kidneys).

SIN NOMBRE VIRUS

In 1993 a new hantavirus disease was recognized in the southwestern United States. The illness was at first referred to as Four Corners Disease, named for the area where the disease was first observed, where Arizona, New Mexico, Colorado, and Utah meet. The agent responsible was called the Sin Nombre (an area in New Mexico which in Spanish means “no name”) virus. The victims of the virus developed influenza-like symptoms—including fever, muscle aches, cough, and headache—which rapidly worsened. Fluid and white blood cells accumulated in the lungs, causing hypoxia (low blood-oxygen levels), shock, and, in many cases, death from a type of lung failure called acute respiratory distress syndrome, also known as hantavirus pulmonary syndrome. Within a short time, cases were found in other states. By the end of 1995, 123 cases, with a fatality rate of 51 percent, had been confirmed from 23 states. The disease was also identified in Canada, Brazil, Venezuela, and Argentina.

The search for the cause of this mysterious disease began with typical epidemiological studies that involved interviewing survivors and people who came in contact with the victims. Blood samples from victims shared evidence of antibodies against hantaviruses, an indication that they had been exposed to hantavirus in the past, and that this earlier exposure had initiated an immune response. To prove which hantavirus was indeed the cause of the victims' death, scientists used the polymerase chain reaction (PCR). This technique is used to rapidly amplify DNA strands. Once amplified, specific methods are used to identify the specific virus. Scientists determined with certainty that hantavirus was present in the tissues of the victims and determined that the disease was caused by a previously unknown hantavirus. Hantavirus specimens from different areas were compared, revealing that several previously unknown viruses were active in the United States. The entire genetic structure of the Sin Nombre virus was determined, and diagnostic tests were created. The same methods are being used in attempts to develop a vaccine. (For a description of vaccines, See Immunization.)

The primary host of Sin Nombre virus in the southwestern United States is the deer mouse, Peromyscus maniculatus. In large sections of this part of the country, 10 to 35 percent of deer mice are infected, and in certain areas about 80 percent of deer mice carry the virus.

Sin Nombre virus, like other hantaviruses, does not cause disease in its rodent hosts. The virus is shed in the saliva, urine, and feces of these animals for many weeks and perhaps for the lifetime of the animal. Human infection occurs when dust containing infected dried rodent excretions is inhaled. Sin Nombre and the other newly discovered hantaviruses probably have long been present in the region of the western United States inhabited by deer mice. The virus was recognized in 1993 only because of the number and clustering of human cases, after two particularly wet winters and an abundant supply of rodent food caused an increase in rodent populations, which then led to a rise in the incidence of the disease.

PREVENTION

The risk of infection by hantaviruses can be reduced by preventing rodents from living in or near human dwellings. Rodent nests and droppings should be wetted down with a disinfectant before they are removed.

Emphysema

Emphysema, progressive respiratory disease characterized by coughing, shortness of breath, and wheezing, developing into extreme difficulty in breathing, and sometimes resulting in disability and death. Although the exact cause is unknown, bronchial spasm, infection, irritation, or a combination of the three seem to be contributory. The highest degree of occurrence is among heavy cigarette smokers, especially those exposed to polluted air. Children who suffer from bronchitis or asthma are also susceptible. In recent years emphysema has become a serious public health problem in terms of rapidly increasing numbers of disabilities and deaths.

In the course of the disease the passages leading to the air sacs of the lungs become narrowed. Air is trapped in the sacs, and the tissues of the lungs lose their natural elasticity and undergo destructive changes. Symptoms akin to the common cold or asthmatic wheezing may result. As the disease progresses the volume of residual air trapped in the lungs increases, and the volume of each breath decreases. The lungs increase in size, and in severe cases the patient develops a characteristic “barrel chest.” The lungs become unable to supply enough oxygen to the body tissues. This reduction in oxygen intake causes the heart to pump faster; consequently, the heart becomes strained. Excessive carbon dioxide in the blood gives the patient a bluish skin color.

Although the deterioration in the lungs brought about by emphysema is permanent and irreversible, treatment can give relief and increase functioning capacity. Abstention from smoking is essential, and change of occupation or residence may be necessary if air pollution or occupational pollution aggravates the condition. Bronchial dilators, special breathing exercises, and antibiotics are also helpful. Therapy is most successful in instances when the disease is diagnosed at an early stage.

The term emphysema is also used to describe infiltration of air into connective tissue and between air cells of the lungs.

Cough

A cough is a forceful release of air from the lungs that can be heard. Coughing protects the respiratory system by clearing it of irritants and secretions.

Cough - Description

While people can generally cough voluntarily, a cough is usually a reflex triggered when an irritant stimulates one or more of the cough receptors found at different points in the respiratory system. These receptors then send a message to the cough center in the brain, which in turn tells the body to cough. A cough begins with a deep breath in, at which point the opening between the vocal cords at the upper part of the larynx (glottis) shuts, trapping the air in the lungs. As the diaphragm and other muscles involved in breathing press against the lungs, the glottis suddenly opens, producing an explosive outflow of air at speeds greater than 100 mi (160 km) per hour.

In normal situations, most people cough once or twice an hour during the day to clear the airway of irritants. However, when the level of irritants in the air is high or when the respiratory system becomes infected, coughing may become frequent and prolonged. It may interfere with exercise or sleep, and it may also cause distress if accompanied by dizziness, chest pain, or breathlessness. In the majority cases, frequent coughing lasts one to two weeks and tapers off as the irritant or infection subsides. If a cough lasts more than three weeks it is considered a chronic cough, and physicians will try to determine a cause beyond an acute infection or irritant.

Coughs are generally described as either dry or productive. A dry cough does not bring up a mixture of mucus, irritants, and other substances from the lungs (sputum), while a productive cough does. In the case of a bacterial infection, the sputum brought up in a productive cough may be greenish, gray, or brown. In the case of an allergy or viral infection it may be clear or white. In the most serious conditions, the sputum may contain blood.

Cough - Causes and Symptoms

In the majority of cases, coughs are caused by respiratory infections, including:

colds or influenza, the most common causes of coughs

bronchitis, an inflammation of the mucous membranes of the bronchial tubes

croup, a viral inflammation of the larynx, windpipe, and bronchial passages that produces a bark-like cough in children

whooping cough, a bacterial infection accompanied by the high-pitched cough for which it is named

pneumonia, a potentially serious bacterial infection that produces discolored or bloody mucus

tuberculosis, another serious bacterial infection that produces bloody sputum

fungal infections, such as aspergillosis, histoplasmosis, and cryptococcoses.

Environmental pollutants, such as cigarette smoke, dust, or smog, can also cause a cough. In the case of cigarette smokers, the nicotine present in the smoke paralyzes the hairs (cilia) that regularly flush mucus from the respiratory system. The mucus then builds up, forcing the body to removed it by coughing. Post-nasal drip, the irritating trickle of mucus from the nasal passages into the throat caused by allergies or sinusitis, can also result in a cough. Some chronic conditions, such as asthma, chronic bronchitis, emphysema, and cystic fibrosis, are characterized in part by a cough. A condition in which stomach acid backs up into the esophagus (gastroesophageal reflux) can cause coughing, especially when a person is lying down. A cough can also be a side-effect of medications that are administered via an inhaler. It can also be a side-effect of beta-blockers and ACE inhibitors, which are drugs used for treating high blood pressure.

Cough - Diagnosis

To determine the cause of a cough, a physician should take an exact medical history and perform an exam. Information regarding the duration of the cough, what other symptoms may accompany it, and what environmental factors may influence it aid the doctor in his or her diagnosis. The appearance of the sputum will also help determine what type of infection, if any, may be involved. The doctor may even observe the sputum microscopically for the presence of bacteria and white blood cells. Chest x rays may help indicate the presence and extent of such infections as pneumonia or tuberculosis. If these actions are not enough to determine the cause of the cough, a bronchoscopy or laryngoscopy may be ordered. These tests use slender tubular instruments to inspect the interior of the bronchi and larynx.

Cough - Treatment

Treatment of a cough generally involves addressing the condition causing it. An acute infection such as pneumonia may require antibiotics, an asthma-induced cough may be treated with the use of bronchodialators, or an antihistamine may be administered in the case of an allergy. Physicians prefer not to suppress a productive cough, since it aids the body in clearing respiratory system of infective agents and irritants. However, cough medicines may be given if the patient cannot rest because of the cough or if the cough is not productive, as is the case with most coughs associated with colds or flu. The two types of drugs used to treat coughs are antitussives and expectorants.

Antitussives

Antitussives are drugs that suppress a cough. Narcotics--primarily codeine--are used as antitussives and work by depressing the cough center in the brain. However, they can cause such side effects as drowsiness, nausea, and constipation. Dextromethorphan, the primary ingredient in many over-the-counter cough remedies, also depresses the brain's cough center, but without the side effects associated with narcotics. Demulcents relieve coughing by coating irritated passageways.

Expectorants

Expectorants are drugs that make mucus easier to cough up by thinning it. Guaifenesin and terpin hydrate are the primary ingredients in most over-the-counter expectorants. However, some studies have shown that in acute infections, simply increasing fluid intake has the same thinning effect as taking expectorants.

Cough - Alternative treatment

Coughs due to bacterial or viral upper respiratory infections may be effectively treated with botanical and homeopathic therapies. The choice of remedy will vary and be specific to the type of cough the patient has. Some combination over-the-counter herbal and homeopathic cough formulas can be very effective for cough relief. Lingering coughs or coughing up blood should be treated by a trained practitioner.

Many health practitioners advise increasing fluids and breathing in warm, humidified air as ways of loosening chest congestion. Others recommend hot tea flavored with honey as a temporary home remedy for coughs caused by colds or flu. Various vitamins, such as vitamin C, may be helpful in preventing or treating conditions (including colds and flu) that lead to coughs. Avoiding of mucous-producing foods can be effective in healing a cough condition. These mucous-producing foods can vary, based on individual intolerance, but dairy products are a major mucous-producing food for most people.

Cough - Prognosis

Because the majority of coughs are related to the common cold or influenza, most will end in seven to 21 days. The outcome of coughs due to a more serious underlying disease depends on the pathology of that disease.

Cough - Prevention

It is important to identify and treat the underlying disease and origin of the cough. Avoid smoking and coming in direct contact with people experiencing cold or flu symptoms. Wash hands frequently during episodes of upper-respiratory illnesses.

Key Terms

Antitussives
Drugs used to suppress coughing.

Expectorant
Drug used to thin mucus.

Gastroesophageal reflux
Condition in which stomach acid backs up into the esophagus.

Glottis
The opening between the vocal cords at the upper part of the larynx.

Larynx
A part of the respiratory tract between the pharynx and the trachea, having walls of cartilage and muscle and containing the vocal cords.

Sputum
The mixture of mucus, irritants, and other substances expelled from the lungs by coughing.

Byssinosis

  Byssinosis is a chronic, asthma-like narrowing of the airways. Also called brown lung disease, byssinosis results from inhaling particles of cotton, flax, hemp, or jute.

Byssinosis - Description

Although inhaling cotton dust was identified as a source of respiratory disease more than 300 years ago, byssinosis has been recognized as an occupational hazard for textile workers for less than 50 years. More than 800,000 workers in the cotton, flax, and rope-making industries are exposed in the workplace to airborne particles that can cause byssinosis. Only workers in mills that manufacture yarn, thread, or fabric have a significant risk of dying of this disease.

In the United States, byssinosis is almost completely limited to workers who handle unprocessed cotton. More than 35,000 textile workers have been disabled by byssinosis and 183 died between 1979 and 1992. Most of the people whose deaths were due to byssinosis lived in the textile-producing regions of North and South Carolina.

Byssinosis - Causes and Symptoms

Wheezing, shortness of breath, and a feeling of tightness in the chest occur occasionally during the early stages of the disease. Symptoms are usually more pronounced when returning to work after a weekend, holiday, or vacation and subside as the worker becomes reaccustomed to the environment.

As many as 25% of workers with byssinosis have symptoms that continue or recur throughout the workweek. More severe breathing problems seem to result both from exposure to high levels of dust and from longer dust exposure. Workers who also smoke cigarettes suffer the most severe impairment.

Byssinosis - Diagnosis

Tests that detect decreasing lung capacity during the workday are used to diagnose byssinosis. Obstructive patterns are likely in patients who have had recurrent symptoms for more than 10 years.

Byssinosis - Treatment

Therapy for early-stage byssinosis focuses on reversing airway narrowing. Antihistamines may be prescribed to reduce tightness in the chest. Bronchodilators (drugs used to relax breathing passages and improve air flow) may be used with an inhaler or taken in tablet form. Reducing exposure is essential. Any worker who has symptoms of byssinosis or who has trouble breathing should transfer to a less-contaminated area.

Byssinosis - Prognosis

Smoking, impaired lung function, and a history of respiratory allergy increase a textile worker's risk of developing byssinosis. Prolonged exposure makes patients wheeze more often and can cause chronic bronchitis. It does not lead to permanently disabling lung disease.

Byssinosis - Prevention

Eliminating exposure to textile dust is the surest way to prevent byssinosis. Using exhaust hoods, improving ventilation, and employing wetting procedures are very successful methods of controlling dust levels to prevent byssinosis. Protective equipment required during certain procedures also prevents exposure to levels of contamination that exceed the current United States standard for cotton dust exposure.

Asthma

Asthma is a lung disease that causes obstruction of the airways. It is an overreaction of the body’s immune system usually caused by exposure to an allergen, a substance that the body perceives as foreign and dangerous.

During an asthma attack, spasms in the muscles surrounding the bronchi (small airways in the lungs) constrict, impeding the outward passage of air. Asthma sufferers often describe this plight as “starving for air”. Typical symptoms of an asthma attack are coughing, wheezing, a feeling of tightness in the chest, and difficulty breathing. An attack can last for a few minutes or several hours.

The spasms characterizing an acute attack are not the cause of the disorder, but a result of chronic inflammation and hypersensitivity of the airways to certain stimuli. An attack can be triggered if a susceptible individual is exposed to an allergen, but irritants, infection, stress, exercise, use of aspirin, ibuprofen, naproxen, or other NSAIDs – or even rapid changes in weather and humidity- can trigger an attack.

Common asthma provoking allergens include animal dander, cockroach allergens, pollens, mold, pet dander, chemicals, drugs, dust mites, environmental pollutants, feathers, food additives ( such as monosodium glutamate, sulfites such as sodium metabisulfite), sea food, dairy products, nuts, yeast-based food, fumes, mold, and tobacco smoke.

Factors that can trigger non allergic asthma include adrenal disorders, anxiety, temperature changes, exercise, extremes of dryness or humidity, fear, laughing, low blood sugar, and stress. A respiratory infection like bronchitis is the most common provoker. Whatever the particular instigator, the bronchial tubes swell and become plugged with mucus. This inflammation further irritates the airways, resulting in even greater sensitivity. The attacks become more frequent and the inflammation more severe.

Asthma epidemics related to atmospheric contamination – situations in which dust and chemical particles are abundant, especially in enclosed environments- are well known. Occupational exposure to certain substances, such as urethrane and polyurethrane, used in the adhesives and plastic industry, along with rubber epoxy resins from paint, textile cleaner’s fumes, dry cleaning chemicals, and others also may be major risk factors.

Asthma symptoms may resemble those of other diseases, such as emphysema, bronchitis, heart burn, and lower respiratory infections.

Common signs and symptoms of asthma include: recurrent wheezing, coughing, trouble breathing, chest tightness, symptoms that occur or worsen at night, symptoms that are triggered by cold air, exercise or exposure to allergens.

Wheezing — high-pitched whistling sounds when you breathe out — is one of the main signs of asthma and indicates obstructed airways.

Although your symptoms, medical history and physical examination may suggest that you have asthma, lung (pulmonary) function tests may be needed to confirm an asthma diagnosis. Lung function tests may include one or more of the following tests:

a. Spirometry

This noninvasive test measures how well you breathe. During spirometry, you take deep breaths and forcefully exhale into a hose connected to a machine called a spirometer. Spirometry testing reveals two measurements that are important in diagnosing asthma:

Forced vital capacity (FVC), which is the maximum amount of air you can inhale and exhale.

Forced expiratory volume (FEV-1), which is the maximum amount of air you can exhale in one second.

The two measurements are compared. If certain key measurements are below normal for a person your age, it may be a sign that your airways are obstructed. Your doctor may ask you to inhale a bronchodilator drug used in asthma treatment to open obstructed air passages and then try the test again. If your measurements improve significantly, it's likely that you have asthma. Your doctor may still suspect that you have asthma even if your initial spirometry measurements are normal. If so, you may need additional tests.

b. Challenge test

During this test, your doctor deliberately tries to trigger airway obstruction and asthma symptoms by having you inhale an airway-constricting substance or take several breaths of cold air. If you appear to have exercise-induced asthma, you may be asked to do vigorous physical activity to trigger symptoms.

After triggering your symptoms, you retake the spirometry test. If your spirometry measurements are still normal, it's likely that you don't have asthma. But if your measurements have fallen significantly, it may mean you have asthma.

Treatment

The following treatments are usually administered concurrently to achieve the most rapid resolution of the exacerbation.

Oxygen. To achieve arterial oxygen saturation of a 90% (a 95% in children), oxygen should be administered by nasal cannulae, by mask, or rarely by head box in some infants. PaCO2 may worsen in some patients on 100 percent oxygen, especially those with more severe airflow

Obstruction. Oxygen therapy should be titrated against pulse oximetry to maintain a satisfactory oxygen saturation.

Rapid-acting inhaled ß2–agonists. Rapid-acting inhaled beta2-agonists should be administered at regular intervals. Although most rapid-acting beta2-agonists have a short duration of effect, the long-acting bronchodilator formoterol, which has both a rapid onset of action and a long duration of effect, has been shown to be equally effective without increasing side effects, though it is considerably more expensive.

The importance of this feature of formoterol is that it provides support and reassurance regarding the use of a combination of formoterol and budesonide early in asthma exacerbations. A modestly greater bronchodilator effect has been shown with levabuterol compared to racemic albuterol in both adults and children with an asthma exacerbation. In a large study of acute asthma in children and in adults not previously treated with glucocorticosteroid, levabuterol

treatment resulted in lower hospitalization rates compared to racemic albuterol treatment, but in children the length of hospital stay was no different.

Studies of intermittent versus continuous nebulized shortacting beta2-agonists in acute asthma provide conflicting results. In a systematic review of six studies, there were no significant differences in bronchodilator effect or hospital admissions between the two treatments. In

patients who require hospitalization, one study found that intermittent on-demand therapy led to a significantly shorter hospital stay, fewer nebulizations, and fewer palpitations when compared with intermittent therapy given every 4 hours. A reasonable approach to inhaled therapy

in exacerbations, therefore, would be the initial use of continuous therapy, followed by intermittent on-demand therapy for hospitalized patients. There is no evidence to support the routine use of intravenous beta2-agonists in patients with severe asthma exacerbations.

Epinephrine. A subcutaneous or intramuscular injection of epinephrine (adrenaline) may be indicated for acute treatment of anaphylaxis and angioedema, but is not routinely indicated during asthma exacerbations.

Additional bronchodilators.

Ipratropium bromide. A combination of nebulized beta2- agonist with an anticholinergic (ipratropium bromide) may produce better bronchodilation than either drug alone and should be administered before methylxanthines are considered. Combination beta2- agonist/anticholinergic therapy is associated with lower hospitalization rates and greater improvement in PEF and FEV1. Similar data have been reported in the pediatric literature . However, once children with asthma are hospitalized following intensive emergency department treatment, the addition of nebulized ipratropium bromide to nebulized beta2-agonist and systemic glucocorticosteroids appears to confer no extra benefit.

Theophylline. In view of the effectiveness and relative safety of rapid-acting beta2-agonists, theophylline has a minimal role in the management of acute asthma. Its use is associated with severe and potentially fatal side effects, particularly in those on long-term therapy with

sustained-release theophylline, and their bronchodilator effect is less than that of beta2-agonists. The benefit asadd-on treatment in adults with severe asthma exacerbations has not been demonstrated. However, in one study of children with near-fatal asthma, intravenous

theophylline provided additional benefit to patients also receiving an aggressive regimen of inhaled and intravenous beta2-agonists, inhaled ipatropium bromide, and intravenous systemic glucocorticosteroids.

Systemic glucocorticosteroids. Systemic glucocorticosteroids speed resolution of xacerbations and should be utilized in the all but the mildest exacerbations, especially if:

• The initial rapid-acting inhaled beta2-agonist therapy fails to achieve lasting improvement

• The exacerbation develops even though the patient was already taking oral glucocorticosteroids

• Previous exacerbations required oral glucocorticosteroids.

Oral glucocorticosteroids are usually as effective as those administered intravenously and are preferred because this route of delivery is less invasive and less expensive.

If vomiting has occurred shortly after administration of oral glucocorticosteroids, then an equivalent dose should be re-administered intravenously. In patients discharged from the emergency department, intramuscular administration may be helpful, especially if there are concerns about compliance with oral therapy. Oral glucocorticosteroids require at least 4 hours to produce clinical improvement.

Daily doses of systemic glucocorticosteroids equivalent to 60-80 mg methylprednisolone as a single dose, or 300-400 mg hydrocortisone in divided doses, are adequate for hospitalized patients, and 40 mg methylprednisolone or 200 mg hydrocortisone is probably adequate in most

cases. An oral glucocorticosteroid dose of 1 mg/kg daily is adequate for treatment of exacer-bations in children with mild persistent asthma. A 7-day course in adults has been found to be as effective as a 14-day course, and a 3- to 5-day course in children is usually considered appro-priate. Current evidence suggests that there is no benefit to tapering the dose of oral glucocorticosteroids, either in the short-term or over several weeks.

Inhaled glucocorticosteroids. Inhaled glucocorticosteroids are effective as part of therapy for asthma exacerbations. In one study, the combination of high-dose inhaled glucocorticosteroids and salbutamol in acute asthma provided greater bronchodilation than salbutamol alone, and conferred greater benefit than the addition of systemic glucocorticosteroids across all parameters, including hospitalizations, especially for patients with more severe attacks. Inhaled glucocorticosteroids can be as effective as oral glucocorticosteroids at preventing relapses. Patients discharged from the emergency department on prednisone and inhaled budesonide have a lower rate of relapse than

those on prednisone alone. A high-dose of inhaled glucocorticosteroid (2.4 mg budesonide daily in

four divided doses) achieves a relapse rate similar to 40 mg oral prednisone daily.

Cost is a significant factor in the use of such high-doses of inhaled glucocorticosteroids, and further studies are required to document their potential benefits, especially cost effectiveness, in acute asthma.

Magnesium. Intravenous magnesium sulphate (usually given as a single 2 g infusion over 20 minutes) is not recommended for routine use in asthma exacerbations, but can help reduce hospital admission rates in certain patients, including adults with FEV1 25-30% predicted at presentation, adults and children who fail to respond to initial treatment, and children whose FEV1 fails to improve

above 60% predicted after 1 hour of care. Nebulized salbutamol administered in isotonic magnesium sulfate provides greater benefit than if it is delivered in normal saline. Intravenous magnesium sulphate has not been studied in young children.

Helium oxygen therapy. A systematic survey of studies that have evaluated the effect of a combination of helium and oxygen, compared to helium alone, suggests there is no routine role for this intervention. It might be considered for patients who do not respond to standard therapy.

Leukotriene modifiers. There is little data to suggest a role for leukotriene modifiers in acute asthma.

Sedatives. Sedation should be strictly avoided during exacerbations of asthma because of the respiratory depressant effect of anxiolytic and hypnotic drugs. An association between the use of these drugs and avoidable asthma deaths has been demonstrated.

The following are the nutrients, herbs, and other recommendations beneficial to thwart atherosclerosis:

NUTRIENTS

Supplement	Suggested Dosage	Comments
Essential
Pantothenic acid (Vit B6)	50 mg 3x a day	The anti stress vitamin
Quercitin-C from Ecological Formulas plus bromelain	500 mg 3x a day 100 mg 3x a day	Powerful immunostimulants. Antihistamine effect
Vitamin C with bioflavonoids	1500 mg 3x a day (avoid high doses when with kidney stones)	Needed to protect lung tissue and keep down infection. Also increases air flow and fights inflammation
Zinc lozenges	Do not take over 100 mg daily	Can shorten an attack or halt one before it becomes severe.
Very Important
Betaine HCl with pepsin	As directed on label, or as prescribed	Combats malabsorption problems
Coenzyme Q	100 mg daily	Has the ability to counter histamine
Magnesium plus calcium	750 mg daily 1500 mg daily	May stop the acute asthmatic episode by increasing the vital capacity of the lungs. Has a dilating effect on the bronchial muscles. Use chelate forms
Multivitamin and mineral complex with Selenium Vitamin B12	As directed on the label 200 mcg daily 2000 mcg daily	Necessary for enhanced immune function. Use a high potency formula. Destroys radicals from air pollutants

Herbs

Lobelia extract is helpful during an asthma attack attack; it is a bronchial soothing muscle relaxant and expectorant. Do not take long term.

Boswellia, an Indian herb (also known as frankincense), in studies was shown to reduce the number of asthma attacks.

Mullein oil is said to be a powerful remedy for bronchial congestion. The oil stops cough, unclogs bronchial tubes, and helps clear up asthma attacks. Users say that when they take it in tea or fruit juice, the effect is almost immediate.

Proponents of the East Indian mind-body-earth philosophy called Ayurveda recommend the following herbs for people with asthma: vasaka (Adhatoda vasica) relieves cough, bronchitis, and other asthmatic symptoms; boswellia (Boswellia serrata), to relieve pain or inflammation; and tylophora (Tylophora indica) for respiratory relief.

Other herbs beneficial for asthma include Echinacea, licorice root, and slippery elm bark tablets. Licorice root, ginger root, and elderberry open up the respiratory tract.

Caution: Do not take Echinacea if you have an autoiimune disorder. Do not use licorice on a daily basis for more than seven days in a row, and avoid it completely if you have high blood pressure.

Recommendations:

Homeopathic use of belladonna have been shown to relax the bronchioles in the lungs which alleviates the wheezing symptoms in an asthma attack.

Eat a diet consisting primarily of fresh fruits and vegetables, oatmeal, brown rice, and whole grains. The diet should be relatively high in protein, low in carbohydrate, and contain no sugar.

Include garlic and oinions in your diet. These food contain quercatin and mustard oils, which have been shown to inhibit an enzyme that aids in releasing inflammatory chemicals.

Avoid gas-producing foods, such as beans, brassicas ( broccoli, cauliflower, and cabbage) and large amounts of bran. Gas can aggravate an asthmatic condition by putting pressure in the diaphragm.

Do not eat ice cream or drink extremely cold liquids. Cold can shock the bronchial tubes into spasms.

Use a juice fast, a fast using distilled water or lemon juice or a combination of both for three days each month to help rid the body of toxins and mucus.

Eat lightly- a large meal can cause shortness of breath by making the stomach put pressure on the diaphragm

Practice methods to relieve stress as they can trigger an attack.