Quinine

Quinine, drug that reduces fever in the treatment of malaria. Although quinine kills certain forms of the parasite that causes malaria, it cannot kill the parasite in all stages of its life cycle. Quinine, therefore, is not a true cure for malaria, but is useful in suppressing and controlling the recurring attacks of fever that characterize the disease. In many areas, quinine has been largely replaced by synthetic antimalarial drugs that produce fewer side effects and are more effective. However, quinine is still used in areas of the world where the synthetic drugs are not available, are not effective against particular strains of malaria, or are too expensive. Quinine is also used as a muscle relaxant to treat nighttime leg cramps.

Quinine is found in the root, bark, and branches of cinchonas and other trees native to the Andes mountains in South America.

Malaria

Malaria, debilitating infectious disease characterized by chills, shaking, and periodic bouts of intense fever. Caused by single-celled parasites of the genus Plasmodium, malaria is transmitted from person to person by the bite of female mosquitoes.

Malaria in humans is caused by four species of Plasmodium parasites. Plasmodium falciparum is the most common species in tropical areas and is transmitted primarily during the rainy season. This species is the most dangerous, accounting for half of all clinical cases of malaria and 90 percent of deaths from the disease. Plasmodium vivax is the most widely distributed parasite, existing in temperate as well as tropical climates. Plasmodium malariae can also be found in temperate and tropical climates but is less common than Plasmodium vivax. Plasmodium ovale is a relatively rare parasite, restricted to tropical climates and found primarily in eastern Africa.

The fever that characterizes malaria develops when merozoites invade and destroy red blood cells. The destruction of red blood cells spills wastes, toxins, and other debris into the blood. The body responds by producing fever, an immune response that speeds up other immune defenses to fight the foreign invaders in the blood. The fever usually occurs in intermittent episodes. An episode begins with sudden, violent chills, soon followed by an intense fever and then profuse sweating that brings the patient’s temperature down again. Upon initial infection with the malaria parasite, the episodes of fever frequently last 12 hours and usually leave an individual exhausted and bedridden. Repeated infections with the malaria parasite can lead to severe anemia, a decrease in the concentration of red blood cells in the bloodstream. The malaria parasite consumes or renders unusable the proteins and other vital components of the patient’s red cells.

Malaria is difficult to diagnose based on symptoms alone. This is because the intermittent fever and other symptoms can be quite variable and could be caused by other illnesses. A diagnosis of malaria is usually made by examining a sample of the patient’s blood under the microscope to detect malaria parasites in red blood cells. The different species of Plasmodium can be distinguished by their appearance under the microscope. Parasites can be difficult to detect in the early stages of malaria, in cases of chronic infections, or in Plasmodium falciparum infections because often in these cases, not many parasites are present. Recent advances have made it possible to detect proteins or genetic material of Plasmodium parasites in a patient’s blood.

Malaria is treated with drugs that block the growth of the Plasmodium parasite but do not harm the patient. Some drugs interfere with the parasite’s metabolism of food, while others prevent the parasite from reproducing. Drugs that interfere with the parasite’s metabolism are related to quinine, the first known antimalarial drug. Quinine is a chemical derived from the bark of the South American cinchona tree and was used as a fever remedy by the ancient Inca in the 15th century. This drug has a bitter taste and produces severe side effects, such as nausea, headache, ringing in the ears, temporary hearing loss, and blurred vision, and large doses can be fatal. However, quinine is still sometimes used in treating malaria today, particularly in developing nations, because it is inexpensive and effective.

Mumps

Mumps, acute infectious disease caused by a virus that mainly attacks glandular and nervous tissues, frequently characterized by swelling of the salivary glands. The disease is worldwide in distribution and can occur in epidemics. Its incidence is highest between the ages of 5 and 9, but mumps may attack persons of any age. Because the salivary gland most often affected is the parotid, mumps is also known as epidemic parotitis. The disease rarely involves the sex glands, the meninges, or the pancreas.
Mumps is spread from person to person by droplets sprayed from the respiratory tract of infected persons, and it is highly contagious. The incubation period of the disease varies from 15 to 21 days. Few fatalities result from mumps, and one attack usually confers complete immunity, because only one antigenic type of virus causes this disease. In children, the first symptoms are usually a mild fever, a feeling of illness and chilliness, loss of appetite, and dryness of the throat. This is followed by soreness and swelling around the ears, and a higher fever. These symptoms are usually gone by 12 days. In adult males, inflammation of the testes occurs in up to 20 percent of the cases, but resultant sterility is rare. In children, infection of the auditory nerve can cause deafness, but this is also a rare result.

Persons exposed to mumps are usually quarantined. Many persons have mumps in such a mild form, however, that it is not recognized, but they still acquire immunity to the disease.

Rabies

Rabies, acute, contagious infection of the central nervous system, caused by a specific virus that enters the body through the bite of an animal. All warm-blooded animals are susceptible, but in North America the disease is most common in skunks, foxes, bats, raccoons, dogs, and cats. Most of the cases of rabies in humans are caused by the bite of one of these animals. The incubation period in humans varies from three weeks to 120 days, with an average of about four to six weeks. Rabies is virtually always fatal when vaccine is not administered.

Modern treatment, following a bite by a rabid or presumed rabid animal, consists of immediate and thorough cleansing of the bite wound and injection into the wound and elsewhere of hyperimmune antirabies serum. A 14- to 30-day course of daily injections of rabies vaccine is then given; booster doses are given 10 days after this course and again 20 days later.

Immunization

Immunization, also called vaccination or inoculation, a method of stimulating resistance in the human body to specific diseases using microorganisms—bacteria or viruses—that have been modified or killed. These treated microorganisms do not cause the disease, but rather trigger the body's immune system to build a defense mechanism that continuously guards against the disease. If a person immunized against a particular disease later comes into contact with the disease-causing agent, the immune system is immediately able to respond defensively.

Scientists have developed two approaches to immunization: active immunization, which provides long-lasting immunity, and passive immunization, which gives temporary immunity. In active immunization, all or part of a disease-causing microorganism or a modified product of that microorganism is injected into the body to make the immune system respond defensively. Passive immunity is accomplished by injecting blood from an actively immunized human being or animal.